Thanks Mark! The original pieces of art were scanned in by a reproduction house. What tools in Photoshop would YOU use to get the maximum details in the shadows without lightening the pic: Curves, Saturation, Brightness, Contrast, Shadows/Highlights, selective color? Some of these tools can really make the canvas reproduction look overly processed.
Gar
I do 99% of my image editing work in Lightroom and very seldom need to use Photoshop. I use whichever tools the photograph needs, under softproof, and watch what my adjustments are doing to the appearance of the photograph. Doing this under softproof is essential to avoid surprises coming out of the printer. The ultimate constraints in a print workflow are the printer, the paper, the profile, the inks and from those the resulting gamut and dynamic range. (For example, the lowest L* reading I obtained from Epson Legacy Fibre paper in a P800 using the Epson ABW mode was 15. Any image information below 15 is therefore unavailable in print.) Within those constraints you use the editing tools in the image processing application to optimize the results. For working particularly on shadow detail, there are no hard rules, but I often find playing between Exposure, Shadows, Blacks, Clarity and Contrast goes a long way to achieve the needful, while in some cases the Lightroom Tone Curve, starting-off from linear, can be tweaked to advantage. All of this can be usually managed without making the photograph look over-processed - in fact one wants to avoid that and usually can, but so much is image-dependent. It is good to begin this workflow without preset "Auto" Adjustments, as you often find yourself having to undo what the Auto did before getting to what you want. Years ago, I was able to smarten-up shadow detail quite a bit in Photohop using several Blend Modes with masks, but since Lightroom has become such a powerful image editor, I have not had reason to revert to those rather intensive techniques.