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03-26-2011, 11:22 AM   #1
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Is a full frame lens on an aps-c, a negative?

The Sigma 85mm 1.4 is said by the manufacturer to be specially designed for use on full frame cameras. Is there any reason to believe that this lens will perform significantly worse on an aps-c size camera such as a K-x? This lens seems to get much higher overall scores on full frame cameras on the DxOMark website (they have only tested it on several canon bodies), but it is possible that the lens may have scored higher because the camera body/sensor was newer (evolution of digital photography is dizzying). But the K-x, though middle aged (and discontinued, I know) is still quite a high performing camera in terms of it's sensor and ISO performace, etc. when compared to other cameras. I also should mention that problems with third party lenses on Canons seem to be rampant (back/front focusing, no focus, jerk focus, contact errors). Probably known compatability issues Canon uses to their advantage to make profit from their products. Here's one of the more convincing reviews of the sig 85 i've found. Dan Freeman Photography Sigma 85mm f/1.4 EX Review (ish)

And here's a comparison of sharpness between the Sigma 85 1.4 at F 1.4 and the Nikon 50mm 1.4 at F 8!! Dan Freeman Photography Sigma 85mm vs Nikon 50mm f/1.4 Comparison


Last edited by outsider; 03-26-2011 at 09:13 PM.
03-26-2011, 11:24 AM - 1 Like   #2
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Not really. Digital-only lenses deal a little better with flare, but you can get around most of those issues with a good hood. (Full frame lenses have a different shaped rear element, can cause more internal reflections). However I don't really have any problems with my full frame lenses.

DXO scores have a lot to do with the body.

I would not worry about it too much. Just consider that 85mm is pretty long on ASP-C.

Another option would be the DA* 55 1.4, which gives you the same FOV of the 85mm 1.4 on a full frame camera.
03-26-2011, 11:32 AM - 1 Like   #3
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QuoteOriginally posted by outsider Quote
The Sigma 85mm 1.4 is said by the manufacturer to be specially designed for use on full frame cameras. Is there any reason to believe that this lens will perform significantly worse on an aps-c size camera such as a K-x? This lens seems to get much higher overall scores on full frame cameras on the DxOMark website (they have only tested it on several canon bodies), but it is possible that the lens may have scored higher because the camera body/sensor was newer (evolution of digital photography is dizzying). But the K-x, though middle aged (and discontinued, I know) is still quite a high performing camera in terms of it's sensor and ISO performace, etc. when compared to other cameras. I also should mention that problems with third party lenses on Canons seem to be rampant (back/front focusing, no focus, jerk focus, contact errors). Probably known compatability issues Canon uses to their advantage to make profit from their products.
No issues at all. You will actually have less vignetting than you would shooting on a 35mm sensor, since the edges are already cropped out. You are also "future-proof" if Pentax ever decided to release a full frame sensor.

APS-C tends to stress lenses in different ways then full frame. Full frame tends to be harder on borders and corners of lenses, while APS-C (being more pixel dense) tends to stress the center performance of a given lens harder. The kx is nowhere near the pixel density of the 7D (18 megapixels) and I doubt you would see any issues.
03-26-2011, 11:55 AM   #4
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QuoteOriginally posted by outsider Quote
The Sigma 85mm 1.4 is said by the manufacturer to be specially designed for use on full frame cameras. Is there any reason to believe that this lens will perform significantly worse on an aps-c size camera such as a K-x?
Other than it being a Stigma, probably not.

03-26-2011, 12:20 PM - 1 Like   #5
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In theory, it should perform slightly better because more of the photo on an aps-c camera will be from the center areas of the lens, which is generally the sharpest (in theory). A full frame lens is a little larger in diameter. All film lenses are FF with the exception of the IX Nikkors which were for aps film cameras. A FF lens that is good an a FF digital camera will perform just as well on an aps-c digital camera. There are just as many pixel peepers using FF cameras.
03-26-2011, 12:26 PM   #6
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I get your drift. Believe me, i'm not a big fan of sigma either, even though lenses are their specialty, they've just never produced what i'd consider a great lens. And I never liked that sand paper textured B.S. on their lenses either. No one's throwing a football. But this lens seems to be different. If you do your research, you'll see that it performs very well to consumers and in lab tests. So, why not. I felt this way about tamron and after being convinced to get the 70-200 i couldn't be happier.
03-26-2011, 12:28 PM   #7
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Nice...thanks for the advice
03-26-2011, 12:49 PM   #8
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It may be physically bigger if it covers full frame. The DA15 is one of the primes that is most limited to APS-c. It throws a very defined little circle on a film frame. Compare it to the film frame K/A 15/3.5. The DA15 is half the size and 1/3 the weight. I don't think the half stop of speed is the main reason.


Last edited by GeneV; 03-26-2011 at 04:24 PM.
03-26-2011, 02:31 PM   #9
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Short answer - no. Long answer - no, not really.

People fall all over the FA Limiteds (Pentax full-frame lenses) which seem to work reasonably well.

Sigma makes good ones and bad ones, like everyone else. I had an 18-50 that was pretty nice, and a budget 70-300 that was less so (and suffered an aperture-blade death.
03-26-2011, 03:25 PM   #10
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QuoteOriginally posted by outsider Quote
I get your drift. Believe me, i'm not a big fan of sigma either, even though lenses are their specialty, they've just never produced what i'd consider a great lens. And I never liked that sand paper textured B.S. on their lenses either. No one's throwing a football. But this lens seems to be different. If you do your research, you'll see that it performs very well to consumers and in lab tests. So, why not. I felt this way about tamron and after being convinced to get the 70-200 i couldn't be happier.
I would consider the 150 macro, the 70 macro, and the 100-300 f/4 HSM to be great lenses.

The 50-150 2.8 and 70-200 2.8 are very good lenses.


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03-26-2011, 03:49 PM   #11
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QuoteOriginally posted by jsherman999 Quote
I would consider the 150 macro, the 70 macro, and the 100-300 f/4 HSM to be great lenses.

The 50-150 2.8 and 70-200 2.8 are very good lenses.


.
Agreed, especially with the 150 Macro. I also think the 17-50 2.8 os hsm, 10-20, and 8-16mm lenses are, at the least, very good.
03-26-2011, 04:18 PM - 1 Like   #12
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Shootin' full-frame lenses on an APS-C is like eatin' the seedless heart out of a watermelon -- almost all the good stuff with none of the spittin'.

H2
03-26-2011, 04:33 PM - 1 Like   #13
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"Is a full frame lens on an aps-c, a negative?"

Generally, since the aps-c sensor only sees the central portion of the image circle, performance is better. Due to the smaller physical size of aps-c sensor, diffraction effects will be seen at smaller f/# than on full frame.

A negative? Yes, imho, because I have FF digital body (5Dc) and film cameras (Spotmatics, of course!) I will probably get flamed for this: aps-c cameras are mere toys compared to FF! No flame please unless you have FF body!
03-26-2011, 04:36 PM   #14
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QuoteOriginally posted by outsider Quote
The Sigma 85mm 1.4 is said by the manufacturer to be specially designed for use on full frame cameras.
Compare the reviews on photozone of the Canon 50/1.2, on APS and FF, and see for yourself.
03-26-2011, 04:53 PM   #15
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QuoteOriginally posted by rhodopsin Quote
aps-c cameras are mere toys compared to FF! No flame please unless you have FF body!
Yes ASP-C cameras are nice, compact IQ machine "toys" while fullframe DSLRs are massive, heavy "real" cameras. .

For a pro, understandable tradeoff. But I like ASPC for the same reason I like Pentax primes...
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