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11-17-2013, 07:15 AM   #1
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What is special about APS-C specific lenses.

Many lenses (the DAs) say they are designed specifically for non-full frame and they won't work properly with full frame. Not that I'm getting a FF, but I'm curious about this issue. What is it about their design that makes them inappropriate for a full frame. I would think the effect of the focal length would change, but I don't understand why it should be otherwise different. Can somebody enlighten me?

11-17-2013, 07:23 AM - 1 Like   #2
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The resultant image circle from the ASP-C lens is smaller than that of a full frame lens.



The individual lens elements are sized accordingly. Also, since the image circle is smaller, its Field of View or Angle of View, if you will, is also reduced. Here is a good overview...
11-17-2013, 07:48 AM   #3
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Thanks Interested-observer, that article was excellent.
11-17-2013, 08:53 AM   #4
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The DA's will work on FF/35mm in a way. I have used my DA18-55 on my film cameras a couple of times. The thing to watch for is vignetting. Also if the camera can't set Aperture then the lens will only shoot wide open. The vignetting was very faint on my ZX-7 and not on all the settings.

11-17-2013, 08:58 AM   #5
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QuoteOriginally posted by patrick9 Quote
The DA's will work on FF/35mm in a way. I have used my DA18-55 on my film cameras a couple of times. The thing to watch for is vignetting. Also if the camera can't set Aperture then the lens will only shoot wide open. The vignetting was very faint on my ZX-7 and not on all the settings.
If you use a body that dont handle "A" fonction, then the lens will be stop down to minimum aperture (like f22) and not to maximum aperture when shooting.
11-17-2013, 09:57 AM   #6
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QuoteOriginally posted by Catscradle Quote
Many lenses (the DAs) say they are designed specifically for non-full frame and they won't work properly with full frame. Not that I'm getting a FF, but I'm curious about this issue. What is it about their design that makes them inappropriate for a full frame. I would think the effect of the focal length would change, but I don't understand why it should be otherwise different. Can somebody enlighten me?
APS-C lenses are much more compact than FF lenses, and more affordable since you don't need to use as much glass. That's the main motivation for going APS-C only (i.e. look at the DA limiteds).

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11-17-2013, 12:35 PM   #7
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QuoteOriginally posted by aurele Quote
f you use a body that dont handle "A" fonction, then the lens will be stop down to minimum aperture (like f22) and not to maximum aperture when shooting.
Yeah. My mistake. My mind sometimes works in reverse I guess.
11-17-2013, 01:12 PM   #8
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On an APS-C camera it isn't just the sensor that is smaller, but also the mirror. APS-C lenses are allowed to protrude into the body a bit, taking advantage of a shorter distance from the sensor. If they could be mounted to a FF camera they would bash on the mirror. With FF it is a constant concern when using old lenses. Even though they worked on some film cameras some of them will hit the mirror on new digitals.

11-17-2013, 01:28 PM   #9
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I always thought FF lenses offer a bit more sharpness since there is a larger center area that is sharper. The softer corners are cropped out.

Are there any FF Pentax K-mount or M42 lenses that interfere with the mirror? I heard of other brands like Canon having problems with FF M42 lenses.
11-17-2013, 01:40 PM   #10
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The long M42s are fine, some of the shorter ones can hit. K-mounts need a small modification.
Compatibility list of M42 lenses on Canon EOS 5D dslr
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