Today’s Question: In the context of fine resolution of details in a large print size, what is the difference between, say, a 26-megapixel APS-C sensor versus a 26-megapixel full-frame sensor? Will the full frame sensor be that much better to be worth the extra cost?
Tim’s Quick Answer: All other things being equal, including the number of megapixels for the sensors, the full-frame sensor will generally offer greater dynamic range and lower noise levels, which can translate into improved image quality.
More Detail: When two sensors of a different physical size have the same megapixel resolution, there will obviously be a difference in terms of the size of each photosite (pixel) within the sensor. A larger photosite translates into an ability to essentially capture more light. That, in turn, means that the difference between a “full” and “empty” photosite will be greater.
This results in greater potential dynamic range for the larger sensor, as well as reduced noise levels based on being able to capture more light.
Of course, there are many other factors that impact the final quality of the image, including many different factors related to an individual image sensor. Therefore, you can’t assume that a full-frame sensor will always offer better image quality compared to a smaller sensor size.
To be sure, greater resolution (as in more megapixels) can provide larger potential output sizes. And a larger image sensor has the potential to provide higher dynamic range and lower noise levels. Both of these can provide higher image quality, but the reality depends on the specifics of the sensor and image processing (both in the camera and after capture). This is why there is really no replacement for testing the output from different image sensors to determine the relative quality potential of each.