Performance of Sigma 85mm F1.4 EX DGM on Canon 60D

Question

As the Sigma 85mm f/1.4 EX DG HSM was originally designed for Full-frame cameras, how would the performance be affected if I use it on Canon 60D (APS-C camera).

Q1) I need confirmation that this lens can be used on Canon 60D ?

Q2) In the Sigma official statements "When used on digital cameras with an APS-C size image sensor, the lens effectively becomes a 127.5mm F1.4 lens"

Can some kind soul here please explain to me in simple layman terms what does that mean?

ie instead of telling people that i have a 85MM Lens, now, I have a 127.5mm lens - can i tell people that i have a 127.5mm lens?

Q3) Will the perforamance of this lens suffer / be worse off since i am using a APS-C camera instead of a Full Frame Camera in which this lens was designed for?

Q4) Note! If the camera body does not support HSM, autofocus will not be available. Does Canon 60D have this function?

I am sorry that I have asked many questions but I do hope someone can please explain to me.

Answer 1

I have the Sigma 85mm lens and I am using it on a Canon APS-C sensor camera, the Canon 30D.

Q1 - Does it work? Oh Yeah! I have been so impressed with the performance, I consider it the best lens I own right now.

Q2 - If you put this lens on a "full frame" camera, you get the normal 85mm photo. If you put it on your 60D, you get what appears to be a larger picture. It is a picture that is equivalent to one that you would get if you put a 135mm (there is no 136mm lens which is the actually length) lens on a full frame camera (not your 60D). The way this is figured is to multiply the focal length of the lens times 1.6 (the crop factor). So 85 x 1.6 = 136 (not 127.5 - that length is correct for Nikon APS-C cameras)

Q3 - No suffering will take place.. the photos are simply amazing!

Q4 - The HSM is the same as USM on a Canon lens, and it works just fine on a Canon 60D

Here is a web site that I created because I love this lens so much.. www.sigma85mm.com

Answer 2

Q1 Yes

Q2 When used on an Canon APS-c sensor the lens has the same field of view as an 136mm lens on would have on a full frame body. The focal length is an intrinsic property of a lens and so doesn't change when mounted on a different camera. However most people use focal length [incorrectly] as a measure of field of view.

Q3 There are pros and cons to mounting the lens of an APS-c body. An 85mm lens on an APS-c body will be more prone to flare than a 136mm lens on a full frame body (the reason for this is that a lightsource that is out of frame on a crop body will still be in the FF frame and so light will not be occluded and can cause flare). You would also assume a lens designed for a crop sensor would be sharper as for the same number of megapixels smaller sensors will have higher pixel densities. This is not a hard and fast rule however. Finally using the lens on a crop sensor will avoid the extreme corners where a lens will often vignette or lose sharpness. The Sigma 85 f/1.4 is quite long but also very fast so will probably display soft corners wide open.

Q4 The lens will autofocus on the 60D (and all Canon EOS bodies).

Answer 3

Any EF Lens will work on an EF-S (APS-C) mount without issues.

The only difference is that the effective focal length will be 1.6 times the Full Frame equivalent, because the sensor size is smaller.

Regarding HSM support, I believe that is in reference to a Nikon mount version of the lens. Because the AF motors are in the lens for all Canon mount lenses specific body support is not needed. For other brands the body may include an AF motor, so it would need to be supported.