Scale focusing and the 1.5 crop factor

[kshapero]

Since the R-D1 as well as a ton of DSLR's have a 1.5 crop factor which makes a 35mm lens a 50mm. That being the case wouldn't I get the advantage of the 35mm's more flexible scale focusing then using a 50mm lens at FF?

 

[LCT]

You'll gain one f-stop DoF roughly in that you'll get approx. the same DoF with a 35mm lens at f/2.8 on the R-D1 as with a 50mm lens at f/4 on a FF camera.

 

[kshapero]

sounds like a bonus. of course I am giving the wide angle of the lens.

 

[yanidel]

You'll gain one f-stop DoF roughly in that you'll get approx. the same DoF with a 35mm lens at f/2.8 on the R-D1 as with a 50mm lens at f/4 on a FF camera.

so is it correct to say that the scale of focus distance on the lenses cannot be used to estimate the dof?

 

[Sam N]

The focus distance does not change.

The distance scale on the lens is still accurate.

The only issue is that some people like to use a smaller circle of confusion for cropped digital sensors, so the DOF scale might be off (if you are one of those people).

For example, in this chart the COC for the R-D1 is .020 vs .030 for the film cameras.
http://www.rangefinderforum.com/forums/showpost.php?p=770671&postcount=62

 

[LCT]

so is it correct to say that the scale of focus distance on the lenses cannot be used to estimate the dof?

They cannot be used as is because the DoF markings of the lenses are designed for film i.e. for a larger CoC than cropped digital. I personally use the DoF markings of the nearest faster f-stop of my lenses i.e. f/5.6 when i choose f/8 for metering by example. Some other photographers prefer 2 f-stops (f/4 in my example), specially if they print larger than A4.

 

[pvdhaar]

I'd say that the advantage of focal length ratios between a 50 and a 35, in other words 1.4x, are cancelled by the 1.5x crop factor. So, guesstimating focus for a 35 on DX format is just as hard as for a 50 on FF.

In practical terms, I've found that for me 35/2.8 is about as good as I am in guesstimating on FF (i.e. with a Minox 35). That would correspond to a 50 stopped one down further. Something that by pure coincidence coincides (love it when I can string such words together) almost with the focal length and max. aperture of the very first scale focused Barnack.

 

[RichC]

http://www.richcutler.co.uk/r-d1/r-d1_02.htm

:angel: