I'm currently figuring out InDesign to make spreads for photo albums. Now I have a question about sizing images:
I have a 4256x2832 pixel image @ 300dpi and I would like to have it in a image frame of 70x30 cm (27,56x11,81 in). Normally when I send this image to a print store in order to print, it is no problem to print it in 75x50cm (29,53x19,69 in). But when I place this in the frame InDesign, the image is way smaller than the frame, only 14,2x9,4 cm (5,59x3,7 in). When I select Fill Frame Proportionally, the image will be more than 400%, so 4 times bigger than it is! Then I also see the pixels on my screen, which is not what I want of course. I guess it has something to do with resolutions, but how does it work? Is there a way to have this image in my spread with a 70x30 cm size without seeing the pixels when printed? So same quality like when a print store prints it directly?
Pixels are pixels, and the number of them in the image doesn't change when you scale unless you resample. ID does not resample when scaling, so yes, if you need to scale the image to get to that size in ID the "effective" resolution is going to change in inverse proportion to the scaling factor. In this case, you are down to about 75 ppi effective resolution, and that seems pretty low for printed output, but it depends on the printing method. I don't know why you would get a different result on the same equipment printing the same size direct from Photoshop or ID unless the print settings are different.
First, make sure you are looking at the best quality screen preview in ID. View > Display Performance > High Quality Display. Second, when printing from ID if the image quality seems to have suffered compared to printing the same size from Photoshop it usually helps to set the Send Data field in the Graphics pane of the Print dialog to ALL instead of Optimized Subsampling.