Old Lens on a New Canon

[Tim Spencer]

I have a Rebel XS which is a non-full frame. So I know that means my 17-55 lens is equal approx. to a 27 - 88 in terms of comparing to the 35 mm film world. (Utilized a factor of 1.6).

My question is - I have old manual Pentax lenses that I can use with an adapter. For example, a 50mm. So will the 50mm equate to 80mm on my Canon? Or will it be a straight 50 or what exactly?

Thanks,

Tim

[inkista]

Focal lengths DO NOT CHANGE, regardless of how big the sensor behind the lens is. The focal length is a physical property of the lens, and does not change unless you physically change the design of the lens. What's changing is the field of view/scene coverage, due to the size of the image plane. It's similar to cropping off the image, which is why it's also called a "crop factor". To me, "focal length multiplier" is a misnomer.



So, your K-mount 50mm lens will still be a 50mm lens, but is going to have the same FoV as an 80mm lens would have mounted on a 5D or 35mm film SLR.

Whether a lens is EF or EF-S, the focal lengths are the same. What's different is how big the image circle projected by the lens has to be to cover the frame.

[Tim Spencer]

Inkista:

Thank you - clears it up!