Sigma 50-100mm Art Lens


9 Sep 2018 8:51PM
I have been told this is for apc cameras like the Canon 7d etc becuase of the shading at the edges on a full frame camera .. So what i would love to know will it work ok on my Canon 1D MK3 which has a crop of 1.3 not 1.6 any thoughts please

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Chris_L Plus
4 4.9k United Kingdom
9 Sep 2018 9:23PM
I used a Sigma 10-20 on a 1D Mk II and it was a pain, not worth doing.

DC and EF-S lenses need to be used on APS-C cameras.

In fact the EF-S lenses can't be easily fitted to cameras with larger sensors like yours.
9 Sep 2018 9:58PM
The lens actual has red and white dots but you get heavy vignetting on the full frme but seeing the 1dmk3 has a crop of 1.3 thought it might work
Philh04 Plus
13 1.9k United Kingdom
10 Sep 2018 10:04AM
It should work ok as the Sigma lenses are not designed with the short back focus that Canons EF-S lenses have, which is more of a problem with wider angle lenses (that is why you do not see tele EF-S lenses).

That focal length range and aperture (will be an effective 65mm - 130mm f2.34 on your 1.3 crop) could be useful as a portrait lens where any vignetting may not be important.

Perhaps outline what your uses will be.
Chris_L Plus
4 4.9k United Kingdom
10 Sep 2018 12:09PM
Phil's wrong, you won't get an effective increase in focal length.
Philh04 Plus
13 1.9k United Kingdom
10 Sep 2018 12:38PM

Quote:Phil's wrong, you won't get an effective increase in focal length.

I used wrong word Chris... I should have used equivalence...

1.3 crop will give an equivalence of 65mm to 130mm f2.34...

i.e the FoV and DoF
Chris_L Plus
4 4.9k United Kingdom
10 Sep 2018 1:38PM
It won't give you the equivalent of that either. It's as if you've multiplied 50 x 1.3 and 100 x 1.3. That would work for you if you were going from a full frame lens to an APS-H camera, but you're not.
Philh04 Plus
13 1.9k United Kingdom
10 Sep 2018 1:54PM

Quote:It won't give you the equivalent of that either. It's as if you've multiplied 50 x 1.3 and 100 x 1.3. That would work for you if you were going from a full frame lens to an APS-H camera, but you're not.

How else would it work?

The lens is designed to work on an APS-C sensor where it is the equivalent to an 80mm - 160mm f2.8 (Canon 1.6).

How is the way that equivalence calculated going to change?
Chris_L Plus
4 4.9k United Kingdom
10 Sep 2018 1:54PM
To help you get your head round this, look at the diagram below. If the camera (on the left) has a bigger sensor it won't see less of the image circle, if anything it will see more

250184_1536584001.jpg



How would the larger sensor ever see a cropped field of view (on the right)?

Next you'll be saying that if he puts in on a 5D full frame there'd be even more of a crop! 🤣
Philh04 Plus
13 1.9k United Kingdom
10 Sep 2018 2:16PM

Quote:To help you get your head round this, look at the diagram below. If the camera (on the left) has a bigger sensor it won't see less of the image circle, if anything it will see more


Your last post has nothing to do with equivalence... we all know that a lens designed to work on a crop sensor has a smaller image circle but that has no relevance to the equivalence calculations which are (in simple terms so you can understand) all to do with FoV and DoF.

Even with a smaller image circle a lens will still have an equivalence, in fact on the Sigma website the 50 - 100 Art lens is quoted as being the equivalent to 75mm - 150mm (Nikon).

As far as Canon is concerned;

that lens mounted on a FF body will be a 50mm - 100mm f1.8

Mounted on an APS-H it will be equivalent to a 65mm - 130mm f2.34

Mounted on an APS-C it will be equivalent to an 80mm - 160mm f2.8

The image circle will of course be identical on all three sensor sizes and will more than likely result in severe vignetting on the full frame and obviously little or no vignetting on the APC-C body...


Quote:Next you'll be saying that if he puts in on a 5D full frame there'd be even more of a crop!

Funny Tongue
Chris_L Plus
4 4.9k United Kingdom
10 Sep 2018 2:25PM
Phil, there won't be any image to crop

If you took a full frame 50mm lens and and put it on a 1.3 you'd get a crop giving you 65mm equiv.

But it isn't full frame because of the small image circle, there won't be any crop, the image circle won't even cover the whole sensor.

Crop factors only work when the reference point is a 35mm full frame sensor with a full frame lens. It's irrelevant or misleading otherwise.

Philh04 Plus
13 1.9k United Kingdom
10 Sep 2018 2:34PM

Quote:Phil, there won't be any image to crop

If you took a full frame 50mm lens and and put it on a 1.3 you'd get a crop giving you 65mm equiv.

But because of the small image circle, there won't be any crop, the image circle won't even cover the whole sensor.



We are talking about equivalence... off course the image circle will be smaller on a lens designed for APS-C...

Even a 50mm lens designed for APS-C is going to be a 65mm equivalent on an APS-H.. whether the lens will provide enough coverage is another matter and it is possible (depending upon the intended use) that the coverage on APS-H might be marginally sufficient.

It does not matter about what format the lens is designed to cover there will still be an equivalence.


Quote:It's irrelevant or misleading otherwise.

Of course it isn't if it was then the manufacturer wouldn't quote an equivalence...

Oh and for your information equivalence works the other way round too..
Philh04 Plus
13 1.9k United Kingdom
10 Sep 2018 3:28PM
Just a bit more info for the OP... looking around the 50mm - 100mm f1.8 will indeed work on your 1.3 crop body... wide aperture lenses will vignette slightly when shot wide open and will improve as they are stopped down... the amount of vignette wide open has been measured at 1.7EV at both 50mm and 100mm which is not a major problem.

So my original statement that you will have an equivalent to a 65mm to 130mm f2.34 stands.
Chris_L Plus
4 4.9k United Kingdom
10 Sep 2018 3:29PM

Quote:equivalence works the other way round too


It does not.

You are probably one of those people who after paying 250 inc VAT for some equipment calculates that the VAT you paid was 50 (assuming VAT rate was 20% at the time)
Chris_L Plus
4 4.9k United Kingdom
10 Sep 2018 3:34PM
Try to understand this Phil. If I attach a full frame 65 to 130mm lens to a full frame 5D and invite the OP to look through and say to him that's the same field of view you will get when you attach that Sigma 50 to 100mm APS-C lens to your 1D Mk 3 that will not be the case.

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