Every time I think I understand colourspace conversions (or something else to do with digital capture), someone on the list shatters my illusions! Learning new things is one of the great benefits of PDML.
Thanks for posting that explanation, Godfrey. Cheers Brian ++++++++++++++++++++++++++++++++++ Brian Walters Western Sydney Australia http://members.westnet.com.au/brianwal/SL/ On Wed, 09 Jul 2008 11:52:04 -0700, "Godfrey DiGiorgi" <[EMAIL PROTECTED]> said: > There's no mystery to it other than that you need to understand > colorspaces better. > > ProPhoto RGB describes a much larger color gamut than Adobe RGB or > sRGB. If you have subtle colors in ProPhoto RGB and they disappear > when you convert to sRGB or Adobe RGB, they've been clipped as they > cannot be represented in the target colorspace. Once clipped, they > cannot be recovered by converting back to the larger colorspace ... > the data has been lost, you need to go to the original file to > retrieve them. You might try different rendering intents ... Relative > Colorimetric basically moves all 'out of bound' colors to the limits > of a particular colorspace where Perceptual attempts to translate all > colors into the target colorspace as best can be arranged. > > Here's a way to see what's going on: convert a RAW file to a > [EMAIL PROTECTED], ProPhoto RGB file and open it in Photoshop. Have the > Histogram palette open, full RGB display. Then convert the colors to > the Adobe RGB profile with Relative Colorimetic intent ... toggle the > action with the "undo" command a couple of times and watch the > histograms. You'll see where the clipping is. Do the same with the > Perceptual intent. Once you see where the clipping is, go back to the > ProPhoto RGB rendering and adjust the color rendering to move values > in those areas back into the "safe" zone. Then you can convert to a > smaller profile with greater ease. > > (When you're working with a printer output profile, you can do the > same thing using the proofing setup and even turn on gamut warning > flags, but I don't recall that Photoshop 7 has these features. I have > PS CS2.) > > Godfrey > > > On Jul 9, 2008, at 11:18 AM, P. J. Alling wrote: > > > Raw Shooter Essentials, it's much better looking, without any > > Photoshop > > work before export as a TIKF. I recently started using ProPhoto color > > space in my work flow which seems to give better results, if I > > remember > > to convert the profile in Photoshop before output, so I changed > > back to > > the Adobe RGB profile and it made no difference. The last set of > > fireworks I processed, some time ago looked exactly the same when > > imported into Photoshop after conversion. > > > > http://home.earthlink.net/~morephotos/fireworks/PESO_-- > > _fireworks1a.html > > > > It's really quite annoying. > > > > David J Brooks wrote: > >> I like the pattern of the blast, very good. > >> > >> What do you convert with.? > >> > >> Dave > >> -- -- http://www.fastmail.fm - IMAP accessible web-mail -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
