High ISO support

[Richard447]

I have a Pentax K3 III, and once the files ISO exceeds 65535 the EXIF data then only shows 65535.  Is there anywhere else that it will show the correct ISO?

[Dan C]

Hi @Richard447,

Welcome to the Affinity Forums 

I can confirm the Affinity apps certainly should show the ISO as taken on the camera - though I haven't personally been able to find a sample RAW file from this model with such a high ISO set.

Could you please provide a sample RAW file to the below link for me, so that I can test this here and report the issue to our developers as required?

https://www.dropbox.com/request/6n4a10DZ4H5jO5qyNWWZ

Once uploaded, please reply here to let me know. Many thanks in advance!

[David in Яuislip]

15 hours ago, Dan C said:

I haven't personally been able to find a sample RAW file from this model with such a high ISO set.

Neither have I, however here's a link to an iso 819200 jpg
https://www.amateurphotographer.co.uk/wp-content/uploads/2021/08/ISO819200-Pentax_K3_Mark_III-acr
.jpg
I've split it into two lines so the picture doesn't show here
Exiftool shows this

Software                        : Adobe Photoshop Camera Raw 13.3 (Macintosh)
Make                            : RICOH IMAGING COMPANY, LTD.
Camera Model Name               : PENTAX K-3 Mark III
ISO                             : 65535
Sensitivity Type                : Standard Output Sensitivity
Standard Output Sensitivity     : 819200

and Affinity Photo shows the same

Also see here
https://photofocus.com/reviews/pentax-k-3-mark-iii-a-superb-dslr-that-simply-costs-too-much/#h-high-iso-performance

"Editor’s note: For reasons unknown to us, anything above ISO 51,200 displays as ISO 65,353 in the EXIF data)."

There is some clever stuff here https://exiv2.org/tags-xmp-exifEX.html
which I might understand after more coffee but at first glance it looks like Ricoh/Pentax has dropped a clanger

[NotMyFault]

The exif tag for iso speed is encoded as SHORT 16bit, maximum value 65536.

https://www.iso.org/standard/73758.html
pay 119 CHF to get access to iso standard 12232:2019 where you can learn the exact details,

Some more hints: according to

https://developer.adobe.com/xmp/docs/XMPNamespaces/exif/

exif:ISOSpeedRatings

EXIF tag 34855, 0x8827. ISO Speed and ISO Latitude of the input device as specified in ISO 12232. A native Exif ISO value of exactly 65535 indicates an ISO value of above 64K, which cannot be stored in the native Exif Tag 34855. The real value should be stored in the XMP

[Dan C]

Many thanks both for the info provided, this is certainly helpful!

I've spoken with our devs here and we believe we should be able to add support to parse this information in the future - so I'm getting this logged with our devs now

[Tom Lachecki]

An ISO number can be given on a number of different scales, ISO Speed being one and Standard Output Sensitivity being another.

If a high ISO Speed were found in the XMP (working around the upper bound for the field in EXIF data) we would be able to report it.

So for the most part I think we're showing the correct values in the correct place here, except that we could hide the out-of-bounds, placeholder ISO Speed value of 65535.

[v_kyr]

On 3/7/2022 at 12:11 PM, NotMyFault said:

The exif tag for iso speed is encoded as SHORT 16bit, maximum value 65536.

Make that 65535, since 2¹⁶-1 = 65535.

Further in all prog languages a primitive data type like "unsigned short int"  is usually defined as a max like (USHRT_MAX  65535), which we can for example quickly tryout/test in C ...

#include <stdio.h>
#include <limits.h>

int main() {
   printf("The maximum value of UNSIGNED SHORT INT = %d\n", USHRT_MAX); 
   
   return(0);
}
----------------------
> cc -o test test.c
> ./test
The maximum value of UNSIGNED SHORT INT = 65535

 

Sounds pedantic I know, LOL!

[Affinity Info Bot]

The issue "ISO Value from EXIF data is capped at 65536" (REF: AFP-4990) has now been fixed by the developers.
This fix is included in build 2.1.0.1709 (or later) which is already available as a customer beta and will be included in the next release.
Customer beta builds are announced here and you can participate by following these instructions.

If you still experience this problem once you are using that build version (or later) please make a new thread referencing this one.