Any Minolta/Sony users using UFRaw and GIMP?

On Fri, 18 Apr 2014 11:06:59 -0400, PeterN
wrote:

On 4/17/2014 8:32 PM, Eric Stevens wrote:
On Thu, 17 Apr 2014 18:15:50 -0400, nospam
wrote:

In article , Eric Stevens
wrote:

But
since you like quick and dirty processing, why don't you use the many
color curves in LAB. Ater all you can apply a curve into a channel in
LAB and get far more precise results than you can in ACR.

i don't like working in lab and do not find any advantage whatsoever,
both in results and workflow.

dan marguilis is one of the biggest proponents of the workflow, and
after reading his book, i was very unimpressed. it all can be done in
rgb just as easily and likely with better results because you skip two
conversions (which are not lossless).

But doesn't the Adobe color engine work in Lab anyway?

internally, but that's not the same as making a conversion of the image
twice.

What are the two conversions?


While it's rare that one can be certain what he's referring to: my vote
would be converting the image to LAB & back to RGB. Two or three quick
keystrokes in each direction.

As opposed to the following example where an RGB input is converted to
CMYK for output to a printer and back to RGB for review on a screen.
This requires numerous trips backwards and forwards through the Adobe
(Lab) colour engine.

RGB(source) -Lab (Adobe engine space) -CMYK(printer) - Lab
-RGB(screen).
--

Regards,

Eric Stevens

On 18 Apr 2014 11:01:46 GMT, Sandman wrote:

In article , Eric Stevens wrote:

Sandman:
Classic troll diversion. You have yet to tell us how
it is *evident* that:

1. It has improved his workflow 2. His workflow was previously
ineffective

Eric Stevens:
That nospam claims this is evident from his writings.

Sandman:
Classic unsubstantiated claim. Please quote nospam claiming that
his workflow was previously ineffective, please. Merely claiming
stuff won't get you anywhere.

Have you not noticed the paen of praise for the enormous effect
Light Room has had on his work flow emerging from nospam?

Dear me! Have just joined this thread?

You have yet to point to a quote from nospam saying his previous workflow
was ineffective. A tool making something more effective does not equate to
the former method being ineffective.

This a trick which you have tried several times already. Nospam issues
a cloud of statements, somebody eventually works out what he is trying
to say and summarises it in a single concise statement, you then
challenge them to tell you where nospam actually said that.

Well of course he didn't actually say that. The particular meaning
congealed from with a cloud of diffuse verbiage.

Apart from that, effective vs ineffective is a matter of relativity.
Further, the two points which you question are summaries which have
been put to nospam as questions. Neither of them has to be true: it's
up to nospam to choose.

Sandman:
I am. Making fun of trolls on usenet is something
I have time to do before we go out or at night when get
back.

Tony Cooper:
Take a break, then.

Sandman:
Why? I enjoy making you look like a fool.

Eric Stevens:
At the moment you seem to be rehearsing in front of a mirror.

Sandman:
Best endorsement I could get.

From your mirror?

From you.
--

Regards,

Eric Stevens

On Fri, 18 Apr 2014 08:36:28 -0400, nospam
wrote:

In article , Eric Stevens
wrote:

Classic troll diversion. You have yet to tell us how it is
*evident* that:

1. It has improved his workflow 2. His workflow was previously
ineffective

That nospam claims this is evident from his writings.

Classic unsubstantiated claim. Please quote nospam claiming that his
workflow was previously ineffective, please. Merely claiming stuff won't
get you anywhere.

Have you not noticed the paen of praise for the enormous effect Light
Room has had on his work flow emerging from nospam?

that doesn't mean what i did before was ineffective. that's nothing but
a straw man.

'Effectiveness' or 'ineffectiveness' is a matter of relativity.

before lightroom, my workflow was the best it could be at the time,
given what was available.

And compared with your post-Lightroom work flow it was relatively
ineffective.

after lightroom, my workflow became more productive.

I can accept that.
--

Regards,

Eric Stevens

In article , PeterN
wrote:

But doesn't the Adobe color engine work in Lab anyway?

internally, but that's not the same as making a conversion of the image
twice.

What are the two conversions?

While it's rare that one can be certain what he's referring to: my vote
would be converting the image to LAB & back to RGB. Two or three quick
keystrokes in each direction.

only an idiot would not understand what i'm referring to, and it has
nothing to do with the number of keystrokes either.

Only a newbie to thisgroup, or an idiot, would take you at face value.

One omre to my list.

which has nothing to do with the topic. diversion noted.

In article , PeterN
wrote:

katrin is also a *very* entertaining speaker.

I completely agree. However, I don't go to her lectures ot be
entertained. She is one of the most knowledgeable Photoshop artists and
lecturers around. I have gone to several of her PS lectures &
workshops, and learned something new at each one.

i didn't go to be entertained. i went to a session of hers at photoplus
some years back. that's also where i met martin evening too.

When your first comment about her presentations refers to entertainment,
you are doing a highly talented person a grave disservice.

nonsense. my first comment was a recommendation of her books.

you are as usual, wrong.

In article , PeterN
wrote:

What are the two conversions?

rgb-lab-rgb

But isn't that exactly what the colour engine has to do?

