Understanding Nikon's Flash Modes

Nikon cameras have several flash modes that change how the flash output from the camera's popup flash works. Many photographers do not fully understand each of the modes. I am going to use a Nikon D7000 as an example in this article. Virtually all Nikon's have the same flash modes, although you may access them from a menu or rear LCD monitor, instead of the upper control panel LCD (like on the D7000 and D300S).

Primarily, this article is designed to help you understand the purpose of each of the flash modes. You may need to refer to your camera's users manual if you cannot figure out how to switch between the modes.

Nikon's Popup Speedlight Flash

Five Basic Flash Modes

Following are the five basic flash modes and a description of how each works. The camera will often combine these flash modes as you use different shooting modes on the Mode dial. See the list of shooting modes at the end of this section.

Auto

Auto flash mode (figure 1) is usually available only when you are using various SCENE modes, if your camera has SCENE modes. It lets the camera decide when and what type of flash to use. You have no control over the flash when you use Auto mode.

Figure 1 – Auto flash Mode (SCENE modes only)

You can select this mode if you are unsure about which mode to use in a certain circumstance and the camera will do its best to give you a well-exposed picture.

Fill Flash (Front-Curtain Sync)

In Fill flash (Front-curtain sync mode), the camera tries its best to balance the light if you’re using a lens that has a CPU in it (figure 2).

Figure 2 – Front-curtain sync (fill flash)

A CPU lens, like an AF-S Nikkor G or D lens, provides subject distance information that helps balance ambient light and light from the flash equally and works to make the light look very natural. If you use this correctly outdoors, it will be hard to tell that you were using flash, except for the catch light in your subject’s eyes and the lack of damaging shadows. The flash simply fills in some extra light without overpowering the ambient light. In a situation where there is very little ambient light, the camera will use only the flash to get a correct exposure. It only balances with ambient light if there is enough ambient light to balance with in the first place.

There is a side effect to using this mode with slow shutter speeds. Fill flash simply causes the flash to fire as soon as the front shutter curtain is out of the way and before the rear shutter curtain starts closing. If there is some ambient light and the shutter speed is long—like 1/2 second—and the subject is moving, you’ll see a well-exposed subject with a blurry trail in front of it. The flash correctly exposes the subject as soon as the front curtain gets out of the way, but the ambient light continues exposing the subject before the rear curtain closes, and since it is moving you may see a ghostlike blur before or in front of the well-exposed moving subject in the picture. This can be seen at shutter speeds as fast as 1/60s if ambient light is strong enough and the subject is moving.

Red-Eye Reduction

Red-eye reduction is not really a flash mode (figure 3). It simply means that the AF-assist illuminator shines brightly in the face of your subject before the flash fires using Fill flash (front-curtain sync).

Figure 3 – Red-eye reduction

It is hoped that the bright AF-assist illuminator will cause your subject’s pupils to close somewhat and reduce the red-eye effect. It acts like you are using Fill flash (Front-curtain sync mode) otherwise.

Slow Sync

Slow sync mode lets the camera use ambient light to make a good exposure and then fires the flash to add some extra light, rounding out the shadows or better exposing a foreground subject (figure 4). Use this mode in people shots outdoors or where you want ambient light to provide the primary exposure and the flash to add a sparkle to your subject’s eye and remove dark shadows from faces.

Figure 4 – Slow sync

This is closely related to Fill flash, except that the ambient light is more important to the camera than the light from the flash. Be careful when using this mode indoors since it will expose for ambient light and only assist with some flash light. You can get some terrible ghosting and blurred handheld shots when using Slow sync indoors if the light levels are low, which they usually are. Ambient light rules in this mode!

Rear-Curtain Sync

Rear-curtain sync is the opposite of Fill flash, or Front-curtain sync (figure 5). The flash waits to fire just before the rear curtain starts to close. The entire shutter speed time is just ending when the flash fires. This causes a ghosting effect for moving subjects in higher ambient light with slow shutter speeds.

Figure 5 – Rear-curtain sync

You press the Shutter-release button, the front curtain opens, ambient light starts hitting the sensor, and the sensor starts recording the subject. Just as the shutter’s rear curtain is about to close, the flash fires, exposing the subject at its current position. The subject was fully exposed by the flash at the end of the shutter speed time, so the ambient light had time to register the subject before the flash fired, thereby making a blurred ghost behind or after the well-exposed but moving subject.

Flash Mode Combinations

In most Nikons you can use the flash modes individually or in combinations. In certain automatic camera modes you'll see flash combinations such as: Slow sync + Red-eye reduction or Rear curtain + Slow sync. When you see these combinations, just realize that the combined functions work no differently than the individual modes. In other words, if you have Slow sync + Red-eye reduction, the camera just executes the individual modes in the most beneficial order. They are still individual modes, just executed in a certain sequence.

Read your users manual, or one of my Mastering the Nikon DSLR books, and figure out how your flash works. You'll learn how to do things like balance outdoor ambient light with your flash or even do some interesting ghosting effects.

Keep on capturing time...
Darrell Young
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Understanding Nikon's Flash Commander Mode

Many advanced to semi-pro Nikons—with pop-up Speedlight flash units—have a flash Commander mode, with full Nikon Creative Lighting System (CLS) technology built right into the camera. In Commander mode, the camera can function as a controller for multiple Nikon Speedlight flash units.

