On 14/12/06, Boros Attila <[EMAIL PROTECTED]> wrote: > So there is really no silver bullet, and I should consider choosing a > color space based on what kind of image I'm working with, and what the > final output will be, and working with ProPhotoRGB in 16 bit is just a > safe bet. Then the final step will be to convert to sRGB before saving > for web. Can there be a loss of image detail/color when I perform such > a conversion?
This is what I've chosen to do (and so it seems a lot of other colour management aware photographers), if you start with too much you can always scale down but you can never get data back that's lost. The way the detail is transformed depends on the rendering intent applied during the CS conversion process, see my previous reply for a good reference. > Let's say I have an image which fits perfectly into sRGB. > > A.) > - I use ACR to open the image in Photoshop using ProphotoRGB. > - Apply levels, curves, sharpening etc. > - Convert to sRGB then save for web. > > B.) > - I use ACR to ipen the image in Photoshop using sRGB. > - Apply levels, curves, sharpening etc. > - No need to convert, this is already sRGB so just save for web. > > Assuming that in both cases I work in 16 bits/channel mode will there > be any differences between A.) and B.)? With other words, can > colorspace conversions lead to a loss of information? It would seem > that in B.) there is no color space conversion, it's sRGB all the way, > but there is a catch: the article says that ProPhotoRGB is Camera > Raw's native colour space. So if I get this right there will be a > conversion in both cases. ACR offers a choice of several colourspaces the widest of which is ProPhoto RGB and if the device profiles that I've seen for most of the current DSLRs are at all accurate even that doesn't quite accommodate all the colour gamut that these cameras are capable of recording. Colourspace conversion can alter data detrimentally, you have to be aware of the limitations of each colourspace and also how the rendering intent that's chosen will attempt to clip or compress the data that lies outside the new gamut plus there are other factors such as black point compensation. The bottom line is pretty simple though, if you can afford the file space to save 16 bit files and if your machine doesn't grind to a halt when editing 16 bit files you may as well convert and edit in the widest colourspace available. Then you can always convert to sRGB or any other smaller gamut CS for web or print, also reduce the bit depth after CS conversion not before. The following article is probably the best of read on colour managed workflows: COLOUR MANAGEMENT WORKSHOP NOTES 2005 Copyright Les Walkling 2005 Version 2005:6 http://media-arts.rmit.edu.au/Les_Walkling/Colour_Management_Notes.pdf#search=%22Epson%207600%22 -- Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://home.swiftdsl.com.au/~distudio//publications/ Pentax user since 1986, PDMLer since 1998 -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