It gets fed an RGB file from outside, then converts it to Lab for it's
own processing and then converts it back to RGB for output to the
monitor. It may also convert it to CMYK for output to a printer or
saving it to a disc.
http://www.eizo.com/global/library/m...nt/cms/02e.jpg is the kind
of diagram commonly used to explain this.

it doesn't.

from "color management for photographers: hands on techniques for
photoshop users" by andrew rodney, page 53:

Editing in LAB: I have nothing against the LAB color model. However,
there are a group of people who feel that editing in LAB is the only
way to accomplish specific corrections, making it sound like a macho
editing space. It is true, there are a few correction techniques that
rely on a document being in LAB color space. The question becomes
whether its worth taking the time or worse, producing image
degradation to convert from a working space to LAB and back. Every
time a conversion to LAB is produced, the rounding errors and severe
gamut mismatch between the two spaces can account for data loss,
known as quantization errors. The amount of data loss depends on the
original gamut size and gamma of the working space.

...

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.

All of which is meaningless.simply put:
the LAB color space is larger than RGB. Conversion ot RGB is loseless.
Conversion from LAB to RGB may not be b looseness, but for pictorial
photography purposes, you will not notice any loss. Try it 10 times and
ost the results. Let the readers try it and see ifthey can see any
difference.

it's not meaningless and there is a loss in *either* direction.

you might not care but others do.

Most talented photographers I respect agree with my statement.

then they're not as talented as you think or they don't understand what
they're doing any more than you do.

andrew rodney, chris murphy, jeff schewe and bruce fraser, all of whom
are *very* well respected in the industry and have authored one or more
books on this very topic have commented on more than one occasion about
the drawbacks to a lab based workflow.

In article , PeterN
wrote:

It's not a color conversion. It's a conversion from one color space to
another.

make up your mind.

Write an unambiguous and accurate statement.

take your own advice.

you said it's not a conversion but it's a conversion. you haven't any
clue what you're talking about.

In article , Eric Stevens
wrote:

Fraser, Murphy and Bunting (Color Management) regard Lab as the work
horse of color management systems.

it is, but photoshop doesn't work the way you think it does.

Maybe so but you have yet to explain how you think it works and how
working inLab mode requires twice as many conversions as working in
RGB.

i quoted from andrew rodney's book which explained it.

Wikipedia http://en.wikipedia.org/wiki/Lab_color_space says

"Because Lab space is much larger than the gamut of computer
displays, printers, or even human vision, a bitmap image
represented as Lab requires more data per pixel to obtain the same
precision as an RGB or CMYK bitmap. In the 1990s, when computer
hardware and software were limited to storing and manipulating
mostly 8-bit/channel bitmaps, converting an RGB image to Lab and
back was a very lossy operation. With 16-bit/channel support now
common, the loss due to quantization is negligible."

But none of this explains why you think Lab requires extra color
conversions.

yes it does.

As above: please explain why.

the answer to that was given in what i quoted.

This is the third or fourth time of asking. I'm not trying to argue.
I'm trying to find out.

then read what was posted.

In article , Eric Stevens
wrote:

Classic troll diversion. You have yet to tell us how it is
*evident* that:

1. It has improved his workflow 2. His workflow was previously
ineffective

That nospam claims this is evident from his writings.

Classic unsubstantiated claim. Please quote nospam claiming that his
workflow was previously ineffective, please. Merely claiming stuff won't
get you anywhere.

Have you not noticed the paen of praise for the enormous effect Light
Room has had on his work flow emerging from nospam?

that doesn't mean what i did before was ineffective. that's nothing but
a straw man.

'Effectiveness' or 'ineffectiveness' is a matter of relativity.

given that lightroom didn't exist then, what i was doing was the most
effective workflow at the time.

before lightroom, my workflow was the best it could be at the time,
given what was available.

And compared with your post-Lightroom work flow it was relatively
ineffective.

however, at the time, there was no lightroom so that's not relevant.

what i did then would be ineffective now because there are much better
ways to do things.

in the future, lightroom may be considered to be a clunky and
inefficient workflow after something new comes along, but until that
happens, lightroom is about the best there is for the majority of
users.

after lightroom, my workflow became more productive.

I can accept that.

that's what i said originally.

On 4/18/2014 6:39 PM, Eric Stevens wrote:
On Fri, 18 Apr 2014 11:06:59 -0400, PeterN
wrote:

On 4/17/2014 8:32 PM, Eric Stevens wrote:
On Thu, 17 Apr 2014 18:15:50 -0400, nospam
wrote:

In article , Eric Stevens
wrote:

But
since you like quick and dirty processing, why don't you use the many
color curves in LAB. Ater all you can apply a curve into a channel in
LAB and get far more precise results than you can in ACR.

i don't like working in lab and do not find any advantage whatsoever,
both in results and workflow.

dan marguilis is one of the biggest proponents of the workflow, and
after reading his book, i was very unimpressed. it all can be done in
rgb just as easily and likely with better results because you skip two
conversions (which are not lossless).

But doesn't the Adobe color engine work in Lab anyway?

internally, but that's not the same as making a conversion of the image
twice.

What are the two conversions?


While it's rare that one can be certain what he's referring to: my vote
would be converting the image to LAB & back to RGB. Two or three quick
keystrokes in each direction.

As opposed to the following example where an RGB input is converted to
CMYK for output to a printer and back to RGB for review on a screen.
This requires numerous trips backwards and forwards through the Adobe
(Lab) colour engine.

RGB(source) -Lab (Adobe engine space) -CMYK(printer) - Lab
-RGB(screen).

I usually have only one round trip, two at the most.

--
PeterN