macro lenses

[perfectpixel]

here's a newbie question:
what is the difference beteween a 100mm macro and say, a 50mm macro?
I understand the diference in focal lenght for the lenses in regular shooting, but what is the impact on the macro capability of these lenses?

[evilenglishman]

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[EXA1a]

here's a newbie question:
what is the difference beteween a 100mm macro and say, a 50mm macro?
I understand the diference in focal lenght for the lenses in regular shooting, but what is the impact on the macro capability of these lenses?
With a 100mm you get a longer working distance. That's important for getting a good lighting between the lens and the object.
For example, with a hypothetical 14mm macro, an ant could be walking on the front lens element to be in focus for a 1:1 magnification (could be interesting but is not practical).

--Jens--

[DaveG]

here's a newbie question:
what is the difference beteween a 100mm macro and say, a 50mm macro?
I understand the diference in focal lenght for the lenses in regular shooting, but what is the impact on the macro capability of these lenses?

The 50 will do 1:2 reproduction. That means that if the subject is 1 cm long it'd be .5 cm long on the sensor. You can add an extension tube to the 50 to give you 1:1 reproduction - i.e. 1 cm long in real life and 1 cm long on the sensor - but you will lose your ability to focus the lens to infinity while the extension tube is aboard.

The 50 is less expensive than the 100, but as soon as you add the glass extension tube the prices are similar.

The 100 f2.8 macro will do 1:1 reproduction without a tube and WILL let you focus focus to infinity without adding or removing anything.

The 100 will give you a greater camera to subject distance than the 50. This is a good idea if the subject is something that might bite; but mostly I've found that it helps me from getting in the way of the light. I also have more room if I want to use reflectors to push a little light back into the subject. And of course the 100 will also give me a nicer perspective than the 50.

Now if you were planning on copying small two dimensional objects from a copy stand, the focal length of the 100 would be way too long. But that kind of copying is pretty much a thing of the past as we all seem to have scanners to do that.

Both of the lenses can be used for regular non-macro photography as well. A 100 mm f2.8 lens is reasonbly quick for that focal length. But a 50 f2.8 is slow, and that's something to think about too. All in all the 100 macro was a better choice for me.

[E.D. Sterns]

All else being equal, a 100mm lens will allow you to achieve the same magnification as a 50mm lens while being ~2 times as far from your subject. All minimum focus distances are measured from the film (or sensor) plane, so given the increased length of a 100mm lens over a 50mm the distance of the end of the lens from your subject is only slightly greater when using the 100mm. Longer lenses are better for skittish subjects that you can't get close to. Shorter lenses are easier to handhold.

When using flash lighting, shorter lenses are easier to achieve directional lighting effects with as well. Longer lenses require longer flash brackets or other means of getting the flash units further away from the center of the lens.

If you ever desire greater magnification than your lens will allow, and you decide to add extension tubes, greater magnification is possible with the shorter lens given the same amount of extension. Diopters typically get longer lenses in closer though.

At macro distances, given equal magnification, longer lenses will have slightly greater depth of field than shorter lenses. This has to do with entrance and exit pupil sizes.

I'd say, all else being equal, it's best to use the shortest macro lens which will enable you to get the shot you want. But we know that all else is rarely equal. A good macro lens in the 100mm range would probably be the most useful in the greatest number of situations.