Hyperfocal distance


Link Posted 25/11/2006 - 19:23
I am looking for a 28 mm lens and was wondering, would the hyperfocal distance still relate to a 28 mm or should I treat it as a 42 mm?

Daniel Bridge

Link Posted 25/11/2006 - 19:33
Hi Hazza,

I think hyperfocal distance relates to the true focal length, so use the ones for the 28mm. I believe this is the reason that large format landscape work tends to be done at f/45 and using lens tilt - so that depth of field on the 100mm 'wide-angle' lenses is sufficient. I could be wrong though.

Best thing - try it and see. If it looks sharp enough, it is.



Link Posted 25/11/2006 - 20:21
The focal length of a lens remains the same, whether it is on a full frame film body or an APS-C sized digital body. The 42 mm is the equivalent field of view. So calculate your hyperfocal distance based on 28mm.
Tim the Ammonyte
K10D & sundry toys


Link Posted 26/11/2006 - 00:03
A 28mm lens remains a 28mm lens regardless of the format it is used on. What changes is the field of view.

As an example, a 24mm lens would be a standard on 110 format, a modest wide angle on a DSLR, an wide angle on 35mm and an incredible ultra wide angle on 6x6cm
Best regards, John


Link Posted 26/11/2006 - 00:34
The hyperfocal distance depends on the focal length, aperture and the "Circle of Confusion" value appropriate for the format in use (and the desired enargement size of the final print).

If you play with a DOF calculator (eg www.dofmaster.com) you will see what I mean.

Using a 28mm lens at f8 and using CoC values appropriate for small prints gives the following values for hyperfocal distance:

*istD (CoC 0.02mm): 4.93 m
35mm Film (CoC 0.03mm): 3.29 m

In other words, the 28mm on the *istD has a smaller depth of field for the same aperture (because the CoC is smaller) and so the hyperfocal distance is further away.



Link Posted 26/11/2006 - 08:16
Thanks guys, I think I've got it now, and thanks for the link Reuben.
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