This is quite a stupid question but one I really need an answer for.
I have been illustrating a children's picture book. Its a personal project me and my wife have been undertaking. They are photoshop digitaly drawn files. Now the images at present are A4 CMYK tifs with dpi's of around 1000. I am nearly finished all the final painting and have finally gotten around to the question of mastering the images, flattening them etc.
I have only a limited illustration training so wasn't quite sure what format to go with so chose one that I knew wouldn't compress the work. Likewise with the dpi count. Because I plan to send this work off to multiple publishers etc who will all have different standards I was wanting to know what I should downscale my resolution to and save the file type as - masters so I can make smaller versions from these if needs be.
And are there any other things I should worry about.
rule of thumb is yor file should be between 1 1/2 - 2 times of your publisher's (printer's) screening resolution. If your book will be printed at 150 lines/inch (aka "line screen") you should be good anywhere between 225-300 ppi.
If printed at 200 line screen your file should be between 300-400 ppi.
Commercial printers use either 150, 175 or 200 line screen. Most use either 150 or 175 line screen.
So, to stay on the safe side downsample it to 400 so it could be printed at even 200 line screen. Everything higher would be excessive and just make the file size unnecessary large.
Excessive resolution will NOT give you a better printed image.
If you know which printer will be used to print your book, check with them what screen ruling they use (most likely 150 or 175).
A flat tiff or ps file will be acceptable to ANY printing house.