I've converted them to tifs, and will keep them in grayscale colour space, assuming those to be obvious first steps.
Some B&W images left in a color color space (by accident) have actually printed better in POD in the past, than those left in a grayscale space. Why might this be? Is it that the overall values or histogram settings in colour – which may differ from, but can be calibrated for the same end result in a grayscale space, I imagine – were somehow optimal?
I assume that by POD you are referring to Print On Demand?
Quite frankly, the “problems” would seem to be more an issue of GIGO – Garbage In, Garbage Out – than anything to do directly with the file format of the images, especially if those images are monochrome.
I would strongly agree with Bob Levine in terms of EPS (Encapsulated PostScript) being an archaic file format. That having been said, a properly prepared photographic image with proper exposure, contrast, and resolution saved as EPS from Photoshop and placed in InDesign should render no differently than a TIFF, JPEG, or PDF (depending upon the compression used in the EPS) image without any ICC profiles placed into an InDesign document. I seriously doubt that simply converting your EPS files to TIFF would help in any way whatsoever, although in the process of simply opening the images in Photoshop, you might see what the real quality (or lack thereof) of the images is.
Many problems associated modern day monochrome images today is the fact that most such images were shot digitally as color images as opposed to being shot on black and white film. Unfortunately, there is no single conversion of color to monochrome that is optimal for all images. Much depends upon the exposure, light contrast, and especially the color contrasts within the original color image. In the days of analog film photography, professional photographers often used color filters with black and white film to deal with the issues of color contrast (for example, yellow and orange filters for outdoor scenic shots to provide for a darker sky with deeper contrast with the clouds, the “big sky” effect). Converting color digital images to monochrome by using the simplest Photoshop tools without regards to image content will definitely yield many suboptimal, washed-out looking images.
Also, after applying one or another of the Photoshop conversions to monochrome, the image usually is still RGB. One needs to then convert the image that looks grayscale to actual grayscale. Otherwise, you end up with an RGB image for which for every pixel R=G=B, a situation which could lead to some “interesting” and likely undesirable printed output, especially if printed on a color device.
Another issue to consider is one of color management. Whether one wants it or understands it, color management is really always on in Adobe applications. If you don't use profiles and the wrong assumption is made with regards to the color space of content, you can get suboptimal results, in grayscale such results being muddiness, poor contrast, etc. And to get back to the file format issue, EPS doesn't support ICC color management directly.
Thank you for that very thorough post. To begin with, the images are all of rather high quality, far higher than necessary in terms of resolution for images that appear in the layout as 7cm x 7cm (they could easily work on A4 or larger).Some were likely supllied originally from archival digital files of several major European museums. It's very safe to say, there's no issue with their quality.
The main issue falls back to optimization for print-on-demand, which for basic B&W printing, the images will always be degraded severely. Merely trying to make the best of the situation, and there is certainly room for improvement based upon the wide range of results seen with that printing process. The photos will turn low res, but text remains consistent in quality despite this, always printed at 600 dpi.
Given that copies will print with wide variances (some too light, others too dark), I'm attempting to find and follw recommendations for these conditions. I suspected converting to TIF would not, in this case, change their appearance, I'm just following what's strongly advised, leaving EPS behind.
I'm sorry if this is really too general of a question that doesn't hint at an appropriate knowledge of the intricacies involved in achieving the desired results. So much with on demand printing will continue to come down to trial and error, I suspect, at least in regards to the images.