You can use normal i-TTL flash technology with the camera’s built-in flash for single-flash usage or Commander mode and the built-in flash to control up to two groups of an unlimited number of external Nikon Speedlight flash units. Nikon currently makes the powerful SB-900 flash unit, along with its slightly less powerful SB-700 and SB-600 brothers, and smaller specialty Speedlight units, such as the SB-R200.

Many of us have an external flash unit or two—usually the SB-900, SB-800 (now discontinued), SB-700, SB-600, or SB-400 (not CLS compatible). The specialty SB-R200 flash unit is designed to be used on various brackets available from Nikon and will work in conjunction with the bigger Speedlight flash units. A Nikon having Commander mode allows you to arrange professional lighting setups using relatively inexpensive and very portable Speedlights.


What Is Commander Mode and How Does It Work? 

Commander mode is controlled through a menu in your Nikon. If you examine the Commander mode screen shown in figure 1, you’ll note that you have controls for the built-in flash and two groups (A and B), or banks, of external flash units. You’ll also see that you can set exposure compensation for either of these.

Figure 1 – Commander mode

If the main flash is too bright, you can either move it farther away or dial its power down by setting compensation (exposure comp.) to underexpose a little. You can set compensation in 1/3-stop increments, so you have very fine control of each group’s flash output. The point is that you can experiment until you get the image just the way you want it. Sure, you could do things the old way and use a flash meter or get your calculator and figure out complex fill ratios. Or, you can simply use CLS to vary your settings visually until the image is just right.

Isn’t it more fun to simply enter some initial settings into your Commander mode screen and then take a test shot? If it doesn’t look right, change the settings and do it again. Within two or three tries you’ll probably get it right, and you will have learned something about the performance of your Creative Lighting System. In a short time you’ll have a feel for how to set the camera and flash units and will use your flash/camera combo with authority.

Note: If you leave Custom setting Menu > Bracketing/flash > Modeling flash set to the factory default of On, you can test-fire your single Speedlight’s—or all speedlights in Group A and B’s— built-in modeling light by pressing and holding the camera’s Depth-of-field preview button.


Using Commander Mode

Let’s start by putting your camera into Commander mode. We’ll do that by changing Custom Setting Menu > Bracketing/flash > Flash cntrl for built-in flash to Commander mode (CMD). Look at figure 2 for the screen series to set this option.

Figure 2 – Setting the camera to Commander mode

Since this article is about controlling multiple flash units, we’ll have to change the settings in the Commander mode screen, as shown in figure 2, image 4. We’ll examine each of the settings available under the Commander mode.

TTL is the easiest to use since it allows you to set exposure compensation for the built-in flash as well as each of your flash groups. Next, we’ll look at M mode, since that gives you fine control of your flash from full-power (1/1) to 1/128 power. We’ll briefly look at AA mode. Then finally, we’ll consider the – – (double-dash) mode, which prevents the camera’s built-in flash from firing the main flash output but does not stop the necessary monitor pre-flashes, nor the firing of the external flash units.

When your camera is controlling external Speedlights using its built-in Commander mode, you must always raise the built-in flash on your Nikon. The camera communicates with the external flash units during the monitor pre-flash cycle.

Always position the sensor windows on the external Speedlights where they will pick up the monitor pre-flashes from the built-in flash. Take particular care when not using a tripod.


Commander Mode Settings 

Basically, the Mode fields on the Commander mode screen will display the selections listed below. Use the Multi Selector thumb switch to change the values, as shown in figure 3.

Figure 3 – Commander mode screen

Here are the four Commander mode settings:

• TTL, or i-TTL mode
• AA, or Auto Aperture mode
• M, or Manual mode
• – –, or double-dash mode (what else would one call it?)

You’ll find each mode in the Mode box shown in yellow in figure 3. Use the Multi Selector thumb switch to scroll up or down and select a mode. AA mode is not available for the Built-in flash, so you will only see AA in the Mode boxes following Groups A and B. Now, let’s examine each mode in more detail:

• TTL Mode – The TTL setting allows you to use the full power of i-TTL technology. By leaving Mode set to TTL (as shown in figure 3) for the Built-in flash or Group A or B, you derive maximum flexibility and accuracy from all your flash units. In this mode, the Comp. setting will display exposure values from -3.0 EV to + 3.0 EV, a full 6-stop range of exposure compensation for each group of Speedlights. You can set the Comp. in 1/3 EV steps for very fine control.
• AA Mode – I am only briefly touching on the AA mode, since it is an older non-i-TTL technology included for those accustomed to using the older technology. It is not available for the built-in Speedlight on the Nikon, or for the SB-600. You can safely ignore the AA mode, unless you want to experiment with it. It may not provide as accurate a flash exposure as TTL mode though, since it is not based on the amazing i-TTL technology. Otherwise, it works pretty much the same as TTL mode.
• M Mode – This allows you to set different levels of flash output in 1/3 EV steps for the Built-in flash or the Speedlights in Group A or B. The settings you can put in the Comp. field are between 1/1 (full) and 1/128. The intermediate 1/3-stop settings are presented as decimals within the fractions. For example, 1/1.3 and 1/1.7 are 1/3 and 2/3 stops below 1/1 (full). Many people are used to working with flash units this way, so it seems more familiar. CLS is willing to oblige those experienced in working manually.
• - - Mode (double-dash mode) – The built-in Speedlight will not fire the main flash burst in this mode. It will fire the monitor pre-flashes, since it uses them to determine exposure and communicate with the external flash groups. Be sure you always raise the camera’s built-in flash in any of the Commander mode modes; otherwise, the external flash groups will not receive a signal and won’t fire their flashes. When you set the Mode for Group A or B to double-dash (– –) mode, that entire group of flashes will not fire any flash output. You can use this mode to temporarily turn off one of the flash groups for testing purposes.

