FocusDistanceUpper/FocusDistanceLower

[pengler]

Hi

I'm trying to read out FocusDistanceUpper/FocusDistanceLower on a Canon EOS 5D Mark II with an EF 50mm f/2.5 Macro lens attached and get always 0. Other combinations with the same camera (e.g. with an EF70-200mm f/4L USM attached) seems to work perfect.

Has somebody any idea what's going wrong? Is maybe the EF 50mm f/2.5 Macro lens faulty because other cameras show the same result.

Thanks for support.

[Phil Harvey]

It seems that these numbers aren't written for all lenses.

I have 5DmkII samples with 4 different 50mm lenses.  Of these, pictures with the Canon EF 50mm f/1.2L and Sigma 50mm f/2.8 EX (which has the same LensType number as your Canon EF 50mm f/2.5 Macro) have these values written properly, but pictures with the Canon EF 50mm f/1.4 USM and Carl Zeiss Planar T* 50mm f/1.4 do not.  I can't say why.

But I wouldn't lose too much sleep over this.  I don't think these numbers are very accurate anyway.

- Phil

[pengler]

Hi Phil,

Thanks for your reply. At least I know now that there is no mistake in our maker note reader nor that the lens is faulty.

- Peter

[sjs]

It seems that these numbers aren't written for all lenses. [...] I can't say why.

That's simply because not all Canon lenses report distance information to the camera body. Check the lists at http://www.bobatkins.com/photography/eflenses/lens_list.php or http://canon-eos.serveblog.net/geraet/index.htm and note the "E-TTL II support" information. (E-TTL II relies - among other things - on the focusing distance information to compute the appropriate flash power.)


Regards,

Sebastian

[Phil Harvey]

That's simply because not all Canon lenses report distance information to the camera body.

Makes perfect sense.

- Phil