Hello Patrice, Wednesday, December 13, 2006, 12:23:41 AM, you wrote:
PLG> I've imagined a lengthy, but very accurate metaphor for this: PLG> Imagine you have a field of land. It is your color space. It contains PLG> flowers and trees (each of them is a different color). You want to PLG> measure the positions of these flowers and trees in this field (each PLG> position corresponds to a given color). You can do so by dividing the PLG> field in equal portions, marked by poles. You can't position a tree in PLG> the field in a better precision than the distance between two poles. The PLG> problem is that you only have a limited number of poles. PLG> Now you are given the choice between a smaller field (sRGB color space) PLG> and a larger field (ProPhoto). The smaller field is contained in the PLG> larger one, so there are trees that are in the larger field, but not in PLG> the smaller field (these are very saturated colors.) You want the larger PLG> field to get an image correctly measured if important parts of this PLG> image (a lot of the trees) are only in the larger field. PLG> But this comes at a price. As you still have the same amount of poles PLG> whichever field you choose (say 256x256), if the larger field is chosen, PLG> more land needs to be covered, then the poles will be planted wider PLG> apart from each other. You can measure more land, but with less precision. PLG> If you chose to map the larger field, but all your trees are in the PLG> smaller anyway, all you get, regarding YOUR trees, is a coarser precision. Thanks Patrice, that was a very good metaphor. PLG> Therefore, for an image with important detail in saturated colors PLG> (flowers?), consider working with a wide color space. If you're pretty PLG> sure your image only contains colors with lower saturation (portrait?), PLG> prefer a narrower color space and you'll have a better rendition of most PLG> of your image. PLG> Or, use not 256 poles in each direction, but 65536 (16 bit instead of 8) PLG> throughout your workflow, and use wide color space until the very last PLG> point. 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? 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. PLG> Just my 2 cents (a bit long, but these are Euro cents). Thank you Patrice, it is well worth it:) -- Attila -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
