What exactly does Soft Proofing do?

From: "Greg"

I’d like to know exactly what soft proofing does.

1. Convert from the image space to the output space, using the rendering intent which the user selects

The soft proof is just an on-the-fly conversion, not an actual conversion (you’d need to do Image > Mode > Convert to Profile to actually convert the numbers in the file to the new numbers). Ideally this will let you preview *on your monitor* what the print will look like. In practice you need an excellent monitor profile and an accurate printer (or whatever) profile to get a decent match, but that’s what it’s trying to accomplish. Works pretty well for me.

Also, what exactly does the "simulate paper white" setting do?

The brightness range of your monitor is greater than that of paper. Setting this option basically dulls down the on-screen view (proof) by reducing the dynamic range (dims the whites and blacks) to better match the limited dynamic range of the paper compared to the monitor. One guru recommends turning your head or closing your eyes when you do this or else ‘it’s discouraging to watch your image die!’ (g)

Or, is it simply not possible to describe Photoshop’s soft proofing in a simplified manner like the above?

It’s pretty simple to describe … you just preview what the print will (hopefully) look like, based on the printer profile. The concept is ingeniously simple, the actual implementation is more or less accurate depending on the quality of your monitor and printer profiles.

Bill

"Bill Hilton" wrote in message

From: "Greg"

I’d like to know exactly what soft proofing does.

1. Convert from the image space to the output space, using the rendering intent which the user selects

The soft proof is just an on-the-fly conversion, not an actual conversion (you’d need to do Image > Mode > Convert to Profile to actually convert

the

numbers in the file to the new numbers).

Yes, I did actuall understand this already. That’s why I referred to the result of this conversion as an "intermediate" image.

I already understand (reasonably well, I think!) how to use soft proofing. I want to know how it *works*.

Are those two steps (which I listed in my original post) what Photoshop 7.01 actually does, to create the soft proof?
It may not be two seperate steps like that – Photoshop may do the *equivalent* in one step – that’s fine – I just want
to know how Photoshop actually creates the soft proof. I.e, what is Photoshop actually doing, under the hood, to create the soft proof.

Thanks,
Greg.

Greg wrote:

1. Convert from the image space to the output space, using the rendering intent which the user selects

Only if you pick Custom inside Proof Setup. If you pick say Working CMYK, the rendering intent from the document space to the proof space is dictated by the color settings (I mean Edit > Color Settings > Advanced Mode > Conversion Options.

2. Convert from this intermediate image, which is now in the output space, to the monitor space, using absolute rendering intent.

It only uses absolute rendering to the monitor if paper white is chosen, as far as I know. Otherwise the rendering intent to the monitor is relative colorimetric.

Also, what exactly does the "simulate paper white" setting do?

It tries to simulate how the colours are effected by the colour of the paper (it therefore requires accurate media profiles).

Does this change the rendering intent in step 2?

Yes.
When Paper White and Ink Black are turned off, you’ll get a relative colorimetric rendering from the proof space to the monitor. (It maps paper white to monitor white and ink black to monitor black).

If you turn Simulate: Ink Black on, black point compensation from the proof space to the monitor gets turned off, so the black on the monitor simulates the black of the final output.

When you turn Simulate: Paper White on, you’ll get an absolute rendering from the proof space to the monitor. That’ll give you "dull" colours on the monitor, as Bill Hilton describes, because Photoshop tries to simulate the dynamic range of the output on the monitor and the dynamic range of the output is often much smaller than the dynamic range of the monitor.

—
Regards
Madsen.

Thanks – that’s exactly what I wanted to know. I guess I should be able to do some simple
tests now to verify this.

Regards,
Greg.
"Thomas Madsen" wrote in message

Greg wrote:

1. Convert from the image space to the output space, using the rendering intent which the user selects

Only if you pick Custom inside Proof Setup. If you pick say Working CMYK, the rendering intent from the document space to the proof space is dictated by the color settings (I mean Edit > Color Settings > Advanced Mode > Conversion Options.

2. Convert from this intermediate image, which is now in the output space, to the monitor space, using absolute rendering intent.

It only uses absolute rendering to the monitor if paper white is chosen, as far as I know. Otherwise the rendering intent to the monitor is relative colorimetric.

Also, what exactly does the "simulate paper white" setting do?

It tries to simulate how the colours are effected by the colour of the paper (it therefore requires accurate media profiles).

Does this change the rendering intent in step 2?

Yes.
When Paper White and Ink Black are turned off, you’ll get a relative colorimetric rendering from the proof space to the monitor. (It maps paper white to monitor white and ink black to monitor black).

