Small format lenses on 135 format bodies

To keep this topical, I was thinking about any concept of using EF-S lenses on future Canon 135 format digital bodies. The genesis of course was the announcement that the upcoming Nikon D3 will work (cropped) with Nikon DX lenses.

For one, due to Canon's decision to make EF-S with short back focus there are of course serious physical problems with clearing the mirror.

For two, the real value of being able to use the small format lenses will probably not bear up with real use. Does anyone really want to buy something as expensive as the D3 and then crop it to a 6MP APS-C camera with every shot.

But now the real question (thanks for bearing with me).....I can't really imagine how well the Nikon DX on FX would work. Think about this.....when you mount the DX lens on the camera it will normally auto-crop the image from the sensor to discard the weak / vignetted image. But what the heck do you see in the viewfinder? Do you see the whole image with some guidance lines? Is there some magic hocus pocus to enlarge the viewfinder image?

After I thought all of this through I guess I can't see the ability to mount the DX/EF-S lenses on 135 format really having any practicality....anyone have other thoughts?

Final note - Here is the irony. For decades photographers have complained about the consumer and prosumer cameras only having 95% or so frame coverage in the viewfinder. Now Nikon finally offers up a viewfinder with 200% coverage....and people are probably going to complain.

You see black corners in the viewfinder. Like with a 180 degree fisheye on a full frame.

Only if they have IQ below 50

I've been unable to understand why anyone would want to mount an EF-S lens on a full frame body in the first place. There are 64 different lenses listed on the Canon USA website, of which only 5 are EF-S. The rest are EF lenses. All of the EF lenses will work on a full-frame (135) camera. In fact, most of them were originally developed for 35mm film cameras before the advent of the 1.6X digital cameras. There's certainly enough lens selection available for full frame cameras without worrying about using lenses optimized for the smaller sensors on them. And that's just Canon... How many more lenses are available from third party manufacturers like Tamron and Sigma?

JeffreyG wrote in post #4220893
For one, due to Canon's decision to make EF-S with short back focus there are of course serious physical problems with clearing the mirror.

Do Nikon DX lenses not use short back focus? I guess not if they are able to mount on the new D3? I thought short back focus was necessary to build lenses like the EF-s 10-22, but Nikon has the DX 10 mm fisheye and the 12-24 DX zoom so maybe not? Can anyone clear this up?

I agree that there is no reason to WANT to mount an EF-s lens on a full frame, with the possible exception of the 17-55 f2.8 IS, since no EF lens in this range has both 2.8 and IS. However when I see people say "I wish I could use my EF-s 60 macro... or 10-22 on my full frame camera" I just think "then you should have bought the Sigma 70 mm macro or 16-35L instead!

David

Who calls it 135 these days?

liquefied wrote in post #4223573
Who calls it 135 these days?

I do