[okto]

I was watching a DA 40 Limited on eBay, and noticed the seller says it has a 60mm equivalent view because of the crop factor. He says he's used it for a year on a DSLR and gotten a 60mm view, and that there's no vignetting with a film or full-frame digital SLR.
As I understood it, the focal lengths of the DA lenses are calculated for an APS-C sensor, so no crop factor is involved; which is right?

His message:
"Thanks, but that is not how I understand it. The lens is in fact designed for the smaller image circle, but the 40mm is a 35mm frame designation and is affected by the crop factor of the APS sensor. I've used the lens for a year, and it produces a 60mm angle of view on a DSLR. It works fine as a 40mm on a 35mm slr, with no vignetting. "

[Matjazz]

Focal length doesn't change with camera. What he wanted to say is that if you put a 40mm lens on a apsc sized sensor you get the same field of view as if you put a 60mm lens on leica standard film.
The "backdraw" of DA lenses is that they have smaller image circle (apsc sensor is smaller than film) so they usually introduce heavy vignetting when used on film. However I heard some reports that some DA lenses do good on film but not without any vignetting at all. I can't confirm or deny sellers statement about DA 40 Limited lens not vignetting on film but if I was buying lenses for film only I'd stay away from DA.

[Ole]

The DA 40mm works fine on 35mm film. It's probably the exception in the DA line, having inherited its optical design from the M 40mm.

Note, it has no aperture ring and is therefore suitable only for film bodies which can set the aperture.

[okto]

Focal length doesn't change with camera. What he wanted to say is that if you put a 40mm lens on a apsc sized sensor you get the same field of view as if you put a 60mm lens on leica standard film.

So the field of view on my K100D when I have my DA 18-55 all the way wide is the same as a 27mm on a full frame, and all the way tele is the same as an 83mm?

[ercole69]

Yes, it's correct