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sRGB and Soft-Proof Monitor


mattmatic 17 598
13 Jun 2005 1:52AM
A colour-management question that has me going round the bend!

When I convert to sRGB in Photoshop there is a huge difference when saving for web. It is the same difference when using the "Soft Proof" and selecting "Monitor". Can anyone explain this?

All my monitors are profiled using a Spyder Pro.

Here's some more background. Capture One shows the colours as I want. I pull the image into Photoshop CS and the image looks the same (as I'd expect). If I soft-proof for my dye-sub printer there is a small change of colour rendition, and using the colour managed output I get what I see from the printer. It may be partly down to the fact that the new laptop was profiled at D5000, gamma 1.8 (rather than D6500 gamma 2.2) - the colour rendition seems better (the backlight on the LCD is not very bright, and can't seem to "reach" D6500, or that's what I found in practise... but that was before I discovered the soft-proof issue.)

However, when saving for web the on screen image goes washed out (loss of saturation, increase in brightness, decrease of contrast). My last few portfolio images were done this way, and then I look back on the web (even on the same PC) and the result is washed out. The last image (the "Busy Busy Busy" ) I used Soft-Proof Monitor, then tweaked the sat and curves before Save For Web.

Now, what's even more strange is that on another PC there is hardly any difference between the non-proofed sRGB and the proofed one.

I'm confused! Can anyone shed any light on:
1) What are you looking at when not using Soft-Proof-Monitor?
2) When saving for Photobox (which is sRGB) do I trust what I see in the sRGB space within Photoshop, or do I have to get into soft-proofing again?

(More details can be provided)

Thanks!!
Matt
mattmatic 17 598
13 Jun 2005 3:57AM
Any clues?
philwig 16 817 1
13 Jun 2005 5:27AM
Ok, so images are good when viewed on this machine in Adobe PS, and these match your printer. Plus you used a machine to calibrate the system, so we're happy that those bits are working ok.

saving for web


Quote:When I convert to sRGB in Photoshop there is a huge difference when saving for web. It is the same difference when using the "Soft Proof" and selecting "Monitor". Can anyone explain this?


I don't know what your working colour space is. Often people use Adobe RGB, which as you'll know is a bit bigger than sRGB, so you may see a little change when conevrting. That said, it depends on your "rendering intent". What are you using? "Convert" is generally used to shift colour-spaces without affecting the image much - if you see changes here then it implies that your rendering intent is unhelpful, or you're shooting lots of out-of-target-gamut colours.

"rendering intent" is how you tell Photoshop what it should do in mapping from one space to another... it's going to have to squeeze (or stretch) that space somehow, and the rendering intents are different algorithms for this.



Quote:when saving for web the on screen image goes washed out (loss of saturation, increase in brightness, decrease of contrast).


This is usually what happens if you save (say) Adobe RGB images and look at them through a non-profile aware viewer like Internet Explorer. But above you mention that you're converting to sRGB before save for web. Are you sure you're doing this?


soft proofing


Quote:1) What are you looking at when not using Soft-Proof-Monitor?


I'm not sure that soft proofing to your monitor on your monitor makes a lot of sense, as something to do. If you're looking at an Adobe RGB file in PS, it's already transforming the thing..
PS interprets the file using embedded profile
PS chucks it at the video subsystem, which applies any monitor profile and that's what you see.

The clever bit with soft proofing is where it emulates a "foreign" profile on the monitor. I'm not sure how effective it really is, in practice. Most (modern toy) printers have wider gamuts than monitors, I'm told.

photobox


Quote:2) When saving for Photobox (which is sRGB) do I trust what I see in the sRGB space within Photoshop, or do I have to get into soft-proofing again?


The former I think. That's what I do and it works in practice as well as making sense (to me at least). There's a diagram with some of the transforms here although he doesn't cover soft proofing.

working space
Whilst there's a lot of talk about this stuff, if you only want to print to sRGB and view sRGB (eg Photobox and web respectively), then you could just shoot or raw convert in sRGB. You lose some flexibility in controlling how colours are mapped, but it's simpler and there's less scope for errors.
mattmatic 17 598
13 Jun 2005 6:18AM
Phil, thanks for taking the time to reply.

Yes, I am definitely converting to sRGB. What actually happens is that you see the image, fine in sRGB, then when I save for web even the preview window goes washed out (like a simultaneous gamma adjustment and saturation decrease).

If I saved as-is and sent to epz, it would look like that (in fact, my went like that).

Wondering what went on, I discovered that Soft Proof Monitor would produce the same result as the Save For Web window. And yes, I'm completely confused!!

I have been trying some other options this morning, and checking out [link=http://www.drycreekphoto.com]www.drycreekphoto.com
(some good profiling hints there). The online screen tests come out very well on the Toshiba LCD (good black point, zero posterisation and banding in the gamma check). So, I profiled again for D5000, gamma 2.2 - still the same issue. So I put it back to D5000 gamma 1.8 with the Spyder (not Spyder2 unfortunately).

