Match Reference Transform

[dvhirst]

Hello,

I'm looking at the Match Reference transform, and would like to know if there's any interest in / chance for use of additional reference sources, e.g., the IT8 multicolor reflective target or its new variant, which is becoming an ISO standard (ISO 12641-2 (candidate))? Thanks.

[jsachs]

If you are using an IT8, I recommend creating a custom profile instead (using Transformation/Create Profile) as this does a much better job of dealing with large numbers of color patches than Match Reference and can be used to accomplish the same result. I don't see much information online about ISO 12641-2 -- if you have any details, please email them to me (jsachs@dl-c.com).

For use in the field, I would recommend the ColorChecker SG since most IT8 targets are printed on glossy paper and reflections are a problem. The ColorCheckers are pigment based and mounted to a heavy cardboard backing that keeps them flat.

[dvhirst]

Jonathan,

Thanks for your reply and suggestion. For this instance, I'm working indoors with side lighting, so reflections mostly aren't a problem. Out of doors, I agree, a sturdy, non-reflective target is most useful.

DVHirst

[dvhirst]

I'm still trying to work with this transform, I've got an IT8 now, with reference file, but my photo setup is all taken apart. So, I'm left with several images of a Pre-2014 Color Checker, and my subject print. When I apply the Match Reference transform to the image of the CC, the result looks pretty close to what I'm seeing (Image 784.jpg).

Screen shot of CC images

Image 784.jpg (30.46 KiB) Viewed 2642 times

When I try the same transform with my print image, it is not good at all (Image 780.jpg).

Screen shot of print source and reference image / transform.

Image 780.jpg (33.56 KiB) Viewed 2642 times

Suggestions?

[jsachs]

The image of the colorchecker looks way overexposed, so the correction applied by Match Reference darkens the image which is what you are seeing.

It is important that the image of the colorchecker and the subject be taken under exactly the same conditions and that the exposure be such that neither the darkest or lightest patches of the colorchecker be clipped. You also have to make sure you process the image files exactly the same way and don't for example change the exposure for one of them and not the other during RAW development.

One way to do this is to set the exposure with a gray card, and then shoot the subject and then shoot the colorchecker with the same setup. Or, if you have a mini colorchecker, you can place it in the corner of the subject shot.