I hope Rob pops in on this one -- he's good at this, but first off, are you viewing the doc in Overprint Preview? It will probably look darker when you do that. Grayscale is put on the black plate in the CMYK working space, so your CMYK space matters here and you have to view a real output preview to get a sense of what's happening.
A few answers please -
You send from InDesign to the DPM which RIP's and you can preview the seperations at the RIP?
The photo's appear to dark; darker than your experienced eye thinks they should?
You regularly send photos that appear and print ok?
It sounds like this spot pdf was supplied and you cannot modify the photo (although if they appear correct in ID Overprint Preview you probably would not need to).
You know? I guess I should have posted in the Acrobat forum...doh! This is a premade PDF that was sent to me. As a test, I did
drop it into an ID document and sent it that was but its still the same way.
The photos on the screen look fine. Grayscale photos of people and very clean. When viewed after sending to the DPM and seeing on that screen, the faces are almost solid black, it wouldnt be acceptable at all. In the past, ive sometimes drawn transparent white boxes over all the photos overtop of the PDF in ID to force it to go lighter but its just such a backward way about doing what I know has a better and easier way somewhere. Almost always they seem darker on the DPM than on the main computer. We print more solid images like text so it doesnt come up that often. When I get photos that are going, i always start gritting my teeth because I know it always gives me trouble and have to do some makeshift workaround. This goes for Acrobat and Indesign items.
I tried viewing in overprint preview and it doesnt look any different from viewing normally or in separations preview
IMO, you won't get this answered in the Acrobat forum.
Without discussing embedded profiles in the images...if you're hesitatnt about photo's because they print to dark, your wasting the functionality of that DPM. Any decent daylight camera will print line copy at half the materials cost...
I would suggest you have a tech spend a day in the pressroom to calibrate the DPM. We brought one in for 30 days and sent it back, I get better results through a small imagesetter (which is really all your DPM is with the addition of a RIP and material cutter)
You will probably get the best answers here
In short, there are some test files stored hopefully on the RIP's internal drive - test patterns. Pull one up, plate it, run it on job stock at normal ink levels. Measure the screen values. Input these values into the RIP's calibration sets.
If you were to create your own - Create twenty .5" x 4" frames, fill them with tints of black from 5% thru 100%, plate it run it...I'm guesiing that everything over 75% is filled solid