John Howard wrote:
Thinking of adding a DX camera to my birding equipment for the extra reach. Have been reading that the IQ is better than simply going to DX mode on an FX camera. Thinking of the D500, but it is 4 years old. Wondering if there are rumors of a Nikon replacement or upgrade pending. Giving the deals being offered I think maybe. Went to Nikon Rumors and could not get any info. Thoughts?
I see you're using the 46MP full frame Nikon cameras (D850 and Z7). In DX crop mode what's left is approx. 19MP images. That's not bad. It's more of a concern doing DX crops to a 20 to 24MP full frame image. Even a 30MP FX camera's images take a pretty big hit from DX mode.
The D500 might be 4 years old, but that's not necessarily a bad thing. As DSLRs go, it's still one of the best APS-C models.
You might also want to consider the Z50 (since one of the FX models you shoot with is the Z7). The Z50 and D500 have essentially the same 21MP sensors. So does the D7500.
Older isn't necessarily a bad thing. In fact, one of the best DX Nikon DSLRs is the D7200, which was discontinued a couple years ago. It's a 24MP camera... so about 15% more resolution than Z50 or D500. It's also got slightly wider dynamic range than the D500 (so does your D850... I don't know how dynamic range from Z7 or Z50 compares).
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On the other hand, the D500's AF system is probably the most advanced and high performance of the DX models. While the D7500/7200 AF system is good and capable, the D500's is even better. It's essentially the same as in your D850. I don't know how the Z50's compares to D500/D850 or the Z7's AF system, for that matter.
You won't be gaining a whole lot with a D500, though. Might as well just shoot with your D850 in FX mode, then crop images later in post-processing. If you match the DX crop in post, the result is exactly the same as shooting with the camera in DX mode. But an advantage of shooting FX and later doing the crop in post is that you can shift the crop if needed, or adjust it a little larger than DX if that was just "too tight". Frankly, I don't see much purpose of shooting in DX mode unless you're using a DX lens on the camera or perhaps the crop is super critical for some reason and you're taking your time setting up the shot (which is rarely the case when "birding").
Finally, "birding" often means being mobile and trekking with your gear, in which case the weight savings of the DX format cameras might be attractive. Of course, the mirrorless cameras are even smaller and can save even more weight. On the other hand, birding sometimes means taking a lot of shots to get what you wanted, in which case the DSLRs probably get considerably more shots per battery charge.