Distance markings on MF lens should be converted for APS?

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Paul Furman - 26 Jan 2007 07:46 GMT

Should the distance markings on old MF lenses be converted for APS with
a 1.5x factor? I'm guessing not, just the DOF markings need to be
re-thought.

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Colin_D - 26 Jan 2007 10:10 GMT

> Should the distance markings on old MF lenses be converted for APS with
> a 1.5x factor? I'm guessing not, just the DOF markings need to be
> re-thought.

Distance markers are a function of the lens, nothing to do with the
camera format. DoF markers may be not optimal for cropped sensor, but
won't be that far off.

Colin D.

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Philip Homburg - 26 Jan 2007 13:38 GMT

>> Should the distance markings on old MF lenses be converted for APS with
>> a 1.5x factor? I'm guessing not, just the DOF markings need to be
[quoted text clipped - 3 lines]
>camera format. DoF markers may be not optimal for cropped sensor, but
>won't be that far off.

They are one stop off.

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Charles Gillen - 26 Jan 2007 23:20 GMT

> They are one stop off.

Fairly precisely. Example: To shoot on a DSLR with a manual lens set at
F/11, proper hyperfocal distance and correct depth of field reading is
obtained if you set the infinity mark against F/8, NOT F/11. This rule of
thumb has been validated by DOF charts for 35mm re-calculated with a
smaller circle of confusion appropriate for our digital sensors.

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Prometheus - 27 Jan 2007 01:19 GMT

>> Should the distance markings on old MF lenses be converted for APS
>>with a 1.5x factor? I'm guessing not, just the DOF markings need to
>>be re-thought.
>
>Distance markers are a function of the lens, nothing to do with the
>camera format.

True, the focal distance is not dependent on the size of the sensitive
material, only its distance behind it and the focal length.

>DoF markers may be not optimal for cropped sensor, but won't be that
>far off.

I don't think the sensor has been cropped, would a cropped sensor still
work? Anyone willing to cut their sensor up?

The DoF marks on a lens assume that you will enlarge the image by a
certain amount and view it at a specific distance, doing anything else
can make them wrong. You should be aware that they are a guide based on
an assumption which can vary between manufactures of comparable
products.

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Skip - 26 Jan 2007 12:47 GMT

> Should the distance markings on old MF lenses be converted for APS with a
> 1.5x factor? I'm guessing not, just the DOF markings need to be
> re-thought.

The distance from "film" plane to subject remain the same, no matter the
format.

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Skip Middleton
www.shadowcatcherimagery.com
www.pbase.com/skipm

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Alan Browne - 28 Jan 2007 19:18 GMT

> Should the distance markings on old MF lenses be converted for APS with
> a 1.5x factor? I'm guessing not, just the DOF markings need to be
> re-thought.

Since the markings apply to a specific reproduction size of the image
(nominally a print at 8x10), they've always been for guidance in the
first place.

Just close 1 stop and you'll be very close to what the lens marking
suggests, at least for a 8x10 print. (I say close 1 stop as the
magnification factor is higher as the crop FL "multiplyer" grows...).

Alan

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