On 2015-03-24 07:14:54 +0000, Eric Stevens said:

On Mon, 23 Mar 2015 21:22:53 -0700, Savageduck
wrote:

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I would anticipate changes between "Perceptual" and "Relative"
especially in that Perceptual "may change out-of-gamut colors", and
Relative "will clip out-of-gamut colors". In your particular example I
would expect to find that difference in the sky.

Quoting from Jeff Schewe:

"Perceptual Intent either compresses or expands the full gamut of
the color data from the source profile to fit the destination
profile. Gray balance is usually preserved, but colorimetric
accuracy is not preserved because Perceptual rendering generally
requires a shift of all colors away from colorimetric accuracy. The
Perceptual Intent usually includes contrast enhancing distortions
to the L* values and may also include saturation or chroma
enhancing distortions. The general goal is to produce an output
rendering where the color relationships are maintained and is
pleasing to the viewer, and colorimetric accuracy is sacrificed to
achieve that goal. Using a Perceptual rendering alters colors that
are already in the destination profile's gamut to maintain the
perceptual color relationships. Extensive research has been done in
the pursuit of optimization of Perceptual rendering algorithms, and
most companies treat these algorithms as trade secrets. The ICC has
few restrictions on the Perceptual Intent to allow companies the
freedom to implement their proprietary algorithms. As a result,
there is wide variation in the results of Perceptual Intents from
different vendors using some pretty exotic algorithms to adapt and
maintain the color appearance."

So, taking all of that into account, a valid question is "do PS and LR
both use the same algorithms?"

To give you the simple answer; I dont know.

Neither do I, but there is no reason why we should assume they are the
same.

Most importantly, did you have the printer handle color management in
both, or did you have "Photoshop Manages Colors" + appropriate icc
profile, and "Other" with an icc profile selected in LR?
...or did you have different color management in PS and LR?

Tsk tsk. Of _course_ I had PS and LR respectively manage colour. I
used the same paper and the same profile in both.

OK! I was just checking.

I never have the printer manage color in either PS or LR and I will use
a matching icc profile.
Also remember to have color management turned off in the printer
settings in both PS & LR.

Then in the LR print module you have a print adjustment option for
adjusting brightness and contrast in the print. None of these
adjustments are previewed in LR and will only be revealed in test
prints.

Didn't touch it.

You might want to.

Eraly on, I did touch them, but all they did was increase the
differences. I didn't touch them for the four prints.

OK! However, if you are going to use LR to produce your final prints
you might want to tweak those adjustments a tad, and for future
reference save that configuration as a preset.

As to using "Perceptual" or "Relative", that need is going to be
determined by the character of the print and your intent.

Which is why I now think that no firm advice should be given as to
which one is the correct one to use.

Color spaces: with LR, the working color space is Melissa RGB. This is
basicly ProPhoto with a special gamma curve.

Why? I use straight out of the package ProPhoto RGB.

You use ProPhoto. LR uses Melissa. There is obviously a conversion
involved. Re Melissa, see
http://ptgmedia.pearsoncmg.com/imprint_downloads/peachpit/peachpit/lightroom4/pdf_files/LightroomRGB_Space.pdf

or http://tinyurl.com/lk2jmlh

That was interesting information, of which I was previously ignorant. I
have not read anywhere else that there was a different variety of
ProPhoto RGD specifically for use by LR.

Whatever it is, it was
converted to Epson's Pro38 PGPP for printing.

...and another colorspace change? To what purpose?
I can see assigning the appropriate icc profile, but changing color
space twice in midstream is something else.

Converted to Pro38 PGPP because that is the profile for the Pro 3800
printer using Premium Glossy Photo Paper.

So, Epson Pro38 PGPP isn't an obscure colorspace, but a paper/printer
profile. The way you phrased that sentence above led me to believe that
it was a another colorspace, since adding a profile to the mix, doesn't
change/convert the colorspace. It is not an Epson profile I am familiar
with.

In PS, it was ProPhoto RGB converted to sRGB (for screen). I wonder if
this difference is enough to explain my print results?

If you are going to demand consistent print renditions the least you
could do is be consistent with colorspace , paper, and icc profile. So
the print settings were not the same for LR, or PS.

Now that sounds as if that is your LR - PS inconsistency.

I have no control over this: it's LR and PS which require these
things. I have some more thoughts. I will see what happens and report
back.

I wouldn't have gone from ProPhoto RGB in PS to sRGB, regardless if it
was for screen. These days I do very little printing from PS as all the
finished work ends up back in LR as a TIFF, or PSD retaining the
ProPhoto RGB colorspace. All prints are made from those, or virtual
copies of LR adjusted RAW files.
I only create JPEGs in sRGB when I export for sharing using the LR
export dialog.


--
Regards,

Savageduck