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pierrot
9th of May 2005 (Mon), 02:53
I'm a little bit confused by the data I can read from the EXIF files produced by my 20d.

Using the same lens, sometimes the shooting distance is mentioned and sometimes not. As far as I've seen till now, this happens with any lens, be it Canon or 3rd party.

I can't figure out the reason why. Or I didn't made enough cross-testing to isolate the parameter which is responsible for these discrepancies.

Is it the program preset (Auto/P/Av/Tv/M)? Is it a bug in the firmware?

Does anyone have the same problem? :rolleyes:
lancea
9th of May 2005 (Mon), 02:59
I've never noticed a distance, and just checked some shots. What's the name of the EXIF label?
Longwatcher
9th of May 2005 (Mon), 07:15
Just for information:
The distance to focal point information is one of the fields that I seem to remember Canon has encrypted/encoded (whichever) and thus not all programs can see that data field, which is why some people see and some don't.

As to some lenses
Found this on
http://www.bobatkins.com/photography/eosfaq/ettl2.html
"In general, if a lens uses a ring type USM motor, it returns distance information and so is E-TTL II compatible. Not all USM lenses use ring USM motors. Those which do not offer full time manual focus ( e.g. the Canon EF75-300/4-5.6 USM), do not return distance information. Lenses using AFM (arc form motors) do not return distance information (e.g. 50/1.8, 24/2.8).

Notable lenses which you might think would return distance info but don't are the 50/1.4 USM and the 85/1.2L USM. The tilt-shift (T/S) lenses are manual focus, and so of course do not supply distance information.

Non-current lenses which should return distance info include the non-IS telephoto lenses such as the EF 500/4.5L USM, 300/2.8L USM, 600/4L USM "

from
http://www.canonusa.com/templatedata/pressrelease/20040819_eos_20d.html
"by considering the distance information data provided from compatible EF lenses."

So apparently only some lenses can provide distance data.

I could not find a list specifically mentioning which could and which could not provide distance information. Bob Atkins page listed those with ring type USM, but as mentioned not all provide distance info.

Just my memory and research,