If you turn Simulate: Ink Black on, black point compensation from the proof space to the monitor gets turned off, so the black on the monitor simulates the black of the final output.
When you turn Simulate: Paper White on, you’ll get an absolute rendering from the proof space to the monitor. That’ll give you "dull" colours on the monitor, as Bill Hilton describes, because Photoshop tries to simulate the dynamic range of the output on the monitor and the dynamic range of the output is often much smaller than the dynamic range of the monitor.
—
Regards
Madsen.

Photoshop’s soft proofing doesn’t seem to be behaving as described.

I did the following test:

1. Calibrate monitor to D65, and profile with a profiler which creates traditional monitor profiles. (that is, with a media whitepoint that really does match the monitor’s whitepoint)
2. Open a greyscale wedge, and assign it the ColorMatch RGB profile
3. View | Proof Setup | Custom, select an RGB proof profile for my inkjet
printer. The profile has a whitepoint of 5223K. Proof intent = Perceptual, Simulate Paper White enabled

The appearance shifts in hue in the opposite direction to expected. That is, it shifts towards blue. Shouldn’t it shift towards
yellow? If I manually do a relative conversion from ColorMatch, to the printer profile, and then do an absolute conversion from the printer profile to my monitor profile, there is a strong shift to yellow.

I then tried a soft proof in Picture Window Pro 3.5, and it produced the expected result, albeit only when I configured it to use the Windows default CMM. Picture Window Pro now has the option to use the Little CMS CMM, but this CMM resulted in no shift in hue whatsoever. (just lovely – *three* different results! I have not yet contacted the PWP author about this discrepancy)

Greg.

Repeated the test, using sRGB for my monitor profile instead – same result.

Greg.
"Greg" wrote in message

Photoshop’s soft proofing doesn’t seem to be behaving as described.
I did the following test:

1. Calibrate monitor to D65, and profile with a profiler which creates traditional monitor profiles. (that is, with a media whitepoint that

really

does match the monitor’s whitepoint)
2. Open a greyscale wedge, and assign it the ColorMatch RGB profile
3. View | Proof Setup | Custom, select an RGB proof profile for my inkjet
printer. The profile has a whitepoint of 5223K. Proof intent = Perceptual, Simulate Paper White enabled

The appearance shifts in hue in the opposite direction to expected. That

is,

it shifts towards blue. Shouldn’t it shift towards
yellow? If I manually do a relative conversion from ColorMatch, to the printer profile, and then do an absolute conversion from the printer profile to my monitor profile, there is a strong shift to yellow.

I then tried a soft proof in Picture Window Pro 3.5, and it produced the expected result, albeit only when I configured it to use the Windows

default

CMM. Picture Window Pro now has the option to use the Little CMS CMM, but this CMM resulted in no shift in hue whatsoever. (just lovely – *three* different results! I have not yet contacted the PWP author about this discrepancy)

Greg.

"Greg" wrote in message

Photoshop’s soft proofing doesn’t seem to be behaving as described.
I did the following test:

1. Calibrate monitor to D65, and profile with a profiler which creates traditional monitor profiles. (that is, with a media whitepoint that

really

does match the monitor’s whitepoint)
2. Open a greyscale wedge, and assign it the ColorMatch RGB profile
3. View | Proof Setup | Custom, select an RGB proof profile for my inkjet
printer. The profile has a whitepoint of 5223K. Proof intent = Perceptual, Simulate Paper White enabled

The appearance shifts in hue in the opposite direction to expected. That

is,

it shifts towards blue. Shouldn’t it shift towards
yellow? If I manually do a relative conversion from ColorMatch, to the printer profile, and then do an absolute conversion from the printer profile to my monitor profile, there is a strong shift to yellow.

I then tried a soft proof in Picture Window Pro 3.5, and it produced the expected result, albeit only when I configured it to use the Windows

default

CMM. Picture Window Pro now has the option to use the Little CMS CMM, but this CMM resulted in no shift in hue whatsoever. (just lovely – *three* different results! I have not yet contacted the PWP author about this discrepancy)

Greg, the guys that could probably give you the best (and shortest) answer to this and some of your other more intricate CMS questions would be either Chris Cox (a PS engineer) or Bruce Fraser. Their respective e-mail addresses are: Keep it short
and give ’em time to respond, they’re busy…

Good luck.

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I’ve managed to convince myself that Photoshop is at least doing something sensical.

The whitepoint of the printer profile, being 5223K, means that the paper is slightly
bluer than the illuminant which was used to create the profile, which was D50 (5000K).

Perhaps Photoshop’s "simulate paper white" option means "if the paper were to be illuminated
by the monitor’s white, how would it look?". If the paper looked slightly bluer than D50 when
illuminated by D50, then it makes sense that it will also look slightly bluer than D65 if *illuminated*
by D65. If this is the case, then the steps I listed to manually achieve the same thing as a soft
proof with paper white were wrong, and I’m not sure how to tweak the procedure to match yet,
either.

