toptrainer Loc: Wellington

I have Canon 6D with a few lenses, I usually do head shots and events. I have been asked lately to shoot some homes for a friend and with some practice I have become quite good. Question, I have a sigma 17-70 that works on my 80D but vignettes horribly on my 6D. Is there a way to get my sigma lens to be used on my 6D body without vignetting?

GoofyNewfie Loc: Kansas City

No
It’s made to cover the smaller sensor of your 80D.
Not the full frame 6D
It may not vignette at the longer focal lengths, but I’m pretty sure it’s the wider angle you’re after and that’s not going to work.
You’re going to have to use a different lens.

toptrainer Loc: Wellington

Thanks

autofocus Loc: North Central Connecticut

correct answer above from "Goofy" just shot with it on your 80D, as long as that camera is still working

happy sailor Loc: Ontario, Canada

What lenses do you have for your 6D, you have to remember that a 17mm on a Canon crop sensor has the same view as a 27mm full frame lens on your 6D. If you have the Canon 24-105 that many 6D's were sold with in their kit then you already have a wider angle than your Sigma lens would give you on your 80D.

toptrainer Loc: Wellington

I do have the 24-105

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If Canon had built that lens it would be shaped to refuse to seat on your 6D. If you try it with a Canon APSC lens you will see for yourself.

BurghByrd Loc: Pittsburgh

Yes, but I think the 80D is a better option for this lens? The Sigma 17-70 was designed for ASP-C (DX) sensors. You could set the 6D camera to shoot in DX mode and use the Sigma 17-70? Your 6D is full frame but uses a ~20MP sensor so a DX crop would render ~15MP. Your 80D body although a smaller sensor (ASP-C) is a ~26MP sensor. So your options with this lens are an 15MP image with the 6D or a 26MP image with the 80D.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Use that on your 6D, but watch your corners. This lens has some field curvature that trashes the corners at wider apertures. Keep your sensor perfectly vertical to avoid converging verticals and you will be ok.

However, there's a lot more to lens selection to make rooms in a house look good - lighting, staging, point of view, and if necessary using a stitched pano to make your field of view wider, and lastly, accurate and consistent white and color balance.

It's rare that you will need a lens that is wider than a 24mm on a 6D. Too wide a lens results in extension distortion, where things in the foreground are huge and things in the background seem like they are in another town.

BebuLamar

Several things you said are not correct.
A 20MP full frame sensor when cropped to APS-C only yield a little less than 8MP and not 15MP.
The Canon DSLR's don't have DX crop because you are not supposed to mount an EF-S lens on a Canon full frame camera and thus Canon doesn't have that mode.

BurghByrd Loc: Pittsburgh

Very well, I stand corrected. You're right about the 8MP, I incorrectly recollected a 3/4 factor but it's more like 4/10. On the other point, I've not seen a FF body that can't be shot cropped, but then again I'm not familiear with the Canon line.

CHG_CANON Loc: the Windy City

No Canon DSLR will detect a cropped lens and enter a 'cropped mode'. Canon is 45% of the total camera market through recent camera sales in 2020, larger than Nikon (19%) and Sony (20%) combined. Canon mirrorless cameras now support adapting both EF and EF-S lenses and will dynamically implement a 'crop mode' for EF-S lenses.

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Canon DX lenses won’t mount to Canon FX bodies so no crop mode.

TriX Loc: Raleigh, NC

To my knowledge, there is no “DX mode” on Canon cameras - that’s a Nikon thing. If your 24-105 isn’t wide enough, either the Canon EF 16-35 f4L or 17-40 f4L are good choices for indoor real estate work unless you want to spring for one of the Canon T&S lenses.

Scruples Loc: Brooklyn, New York

The 17-70mm lens is made for a crop sensor camera which the EOS 80D is. That is why you get great photos on the 70D. The EOS 6D is a full frame camera and the vignette is caused by light hiring the lens at a sharp angle and being obstructed within the lens.

I would like to suggest the use of a 24mm tilt/shift lens. This lens is designed to be used on a full frame camera. The lens bends the light path according to the Scheimpflug principle. Using a regular 24mm lens the image of a building seems to be falling backward because vertical converge in the distance. As this lens is more expensive than a lens of comparable focal length, because of the tilt/shift mechanism.

I would like to suggest the rental of such a lens. Because it is expensive and because you probably won’t use it too frequently in the future. Learning how to use this precision piece of glass takes time and a tripod to steady the camera.

A Canon lens might cost $1800-$2100. A Rokinon lens might cost $800-$1000.

A better bet would be a rental.
One day rental might cost $45 or a one week rental might cost $200-$250.

To learn more about this type of lens or the Principle you can google it rather than I have specs here.