Does a higher megapixel count improve high-ISO image quality?
Asked 3/18/2016
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I use a Sony NEX-6 and notice visible grain at ISO 1600. A newer model has a higher resolution sensor (24MP vs. 16MP), and I’m wondering whether the larger image size or higher megapixel count would make images cleaner at higher ISO settings. In general, does increasing megapixels improve ISO performance, or can it make noise worse when the sensor size stays the same?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
2 Answers
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So I'm trying to wrap my head around if larger image size may result in better ISO sensitivity (so images get less grainy)?
It actually tends to work the other way: larger photosites give better low-light performance because each site has more photons falling on it.
So if you have two sensors with the same physical dimensions, the one with the lower pixel count will generally yield a less noisy (but lower resolution) image. Or, if you have two sensors with the same pixel count but different physical dimensions (e.g. APS-C and full frame), the larger sensor will offer better low-light performance.
The numbers for those two models bears this out. Your NEX-6 offers ISO settings all the way up to 25600, while the NEX-7 only goes up to ISO 16000.
Originally by user4262. Source · Licensed CC BY-SA 4.0
user4262
10y ago
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Generated from our catalog & community — verify before relying on it.
Usually no—if sensor size stays the same, a higher megapixel count does not improve ISO noise, and can often make it a bit worse at the pixel level.
The reason is that with the same physical sensor size, more megapixels means smaller photosites (pixels). Smaller photosites collect fewer photons, which generally reduces low-light performance. By contrast, larger photosites tend to give cleaner results at higher ISO.
So, in general:
- same sensor size + fewer megapixels = better high-ISO performance
- same megapixel count + larger sensor = better high-ISO performance
That means a 24MP APS-C sensor is not automatically better in low light than a 16MP APS-C sensor just because it has more resolution. You may gain detail, but not cleaner high-ISO files.
For the specific cameras mentioned, the available ISO ranges also reflect this: the NEX-6 goes up to ISO 25600, while the NEX-7 tops out at ISO 16000.
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