Since the built-in flash’s monitor pre-flashes always fire, be careful that they do not influence the lighting of your image. Use a smaller aperture, or move the camera farther away from your subject if the pre-flashes add unwanted light.

What Are Monitor Preflashes?

When you press the Shutter-release button with the pop-up flash open, the camera’s built-in Speedlight fires several brief preflashes and then fires the main flash burst. These preflashes fire whenever your camera is set to TTL mode, even if your Nikon is controlling multiple flash units through CLS. The camera can determine a very accurate exposure by lighting your subject with a preflash, adjusting the exposure, and then firing the main flash burst.


Setting the Channel (CH) for Communication

Look at Figure 4, or your camera’s Commander mode screen, and you’ll notice that just below Group B there is a Channel (CH) selection. The number 3 that I selected in the yellow Channel (CH) box is the communication channel your Nikon expects to use to talk to the external flash groups (factory default is 1).

Figure 4 – Commander mode – Channel of communication

There are four channels available (1–4), just in case you happen to be working in the vicinity of another Nikon user who is also using Commander mode. By using separate channels, you won’t interfere with each other.

Note: It is important to realize that all external flashes in all groups must be on the same channel. This involves setting up your individual flash units to respond on a particular channel. They might be in separate groups but must be on the same channel. Each external Speedlight flash will have its own method for selecting a Group and Channel. Refer to the flash unit's user's manual.

Learning to use Commander Mode and Nikon's Creative Lighting System will enable you to set up complex lighting arrangements with much less effort than in previous years. Use your Nikon and its Commander Mode to become a real lighting technician.

Keep on capturing time...
Darrell Young
See my Nikon books here:
http://www.photographywriter.com/NikonBooks.asp
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Understanding Nikon's Auto FP High-Speed Flash Sync Mode

Flash sync speed is the shutter speed at which your popup or external flash unit can be used to take a picture without the camera's shutter curtains getting in the way of light from the flash. Most cameras are limited to a maximum flash sync speed of 1/250 of a second (1/250s) shutter speed. Anything faster will cause a dark banding effect on the picture because the secondary shutter curtain is partially covering the imaging sensor when the flash fires.

The Custom Setting Menu > Bracketing/flash > Flash sync speed setting lets you select a flash synchronization speed from 1/60s to 1/250s. Or, if you prefer, you can use the two Auto FP high-speed sync modes on many Nikon DSLR cameras—1/250 s (Auto FP) or 1/320 s (Auto FP).

Auto FP high-speed sync mode allows you to use shutter speeds faster than 1/250s. Many do not know whether they should use the Auto FP high-speed sync mode at all times or only when needed. Some do not fully understand what this special camera setting is supposed to accomplish. This article may help.

The Auto FP high-speed sync modes are available only with certain external Speedlights, not with the built-in pop-up Speedlight. Currently, the five Nikon Speedlights that can be used with your Nikon in Auto FP high-speed sync modes are as follows:

• SB-900
• SB-800
• SB-700
• SB-600
• SB-R200

Auto FP high-speed sync enables the use of fill flash even in bright daylight with wide aperture settings. It allows you to set your camera to the highest shutter speed, up to 1/4000s or 1/8000s with some Nikons, and still use the external flash unit to fill in shadows. There are two upcoming subsections in this article, Auto FP High-Speed Sync Review and Special Shutter Speed Setting X + Flash Sync Speed, that provide a detailed discussion on how the Auto FP high-speed sync system works.

Here are the menu screens used to select a Flash Sync Speed:

Figure 1 – Flash sync speed choices

The following are your Flash sync speed choices in most Nikon DSLRs (figure 1):

• 1/320 s (Auto FP)
• 1/250 s (Auto FP)
• 1/250 s
• 1/200 s
• 1/160 s
• 1/125 s
• 1/100 s
• 1/80 s
• 1/60 s

When you’re using Auto FP high-speed sync mode, the output of your flash is reduced, but it doesn’t cut off the frame for exposures using a shutter speed higher than the normal flash sync speed (X-sync). Why? Let’s review.


Auto FP High-Speed Sync Review

In a normal flash situation, with shutter speeds of 1/250s and slower, the entire shutter is fully open and the flash can fire a single burst of light to expose the subject. It works like this: There are two shutter curtains in your camera. The first shutter curtain opens to expose the sensor to your subject, the flash fires to provide light for the correct exposure, then the second shutter curtain closes. For a very brief period of time, the entire sensor is uncovered. The flash fires during the time when the sensor is fully uncovered.

However, when your camera’s shutter speed is faster than 1/250s, the shutter curtains are never fully open for the flash to expose the entire subject in one burst of light. This is because at fast shutter speeds the first shutter curtain starts opening and the second shutter curtain quickly follows. In effect, a slit of light scans across the surface of your sensor, exposing the subject. If the flash fired normally, the width of that slit between the shutter curtains would get a flash of light, but the rest of the sensor would be blocked by the curtains. A band of the image would be correctly exposed, and everything else would be underexposed.

