What’s the difference between pixel pitch and pixel density?
Asked 12/27/2011
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I understand that pixel density describes how many pixels fit into a given distance or area, but I’m confused about how that differs from pixel pitch. What is the relationship between the two, and how should photographers interpret it when looking at camera sensors or displays? I’ve also seen formulas that convert from pixels per square centimeter to pixel pitch, which seems to assume square pixels.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
14y ago
2 Answers
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It's just a reciprocal relationship. Where pixel density measures, say, the number of pixels per inch, pixel pitch measures the number of inches per pixel (or the center-to-center spacing between pixels).
Pixel pitch expressed as a linear measurement, and if the pixels are non-square you may see two values specified. Pixel density, on the other hand, may be expressed as a linear measurement (pixels per inch or millimeter or what have you) or as an area measurement (pixels per square inch or pixels per square millimeter) -- your equation assumes an area measure of pixel density and square pixels, and converts to a linear value.
I should probably add that pixel pitch is usually used to state device specifications (screens or sensors) -- you wouldn't often see it used to describe, say, the resolution settings you used to print an image.
Originally by user2719. Source · Licensed CC BY-SA 4.0
user2719
14y ago
0
Generated from our catalog & community — verify before relying on it.
Pixel pitch and pixel density describe the same spacing from opposite directions.
- Pixel pitch = the physical distance from the center of one pixel to the next, usually in mm or µm.
- Pixel density = how many pixels fit into a given length or area, such as pixels per inch (ppi) or pixels per cm².
If density is given as a linear value, pitch is its reciprocal after unit conversion. For example, if a display has pixels per inch, then pitch in mm is 25.4 ÷ ppi.
If density is given as an area value (pixels per square cm, etc.), you first take the square root to get a linear density, then invert it to get pitch. That’s why the formula you found uses a square root: it assumes square pixels and area-based density.
For photographers, pixel pitch is most commonly used in sensor and display specs. Smaller pitch means pixels are packed more tightly; larger pitch means they are spaced farther apart. In practice, they are just different ways of expressing the same underlying pixel spacing.
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