wrote:

Mike Russell wrote:

wrote:

In PS CS' Shadow/Highlight tool, how are the Black and White Clip % values defined? The tiniest change in these values can cause major changes in the shadow and highlight.

For example, to bring out shadow details and to keep highlight unchanged, I find that I have to reduce the White Clip value to .001% (smallest value). Any value above it would blow out the highlight to 255 and raise too much shadow, even if the Highlight amount is set to zero and the Shadow amount is minimized to 1.
Would appreciate some help. Thanks.

The new shadow/highlight tool does offer some exciting new possibilities for manipulating brightness information that was difficult to do previously, even with curves. The key seems to be the dynamic mask that is generated using the radius settings, which are unique to this tool.

What is a dynamic mask, and how do you generate one from this tool, and
how do you use it?

The mask is my own guess about how the internals of S/H operate. It is an integral part of the mathmatics, and AFAIK there is no way to use it outside of the command. You may be able to approximage the mask using a combination of gaussian blur and levels.

As for the thresholds - my advice is not to use them. They may be of interest if you wish to quickly clip shadow and highlight detail, but this job is best done manually. As jjs suggests, it is better done using curves.

I always lower the thresholds to reduce clipping, as in the Auto tools. I lower them from the default .01% to .001% in this case. My

question

is why would changing from .001% to .002% make such a drastic difference in the Shadow/Highlight tool.

I don't recommend clipping your highlights and shadows this way. It's too blunt a weapon to use on your images. Unless your time per image is very limited, it's much more effective to use curves to control your shadow and highlight explicitly, based on your chosen shadow and highlight areas The threshold numbers may well have a different significance for the Shadow/Highlight command.

As with any new tools in a new PS rev, none of the CS books go into any details about Shadow/Highlight. The authors are all too eager to rush their books to the market.

The publishers certainly are looking at the bottom line, and perhaps we can forgive them this. It's also true that Adobe has not, AFAIK, provided details. I would not be surprised if a patent is in the works. --

Mike Russell
www.curvemeister.com
www.geigy.2y.net

toomuch

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Shadow/Highlight tool question