What happens to your external Nikon Speedlight to allow it to follow that slit of light moving across the sensor? It changes into a pulsing strobe unit instead of a normal flash unit. Have you ever danced under a strobe light? A strobe works by firing a series of light pulses. Similarly, when your camera’s shutter speed is so high that the Speedlight cannot fire a single burst of light for a correct exposure, it can use its Auto FP high-speed sync mode and fire a series of light bursts as the slit between the shutter curtains travels in front of the image sensor. The Speedlight can fire thousands of bursts per second. To a photographer or subject it looks like one flash of light, even though it is hundreds or thousands of bursts of light, one right after the other.

When the camera is in Auto FP high-speed sync mode, you’ll see something like this on your Speedlight’s LCD monitor: TTL FP or TTL BL FP. The FP designation tells you that the camera and Speedlight are ready for you to use any shutter speed you’d like and still get a good exposure, even with wide-open apertures!

You can safely leave your camera set to 1/320 s (Auto FP) or 1/250 s (Auto FP) all the time since the Auto FP high-speed sync mode does not kick in until you raise the shutter speed above the maximum setting of 1/250 s. With slower shutter speeds, the flash works in normal mode and does not waste any power by pulsing the output.

This pulsing of light reduces the maximum output of your flash significantly but allows you to use any shutter speed while still firing your external Speedlight. The higher the shutter speed, the lower the flash output. In effect, your camera is depending on you to have enough ambient light to offset the loss in power. I’ve found that even my powerful SB-900 Speedlight can provide only enough power to light a subject to about 8 feet (2.4 m) when I use a 1/8000 second shutter speed. With shutter speeds that fast, there needs to be enough ambient light to help the flash light the subject, unless you are very close to the subject.

However, now you can use wide apertures to isolate your subject in direct sunlight—which requires fast shutter speeds. The flash will adjust and provide great fill light if you use Auto FP high-speed sync mode.

Note: If your flash fires at full power in normal modes, the flash indicator will blink in the Viewfinder to let you know that all available flash power has been expended, and you need to check to see if the image is underexposed. When the camera is firing in Auto FP high-speed sync mode, that doesn’t happen. You won’t get a warning in the Viewfinder if the image does not have enough light. Check the histogram often when using Auto FP high-speed sync mode.


Special Shutter Speed Setting X + Flash Sync Speed

When using exposure modes Manual (M) or Shutter priority auto (S), you can turn the shutter speed all the way down to 30 seconds, then to bulb. There is one more setting below bulb, named X + Flash sync speed. This special setting allows you to set the camera to a known shutter speed and shoot away. You will see X 250 if Custom Setting e1 Flash sync speed is set to 1/250s. Whatever Flash sync speed you select will show up after the X. If you selected a Flash sync speed of 1/125s, then X 125 will show up as the next setting below bulb. Selecting a Flash sync speed of 1/60s means that X 60 will show up below bulb, etc.

The shutter speed will not vary from your chosen setting. The camera will adjust the aperture and flash when in Shutter priority auto (S) mode, or you can adjust the aperture while the flash controls exposure in Manual (M) mode.

This special X-Sync mode is not available in Aperture priority auto (A) or Programmed auto (P) modes since the camera controls the shutter speed in those two settings. You’ll use this setting primarily when you are shooting in Manual (M) or Shutter priority auto (S) mode and want to use a known X-Sync speed.

My Recommendation: I leave my camera set to 1/320 s (Auto FP) (as shown in figure 1, image 3) all the time. The camera works just like it normally would until one of my settings increases the shutter speed to faster than 1/250s, at which time it starts pulsing the light to match the travel of the shutter curtains. Once again, you won’t be able to detect this high-frequency strobe effect since it happens so fast it seems like a single burst of light.

Remember that the flash loses significant power (or reach) at faster shutter speeds since it is forced to work so hard. Be sure you experiment with this setting to get the best results. You can use a big aperture, like f/1.8, to create a very shallow depth of field in direct bright sunlight since you can use very fast shutter speeds. This will allow you to make images that many other cameras simply cannot create. Learn to balance the flash and ambient light in Auto FP high-speed sync mode. All this technical talk will make sense when you see the results. Pretty cool stuff!

Keep on capturing time...
Darrell Young
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http://www.photographywriter.com/NikonBooks.asp
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Understanding the Nikon ISO Sensitivity Auto Control (ISO-AUTO)

The ISO Sensitivity Auto Control (ISO-AUTO), found under the Shooting Menu, is a powerful feature in many Nikon DSLR cameras. It's used to allow the camera to automatically control the ISO sensitivity and shutter speed, according to the light levels sensed by the camera. It's very helpful when you don't have time to deal with exposure issues—yet must get the pictures.

FIG 19C – Enabling the ISO Sensitivity Auto Control

Once you’ve set  ISO sensitivity auto control to On, you should immediately set two values, according to how you shoot:

• Maximum sensitivity
• Minimum shutter speed

Here’s some detail on these two settings:

Maximum Sensitivity

The Maximum sensitivity setting is a safeguard for you (see FIG 19D). It allows the camera to adjust its own ISO sensitivity from the minimum value of ISO 200 to the value set in Maximum sensitivity, according to light conditions.  The camera will try to maintain the lowest ISO sensitivity it can use to get the picture.  However, if need be it can rapidly rise to the Maximum sensitivity level.  This setting overrides the normal ISO sensitivity setting.

