THE STUDIO NOTEBOOK
Pixels first. Print size second.
Print detail depends on how many source pixels you have for each inch of paper. Pixels per inch (PPI) is a useful planning measure. Printer dots per inch (DPI) describes printer output; the terms are often used interchangeably in image-export menus, but they are not the same thing.
The useful calculation
Divide image width in pixels by print width in inches. Do the same for height. For an uncropped 2400×3000 image printed at 8×10 inches, both calculations give 300 PPI.
At 16×20 inches, that same image gives 150 PPI. Changing a metadata field to 300 does not create new source detail.
Cropping reduces available detail
FolioKiln calculates source PPI after the crop, before resizing. A 2400×3600 portrait cropped to 4:5 keeps 2400×3000 pixels. At 8×10 inches, that is 300 PPI. The 2:3 preset at 12×18 inches uses the whole original but only has 200 PPI.
What our exports do
Full-size exports use preset inch dimensions multiplied by 300 to choose the output pixel dimensions. JPEG density metadata is also set to 300 PPI. When the source has fewer pixels, the browser resamples it. Resampling can smooth a larger image; it cannot recover details that were never there.
300 PPI is a target, not a guarantee
Suitable resolution depends on artwork, paper, print process, viewing distance, and your standards. Compression, blur, and color differences also matter. Inspect the exported file and order a small proof before selling large prints.