Is there a conversion factor when using lenses on Digi SLRs?

[IainB]

I have been told that any lens length should be multiplied by 1.6 when used on a digital slr. For example, a 28mm lens would actually be 45mm approx when used on digital. Can anyone confirm this?
Humble G1 owner drooling at the thought of upgrading to something else...

[MHaberman]

I have been told that any lens length should be multiplied by 1.6 when used on a digital slr. For example, a 28mm lens would actually be 45mm approx when used on digital. Can anyone confirm this?
Humble G1 owner drooling at the thought of upgrading to something else...

Depends on what camera you have. 1.6 is the correct multiplier for the 300D and 10D... Some cameras have 1.3 multipliers and some of the 1D series of cameras from Canon have 1.0 for the multiplier.

-Matt

[Jesper]

Yes, the "magnification" or "crop" factor. Everybody knows about it, but if you have a closer look it seems to be more complicated than what you think at first glance. An 28mm lens on a camera with an 1.6x factor (like the 10D or 300D) does not produce exactly the same image as a 45mm lens on a full-frame film camera. Perspective etc. also change.

The cause of the crop factor is the difference in size between a film frame (36 x 24 mm) and the size of the sensor of digital cameras (the sensor of the 10D and 300D is smaller, 22.7 x 15.1 mm).

Here is an elaborate explanation:
Understanding the DSLR Magnification Factor (http://www.luminous-landscape.com/tutorials/understanding-series/dslr-mag.shtml)

[redbutt]

I'm not intending to bash anyone here, but hasn't this subject been beaten to death. Somehow, someone needs to magically change all references of "focal length multiplication factor" to "field of view crop". That article referenced in the post above is great...that should be stickied to the top of this thread.

I have been told that any lens length should be multiplied by 1.6 when used on a digital slr. For example, a 28mm lens would actually be 45mm approx when used on digital. Can anyone confirm this?
Humble G1 owner drooling at the thought of upgrading to something else...

[IainB]

Thanks to all for the explanation and the link. Sorry to have raised an issue that apparantly has been 'done to death'. It's new to me.

[Andy_T]

Iainb,

just for info ... the G2 also has a 'focal length multiplier' ... it's 5x :shock:

That's why on your lens you'll find something like '7.2 - 21 mm' (actual zoom length) and in the manual it says '35-105 mm equivalent'

Best regards,
Andy

[hmhm]

The angle of view that a lens yields depends on the focal length of the lens and the "format". Format used to mean the size of the film (e.g. "35mm"), but in our context we mean the size of the digital camera's sensor. Longer focal lengths yield smaller angle of view, smaller sensors yield smaller angle of view.

We talk about "focal length multipliers" with DSLRs that have sensors smaller than 35mm film because we're all assumed to be experts in 35mm film photography and novices in digital photography, and thus we need to "convert" everything into 35mm equivalents so we can get our bearings back. A 100mm lens on a 10D gives the same angle of view as a 160mm lens on a 35mm film camera. Depth of field will be slightly different, but perspective will be identical.

Of course, if the bulk of your experience is with a "G series", then maybe you'd rather convert to "G equivalent"! In that case, the 10D is approximately a ".3 crop". :)
-harry

[IainB]

Clearly I have a lot to learn but I feel well tutored now. Great stuff.