FIG 19D – Setting the ISO Sensitivity Auto Control’s Maximum Sensitivity

If you would prefer that the Maximum sensitivity not exceed a certain ISO value, simply select from the list shown in image 3 of FIG 19D. The Maximum sensitivity default is ISO 3200. That’s too high for my tastes since it will let the camera take the ISO sensitivity all the way up to ISO 3200 in a low-light situation.  Too much noise potential for me!  Maybe not for you?  In any case, I set my camera to ISO 400 for the Maximum sensitivity as shown in FIG 19C, image 3.

You’ll note that there are only five available settings 400, 800, 1600, 3200, and Hi 1. Whichever one of these settings you choose as a Maximum sensitivity will be the maximum ISO value the camera will use to get a good exposure when the light drops.

Interestingly, the settings in Custom setting b1 do not control what incremental ISO numbers between these primary values can be used.  I carefully setup my D300s to test this, and found that it would often use an intermediate value like ISO 640, 1100, 1250, 2000, or 2200 as the light got darker and darker.  It did this whether I set Custom setting b1 to 1/3, 1/2 or 1 EV step.  Just remember that you have a maximum range from ISO 400 to Hi 1 (ISO 6400) with whatever EV steps in between that the camera decides to use.

What happens when the camera reaches its Maximum sensitivity and there still isn’t enough light for a good exposure?  Let’s find out:

Minimum Shutter Speed

Since shutter speed helps control how sharp an image can be, due to camera shake and subject movement, you’ll need some control over the Minimum shutter speed allowed while the ISO sensitivity auto control is turned On (see FIG 19E).

FIG 19E – Setting the ISO Sensitivity Auto Control’s Minimum Shutter Speed

You can select a shutter speed from the list to set the minimum shutter speed the camera will allow when the light diminishes.  In P – Programmed auto (camera controls shutter and aperture) and A – Aperture priority (camera controls shutter and you control aperture) exposure modes, the camera will not go below the Minimum shutter speed unless the Maximum sensitivity setting still won’t give you a good exposure.

This is the answer to our question in the last section about what would happen when there is not enough light and the camera has maxed out the Maximum sensitivity level.  Even though you’ve selected a Minimum shutter speed, the camera will go below the minimum speed when the light is too low for a good exposure and the Maximum sensitivity ISO number has been reached.

  In other words, in P – Programmed auto or A – Aperture priority exposure modes, if you get into low light and try to take pictures, the camera will try to keep the ISO sensitivity as low as possible until the shutter speed drops to your selected Minimum shutter speed.  Once it hits the selected lowest shutter speed value—like the 1/30s shown in FIG 19E, image 3—the ISO sensitivity will begin to rise up to your selected Maximum sensitivity value, like the ISO 400 shown in FIG 19E, image 2.

Once it hits the Maximum sensitivity value, if the camera still doesn’t have enough light for a good exposure, it won’t keep raising the ISO sensitivity since you’ve artificially limited it with the Maximum sensitivity setting.  Instead, the camera will now go below your selected Minimum shutter speed, by dropping below the 1/30s shown in FIG 19E, image 3.  Be careful, because if the light gets that low, your camera can go all the way down to a shutter speed of 30 seconds to get a good exposure.  The camera had better be on a tripod and have a static subject at shutter speeds that low.

Look at the Minimum shutter speed value as the lowest “safe” speed after which you’ll put your camera on a tripod.  Most people can handhold a camera down to about 1/60s if they are careful, and maybe 1/30s if they’re extra careful and brace themselves.  Below that, it’s blur city for your images.  It’s even worse with telephoto lenses.  Camera movement is greatly magnified with a long lens, and a Minimum shutter speed of 1/250s to 1/500s or more may be required (max is 1/4000s).

For fun, let’s listen to the camera talk to itself while you take pictures in low light with ISO sensitivity auto control enabled.  As we listen in on the D300(s) thinking, we need to know that the current Maximum sensitivity setting is ISO 400, and the Minimum shutter speed setting is 1/30s (as shown in FIG 19E):

Nikon D300(s) thinking: “Okay, Auto ISO is on!  The light is dropping and my current 1/60s shutter speed and 200 ISO sensitivity won’t let me make a good exposure. I’ll slow the shutter speed to the minimum of 1/30s, as my owner specified in my Minimum shutter speed setting.  More pictures are incoming, and the light is still dropping!  I can’t go any lower on the shutter speed for now, since my owner has instructed me to keep the Minimum shutter speed at 1/30s unless I can’t get a good picture.  I’ll have to start raising the ISO sensitivity. Here comes more pictures, and whew, it’s getting dark!  I’ve now raised the ISO sensitivity to my Maximum sensitivity level of ISO 400, which is as high as I am allowed to go.  I have no choice now but to go below the 1/30s Minimum shutter speed my owner has specified.  I hope I’m on a tripod!”

Special note: The other exposure modes, S – Shutter priority and M – Manual, allow you to control the camera in a way that overrides certain parts of the ISO sensitivity auto control.

In M - Manual mode the camera completely relinquishes all control of the shutter and aperture.  It can only adjust the ISO sensitivity by itself, so it can obey the Maximum sensitivity but the Minimum shutter speed is overridden and does not apply.

In S – Shutter priority mode the camera can control the aperture but the shutter speed is controlled only by the camera user.  So, the ISO sensitivity auto control can still control the Maximum sensitivity, but has lost control over the Minimum shutter speed.

