Photoshop Colour Preserving Stretch

[MarkS]

Finally I've put a description of the Photoshop Colour Preserving Stretches (including the Arcsinh Stretch) on my website:
http://www.markshelley.co.uk/Astronomy/Processing/Colour_Preserving_Stretch/colour_preserving_stretch.html

Previous descriptions are scattered over various internet forums.  So now I've put it all together in one place where it can be easily updated.

Mark

[JohnP]

Very nice Mark - excellent work - If I ever..ever..ever get round to imaging again this is going to certainly be getting some good use - cheers,  John

[Carole]

Thanks Mark, booked marked.

Carole

[RobertM]

Very useful work Mark.  For those not aware, there are a number of very interesting threads on colour on the DPreview forum of which Mark has been a major contributor (technical content warning!).

Robert

[MarkS]

Very useful work Mark.  For those not aware, there are a number of very interesting threads on colour on the DPreview forum of which Mark has been a major contributor (technical content warning!).

Thanks Robert.  They'll be another argument thread starting on the DPReview Astrophotography section very soon.  I have almost finished writing up the results and conclusions of weeks of analysis into ACR/Photoshop/Lightroom.

Mark

[Carole]

Am I allowed to post this on this thread?

I found a very useful tutorial on my DVD from Adam Block on the use of lab colour when processing images in Photoshop.  I don't think many people know about this.  I have started using it as part of my workflow.

Carole

[MarkS]

Am I allowed to post this on this thread?

I found a very useful tutorial on my DVD from Adam Block on the use of lab colour when processing images in Photoshop.  I don't think many people know about this.  I have started using it as part of my workflow.

That's interesting.  You can do some interesting things in Lab.  Some time ago, I did try a few experiments in the Lab colour space and I also tried again just recently.  I was hoping it would be possible to apply a stretch to L whilst leaving a and b unchanged - this would then be a genuine colour preserving stretch.  But I didn't find a way to make it preserve colour.  That doesn't mean it's impossible.

Mark

[Carole]

I don't think Lab colour is for doing the initial stretch from linear, but it can great for enhancing colour at a later stage.  I used it to bring my star colours out recently.

I am having a problem stretching RGB combined as linear giving artifacts on some of the channels, if I stretch the individual colours separately before combining into RGB I don't get the artifacts which is annoying as it is stopping me using your arcsinh script on some occasions.

Carole