Image difference - dpx to jp2 conversion

[bl201212]

Hi all,

I'm attempting to compare the difference between two images:

the first (test.dpx.tiff) is a tiff converted from a 10-bit RGB log dpx file with the following command:

'convert.exe c:\test.dpx -set gamma 1.0 -set reference-black 95 -set reference-white 685 c:\test.dpx.tiff'

the second (test.jp2.tiff) is a tiff converted from a lossless lin jp2, which was made from the same 10-bit RGB dpx file with the following command:

'convert.exe c:\test.dpx -set gamma 1.0 -set reference-black 95 -set reference-white 685 define jp2:mode=int c:\test.jp2'
'convert.exe c:\test.jp2 c:\test.jp2.tiff'

What I'm trying to achieve is a comparison of the two tiff images, to tell me how accurate the conversion from log dpx to lin jp2 has been.

I've used 'compare test.dpx.tiff test.jp2.tiff difference.tiff' to create a difference image, and it certainly contains an image, which is a very bright, low-contrast version of the original.

Trouble is, if I use a compare command like 'compare -metric rmse c:\test.dpx.tiff c:\test.jp2.tiff c:\difference.tiff', the result is 0 (0). Same with 'compare -metric mae'...

I can see there's a difference in the difference image, and the filesize of one is slightly larger than the other, so I'm expecting to see some difference in the output of my compare command...am I going wrong here?

Here's the original dpx: https://docs.google.com/open?id=0B7BZz9 ... VRyYV9WS2s

Hope you can help!

AT.

[snibgo]

I downloaded the file and did the two conversions. I can see no visual difference between them. "compare" says there is no difference. Converting with "-compose Difference -composite" makes an entirely black image, which means there is no difference.