Also, it may be a good idea to enable High ISO NR—as discussed a few pages back—when you enable the ISO sensitivity auto control. This is especially true if you leave the camera set to the default Maximum sensitivity value of 3200.  Otherwise, you may have excessive noise when the light drops.

When and why should I use ISO-AUTO?

How much automation do you need to produce consistently excellent images?  Let’s explore how and when automatic self-adjusting ISO might improve or degrade your images. What is this feature all about?  When and why should I use it?  Are there any compromises in image quality in that mode?

Normally you will set your camera to a particular ISO number, such as 200 or 400, and shoot your images.  As the light gets darker, or in the deep shade, you might increase the ISO sensitivity to allow handheld images to continue being made.

If you're in circumstances where you absolutely must get the shot, the ISO sensitivity auto control will work nicely.  Here are a few scenarios:

Scenario # 1:  Let’s say you are a photojournalist and you’re shooting flash pictures of the president as he disembarks from his airplane, walks into the terminal, and drives away in his limousine.  Under those circumstances, you will have little time to check your ISO settings or shutter speeds and will be shooting in widely varying light conditions.

Scenario # 2: You are a wedding photographer in a church that doesn’t allow the use of flash.  As you follow the bride and groom from the dark inner rooms of the church, out into the lobby, and finally up to the altar, your light conditions will be varying constantly.  You have no time to deal with the fluctuations in light by changing your ISO, since things are moving too quickly.

Scenario # 3:  You are at a party, and you want some great pictures.  You want to use flash, but the pop-up Speedlight may not be powerful enough to reach across the room at low ISO settings. You really don’t want to be bothered with camera configuration at this time, but still want some well exposed images.  Light will vary as you move around the room, talking and laughing, and snapping pictures.

These scenarios are excellent environments for the ISO sensitivity auto control.  The camera will use your normal settings, such as your normal ISO, shutter speed, and aperture until the light will not allow those settings to provide an accurate exposure.  Only then will the camera raise the ISO or lower the shutter speed to keep the camera functioning within the shutter/aperture parameters you have set.

Look at ISO AUTO as a “failsafe” for times when you must get the shot, but have little time to deal with camera settings, or when you don’t want to vary the shutter/aperture settings but still want to be assured of a well exposed image.

Unless you are a private detective shooting handheld telephoto images from your car, or are a photojournalist or sports photographer who must get the shot every time regardless of maximum quality, I personally would not recommend leaving your the ISO sensitivity auto control set to On.  Use it only when you really need to get the shot under any circumstances!

Of course, if you are unsure of how to use the “correct” ISO for the light level, due to lack of experience, don’t be afraid to experiment with this mode.  At the very worst, all you might get are noisier than normal images.  However, it may not be a good idea to depend on this mode over the long term, because noisy images are not very nice.

Are there any drawbacks to using ISO-AUTO?

Maybe!  It really depends on how widely varying the light conditions will be when you are shooting.  Most of the time your camera will maintain normal ISO range settings in ISO-AUTO so your images will be their normal low-noise, sharp, masterpieces.  However, at times the light may be so low that the ISO may exceed the “normal” range of 200-800, and will start getting into the noisier ranges above 800 ISO.

Just be aware that the ISO sensitivity auto control can and will push your camera’s ISO sensitivity into a range that causes noisier images when light levels drop, if you’ve allowed it. Use it with this understanding and you’ll do fine. ISO 3200 is the maximum, unless you have set the maximum to a lower number.  Make sure you understand this, or you might get some noisy images.

The ISO sensitivity auto control is yet another feature in our powerful Nikon cameras.  Maybe not everyone needs this “failsafe” feature, but for those who do it must be there.  I will use it myself in circumstances where getting the shot is the most important thing, and where light levels may get too low for normal ISO image making.

Even if you think you might only use it from time-to-time, do learn how to use it for those times.  Experiment with the ISO sensitivity auto control.  It’s fun and can be useful!

Keep on capturing time...
Darrell Young
See my Nikon books here:
http://www.photographywriter.com/NikonBooks.asp
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Photography Basics – RGB Channel and Bit Depth Tutorial

What does all this talk about bit depth and RGB channels mean? What is an RGB channel? What is bit depth? Why would I set my Nikon to use 14-bit bit depth instead of 12-bit bit depth? Here is a short tutorial on bit depth and how it affects RGB color storage in an image.

Your camera records image color with three color channels—one each of red, green, and blue (RGB). You may have seen RGB mentioned in photography literature. Now you know what it stands for. The colors from each channel are combined together to make the color for your image. Bit depth is the potential number of colors contained in each RGB channel for a RAW image file, multiplied together.

Figure 1 – Luminance and RGB channel histograms for a JPEG file

In figure 1 you can see the individual channel histograms for the red, green, and blue channels in the bottom three colored histograms. The white histogram on top reflects the luminance or perceived brightness distribution in the image and is a weighted combination of the three RGB channels. The three lower colored histograms show the exposure level for each RGB channel of an 8-bit JPEG file.

Several current cameras give you the choice of shooting RAW in 12- or 14-bit mode. If you are shooting in 12-bit mode, your camera will record up to 4,096 colors for each RGB channel; therefore, there will be up to 4,096 different reds (R), 4,096 different greens (G), and 4,096 different blues (B). Plenty of color! In fact, almost 69 billion colors (4096 x 4096 x 4096).

If you set your camera to 14-bit mode, the camera can store 16,384 different colors in each RGB channel. Wow! That’s quite a lot more color—almost 4.4 trillion shades (16384 x 16384 x 16384).

