Sensor size and image quality

This is yet another topic that generates intense debate. All I'm going to do here is to say what conclusions I have come to from a practical perspective for my types of subject matter and my working methods.

I like having a camera which is small enough to put into a pocket but which can cover a very large range of focal lengths from wide to telephoto. For the range I want it seems inevitable to me that the camera must use a very small sensor and one must simply put up with the consequences for image quality. I don't think this is at all controversial.

For invertebrates, where I used minimum aperture almost all the time, I don't think it matters what the sensor size is because the effects of diffraction limit image quality to a similar level for all sensor sizes. I have a lot of experience and examples with sensors of 1/2.3", micro four thirds and APS-C size. I have not had a chance to test this yet with my full frame camera. I will be very surprised if that is any different from the others in this respect, but as always I would prefer to be evidence-based on this rather than just leaving it as a supposition and so I intend to run some tests in due course.

For flowers and other botanical subjects I have produced images that I like using cameras with small sensors, but I tend to prefer the look of botanical images captured with sensors of micro four thirds size or larger. For single capture images I have not developed any preference as between micro four thirds and APS-C, having used both quite a lot for botanical subjects. In two exercises where I compared images of the same subject captured with a micro four thirds camera and a full frame camera, here, and here, I could not discern any image quality benefit of using full frame. For stacked images I can only use my Panasonic cameras and I have a strong preference for the micro four thirds G9 over the G80 and the small sensor FZ330.

I am part way through comparing micro four thirds and full frame for sunsets and cloudscapes. Early indications are that full frame may produce noticeably better image quality for sunsets, both for high dynamic range scenes where the sun is still above the horizon and for low light scenes after the sun has set. That is for single shots. For exposure bracketed shots combined using exposure fusion ("HDR") there may be little difference for scenes with high dynamic range when the sun is still above the horizon. However, more thorough testing may change these early impressions.