While I agree the sliders for Print Adjustment (Brightness, Contrast) are a band-aid, what I've found is that the reason people find their prints on the dark side is the result of a few of factors:
- Uncalibrated monitor (speaks for itself)
- User Error: they aren't paying close enough attention while preparing the image; and/or
- the difference between a transmissive-like computer display and a reflective print; and/or
- the background in the Develop and Print modules is set to something other than white.
This last point is often the most contentious and hasn't yet been mentioned in the discussion. Bear with me for a moment...
During the wet darkroom days, the print was our only output so our key visual reference was the white of the paper we used. In fact we typically compared the brightest parts of our print to "paper white" to see how close we were getting.
Fast-forward to LR: In Develop module, if you don't have anything "white" around the image, you don't have that key visual reference (a white point) for brightness and this can
cause images (on screen and prints) to appear too dark (icc profiles aside). In other words, they look great until they are matched up against paper white in a print. For those who pay attention to the histogram this is less of a problem, but not enough users do.
The same could be said about the Print module background - if it is other than white, you may not have a good visual reference. Although in most cases, users print with a white border and this helps to provide an on-screen visual reference, by the time they are in Print module, they may not be thinking about how bright/dark the print is since that's a "Develop module decision" and there are onto the myriad other decisions to be make in Print module. For me, I find I am visually assessing my image right up until I hit "Print". I fact, the Print module is often where I take that last "uncluttered" global look at what I am about to print.
As a result, I've set both my Develop module and Print module backgrounds to white so that I always have a white point visual reference to help ensure my prints are bright enough.