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DPChallenge Forums >> Photography Discussion >> Macro Focus
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 10/18/2010 11:45:30 AM · #1
Can macro lenses focus to infinity, so could I use them as a short telephoto lens?
 10/18/2010 11:47:01 AM · #2
Originally posted by adamelliott111:
Can macro lenses focus to infinity, so could I use them as a short telephoto lens?


Yes
 10/18/2010 11:47:08 AM · #3
For the most part, yes. I know many people use the Canon 100mm f/2.8 macro as a portrait lens.
10/18/2010 11:47:54 AM · #4
Awesome, thanks :D
 10/18/2010 11:47:59 AM · #5
I'd have thought all dedicated macro lenses can focus to infinity. The 100mm and 60mm canon macro lenses certainly can

If you used something like an extension tube or a macro "filter" then it will no longer focus to infinity.
 10/18/2010 11:48:43 AM · #6
It depends on the lens. Most of them should focus on infinity fine, but there are exceptions, the Canon MP-E65mm being one.
 10/18/2010 11:50:04 AM · #7
What decides how close it can focus?
 10/18/2010 11:51:01 AM · #8
Originally posted by gyaban:
It depends on the lens. Most of them should focus on infinity fine, but there are exceptions, the Canon MP-E65mm being one.


There are always exceptions, so yeah, depends on the lens... I'm sure some older macro lenses don't focus to infinity either.
10/18/2010 11:54:22 AM · #9
Originally posted by adamelliott111:
What decides how close it can focus?


Many times it's Barrel length
 10/18/2010 11:56:23 AM · #10
Originally posted by fotomann_forever:
Originally posted by adamelliott111:
What decides how close it can focus?


Many times it's Barrel length


Yup. From WikiPedia: "The further the lens is from the sensor, the closer the focusing distance, the greater the magnification, and the darker the image for the same aperture."

Hence the use of bellows and tubes.
 10/18/2010 11:58:25 AM · #11
So the only reason you pay so much for macro lenses is it's focusing distance, right?
 10/18/2010 12:01:03 PM · #12
Originally posted by adamelliott111:
So the only reason you pay so much for macro lenses is it's focusing distance, right?


Yeah, well... it takes a bit more engineering to get that short focusing distance...

A cheaper alternative is to use extension tubes on non-macro lens.
10/18/2010 12:03:11 PM · #13
Originally posted by adamelliott111:
So the only reason you pay so much for macro lenses is it's focusing distance, right?


Not the only reason: sharpness, chromatic aberrations, distortion, contrast, autofocus speed (if applicable), etc. Just like for any lens really.
 10/18/2010 12:18:23 PM · #14
Originally posted by fotomann_forever:
Originally posted by adamelliott111:
So the only reason you pay so much for macro lenses is it's focusing distance, right?


Yeah, well... it takes a bit more engineering to get that short focusing distance...

A cheaper alternative is to use extension tubes on non-macro lens.


What are the disadvantages to that?
 10/18/2010 12:52:50 PM · #15
Originally posted by adamelliott111:
Originally posted by fotomann_forever:
Originally posted by adamelliott111:
So the only reason you pay so much for macro lenses is it's focusing distance, right?


Yeah, well... it takes a bit more engineering to get that short focusing distance...

A cheaper alternative is to use extension tubes on non-macro lens.


What are the disadvantages to that?


You can't focus to infinity. Using on a normal zoom lens the quality won't be as good as a prime lens. The cheap versions (£10) will not auto focus ... the "propper" versions are still quite expensive, eg the canon extension tubes start at about £60 and are not compatible with all lenses. They have no glass in so the extension tube does not effect the quality of the pic

10/18/2010 05:37:24 PM · #16
Originally posted by bobonacus:

You can't focus to infinity. Using on a normal zoom lens the quality won't be as good as a prime lens. The cheap versions (£10) will not auto focus ... the "propper" versions are still quite expensive, eg the canon extension tubes start at about £60 and are not compatible with all lenses. They have no glass in so the extension tube does not effect the quality of the pic


Extension tubes can work pretty well; I've had decent luck with them, but definitely prefer my dedicated macro lens now that I have it. The Kenko tubes work great and are more reasonable, though still not cheap. Mine were labeled as not working with hypersonic AF but they do (with Sigma HSM and Nikon AF-S).
Some examples of entries I've done using tubes-
You can get a set of tubes and a cheap MF prime to mess around with if you're curious. My 50 1.8 E series was $30 in immaculate condition and was what I used for my initial macro shots.

As was noted before, you can't focus to infinity, so if you're working in the field with insects for example, sometimes its difficult to determine if you're too far away or too close to your subject since the DoF can be so very very thin. When AF searches on a dedicated macro lens you can figure out where you're at a lot easier, in my opinion.
 10/18/2010 07:08:27 PM · #17
Extension tubes work better with some lenses than others. Though the have no glass in them, they can affect the quality of the image produced by the lens, for the following reasons:
- Many lenses have increasing aberrations as you focus closer; putting extension tubes on a lens not designed for close-focus will inevitably lead to greater aberrations such as CA.
- Moving the lens away from the sensor means that you are effectively using less of the image circle. If the lens doesn't have much "headroom" in its resolving power, you can get soft images as a result.
True macro lenses also have other benefits, such as a flat field.
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