Photoshop Soft Proof Setup

[Bruce Pollock]

This is a specific question about the printing Proof Setup dialogue box in Photoshop. After selecting the Device To Simulate (in my case, Epson 3880 Premium Lustre Paper) the next tick box is Preserve RGB Numbers.

All of the Photoshop books I've consulted are fairly consistent in leaving this box unchecked, but they do not explain what it does or why you should not check it. I notice that when I do check it, I lose the ability to select the Rendering Intent options, but apart from that, it's not clear why I should not Preserve RGB Numbers.

Beyond this, the books generally advise selecting Relative Colormetric as the Rendering Intent, checking Black Point Compensation and checking Simulate Paper Color in the dialogue box.

Can anyone explain the 'why' behind the textbook advice on not selecting Preserve RGB Numbers? FWIW, I notice that when I select this option, the proof preview more closely matches the printed output, however, maybe this is just a reflection of how far out of whack my monitor calibration is.

[Tyler Boley]

when checked the RGB numbers sent to the monitor for display reflect what the profiling has determined is that actual character of the printer/settings/paper without correction. This is no indication of what the print will look like (unless no profile is used in the printer path).
Unchecked it sends numbers to the monitor for display that reflect what the print should actually look like when using the profile for correction "from" that raw characterized state.

Checked shows the same behavior "assign profile" does, and unchecked the same as "convert to" does...
Hope that doesn't muddy things too much more.
Tyler

[Francisco Disilvestro]

Preserve RGB/CYMK/Gray numbers shows how the image will look printed if you don´t perform a color space conversion.

According to the late Bruce Fraser, it is useful for CYMK workflows, so you could test if a image prepared for a specific process would work for another CYMK process.
It is basically useless for RGB

Rendering intent: I suggest you try relative colorimetric and perceptual for every image you are going to print and choose the one that work best.

Here is an article that explains the settings. It was written for an older version of Photoshop but the concepts are the same

You need a precisely calibrated & profiled monitor to use soft proof properly. I recommend this article by Andrew Rodney

[Bruce Pollock]

Thanks for the info and the links to the excellent articles.

Unchecked it sends numbers to the monitor for display that reflect what the print should actually look like when using the profile for correction "from" that raw characterized state.Tyler

This explains why my first print was so far out of whack and why it more closely resembled the soft proof with the Preserve RGB Numbers checked. When I went back and looked at my printer settings, I realized that I had not selected a proper profile. So basically, I sent it to the printer in its raw state.

So much to learn, so little time.

[pherold]

I would add that the "preserve numbers" check box can be useful any time you have a situation where you have to send your image through a "black box". If you have profile of that process, but you don't have a means of converting your image to that profile, you can still soft-proof beforehand what your image will look like when it gets through that printing process you have no control over. Okay, so it's not very common for the average photographer. But I've used it at times (even in RGB workflows) and have been very glad it was there.

[Francisco Disilvestro]

If you have profile of that process, but you don't have a means of converting your image to that profile, you can still soft-proof beforehand what your image will look like when it gets through that printing process you have no control over.

I don´t understand this very well. If I have a profile of the output process and can use soft-proof (assuming Photoshop) then I could convert to that profile.

Now, maybe the output process does not accept a file that is not in a working space like sRGB or AdobeRGB, or any other technical reason.

About using preserve numbers in RGB, there are sometimes, when using this option, that the appearance of the image is so far away from the desired state, that I would not even know where to begin correcting the image (i.e. an original image in AdobeRGB, soft proof for Epson Luster on a Epson 3800 printer)

Assuming I can convert to the profile (otherwise I could not do soft proof) but I cannot send a converted output to the printer, an alternate workflow could be:

Original Image AdobeRGB --> Convert to output profile --> Assign AdobeRGB (Here the appearance of the image is horrible)

Now soft proof to the output profile with preserve RGB numbers, desired appearance is restored.

[pherold]

In a previous position I was with an online photo finisher that was just getting into the world of book making, printing cards and the like. We did not have a press in-house so our IT department worked out a way to funnel our customers' images to the off-site litho printer who just got a new Indigo press. Unfortunately, neither our IT folks nor the other printer knew anything about color management, so they did not build in any way to make a conversion to a profile. It's this sort of thing that creates a black box like this. In this case, the workflow was entirely in RGB (until it got through the Indigo), but there was no place to convert to a profile in the workflow.

By the time I was called in to "fix the color," the best I could do was send a target through the Indigo and make a profile of the process. Then, our graphics department could at least soft-proof accurately what their background designs would look like when printed. This was very useful to them, and I looked like a hero! We could also get good looking work through the system if we converted to the profile (as you pointed out) ahead of time in Photoshop. Like I said, it's not a common issue for most people, but having Preserve Colors was sure handy when the situation called for it!