Flycaster: thanks for the contacts.

Greg.

Greg wrote:

Photoshop’s soft proofing doesn’t seem to be behaving as described.

Hmm, if that’s true, then Real World Color Management and Real World Photoshop 7 are wrong too because that’s how they describe the Simulate: Ink Black and Simulate: Paper White function. 🙂

You can find some of it here:
<http://www.creativepro.com/story/feature/15310.html>.

Quote:
| When both Paper White and Ink Black are unchecked, Photoshop uses | Relative Colorimetric rendering with Black Point Compensation to | go from the simulation to your monitor. What that means in English | is that the paper white is mapped to your monitor’s white, and the | printer’s black is mapped to your monitor’s black. If you’re | printing to a bright glossy stock, this view is probably the most | accurate. But if you’re printing to a matte paper it may give you | an overly optimistic view…
|
| The Ink Black checkbox turns off black point compensation in the | rendering from the simulation to your monitor, and attempts to | show you the actual black that will appear in print. If you’re | simulating printing to a glossy paper, you’ll probably just see a | very slight lightening of the shadows. If you’re simulating | printing to watercolor paper, newsprint, or an uncoated stock that | produces relatively weak blacks, the shadows will likely lighten a | lot when you check Ink Black. This setting is useful for | fine-tuning shadow detail, particularly on stocks that produce | weaker blacks…
|
| The Paper White checkbox makes Photoshop do an Absolute | Colorimetric rendering from the simulation space to your monitor. | It attempts to show you the influence of the paper color and also | the true black (when you check Paper White, it automatically | checks, and dims, Ink Black). But to do that, it has to dim all | the colors to change the color of white, it has to reduce the | values in one or more of the channels that it sends to the | monitor, because the only way to change the color from RGB | 255,255,255 (your monitor’s white) is to turn something down. As | a result, your first reaction when checking paper white may be | that your image just died before your eyes. I’ve become accustomed | to looking away from the monitor when I check Paper White so that | I don’t see the change happen. This simple trick makes it a lot | easier to accept the paper color displayed on the monitor as a | true white.

—
Regards
Madsen.

"Thomas Madsen" wrote in message

Greg wrote:

Photoshop’s soft proofing doesn’t seem to be behaving as described.

Hmm, if that’s true, then Real World Color Management and Real World Photoshop 7 are wrong too because that’s how they describe the Simulate: Ink Black and Simulate: Paper White function. 🙂

Hmmmm. 🙂

All I can do is post my observations. 🙂 If I could have misconfigured something to cause the results I’ve
reported, please advise……

Greg.

Actually, Photoshop probably *is* doing the proofing in the way we described. It’s just
that we’ve left out this fine detail of the whitepoint shift to the monitor’s whitepoint. I’m really curious
to know whether this is the intended behaviour or not. I have a feeling, though, that there would be a lot of
users who would assume that no matter what temperature their monitor’s were calibrated/profiled to,
Photoshop would still show an accurate paper white soft proof , as viewed under D50.
It would be really great if the illuminant could be actually entered by the user, actually. At the moment,
it seems that the monitor simply has to be set to match the desired viewing lightsource.

Greg.

"Greg" wrote in message

"Thomas Madsen" wrote in message

Greg wrote:

Photoshop’s soft proofing doesn’t seem to be behaving as described.

Hmm, if that’s true, then Real World Color Management and Real World Photoshop 7 are wrong too because that’s how they describe the Simulate: Ink Black and Simulate: Paper White function. 🙂

Hmmmm. 🙂

All I can do is post my observations. 🙂 If I could have misconfigured something to cause the results I’ve
reported, please advise……

Greg.

Greg wrote:

Hmmmm. 🙂

🙂

All I can do is post my observations. 🙂

Of course.

If I could have misconfigured something to cause the results I’ve reported, please advise……

I agree with Flycaster. You’re so deep into that CMS thing, that the only one that can give you a correct answer is one of the programmers, or you could try Adobe’s color management forum. Many of the color management gurus often visit that forum (Bruce Fraser, Chris Murphy, Andrew Rodney and so forth. Chris Cox too).

<http://www.adobeforums.com/cgi-bin/webx?14@@.eea5b31>.

—
Regards
Madsen.

Greg wrote:

it seems that the monitor simply has to be set to match the desired viewing lightsource.

And I think it should. It doesn’t necessarily have to match the desired viewing light source exactly though. Actually, most people I know agrees that a monitor white point of around D65/6500K gives the best match to the printed image, although the viewing light box is set to D50/5000K, but why it is so, I don’t know. (Real World Photoshop 7 has a theory why it’s so, but it’s just a theory).

—
Regards
Madsen.