Figure 2 shows how to choose 14-bit bit depth when shooting in RAW mode:

Figure 2 – Selecting 12- or 14-bit RAW color depth

Is that important? Well, it can be, since the more color information you have, the better the color in the image—if it has a lot of color. I always use the 14-bit mode. That allows for smoother color changes when a large range of color is in the image. I like that!

Of course, if you save your image as an 8-bit JPEG or TIFF, most of those colors are compressed, or thrown away. Shooting a JPEG image in-camera (as opposed to a RAW image) means that the camera compresses the available image data so it will fit into an 8-bit file. An 8-bit JPEG image file can hold 256 different colors per RGB channel—more than 16 million colors. 16 million colors sounds like a lot of color potential and it is; however, compared to 69 billion colors (12-bits RAW) and 4.4 trillion shades (14-bit RAW) a mere 16 million shades (8-bit JPEG) is positively scrawny (256 x 256 x 256).

There’s a big difference between the number of colors a camera captures in a RAW file and the number stored in a JPEG image file. That’s why I always shoot in RAW; later I can make full use of all those potential extra colors to create a different look for the same image.

If you shoot in RAW and later save your image as a 16-bit TIFF file in your computer, you can store all the colors you originally captured. A 16-bit file can contain 65,536 different colors in each of the RGB channels. Many people save their files as 16-bit TIFFs when post-processing RAW files, especially if they are worried about the long-term viability of their camera’s proprietary RAW format.TIFF provides a known and safe industry-standard format that will fully contain all image color information from a RAW file. Unfortunately, the files are huge when saved in TIFF format. Many are looking into the Adobe DNG format as an alternate RAW format, hoping it will remain viable for the long term.

Nikon's intention is to support its NEF (RAW) format for the long term. Will that be the same for other camera companies. I hope so. If your camera manufacturer stands behind its proprietary RAW format and keeps on supporting it, you’ll be fine. If not, many after market software vendors should step up and support the older RAW formats. RAW seems stable. I can still open the RAW files from my 2002 Nikon D100 in Nikon View NX2 (vs.2.1.2).

Speed Issues: RAW Mode 12-Bit versus 14-Bit Shooting

If your camera offers both 12- and 14-bit RAW shooting modes, check to see if there are any speed penalties for shooting in the higher 14-bit mode. Since there is a lot more color information available in 14-bit mode, your images can have finer gradations of color.

However, some cameras can slow down when used in 14-bit mode because it has to process a lot more color information. Test your camera in both modes before shooting a high-speed event like an air show or car race. Otherwise, the camera may slow down enough to cause you to miss some shots. To me, the speed loss is not important because I am a nature shooter and want the greater image quality 14-bit mode potentially provides. However, some are very sensitive to camera speed and will need to pay attention to this issue.

The Nikon D300S has some penalties for 14-bit bit depth, its frame rate drops from 6 to 2.5 frames per second when shooting in continuous-high release mode (CH). The newer Nikon D7000 does not have the same slowdown so you can safely use 14-bit bit depth all the time.

Keep on capturing time...
Darrell Young
See my Nikon books here:
http://www.photographywriter.com/NikonBooks.asp

Using a Basic Three-Lens Kit

Ever wonder why enthusiast photographers carry around camera bags when most photographers just carry their cameras? Several lenses is why! It is unthinkable for an enthusiast to find him or herself in a situation and not have a lens to cover it.

Figure 1 – A 10-20mm, 16-85mm, and 80-400mm three lens kit

Most photographers end up with a three-lens kit for their daily usage (figure 1). Why three lenses and not just one of the new super-zoom lenses that cover a large range of focal lengths? Primarily, because enthusiasts are interested in above average quality for their images. There are times when convenience overrides quality, but not often for you and me!

Several lens manufacturers provide one-lens-does-it-all solutions. The lenses are very convenient and might even be a good choice when one is forced to use just one lens and camera body for a wide range of photography purposes, such as on a vacation or hike where a lot of walking is required.

For instance, several camera manufacturers offer 18-200mm f/3.5–5.6 zoom lenses. Some aftermarket lens manufacturers offer even wider coverage in one lens. However, no one lens can offer high quality at all focal lengths. There are compromises that must be made when too many focal lengths are crammed into one lens design. In fact, you will not find any truly professional lenses that have a wide range of focal lengths. The pro lenses are made for demanding photographers who will not put up with softness or aberrations at one or more zoom settings.

While not professionals (yet), most enthusiasts reach out for greater quality and end up with three lenses that cover a very wide range of focal lengths. Figure 1 shows a three-lens kit that is similar to what many enthusiasts use. The kit goes from extremely wide angle to long telephoto, with a small amount of overlap in focal lengths. With this type of kit, a photographer is ready for almost any type of shooting situation, and since they do not have too many focal lengths crammed into one lens, the quality of the image is maintained.

Figure 2 – A medium sized camera bag with a camera body, extra batteries and memory cards, a flash unit, and three lenses covering a large range of focal lengths, plus a macro lens

You can carry this type of three-lens kit in a medium-sized camera bag (figure 2). It does not weigh too much and can be carried easily to any location. Many use a small backpack camera bag, while others use an over-the-shoulder style bag. The reason you bought into a camera brand with a system concept is to have a system of lenses and accessories to carry with you.

