CHROMiX

help with soft proofing from color mgmt newbie

I hope I am posting this in the right area - So much of this is over my head right now, but I am trying to understand as much as I can and learn what I don’t yet understand!

I’m a photographer and use a third-party photo lab to do my printing. My lab has just switched from using Fuji papers to the Kodak Endura paper. I have downloaded the new ICC profiles and have soft-proofed my images in photoshop. The images look great in PSCS and when I get my prints back, I am getting a yellowish color cast on the prints (this is new since the switch to the Kodak paper - I had a good handle on what I was going to get from my lab when they were using the Fuji paper). My images are black-and-white, but they are not grayscale images - they are RGB images. The paper that the images are being printed on is color paper - not true B&W, so I understand that slight color casts can happen, but shouldn’t I be able to predict that with a profile and soft proofing?

I was told by my lab’s customer service spokesperson that soft-proofing with the profiles in PS will not show any color casts since the black-and-white image is being printed on color paper. If my image is an RGB image and not grayscale, shouldn’t I still be able to see a color cast if it’s there when I view the soft proof?

Any help would GREATLY be appreciated!!

If the profile you have used is accurate, for your printer’s equipment AND the process they are using to make the print, then you are correct, any residual colour-casts should be visible in Photoshop (certainly if the image is RGB).

My apologies if this is off-track and you have already covered this base…

However, your monitor profiling may distort this, so a visual assessment may not be perfect. (The fact that Fuji papaer was OK before suggests that the problem is where something has changed in the process…Kodak paper is the most likely place to start). If ALL of the pixels show values of R=G=B (eyedropper tool) and the “before” and “after” comparison (by turning the soft-proof ingon and off shows neutral greys everywhere you should probably eliminate the monitor as the cause.

One possibility is that the paper has an optical whitener included so, although it looks white it actually has a blue-ish cast in order to make it appear brighter white. (Very common in inkjet and many other papers.) If you had selected anything other than “relative colorimetric” in your photoshop “print preview” dialog then you might find that the printing process deliberately adds yellow to compensate for the (actual) blue cast in the base-white of the paper. This would mean that the printed greys are really neutral, but APPEAR yellow when you see them aganst the blue-ish (cast) white of the border. Human optical + brain is so good at compensating that the (blueish) white of the paper is interpreted by your brain as “true” white and everything else is assumed to be wrong.

If your printer is using anything except “relative colorimetric” settings there is a risk of this happening, although the level of the risk is probably relatively low for “perceptual” and very high for “absolute colorimetric”.

If this is what is happening then you would probably see a clear transition between (your photo) pure white (R=G=B= 255) and the (unprinted) border of your print. If your white is adjacent to the border then this is very a obvious effect. It would be very easy to make a test print in photoshop (R=G=B only - greyscale but still RGB)

“Relative colorimetric” rendering adjusts the print so that the values printed allow for the blue (usually caused by a fluorescing optical whitener) of the paper, so everything LOOKS OK although everything actually has a blue-cast.

If you want truly neutral greys, then “absolute colorimetric” is needed, but you must crop the print so it has no borders AND dont let any non-neutral white papers anywhere near it!

I am surprised that your printer said that a greyscale image would not soft-proof correctly and will check whether this is true in PSCS before I enter the argument on that one.

Simon

Thanks so much for taking the time to reply! I’m still a little confused. :frowning:

I’m profiling my monitor using an EyeOne Display 2. The same process as when the lab was using the Fuji paper. I never soft-proofed when they were using the Fuji paper - I didn’t need to because I would get exactly what was on my monitor - color casts were a rare issue. My monitor doesn’t seem to be the issue from what you said in your post. When you say, the image shows neutral grays everywhere, you mean without a color cast, correct?

Now, onto the paper issue. I think when I soft-proofed these, I did have “perceptual” selected instead of “relative colorimetric”. This was really due to ignorance, and I have since realized that relative colorimetric is probably what I should have used. I’m not sure I understand what you’re saying about the paper looking yellow against the bluish white of the border - my prints don’t have a white border, and I am not sure if you mean that this would be the case for every print (because it is a characteristic of the paper) and since I soft-proofed with “Perceptual” the added yellow would be more noticeable to me?

The person I spoke with at my lab told me I might try profiling my monitor with a different white point - I currently use 6500K. I find it hard to believe this would solve the problem since this really seems to be an issue with the paper change. I never had a problem before with the Fuji papers.

I am just so confused why I can’t account for this color cast in PS.

Thanks again for taking the time to respond. I appreciate it!

Without looking at the prints I am simply speculating what the problem may be…but if it is any help…

I think a white point of 6500K should be fine, and that the monitor is probably not an issue. Many people recommend and use 6500K.

By Neutral grey Yes- I meant without colour-casts.

“Perceptual” rendering is not well defined, and I am told it depends on a manufacturer’s interpretation of “what looks good”. It is intended to keep colour relationships the same rather than being precise in the arithmetic -which relative colorimetric will be (at the cost of risking losing out of gamut colour relationships). In many cases it is very difficult to see much difference between “perceptual” and “relative colorimetric” particularly when the colours are within the printers gamut (which for neutral greys all except deep blacks and max whites will be).

Borderless prints would increase the effect I was describing - if present ( = make it more visible).

My suggestion was that the colour-cast may be nothing to do with what you are doing, but might have been caused by the printers using “absolute colorimetric” interpretation of your files or perhaps some other interpretation of the data you sent them (ignoring the profile you embedded perhaps).

Quite simply, if you have sent the printers a file which has the values of R=G=B (i.e. only neutral greys) and no instructions to interpret this in a strange way (by this I mean that the file has something like ProPhotoRGB or AdobeRGB embedded) then the print that you get back should have neutral greys ONLY.

Obviously what you actually see may be affected by the lighting you view the print under so there is some opportunity for dispute unless you view the print under an agreed, common-reference light source.

Some people advise only using a reference light source, but in many cases the differences complained about are gross ones and the reference source is really not an issue. (Daylight between 09:00 and 15:00 is relatively reliable in UK 52degreesN - and I suspect also in DC @40N).

In some ways the soft-proofing is a bit of a side issue here, because it is something you do for your own convenience so that you can visualise how the print will look when printed and it should not be influencing what the print actually looks like.

Have the printers looked at the prints you are unhappy with?

That’s good info and makes sense.

No, the printers have not seen the prints. I am trying to reach someone that is a bit more knowledgeable on the technical side of this so that we can work through it. I will likely send these prints back for them to analyze as well.

Thanks again for the info…sure appreciate it!