"Thomas Madsen" wrote in message
[snip]

<http://www.adobeforums.com/cgi-bin/webx?14@@.eea5b31>.

Excellent advice, something frankly I should have thought of. Ian Lyons is a regular poster there too, and if between all those guys Greg can’t get his answer, one probably doesn’t exist.

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"Thomas Madsen" wrote in message

And I think it should. It doesn’t necessarily have to match the desired viewing light source exactly though. Actually, most people I know agrees that a monitor white point of around D65/6500K gives the best match to the printed image, although the viewing light box is set to D50/5000K, but why it is so, I don’t know. (Real World Photoshop 7 has a theory why it’s so, but it’s just a theory).

That’s very interesting – I didn’t know that. I think I feel a headache coming on. 🙂

Greg.

"Greg" wrote in message

Flycaster: thanks for the contacts.

No problemo, and if you by chance find out something that may be of practical value to those of us who are "programming" challenged, let us know. 😉

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"Flycaster" wrote in message

"Greg" wrote in message

Flycaster: thanks for the contacts.

No problemo, and if you by chance find out something that may be of practical value to those of us who are "programming" challenged, let us know. 😉

I will, but this has nothing whatsoever to do with programming, in my opinion. (but everything
to do with colour management). I didn’t really think the issue we’re discussing in this thread
was all that "deep", in fact. I thought soft proofing was a fairly fundamental and important part of
Photoshop, and that there’d be many folks in this newsgroup that would have been able to set
me straight. 🙂

Greg.

Flycaster wrote:

Ian Lyons is a regular poster there too,

Yes he is.

and if between all those guys Greg can’t get his answer, one probably doesn’t exist.

I agree. 🙂

—
Regards
Madsen.

Greg wrote:

I think I feel a headache coming on. 🙂

LOL.
I know the feeling. Sometimes I feel like someone has tightened a leather belt around my forehead. When that feeling comes, it’s time to forget all about it and go to bed. 😉

—
Regards
Madsen.

I still haven’t received an answer to my question from the Adobe forum where I posted this, however,
my question has been answered for me as a result of some rather lengthy discussions with the ICC
about another issue.

Photoshop probably *is* doing an absolute intent conversion from the proof space back to the monitor space,
in the sense that the ICC define the term "ICC-absolute" colorimetry. The ICC consider a D50 white to be
"equivalent" to a D65 white, assuming that the viewer is adapted to each white, respectively, when viewing the
image. So, an ICC-absolute conversion from a D50 document to a D65 monitor will result in the D50 white
being translated to the D65 white. It will *not* appear yellowy on the D65 monitor. An ICC-absolute
conversion *does* maintain the media white (if different to the lightsource the viewer is adapted to), though, and Photoshop is correctly (or appears to be, anyway) producing the paper white on the monitor, *relative* to whatever the actual colour temperature of the monitor happens to be.

However, if one manually converts a D50 image to a D65 monitor profile, and selects absolute intent,
the appearance *will* be yellowy. So there is a discrepancy between a manual profile conversion, and
the absolute colorimetry Photoshop uses for proof profile to monitor profile conversion. Further complicating
this is that the ICC specification now mandates that monitor profiles always put D50 in as the media whitepoint
tag, regardless of the actual hardware whitepoint. The ICC are going to discuss all this in an upcoming meeting –
I’m told they’re going to make all this clearer in a future version of the spec, or even perhaps make some
changes.

Greg.

"Thomas Madsen" wrote in message

Flycaster wrote:

Ian Lyons is a regular poster there too,

Yes he is.

and if between all those guys Greg can’t get his answer, one probably doesn’t exist.

I agree. 🙂

—
Regards
Madsen.

Greg wrote:

I still haven’t received an answer to my question from the Adobe forum where I posted this [..]

No unfortunately not (I’ve watched it carefully but nothing seems to happen).

The ICC are going to discuss all this in an upcoming meeting – I’m told they’re going to make all this clearer in a future version of the spec, or even perhaps make some changes.

Thanks for the feedback.

—
Regards
Madsen.

Note that I haven’t forgotten about the direct contacts I was given. However,
the ICC contacted Adobe (and GretagMacbeth too) for me, and I don’t feel that
I need to email anyone from Adobe directly about this now. The ICC are actually
very approachable, and bent over backwards to help me and explain things to me.

Greg.
"Thomas Madsen" wrote in message

Greg wrote:

I still haven’t received an answer to my question from the Adobe forum where I posted this [..]

No unfortunately not (I’ve watched it carefully but nothing seems to happen).

The ICC are going to discuss all this in an upcoming meeting – I’m told they’re going to make all this clearer in a future version of the spec, or even perhaps make some changes.

Thanks for the feedback.

—
Regards
Madsen.