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I am thinking of purchasing the Nikon D3200 its a 24.2MP camera but the pixel size is 14.8 µm² compared to the D3100 which is 14MP and a pixel size of 25.1 µm².

Is this something that i should worry about, or is it somewhat irrelevant, as the eye cannot see such fine detail?

I am worried about the digital noise. I understand that at higher ISO's like 800, I will see more noise. But at 50/100 ISO, will I notice the difference between the pixel sizes, and ultimately does this constitute to better or worse image quality?

D3100 - £269

D3200 - £329

Last question: is it worth the extra money?

  • This would probably be better asked as three separate questions: one on megapixels, one on noise and one on price - although the last is likely off-topic here unless you've got a particularly unique slant on the issue. – Philip Kendall Dec 30 '13 at 21:56
  • An aside on ISO: on many large-sensor cameras, I believe include both the Nikons you're looking at, ISO 50 will have the same noise characteristics as ISO 100 - this is because it's implemented with the sensor at ISO 100, but then pulling it down by a stop in the processing pipeline. – Philip Kendall Dec 30 '13 at 22:00
  • I'm inclined to agree with Matt, the linked question describes how they relate. Does that answer your question in this regards? – John Cavan Dec 30 '13 at 22:15
  • Im not sure? Both D3100 AND D3200 have similar almost identical sensors. Which is going to give the BEST image quality if i say set them both to 12MP? – PriceCheaperton Dec 30 '13 at 22:19
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Sensor size matters more than pixel size. Diffraction becomes an issue the smaller your aperture becomes and that means that as you stop down, a camera reaches a point where it is "diffraction limited". Basically, the area of light made by diffraction becomes larger than the size of a pixel and thus the resolution can not exceed that point.

The larger the sensor, the more pixels you can fit before getting too small, but if you are, for example, diffraction limited at 15MP and have a 24MP sensor, you will still get the equivalent of a 15MP photo.

There are also some minor trade offs because the light has to maneuver down a small tunnel to get to each photosite on the sensor. The smaller each pixel becomes, the harder it is for light to make it down that tunnel, so the smaller the pixels become, the more light sensitivity is lost, but this is often compensated for by making a sensor with lower noise levels, so it isn't necessarily a disadvantage in all cases.

So yes, pixel size does make a difference in multiple ways, but looking at just the pixel size doesn't give you the entire picture without looking at a number of other factors about the sensor performance. In this particular case, I would expect that the D3200 would have a newer sensor and likely be better in other ways other than just the resolution, so it's probably worth the increase in cost unless you don't need the features it is capable of providing.

  • I was going to run the D3200 at 15MP. << is that what you mean by diffraction? In this example D3100 vs D3200.. Would i see no loss in image quality even though the pixel size is 14.8 µm² ? – PriceCheaperton Dec 30 '13 at 21:59
  • D3200 - APS-C 23.2x15.4mm AND D3100 - APS-C 23.1x15.4mm – PriceCheaperton Dec 30 '13 at 22:04
  • @PriceCheaperton - I mean that if you are not diffraction limited, then the 24MP sensor will pick up more spots, but even if you end up shooting under conditions that are diffraction limited, you don't pay an additional penalty for the higher resolution sensor, just the amount of actual usable resolution ends up lower than the number of pixels the camera has. – AJ Henderson Dec 30 '13 at 22:42
  • @PriceCheaperton On the diffraction limit: photo.stackexchange.com/questions/8304/… – mattdm Dec 31 '13 at 1:22

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