What is special about APS-C specific lenses.

**Catscradle** · 11-17-2013, 07:15 AM

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?

**interested_observer** · 11-17-2013, 07:23 AM - **1 Like**

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...

Crop Sensor (APS-C) Cameras and Lens Confusion

**Catscradle** · 11-17-2013, 07:48 AM

Thanks Interested-observer, that article was excellent.

**patrick9** · 11-17-2013, 08:53 AM

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.

aurele · 11-17-2013, 08:58 AM

Originally posted by patrick9

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.

Adam · 11-17-2013, 09:57 AM

Originally posted by Catscradle

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).

**patrick9** · 11-17-2013, 12:35 PM

Originally posted by aurele

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

.

clicksworth · 11-17-2013, 01:12 PM

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.

6BQ5 · 11-17-2013, 01:28 PM

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.

clicksworth · 11-17-2013, 01:40 PM

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

11-17-2013, 07:15 AM	#1
Catscradle Site Supporter Join Date: Aug 2013 Location: Weymouth, MA Photos: Gallery Posts: 220	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
interested_observer Loyal Site Supporter Join Date: Jun 2009 Location: Tumbleweed, Arizona Photos: Gallery \| Albums Posts: 5,707	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... Crop Sensor (APS-C) Cameras and Lens Confusion

11-17-2013, 09:57 AM	#6
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,608	Originally posted by Catscradle 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). Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

11-17-2013, 12:35 PM	#7
patrick9 Site Supporter Join Date: Feb 2011 Location: Murfreesboro Tennessee Photos: Gallery \| Albums Posts: 3,458	Originally posted by aurele 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.

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11-17-2013, 07:48 AM	#3
Catscradle Site Supporter Join Date: Aug 2013 Location: Weymouth, MA Photos: Gallery Posts: 220 Original Poster	Thanks Interested-observer, that article was excellent.

11-17-2013, 08:53 AM	#4
patrick9 Site Supporter Join Date: Feb 2011 Location: Murfreesboro Tennessee Photos: Gallery \| Albums Posts: 3,458	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
aurele Veteran Member Join Date: Jan 2011 Location: Paris, France Photos: Albums Posts: 3,217	Originally posted by patrick9 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, 01:12 PM	#8
clicksworth Senior Member Join Date: Nov 2013 Photos: Albums Posts: 150	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
6BQ5 Veteran Member Join Date: Jun 2013 Location: Nevada, USA Photos: Albums Posts: 3,348	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
clicksworth Senior Member Join Date: Nov 2013 Photos: Albums Posts: 150	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