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17 mm shows 19mm in EXIF on 17-40mm f4

Started Mar 17, 2019 | Discussions thread
BG454 Veteran Member • Posts: 7,345
Re: 17 mm shows 19mm in EXIF on 17-40mm f4

Interesting that this should come up again after such a long time.

At one time, in the days of APS-C, the 17-40 f4L was my only lens.
I just examined some of the images it created in On1 PhotoRAW2022.5. Using my Canon 30D there are definitely some images that show 17mm in the EXIF, so maybe it depends on either the camera or the EXIF reader to show the correct result.
I later used the same 17-40mm lens on my 6D Mk1 and examining the results shows images with 17mm as the focal length recorded in the EXIF.
The OP says he was reading the EXIF using Canon's DPP software, which I do not use. I can only say that displaying the EXIF using On1 shows focal lengths written as 17mm in the EXIF which appear to be correct.
Unfortunately, I have now sold the lens, so I am unable to carry out any further tests.
I never did find out how the actual EXIF information is generated, but since it is written to the memory card, I would assume it is genrated "in camera" but how the focal length is passed from the lens to the camera is outside of my knowledge.

I can only say that reading the focal length in On1 shows the correct focal length, and is not subject to this "19mm" limitation.

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