Friday, December 9, 2011

Using a Macro Lens or Closeup Diopter Filters

Sometimes you want to get very close to your subject. Maybe you've found a flower that is attractive to you, or a bee taking pollen. Maybe you need to photograph some coins or stamps from your collection for insurance purposes. Any time you need to take a picture up close, you need a macro lens.  A macro lens is especially designed for close-up pictures. Most genuine macro lenses are also prime lenses (see previous section) not zoom lenses. They don’t look much different from a regular prime lens except that the internal lens elements are designed in such as way that it is easy to make “life-size” images.

A true macro lens (figure 1) has a 1:1 ratio, which means it can take a picture of an object and render it in its normal size. A bee on a flower is the same size in the picture as the real bee on a flower. That is hard to do with a zoom lens—or a regular prime lens—because they will not focus close enough.

Some zoom lenses are advertised as "macro" zoom lenses. Those lenses can focus closer than most zoom lenses but they are not true macro lenses. Most macro zooms are limited to about half-life size or a 1:2 ratio, which means a bee on a flower would only be half its normal size in the picture. You just cannot get close enough with most zoom or regular prime lenses. For maximum close ups only a true macro lens with a 1:1 ratio (lifesize) will do.
Figure 1 – AF Nikkor 60mm f/2.8 Macro Lens

In figure 1 is a picture of a real Nikon macro lens, the AF Nikkor 60mm "Micro Nikkor." Nikon calls their macro lenses by the name Micro Nikkor. Most other lens brands use the word Macro. In figure 2 is a macro image of a compact flash memory card with a couple of SD memory cards lying next to it. Notice how realistic the close up image looks. It is a true macro shot taken with the Nikkor macro lens above.

Figure 2 – A picture taken with the AF Nikkor 60mm f/2.8 Macro lens

Real macro lenses are a bit more expensive than standard prime lenses because they are a specialty prime lens. They have special features to make the picture look its best, such as “flat-field” design, which keeps the edges of the picture from curving in a distracting way. Macro lenses are highly corrected lenses, which mean the lens elements are carefully designed to give maximum quality and lack of aberrations (color shifting or shape warping). They are optimized for up close work. That does not mean you shouldn’t use a macro lens to take a picture of a more distant object, they do fine there too. They are simply made to do their best work at 1:1 distances (extreme close ups).

For maximum image quality, it is a good idea to use a real macro lens. However, there are substitutes that cost a lot less money. Let’s consider one low cost way to get extreme close up images without the expense of a macro lens, screw-on closeup filters.

Close Up Diopter Screw-On Macro Filters

The lowest cost way to take close up pictures is to use a set of close up diopter filters on your lens, such as the four pictured in figure 3.
Figure 3 – A set of close up diopter filters for macro shooting on a budget 

These filters cost only a few bucks online and do a reasonably good job with making extreme close ups. I bought a package of four filters with diopters (magnification factor) running from + 1 to +10 (figure 3).

These filters simply screw into the front of your prime lens (or zoom lens) and add magnification to the lens. It is sort of the same principle as using a magnifying glass. You screw the filter onto the front of the lens and it magnifies the close-up subject. There are different diopter “powers” in the filter set so that you can increase or decrease the magnification. The main limitation of diopter close-up filters is a very limited amount of focus control and somewhat lower quality images. They are not as convenient to use by any means, in comparison to a true macro lens. However, they do a pretty good job on taking extreme close up pictures and are much lower in cost.

Figure 4 – Same subject as in figure 2 shot with diopter close up filters

With a diopter filter on your lens it cannot focus sharply on anything farther away than a few inches; therefore, the filter cannot be left on a lens for any other purpose than shooting the macro shots. While these filters can’t possibly give you the same quality edge to edge as a true macro lens (figure 2.30), they do provide the photographer on a budget with a way to make interesting close up pictures without spending a lot of money.  Look on the back of your lens’s cap to see the correct size of filter to buy. The filters must match the screw-in filter size of the lens you will use them with.

Extension Tubes and Lens Bellows

You can get by without a true macro lens or screw-on filters—by using either extension tubes or a lens bellows. I’m not going into any detail about these two options in this article because they require knowing some advanced techniques, such as stop-down metering (no automatic lens aperture), and how to shoot without your camera’s light meter active. I'll cover these ways of shooting macro in a future article. However, remember that these two alternatives exist and check them out when you feel ready (do a Google search on the terms for info).

If you are serious about excellent macro photography and can afford to buy an extra lens, get yourself a true macro lens. It is a lot less hassle to use and gives you much better quality.

Keep on capturing time...
Darrell Young
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