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
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
Thanks Mark, booked marked.
Carole
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
Quote from: 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!).
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
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
Quote from: 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.
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
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