Today’s Question: I noticed the announcement of a 25-megapixel micro four thirds sensor camera, the Panasonic Lumix GH6 (https://bhpho.to/3tpT6sT). Is that about the same image quality, plus or minus 4%, as my 24-megapixel Nikon full frame camera [such as the Nikon Z6 II, https://bhpho.to/36FJQYQ]? Smaller pixels I guess, but I’m not sure how or if that matters.
Tim’s Quick Answer: All other things being equal (which they of course aren’t) the smaller sensor would be expected to produce more noise and not offer as much dynamic range.
More Detail: There are myriad factors that ultimately determine image quality for a given sensor, so it is difficult to make an accurate comparison based exclusively on specifications. The best approach is to directly test different cameras under equal conditions to get a better sense of the relative quality of each sensor.
That said, there are some general properties that impact overall image quality. The size of the individual pixel elements is one of the more significant of these factors. Smaller pixel sites will generally translate into lower dynamic range and more noise. This is because the smaller pixel sites will generally not be able to gather as much light as a larger pixel site.
However, there are many other factors that impact image quality. Signal processing is a significant factor that will vary among different sensors, but the results are difficult to predict without hands-on testing. In addition, sensor manufacturers have made various efforts to improve the performance of their sensors even when they have smaller pixel sites, such as by using lenses to focus the light being captured at each pixel site.
Typically, a larger sensor of a given megapixel resolution would be expected to provide better image quality. Keep in mind, however, that most higher-end camera models offer generally good image quality, and so it is important to weigh other features such as autofocus performance, image stabilization, and other options that may be helpful to you when making a decision about a specific camera mode.