Therefore, you can add some other goodies like extra batteries, memory cards, an external flash, and even a small GPS unit. If you are like most of us, you will be constantly seeking the ultimate camera bag to contain your camera system. If you find it, please let me know!

Keep on capturing time...
Darrell Young
See my Nikon books here:
http://www.photographywriter.com/NikonBooks.asp

Fine Tune Optimal Exposure – How Does it Work?

Have you ever thought your camera's metering system of choice was under or overexposing your images? If you are shooting almost any Nikon from the D90 up, you have the ability to fine tune the exposure, adding or subtracting up to one stop of exposure in 1/6 stop increments.

This allows you to push your camera's exposure in one direction or the other on a semi-permanent basis. I say semi permanent because you can set it back to factory specs any time you want. Fine tuning optimal exposure is like leaving the exposure compensation settings on all the time, except that you don't have to think about it with the fine-tuning system. You just test it (find best exposure), set it, and forget it.

As I briefly mentioned before, the Fine tune optimal exposure setting allows you to fine tune the Matrix metering, Center-weighted area metering, and Spot metering systems by +1/-1 EV in 1/6 EV steps. Nikon has taken the stance that most major camera systems should allow the user to fine tune them. The exposure system is no exception.

You can force each of the three metering systems to add or subtract exposure from what it normally would use to expose your subject. This stays in effect until you set it back to zero. It is indeed fine tuning, since the maximum 1 EV step up or down is divided into six parts (1/6 EV). If you think your camera mildly underexposes highlights and you want it to add 1/2 step of exposure, you simply add 3/6 EV to the metering system. (Remember basic fractions: 1/2 equals 3/6.)

As mentioned, Fine tune optimal exposure works like the normal compensation system, but it allows only one EV of compensation. As shown in figure 1, screen 3, an ominous-looking warning appears when you use Fine tune optimal exposure. It lets you know that your camera will not display a compensation icon, as it does with the +/- Exposure compensation button, when you use the metering fine-tuning system. This simply means that while you have fine tuning dialed in for your light meter, the camera will not remind you that it is fine tuned by showing you a compensation icon. If it did turn on the compensation icon (+/- on the Control panel and in the Viewfinder), it couldn’t use that same icon when you use normal compensation.

You use the Custom Setting Menu > b Metering/exposure > Fine tune optimal exposure setting to adjust the exposure.  Here is the actual Custom Setting number on several common Nikons. This feature is only available on advanced, semi-pro and pro cameras:

• Custom Setting b4 – Nikon D90
• Custom Setting b5 – Nikon D7000
• Custom Setting b6 – Nikon D300, D300S, D700, D3, D3S, D3X
• Custom Setting b7 – Nikon D200, D2X, D2XS

Here are the screens used to set the exposure fine tuning in a Nikon D7000 (screens may vary slightly in other Nikons but not drastically):

Figure 1 – Choosing Fine tune optimal exposure settings

Use the following steps to choose b5 Fine tune optimal exposure settings:

1. Select b Metering/exposure from the Custom Setting Menu and scroll to the right (figure 1, image 1).
2. Select b5 Fine tune optimal exposure and scroll to the right (figure 1, image 2).
3. Select Yes from the warning screen and scroll to the right (figure 1, image 3).
4. Select the metering system you want to adjust. In figure 1, image 4, I selected Matrix metering. Scroll to the right.
5. Scroll up or down in 1/6 EV steps until you reach the fine-tuning value you would like to use (figure 1, image 5, red arrow).
6. In figure 1, image 6, I selected +3/6 (1/2 step EV). Press the OK button to lock in the fine-tuning value for the metering system you selected in step 4.

That’s all there is to it! Remember that you have Fine tune optimal exposure turned on because the camera will not remind you. Watch your histogram to make sure you’re not regularly underexposing or overexposing images when you have the fine-tuning adjustment in place. If needed, adjust the fine tuning up or down, or turn it off. You must fine tune each metering system separately.

Note for D7000 users: Fine tune optimal exposure applies only to the user setting (U1, U2, or non-user setting) you are currently working with. If you are working with U1, then U2 and non-user settings are not changed. Be sure to save the user setting in the Setup Menu if you change one of them.

My Recommendation: Fine tune optimal exposure is a rather controversial setting. On my older Nikon D300, I found that I took better pictures when I ran the Matrix meter 3/6 (1/2 EV step) over the normal setting. The D300’s Matrix metering seemed a bit conservative to me and it worked a little too hard to keep from blowing out the highlights in my images. It seemed to underexpose them by about 1/3 EV step most of the time. I could see this underexposure because on most of my Matrix meter exposed images, the histogram didn’t quite make it to the right edge (lighter values) of the histogram window, which I prefer. I like to expose for the highlights, yet my older D300 seemed to slightly underexpose.

I do not need to change the default on my D7000. If anything, it tends to expose a little on the bright side. If I were to make an exposure adjustment on this camera, I would try –1/6 as a test. However, I doubt that I will make this adjustment on the D7000.

Remember that adjusting an exposure is always an experiment. If you choose to fine tune any of the three metering systems, you should thorougly test it before you do an important shoot. The way I fine tune my camera is based on my own photographic style, and my results can’t guarantee that you would get the same results. It certainly won’t hurt to play with these settings—as long as you remember to set them back to 0 when you’re done—if they don’t perform the way you expect.

Keep on capturing time...
Darrell Young

See my Nikon books at: 

http://www.photographywriter.com/NikonBooks.asp