I've checked the same thing on another machine, and the soft proof does give a difference, but only slight. Maybe you could try it on your monitor and see what difference there is?

BTW, generally my working colour space is AdobeRGB. If I'm working on a TIFF version of a RAW, I'll work with ProPhoto and 16-bit per channel. Of course, I'll always convert to sRGB before saving for web.

Thanks,
Matt
mattmatic 17 598
13 Jun 2005 6:24AM
Maybe there are problems with the Spyder (version one)?
When the Toshiba is proofing for Monitor (D5000/1.8), the results are similar to the desktop proofing for Macintosh (which I believe is 1.8 gamma).
However, if I calibrate the Toshiba as 2.2 (which is the Windows gamma), then I still have differences between the proof and the PS view.
On the desktop, comparing the Windows soft proof to the PS view shows a little saturation loss, but no great change.

I'm soooo confused at this stage, I'm going to have to do something else and come back to it! LOL!

Matt
mattmatic 17 598
14 Jun 2005 8:51AM
Ok. Here's what's going on Smile

Most PC monitors are somewhere around the sRGB colour space, and gamma 2.2 to 2.5. I say most, because not all are, and obviously this Toshiba M200 isn't...

When you select Soft Proof and select Monitor you are looking at the uncalibrated image. In fact, this is what you see in the Save For Web - yes, an uncalibrated version. Now, if the monitor is nearly sRGB, then you'll see very little difference (if any). However, if the monitor is not close to sRGB and 2.2 gamma, then things go completely off!

All web browsers (with the exception of Safari under Mac OS-X perhaps) do not respect the embedded ICC profile of JPG images. Now, whether my Tablet PC edition is correctly respecting the monitor profile is another matter... and I'm not so sure.

For the time being, at least, I'm soft proofing and tweaking before saving for the web, and that seems to get me close. Here are some useful links for calibration, in case you're interested:
www.aim-dtp.net
www.drycreekphoto.com

If anyone's got anything to add, I'd love to hear about it!
Matt
philwig 16 817 1
14 Jun 2005 9:15AM
Sounds like you're getting there, although I'm not sure I understand what you're seeing.

save for web
"save for web" always works fine for me... I think that what you see there is a file without a profile (it doesn't save a profile with it), on your monitor. My monitor's set-up to look pretty close to sRGB, so it's representative of what people will see, say, in IE. The image in "Save for web" should look the same as the same image would do on your machine in IE. So it's dependent upon your monitor set-up. So you should certainly see the same thing in both those places (that's kind of the point of course).

gamma
I haven't seen much in recent years about different monitor gammas. I'm not precisely sure if this is coded in the profile, but I think it should be. That is: I don't think you need to have both a gamma number (which is the gradient of the transfer function) as well as a profile - it's effectively in the profile. I will check this now.


Timo's site
The "AIM" site is a bit controversial to say the least.

The guy there (Timo?) has some very strange ideas regarding images and gamma functions which don't agree with my physics text books at least. I think he's confused. Google around and you'll find that site taken apart in some amusing ways.

Drycreek
The drycreek's a great concept, and I worried about it some way back. These days I use "photobox" and their sRGB is pretty accurate - if I remember correctly I couldn't get an indication from them at the time precisely which machines they might use, so I just went for sRGB.

Now, where did they put the ICC profile specification...
philwig 16 817 1
14 Jun 2005 9:21AM
... found it. Norman K has a summary of the ICC stuff here. From this:

Quote:All monitor profiles have gamma information in TRC tags[...]


TRC = Tone Reproduction Curve, part of the ICC standard.

If you're calibrating by eye or with a machine then you're taking the response of the monitor, including the gamma, into account.
mattmatic 17 598
14 Jun 2005 10:51PM
Thanks for the reply Phil.
I was pretty much aware of most of your points. It's such a shame I can't actually demonstrate what's going on. As I said, it only happens on this one PC, and I'm finding it hard to work out exactly what's going wrong.


Quote:"save for web" always works fine for me... I think that what you see there is a file without a profile

Well, as I said, in the SFW dialog it's the same as Soft-Proof and monitor. Pretty much all web browsers are ICC ignorant - they just throw it away and assume that the image is sRGB. Actually it doesn't matter whether the image hasw the profile embedded or not - the browsers display it the same, and so does the SFW window. I shouldn't have used the term "uncalibrated", because the ICC profile is calibrating the monitor, even for the web. But it's still strange that Photoshop's representation of sRGB is different from the monitor's....

I suppose the crux of the matter is that there is difference between my on-screen Photoshop view and Soft-Proof Monitor (which is why I see the differences in the browsers). As you say, and as I pointed out, on my desktops there is practically no difference when toggling the soft proof (with Ctrl-Y). On this Toshiba M200, even though it's been calibrated with a Spyder v1, there is a huge difference...

