: Is there any way to check resolution of a portion of an image? Essentially I am wanting to verify that once I get a final layout from my contractors, that all of the images they have used

@Michele215

Totally depends on the aplication you are using for your "final layout".

If you are using Indesign, there is the Preflight Window, where iy shows you the ppi of the "Links and Images". (File > Preflight) There are some simmilar inspectors on Corel Draw for example.

On a flatened image, like JPG, there is no way of knowing the source images resolution on a composed image. You need to do that by eye, comparing some borders with the rest of the images resolution. If you see some "funny" saw, they were at a diferent resolution.

In a comment you say: "used in that layout are of at least 300 ppi" You do not need at least 300 ppi. That depends on the paper you are using. You could use a 212 ppi resolution on a 150 lpi output.

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@Ann6370331

What format? This is important.

If you get random JPG/TIFF etc, just check the pixel dimensions and divide by 2x the expected line screen*. If the result is approximately your anticipated desired printed dimensions, you have proper resolution. So if you are printing a magazine at 150lpi on press, the recommended dpi/ppi is going to be 300. A 3000px image will print optimally at 10 inches (3000px/300ppi).

If you have indesign packages, check the Links tool and look for the "effective dpi/ppi." A 3000px "300ppi" image is only 300ppi at 10 inches. If you place it at 5 inches, it is now 600ppi. At 20 inches it is now 150ppi.

If you have to, make a spreadsheet with column 2 as height of every image as laid out (in inches), and then in column 1, make a list of the pixel height of the images. Calculate the numbers as above (col1_px/col2_inches=col3_effective_dpi).

*("Shannon-Nyquist Sampling Theorem": to accurately reproduce a signal you need to provide data at 1.5-2x the sample rate)

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