Wednesday, February 25, 2015

Can someone explain me the concept of image resolution in photoshop in relation to indesign and illustrator?


My file has resolution of 150 ppi, i duplicate that file and made another one of resolution of 300 ppi, with resample checkbox turned off. As a consequence of that, pixels from both images haven't changed and are the same, while only print size changed.


When i exported both files, one with 150ppi and one with 300 ppi, they were the same size 1.0 mb, even the information on jpeg is measuring the same pixels dimensions.


But when i place both of my images in illustrator, the one with 300ppi has smaller size, also when i placed it in indesign the one with 300 ppi is smaller, and the one of 150 ppi is larger.



How so, when they have the same pixel dimensions?


Can someone explain me logic behind this.


Thanks.



Answer



Yes.


Both files have the same number of pixels, so the same file size and image quality.


But when you import your images to InDesign, which takes into account image resolution to print them (since DPI is dots per inch, meaning it's useful to measure how large an image will print in a physical medium) the image with 300dpi will look smaller, because it has more dots per inch. Each pixel will be printed smaller on paper so it can fit more dots per inch.


An image 1000px x 1000px at 1000DPI will print at 1" x 1". The same exact image at 500DPI will occupy 2" x 2" when printed on paper. Simple math, you're just printing the pixels larger. Got it?


Photoshop doesn't care about the resolution, you're editing the image pixels there. 1000px are still 1000px no matter what resolution. It might make a difference when adding text, since the font sizes are usually pt and Photoshop will scale it differently based on the resolution, but if you set a font size to 20px it will also look the same regardless of the resolution. The resolution setting is there because you'll need it when printing.


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