When I spoke of gamma, I meant the monitor's gamma. When you calibrate you specify what gamma and whitepoint you intend using (or simulating). If you calibrate your monitor and make the monitor profile gamma 1.8, then all the images appear lighter in the shadows. Conversely, if you set a higher gamma (say 2.8 - PhotoCAL only allows 1.8, 2.2, and 2.8 as selections), then the images are noticeably darker within the browsers.

The DryCreekPhoto site was interesting because they tested various calibration devices on several monitors. Unfortunately for me the Spyder v1 doesn't come out too brilliant, but I'm not in the position to just get another eye and software. I'll experiment with some of the Tosh's display settings (brightness etc) and recalibrated with the Spyder to see whether the PhotoCAL software is trying to over-compensate for something and producing a dud result.

Too many variables and such strange results! I can't believe I'm the first to find a difference, but it's hugely annoying!! Of course, I'll reply when I find out what on earth is going on. Smile

Matt
lobsterboy Plus
17 15.0k 13 United Kingdom
14 Jun 2005 11:27PM
Matt,

I'm not sure if this is any help or not but the colours on one of my monitors went completly out of wack and whatever proofing options I chose made no difference.

The culpret turned out to be a screen driver update that embeded a new profile on to the monitor. This seemed to overide everything. So take a look at your screen properties, colour tab and make sure the profile there is the one you are expecting it to use.

Just a thought.
Chris
mattmatic 17 598
15 Jun 2005 3:11AM
Thanks Chris. Yes, that was one of the first things I checked. Still cuckoo colour!

I've use PhotoCAL with various screen brightnesses. They all calibrate beautifully and the image is bang on every time with Photoshop. It's just outside of PS (and within SFW & SoftProofMonitor). Sigh! So utterly bizarre.

I'm trying OptiCAL now because that has more options available. So I'm trying to calibrate for gamma 2.2 and native white point. I'll see what happens.

BTW, the Toshiba M200 is a bit like the Wacom Cintiq in that there's a Wacom technology covering over the LCD. You use the pen directly onto the screen, which is really wonderful for Photoshop. However, maybe the coatings or something are messing up the calibration or something...

Matt
lobsterboy Plus
17 15.0k 13 United Kingdom
15 Jun 2005 3:31AM
If you create a profile for your monitor then convert your document to that colour space - do you still get the problem?

If you set a custom soft-proof to use this monitor profile does it occur?
brm 17 76
15 Jun 2005 3:56AM
Matt,

I think I may know why you're not seeing the change when you soft proof it in srgb

When you save for web PS doesn't use a rendering intent, instead it uses 'preserve colour numbers'. To correctly soft proof what it will look like select srgb & tick the 'preserve colour numbers' box - should give an accurate proof.

Incidentally, as far as I know all modern monitors have a native gamma of between 2 & 2.5 ish - the 1.8 gamma for Apple Macs comes from the old b&w monitors and the menus are still set up for that. At least that's what I've read anyway....

hope this helps.

b
mattmatic 17 598
16 Jun 2005 10:49PM
Thanks Chris & B,
Still not completely resolved, but here's some more info.
* I used OptiCAL which has more selections, plus the ability to graph the resulting profile. It even includes an sRGB target.
* Even if I lower the LCD brightness down to almost nothing and calibrate, the result in Photoshop is still calibrated - i.e. images have correct colour when compared with another monitor that's calibrated.
* I decided on D50 gamma 2.2, since most of my editing is done in subdued lighting.
* Even if I calibrate to "sRGB" within OptiCAL, I still get the same difference in the SFW
* Chris - as you suggested, converting to the monitor's profile and then saving yields absolutely no change in colour Smile
* B - you are absolutely right (see the above point)

However, if I save for web using this approach, what will everyone else see? If they see no change on their monitors when soft proofing (i.e. their monitors are actually sRGB outside of PS), then when they view my images they'll be "incorrect"... and that leaves Photobox too. Do I take my in-PS view as being correct, or the out-of-PS view??

Maybe I'll have to set up a controlled experiment.

Someone else suggested that maybe there's a profile conflict going on. However, I've checked in the monitor advanced settings, and the Spyder profile is the chosen, and only, profile for the monitor. I've checked for the latest video card drivers too, but still no difference (it's an NVidia GeForce FX Go5200).

It's still strange that my in-PS calibrated view is not the same as my out-of-PS calibrated view, especially if I profile for sRGB. Grrrr.

Matt
lobsterboy Plus
17 15.0k 13 United Kingdom
17 Jun 2005 12:20AM
Matt,

You have specified that your working space is set to AdobeRGB.

So that I make it when you open an SRGB document you are viewing an SRGB document converted to Adobe RGB. When you soft proof you are looking at SRGB converted to your monitor profile.

So I wonder if its your working colour space that is causing the problems?

Chris

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