I print on a 9800 and generally I am very happy with the results, though going further into the technical side of softproofing and color matching it only gets more and more confusing and wanted to get some views.

I want to initially state that I use a screen calibrated every 120 hrs, using a white of 6500K with a gamma of 2.2 standard priority, my brightness consistent at 85cd/m2 with a varying black point of minimum - 0.4cd/m2. When softproofing I use custom icc profiles for the printer/paper in use. We can safely dispense with the "is your screen calibrated" tips thank you.

Where I am confused is the function of the Simulate Paper Color feature in Photoshops softproofing. I understand that it tries to simulate the dynamic range or contrast ratio of the paper profile loaded by adjusting the screen to match. The concept is easy to understand but the results displayed back to me dont really make much sense, let me explain..

If I am printing to a paper that has a contrast ratio of 225:1 and softproofing that paper on a screen that has say a minimum contrast ratio of 800:1, I will see a dramatic change when checking the Simulate Paper Color feature, yes makes perfect sense, the blacks and whites flatten out to bring it closer to the 225:1 contrast limit of the paper, right?

So why is it when, using a monitor with full control over the contrast ratio, setting my targets to 85cd/m2 for my white point and 0.4cd/m2 for my black, giving me the same contrast ratio of 225:1 I get the same contrast shift when checking the Simulate Paper Color feature. Shouldn't there be no change on screen when using Simulate Paper Color because I have matched the two.

I know the paper contrast ratio is not exactly 225:1 but have been assured its very close, Even when matching my screen I would expect to see some change on screen when checking Simulate Paper Color but its almost as if it does not matter what my screen contrast ratio is, 800:1 or 225:1 or 100:1 the Simulate Paper Color feature always displays back a dramatic and seemingly unchanging result..

My question is, is the Simulate Paper Color feature accurate and do people use it or should I trust my monitor and leave it off. Like I initially stated I am happy with the results of my prints but I just want to understand whats going on. I have this sickness where I need to understand why am I doing what I am doing :-)

Would love to hear some thoughts

Simulate Paper Color is not adjusting all the screen, just the photo you are working on.

So if you are enabling "Simulate Paper Color" after you adjust your screen to 225:1 contrast... it's like you apply a "paper simulation" 2 times

As a general rule, after you calibrate your monitor, you should not make any changes in terms of setting luminosity, contrast. You leave the changes for the icc profile you created that take takes control.

I wasn't using Simulate Paper Color back in the days when I was working for a certified Fogra print house.
We were editing the photos in cmyk mode and was pretty close to what was on paper. There will always be little differences. but not as dramatic as you say it is. The tools also have some tolerance levels.

I mean make sure you are not too picky... The human eye may see some big differences on certain colors. even at Delta E 4 which is still in standard.

We were using efi colorproof xf  and eye one to control the proof printers.  Efi colorproof xf  has also an option to create paper profiles, because paper used in offset printing is different that the paper used by epson or hp proof printers.

You could also send your spectrophotometer to a calibration. Once a year at least. So you have to calibrate the calibration device too

I don't remember exactly who did the spectrophotometer re-calibration, but was efi  or gretagmacbeth , one of them for sure.

You should use the option that gives the best match...
Lots of good  articles and videos at http://digitaldog.net/

Thanks for the input. I figured something like that was happening, so its fair to say the feature does not take into account the monitor and how its set up. I will be leaving it off now letting the monitor control the contrast.

Thanks for the link, will definitely look through those.