Google| Subject | Re: Any Minolta/Sony users using UFRaw and GIMP? |
| From | nospam |
| Date | 04/19/2014 15:59 (04/19/2014 09:59) |
| Message-ID | <190420140959305715%nospam@nospam.invalid> |
| Client | |
| Newsgroups | rec.photo.digital |
| Follows | Eric Stevens |
| Followups | Alan Browne (41m) > nospam Eric Stevens (10h & 49m) > nospam Alan Browne (1d, 3h & 42m) > nospam |
In article <j0l3l9hp5d82kr0djjqinnghltbn07uo98@4ax.com>, Eric Stevens <eric.stevens@sum.co.nz>wrote:
Eric Stevensagain:
My questions are intended to learn why you think working in Lab mode requires making a conversion twice. Your quotation above doesn't address that question at all and certainly it doesn't explain why you think converting an image to Lab mode in PS needs twice as many conversions as leaving it in RGB. After all, PS processes the image in Lab mode. All the conversion to Lab mode actually does is give the user a set of controls which work more directly on the color engine.
Some users are under the impression that Photoshop does all its conversions to and from LAB, converting on-the-fly. this is untrue as it would greatly slow down performance. Instead, Photoshop uses LAB as a reference when conducting many operations. Photoshop is not actually converting pixel data between color spaces unless you, the user, actually ask for this. None of these issues should be interpreted as implying that a conversion from working space to LAB is bad. Just be aware of the issues involved with this kind of conversion and whenever possible, try to use similar techniques that can be conducted in the RGB working space.
in other words, if you convert to lab and back, there are two conversions that otherwise would not have been done.
the conversions are also not lossless, something which is trivial to prove. make the conversion and subtract from the original. if they're identical, the result will be zero, which it definitely is not, and on an image i randomly picked, it's noticeable without subtracting.
04/05/2014-
