Skip to main content
news

Re: Is RGB to Lab lossy? -...

Eric Stevens
SubjectRe: Is RGB to Lab lossy? - was(Re: Lenses and sharpening)
FromEric Stevens
Date10/06/2014 10:35 (10/06/2014 21:35)
Message-ID<csk43a5ksgmeitftukl861detb599ksemg@4ax.com>
Client
Newsgroupsrec.photo.digital
Followsnospam
Followupsnospam (1d, 12h & 51m)

On Sun, 05 Oct 2014 21:05:21 -0400, nospam <nospam@nospam.invalid> wrote:

nospam
In article <s7h13a1fccm418skpdorc8ea5jvm4gm40j@4ax.com>, Eric Stevens <eric.stevens@sum.co.nz>wrote:

Eric Stevens
I couldn't see the difference at all, but then I didn't want to push the screen with excessive brightness. Instead I relied on the subtraction and the histogram to find the differences, which were almost zero.

nospam
'almost zero' is not zero.

you are actually proving my point.

Eric Stevens
nospam has backed off considerably from his original views but I expect that won't stop him from trumpeting them again in the future.

nospam
i have *not* done any such thing. stop lying and twisting what i say.

i have *always* said it's not lossless and it is not.

Eric Stevens
There is nothing you do in image processing which is not lossless.

nospam
straw man.

Not at all. If you are going to criticise conversions to Lab on the graonds that they incur losses, then you have to acknowledge that there are other things you can do in Photoshop which are equally lossy.

Eric Stevens
For some reason the conversion of RGB -->Lab has been particularly singled out for criticism in this respect.

nospam
it's a bad workflow because what can be done with an rgb->lab-rgb conversion can be done *without* the conversion and with better results.

'Bad' is a value judgement. Why should your value judgement be taken any more seriously than anyone elses?

this is a fact, no matter how much you or anyone else say otherwise.

Eric Stevens
It's as lossless as anything else you can do.

nospam
it's more lossy than not doing the conversions.

So is editing/retouching the image. --

Regards,

Eric Stevens

nospam (1d, 12h & 51m)