Choosing pixel or percent borders for consistent frames
When a fixed pixel border beats a percentage one, how percent scales with image size, and how to keep frames even across a set of photos.
Two ways to measure a frame
A pixel border is an absolute value: 40px is 40px no matter how large the image is. A percent border is relative, calculated here from the shorter side, so 5% of a 2000px tall portrait is 100px while 5% of an 800px image is 40px. Absolute borders give you exact control for a single output, and relative borders keep the visual weight of the frame steady as image dimensions change. Knowing which you need saves a lot of trial and error.
When to reach for percent
Percent shines when you process images of different sizes and want the frame to look the same in each. A gallery mixing 4000px camera exports with 800px web crops would look uneven with a fixed pixel border, since 40px is a hairline on the big file and a thick band on the small one. Setting 3% instead scales the border to each image so the proportion stays constant. This is the closer match to how a printed mat or a social template treats a photo.
When a fixed pixel border is better
Reach for pixels when the exact final dimensions matter. If a marketplace requires a 1080 by 1080 listing image and your photo is 1000 by 1000, a 40px pixel border lands you exactly on target. Pixels also help when several images share the same starting size and you want them byte for byte consistent. Because the value never shifts with the source, pixel mode is the predictable choice for spec driven work.
Keeping a batch of frames even
For a cohesive set, decide first whether consistency should be absolute or proportional. If every source image is the same size, either mode produces identical frames, so pick pixels for simplicity. If sizes vary, percent keeps the frames visually matched even though the pixel counts differ. Either way, choose one color and one width and apply them across the whole set rather than eyeballing each image, which is what keeps a grid of photos looking deliberate.