Naive question on color shifts in softproof

[walter.sk]

I've been softproofing my images, and using adjustment layers to make them resemble my original images as much as possible.  This generally requires using curves, hue/saturation, and slight changes in color balance.

I was asked by some friends why the adjustments, particularly in color balance, were needed if the profile for the monitor and the printer profile were accurate.

My understanding is that the dynamic range changes because of the dynamic range of the paper/ink combination, and the saturation changes for the same reason.  Color changes occur also because of the way the out of gamut colors are treated (intent,) and because of the warmth or coolness of the paper involved. 

I responded that the adjustments to the softproofed image were an attempt to compensate for the changes involved in printing on a given paper using the given inks.  My friends said that if the profiles were "really good" these differences would be compensated for in the profiles, with no adjustments needed to the softproofed images.

Are they right? 

They also said if I were to use a good test image to softproof and make adjustments to, that I should be able to copy those adjustment layers to all the images shot with that camera and to be printed with that paper and ink, and not have to tweak the adjustments for individual pictures.

I said that each image would possible have different degrees of out-of-gamut color and degrees of saturation, so no individual set of adjustments could possibly work for all the images.  They continued to say that good profiles should eliminate the need to adjust the softproofed image.

[digitaldog]

I responded that the adjustments to the softproofed image were an attempt to compensate for the changes involved in printing on a given paper using the given inks.  My friends said that if the profiles were "really good" these differences would be compensated for in the profiles, with no adjustments needed to the softproofed images.
Are they right? 

No, you are. There’s also a difference in color gamut after converting from working space to output space. Stick with your workflow, its sound.

[Schewe]

They also said if I were to use a good test image to softproof and make adjustments to, that I should be able to copy those adjustment layers to all the images shot with that camera and to be printed with that paper and ink, and not have to tweak the adjustments for individual pictures.

Who is "they"? They re not right about much...

In point of fact, while the base curves & Hue&Sat adjustments needed may be fairly consistent, given the same output profile, they will still need slight tweaking because no two tone curves and color palette will be the same (unless it's from really similar images).

You'll need to tweak the curve and colors based on what's in the image and how the profile is behaving on the image. You also need to evaluate which rendering intent is optimal for the image and that will require tweaking the adjustments as well.

Sounds like you care more about your prints than "they" do...pat yourself on the back and tell "them" to learn how to print :~)

[Mark D Segal]

Another point is that profiles can't take into account the differences of apparent DMax and DR between transmitted light from your display and reflected light from a print on paper that is never dead-on neutral. The soft-proof goes a long way to bridging this gap in a way that profiles cannot.

[walter.sk]

Thanks, Andrew, Jeff and Mark.  I intended (and still intend) to continue with my workflow.  I just needed to be able to explain more clearly to my friends why they are not correct.