Lens conversion

I have a friend of mine who owns a Canon DSLR. We have been talking back and forth about the possibibility of me buying the camera at a good price as he is wanting to upgrade. I own a telephoto lens for my Canon Rebel, 80-210, what would be the difference in using it from a SLR to a DSLR as for the range?

 

Canon uses 1.6:1 as the conversion for a Rebel XT DSLR lens to the film SLR equivalent. For instance, your 80-210 mm Rebel lens would be about the same as a 50-131 lens when used with the Rebel XT DSLR.

This website gives some information on this subject.
http://www.photo.net/equipment/canon/300D/EOS_300D_lenses.html

 

Only in terms of angle of view, the magnifcation does not change.

 

Yep, I have a Rebel XT. It is a 1.6x "multiplication" of the lens range. For example, my 17-85 lens has an effective (35mm camera) range of 28-135mm.

Harold

 

Hemi, both you and Lenny have me totally confused.

I have a Rebel XT DSLR with a 17-85mm lens. I thought this lens is equivalent to a 27-136mm lens when used with a full-frame 35mm film camera. I may be mistaken, but I thought that the numbers related to magnification, both positive and negative, assuming a 50mm film camera lens has a 1:1 magnification.

Again, I refer to: http://www.photo.net/equipment/canon/300D/EOS_300D_lenses.html

What have I misunderstood?

 

I think if you have a full-size sensor DSLR, like the EOS 1, the lens should perform at the length advertised..

The Digital Rebels and the like like have the smaller sensors, hence the 1.6x factor.

Harold

 

I guess my question now would be...what is the end result?

Given two SLR cameras side by side, one a film Rebel and the other a digital Rebel, each with identical non-zoom lenses shooting the same scene, what would be the size (magnification) difference of the resulting images? Would the DSLR image be 1.6X smaller or larger than the SLR image? Or, as someone earlier suggested, would the difference only be in the field of view?

I will post this question on the Imaging Resource Canon Digital SLR Discussion Forum: http://www.photo-forums.com/WebX?13@52.AqDlb07CTMa.6@.ee946e1. Hopefully someone there will be able to give us an answer.

 

Again, the smaller sensor size of most DSLRs leads to an "apparent magnification." The 17-85 lens produces the same size image on either camera, but the smaller field of view due to the smaller sensor in the DSLR makes it appear to by magnified by 1.6X. The smaller sensor, in effect, crops the image.

 

To put Pete's words in another way....

The same lens projects the same image circle whether on a SLR or a DSLR. Now on a Digital Rebel, the sensor is smaller than a 35mm negative frame so when a picture is taken, the DSLR caputures a smaller area of the same image circle as with a film SLR.

There is no magnifciation what so ever. If anything, think of it as cropping. Where the "magnification" becomes apparent is when you take both images and blow them up to, say, a 4" x 6" photograph. That's where the magnification comes into play. The lesser image circle captured of the digital sensor will need to be blown up more to fit a 4x6 photograph so it would appear to be larger when compared to the film version.

 

Pete, now I understand. The DSLR sensor image, being 62.5% of the area of the SLR film image, appears to be magnified when printed only because it has to be enlarged more than the SLR image to fill the same size paper.

Thanks for clearing that up.

Edit: MK, Thanks....I was composing while you were posting.

 

And this is why film SLR lenses will work on a DSLR, while some DSLR lenses will produce a circular, vignetted image on a film SLR. The larger the circle a lens has to cover, the more expensive it will be. But that does mean that specifically designed DSLR lenses can be brought to market in a good price range. I think a full-image 12-24mm Nikon zoom (or the Canon equivalent) would be in the $5,000-$6,000 range, or more; that it's about $1,000 shows the economies.

 

That's interesting, Pete. I never realized that the cost of fine optics was so critical. From what you say, it sounds as if the cost of a lens is almost exponential relative to image size. Thanks

 

Edit:
I missed the fact there is a second page to this discussion. Looks like Pete covered it.

 

I think it's mostly a matter of how far you have to bend the light and retain acceptable focus. It takes more elements and far better glass to cover a large angle, such as on a film SLR or even a DSLR. That's why you don't see many 10-1 zooms on the larger film or imager sizes. A 10-1 or 12-1 zoom was fairly standard on 16mm movie cameras in the 1970s, but they didn't have much image area to cover.

They do exist in larger format sizes, but are prohibitively expensive and absolutely huge in size. They are pretty much custom-built, and used for "specialized" work.

 

So what I am reading, being the future camera is a Canon 10D, I will have more magnification of an image with the lenses that I have for my SLR? But does that mean my 80-210, on the digi, will be greater asset on the DLSR or a loss? I have been somewhat confused now. I was told that what ever lens I had, take the bigger number and mulitply it by 1.6 and that would be the effective focal length, is that still true?

 

Ray, from what Pete has said, the optics of a Canon (or similar) SLR lens will work fine with a Canon DSLR. Any apparent magnification will occur when you enlarge the DSLR image to fit on photo paper, e.g. 4x6 or 8x10, as mentioned above.

The reason I said "optics" is because your SLR lens, being older, may not have the mechanical or electronic design to use all the capabilities of newer DSLR cameras. I don't know what the difference in capabilities may be, but from what I read there could be quite a few depending on when your lens was made.