Unexpected "FocusDistanceUpper/lower" values in EXIF, when compared to similar image exif values.

[GuidoB]

I have few images that are flagged for several issues and one of them is this data point extracted from EXIF info. 

Ask: To check if such values are realistically possible from a canon camera (not interested in theoretical possibility), considering all 3 images, whose sample exif is shared below, are very similar and allegedly taken from a moving flight. 

Do you have any examples of images with such values, if yes, please share the image that already existed in the public domain. 

MakerNotes:FocusDistanceUpper	6.01 m
MakerNotes:FocusDistanceLower	1.55 m

[johnrmoyer]

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@GuidoB wrote:

The values on your images make sense John. But when you get such values from similar looking cloud images from a flight, that's not acceptable optically speaking. 

Similar to how setting sun + cloud images have the following values- these values seem like they are taken from a different image and copied to cloud image with setting sun ( with sun not even visible in the image)

• EV value of 15
• Shutter speed 1/200 or 1/1000
• Aperture =8

You'd expect such values to come from a brightly lit images, but nope what we see is a dull orange tint clouds with one side slightly more orange due to setting sun. That's an optical anomaly. Mathematically yes the EV value for the shutter speed and Aperture makes sense, but once you know how to map these settings to the image, you know that's not expected. 

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That EF17-40mm f/4L USM lens was designed a very long time ago and the lens contains a primitive CPU which could not report many different values for focus distance. The focus motor could not step in such small increments as some newer designs. You might be expecting too much from such an old design.

These are the photos I made with that lens which were indexed by google when I put them on my web server. All will have Focus Distance from exiftool. https://www.google.com/search?q=EF17-40mm+f%2F4L+USM+site%3A.rsok.com&oq=EF17-40mm+f%2F4L+USM+site%3...

The focus distance reported by the lens is not a result of optics, but is a result of the cpu built into the lens, the ability of the focus motor in the lens, the focal length of the lens, the F Number, and some arbitrary assumptions about print size, viewing distance, and human vision.

The colors one gets from a raw image depend upon what white balance one chooses.

command line:

exiftool -s -LensModel -"focusdistance*" -"ISO" -"*measuredev*" -if '$LensModel eq "EF17-40mm f/4L USM" ' public_html/202[234][A-Z]*/*.jpg

A few of the results

======== public_html/2023Feb15_Wichita_Mntns_NWR/2023feb15_WichitaMountains_IMG_3236c.jpg
LensModel                       : EF17-40mm f/4L USM
FocusDistanceUpper              : inf
FocusDistanceLower              : 6.01 m
ISO                             : 125
MeasuredEV                      : 14.25
MeasuredEV2                     : 32.5
======== public_html/2023Feb15_Wichita_Mntns_NWR/2023feb15_WichitaMountains_IMG_3258c.jpg
LensModel                       : EF17-40mm f/4L USM
FocusDistanceUpper              : 1.55 m
FocusDistanceLower              : 0.94 m
ISO                             : 250
MeasuredEV                      : 13.50
MeasuredEV2                     : 29
======== public_html/2023Feb15_Wichita_Mntns_NWR/2023feb15_WichitaMountains_IMG_3261c.jpg
LensModel                       : EF17-40mm f/4L USM
FocusDistanceUpper              : 6.01 m
FocusDistanceLower              : 1.55 m
ISO                             : 250
MeasuredEV                      : 14.12
MeasuredEV2                     : 32.5
======== public_html/2023Feb15_Wichita_Mntns_NWR/2023feb15_WichitaMountains_IMG_3324c.jpg
LensModel                       : EF17-40mm f/4L USM
FocusDistanceUpper              : inf
FocusDistanceLower              : 6.01 m
ISO                             : 160
MeasuredEV                      : 14.50
MeasuredEV2                     : 33
======== public_html/2023Feb15_Wichita_Mntns_NWR/2023feb15_WichitaMountains_IMG_3329c.jpg
LensModel                       : EF17-40mm f/4L USM
FocusDistanceUpper              : inf
FocusDistanceLower              : 6.01 m
ISO                             : 200
MeasuredEV                      : 14.12
MeasuredEV2                     : 32.5
======== public_html/2023Feb15_Wichita_Mntns_NWR/2023feb15_WichitaMountains_IMG_3330c.jpg
LensModel                       : EF17-40mm f/4L USM
FocusDistanceUpper              : inf
FocusDistanceLower              : 6.01 m
ISO                             : 100
MeasuredEV                      : 14.88
MeasuredEV2                     : 36.5
======== public_html/2023Feb15_Wichita_Mntns_NWR/2023feb15_WichitaMountains_IMG_3341c.jpg
LensModel                       : EF17-40mm f/4L USM
FocusDistanceUpper              : inf
FocusDistanceLower              : 6.01 m
ISO                             : 100
MeasuredEV                      : 14.12
MeasuredEV2                     : 33
======== public_html/2023Feb15_Wichita_Mntns_NWR/2023feb15_WichitaMountains_IMG_3346c.jpg
LensModel                       : EF17-40mm f/4L USM
FocusDistanceUpper              : inf
FocusDistanceLower              : 6.01 m
ISO                             : 125
MeasuredEV                      : 14.25
MeasuredEV2                     : 34.5
======== public_html/2023Jan16_birds_and_cats/2023jan09_thunderbird_IMG_2403c2.jpg
LensModel                       : EF17-40mm f/4L USM
FocusDistanceUpper              : inf
FocusDistanceLower              : 6.01 m
ISO                             : 100
MeasuredEV                      : 14.50
MeasuredEV2                     : 34
======== public_html/2023Jan18_Salt_Plains_NWR/2023jan17_saltplains_IMG_2806c.jpg
LensModel                       : EF17-40mm f/4L USM
FocusDistanceUpper              : 6.01 m
FocusDistanceLower              : 1.55 m
ISO                             : 800
MeasuredEV                      : 13.88
MeasuredEV2                     : 31

[Peter]

@johnrmoyer, are there three tags for Focus Distance Upper?

[johnrmoyer]

Use "-a" option to exiftool to see duplicate tags