Does increasing image resolution also increase bit depth?
Asked 4/29/2019
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I'm trying to understand color representation in digital images. To get smoother gradients and reduce banding, it seems like you need more bits per pixel (bit depth). If an image has higher resolution—more pixels—does that also mean it has more bits per pixel, or are resolution and bit depth separate things?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
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Image resolution (amount of pixels) and bit depth (bits per pixel) can be changed independently. Any combination of high/low resolution and more/less bits per pixel is possible.
Sometimes, however, higher resolution can make up for lower bit depth. Individual pixels become invisible and we start perceiving patterns of pixels as shades, as if the color depth were increased.
This is also the case of film photography, where individual "pixels" can only be black or white, and yet we can clearly see the shades of gray, because the individual image elements are so tiny. (ignoring color film photography for simplicity)
![By Robert James Wallace - Plate VII from "The Silver 'Grain' in Photography" by Robert James Wallace, The Astrophysical Journal, Vol. XX, No. 2, Sept. 1904, pp. 113–122, Chicago. As reproduced by Google Book Search. See also [1]., Public Domain, https://commons.wikimedia.org/w/index.php?curid=12220056](https://i.stack.imgur.com/Iege7.jpg)
Originally by user32811. Source · Licensed CC BY-SA 4.0
user32811
7y ago
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No. Resolution and bit depth are separate properties.
- Resolution is how many pixels the image has overall, such as 6000×4000 versus 3000×2000.
- Bit depth is how much color/tone information each pixel can store, commonly described as bits per channel (for example, 8-bit or 16-bit RGB).
You can have any combination: high resolution with low bit depth, low resolution with high bit depth, or both high or low.
If your goal is smoother gradients and less banding, increasing bit depth is what directly helps, because each pixel can represent finer tonal steps. Higher resolution does not automatically increase those steps.
That said, very high resolution can sometimes make limited bit depth look less obvious, because tiny pixels can blend visually into smoother tones when viewed at normal size or distance. But that is a perceptual effect, not an actual increase in color precision.
So: more pixels does not mean more bits per pixel.
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