Macro lens for Canon AE-1 Program

When you start working in the realm of macro, magnification becomes the primary consideration.
If you want to have that half inch long insect fill up a half inch long image on your negative, you need a lens and system that will give you 1:1 (life size) magnification.
To achieve that, if you are using an unmodified* lens, you need a lens and camera combination that permits moving the lens' nodal point to a distance from the film plane that is twice the focal length of the lens.
That movement of the nodal point will focus the lens at a particular point. The distance that that plane is from the nodal point is a function of the focal length of the lens - a 100mm lens will focus to life size magnification at a distance that is farther away than a 50mm will focus to life size magnification.
What would the advantage of a 50mm macro lens be compared to a 100mm macro lens? Potential lower cost, smaller size when focused at more normal distances and, in some cases a closer working distance (when the desired perspective that arises therefrom is sought).
*I make reference to an unmodified lens, because one of the ways of achieving higher magnifications is to "modify" it - insert higher magnification into the system optically. You can do that if you either add close-up (diopter) filters at the front, or tele-converter elements at the back. When you do that, you can achieve more magnification without reducing your working distance as much.

Is a closer working distance preferred? I would have thought it would be the other way around.

Or is that all subjective to what you want to do with it?

smaller size when focused at more normal distances

Could you elaborate on this? (What is "smaller size"?)

Corey Fehr said:

smaller size when focused at more normal distances

Could you elaborate on this? (What is "smaller size"?)

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The 50mm macro lenses aren't much bigger than most 50mm standard lenses when they are focused at more distant objects. So they are quite suitable for everyday use as a "normal" lens if you don't care about their relatively small maximum aperture (in most cases).
When you use them at closer distances, the helical tends to extend markedly, so they become much larger and more ungainly. That larger size usually doesn't matter much when you are actually working at close distances.
The longer macro lenses tend to be larger and heavier, and their native angle of view isn't suitable (for most) as an everyday, standard lens.

Generally speaking, longer working distance is preferred as it gives more options for lighting.
Smaller size in this case means the shorter focal length lens is generally smaller then the longer focal length lens. For example, a 50mm lens would generally be smaller then the 100mm lens of the same aperture and magnification from the same company.

Corey Fehr said:

Is a closer working distance preferred? I would have thought it would be the other way around.

Or is that all subjective to what you want to do with it?

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Sometimes you want to be really close, because of the resulting perspective and lack of "flattening".
Look at the feeling of depth in the shot (is it a tarantula?) on this page discussing Olympus 50mm macro lenses. I have the f/3.5 version - note how compact it is normally, and how much larger it is when the helical is (partially) extended. http://www.mir.com.my/rb/photograph...ympusom1n2/shared/zuiko/htmls/macrozuikoC.htm
More often though, it is handy to be a bit farther away.

Awesome-thanks everyone!

Matt-I believe that's a "true spider", and not a tarantula. (Nerd alert!)

Corey Fehr said:

Is a closer working distance preferred? I would have thought it would be the other way around.

Or is that all subjective to what you want to do with it?

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For ease of lighting the subject, I prefer the larger working distance of a longer macro lens, such as a 105mm macro vs. a 55mm macro. I have a 55mm macro and am looking for a 105mm macro, for this very reason.

Some live subjects are easier handled with a longer lens.
An example, though not macro describes what I mean. When I shoot close pictures of my birds, I use a 300mm telephoto lens at about 10 feet. Because with a shorter lens at a closer distance, the birds get spooked by the camera. At 10 feet away, the camera is not a threat to them, and I can shoot all I want to.

But the longer macros are more expensive and harder to find than the more common 50/55mm macro lenses.

The 50/55mm macro lens can double as a normal lens (which people have done), whereas the 105mm macro is a short tele, thus less used in general use.

Depending on the type of reptiles you are photographing, you may want a telephoto and some extension tubes. In my neighborhood all 4 of he poisonous varieties found in Texas can be found. Adding an extension tube to your lens allows you focus closer. It seems like you are looking for the "right" answer to the question of what lens or set up to use. For very little money you could get a set of auto extension tubes and a Vivitar Macro focusing teleconverter and start taking pictures with whatever lenses you currently have. Don't get bogged down with "analysis paralysis." Get out there and burn some film.

Corey Fehr said:

Would it be fair to say that the focal length of a macro relies (in part) on what you're going to be doing?

For example, if I'm shooting reptiles and bugs, a 100-200 mm would be relevant because I'd have a greater working distance (approx 10 " on my Canon, the one suggested earlier), but what benefits would a 50 mm with a shorter working distance have?

The magnification ratio would stay the same, is that correct?

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I believe the main benefit of a 50mm or 55mm macro is that it is cheaper than the other focal lengths. I don't really see any other advantages, with the possible exception if you'll be duplicating slides with a bellows unit and dedicated slide duplicator attachment, then a 50mm or 55mm works best.

When it comes to macro lenses I have a fairly large selection, ranging from 55mm to 200mm. I have four in the 90mm to 135mm range and I guess I'd have to say that my preference is for this range, typically 100-105mm. Often a good macro lens in this range can be rather pricey. If you're having to stay on a budget, then my hands-down recommendation is the Tamron 90mm f/2.5 macro, which can usually be found on the used market for half the price or less than that of your typical 100-105mm macro. But the Tamron is an absolutely razor-sharp optic, so no worries regarding the quality of your images. Its only drawback is that shared with many other macro lenses -- it gets down to "only" 1:2. This can be solved easily with the use of a Tamron dedicated 2x teleconverter, a Vivitar macro-focusing 2x teleconverter or simply extention tube(s) of the right length. The latter is the cheapest method, but the first two are also good choices.