Lyle Dunlop - TC Compare

I have wondered what will provide more detail: A crop sensor or a full frame sensor with images cropped later in post processing. I just received a NIkon 500mm f/5.6E PF and I figured I would compare the 500mm on both the D850 and the D7100 with all 3 Nikon teleconverters on both bodies.

On the night of April 12th 2025 there was a full moon which would make the perfect test subject for some data finding. April's full moon is called the Pink Moon due to a flower commonly called "moss pink" that is known to be in full bloom by the time of April's full moon. This year it would also be a "micromoon" due to the moon being in a period in it's orbit where it is the furthest away from earth (the opposite of a supermoon).

All images below are taken at the maximum aperture available for that lens/teleconverter combination. All images were cropped in post to approx 4000x2667, for reference I have listed the diameter of the moon measured in pixels.

In summary; the crop sensor (DX) D7100 is 24.1 Megapixels and the D850 is 45.7MP. DX cameras provide a 1.5x crop factor when compared to a full frame sensor. So a 500mm lens on a full frame camera will have an equivalent focal length of 500mm, but that same lens on a DX body would have an equivalent focal length of 750mm. What I wanted to know was if I took an image with a full frame camera, could I crop it to make up the 1.5x crop factor and would I have a larger or smaller subject? I could also phrase this question as if I cropped both to make the moon appear the same size, which one would have a higher pixel density? Well the answer is that the DX sensor in this test would actually have a larger moon when the image is cropped to the same pixel x pixel size. It's not a massive difference, the moon is about 11% larger in my tests below. This obviously makes sense as the D7100 has slightly over half of the MP as the D850.