Why difference in settings in EXIF data ?

hi gang

trying to understand why when I look at the EXIF data for an image
that's its giving 2 sets of info ......

Camera Model: Canon EOS 5D Mark III
Exposure Time: 1/125
Shutter Speed: 1/128.00
F-stop: f/10.0
Focal Length: 65.00
Exposure Bias: 0
Exposure Program: Manual
Metering Mode: Pattern
Flash Fired: True
White Balance: 0
Aperture: 6.63
exif:ISO 100

note the
exposure Vs shutter speed
F-stop Vs Aperture

Any thoughts ... is there a fault in the camera and the way its storing info for an image ? or ??

regards
Dave

Davenn wrote in post #16643255
Shutter Speed: 1/128.00
F-stop: f/10.0
Focal Length: 65.00

What software are you using? These values are actually stored as rational numbers, not decimal.

EXIF actually stores this in an obscure unit called APEX, which is not the same as f-stop. It looks like the program has served up the raw APEX number without converting it back to f-number.

More software flakiness.

The camera is fine, the software is not.

Hi melcat

Thanks for responding

OK before I responded to your comments I had to check something ....
I checked the image in "Digital Photo Professional" ( which is bundled with the 5D III)
and this is what it gave as shown below ....

The original info that I referred to in the OP is what came from ThumbsPlus V9 ( June 2013)

So As long as I know all is OK with the camera, in future I will always just post the data from Digital Photo Professional

cheers
Dave

A difference of 0.0001875 is what you are worried about? Worry about world peace, global warming, hunger, etc.

no not worried, you misunderstand

just curious as to why one graphics program was giving 2 sets of information for the same image

see first post

cheers
Dave

OK, I hadn't picked up on the 1/125 vs. 1/128 difference. It is probably, and traditionally, actually 1/128s even though the camera says 1/125. Those powers of two must have been considered scary back when the shutter speed scale was standardized; back then it was also clockwork so the error was greater than the difference.

APEX 6.64 = f/10, so that's also close.

There are two sets of values stored, one set as APEX and one as seconds and f-number. The APEX value for shutter speed is called "ShutterSpeedValue" so odds on that's the one presented as "1/128.". I suspect - and have read - the APEX values are the actual values and the others the nominal, but don't have time to check that right now.

^^^ True.
If you start at 1 second, differences of one stop are:
1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/128, 1/256, 1/512, 1/1024, 1/2048, 1/4096, 1/8192. The lcd speed display could show those numbers, no problem, but aesthetically it's just not neat and tidy, so from 1/16 they start rounding it off - 15, 30, 60, 125, etc.

thanks for the explanations guys

appreciated, never heard of the APEX units before ... we live and learn

cheers
Dave