The Nikon P900's lens is in reality a 4.3 to 357mm lens. All you'd need to achieve this on a DSLR is a 200mm zoom lens with a 2x teleconverter and then open your photo in Preview and crop the center.
As for cropping-- the P900 uses a really small sensor with 16 MP. So you couldn't crop a D800 or Canon 5DR very far before you start losing theoretical pixels. OTOH, he practical resolution is probably rather constrained by diffraction effects. Might be useful for a birder with a budget.
As for cropping-- the P900 uses a really small sensor with 16 MP. So you couldn't crop a D800 or Canon 5DR very far before you start losing theoretical pixels. OTOH, he practical resolution is probably rather constrained by diffraction effects. Might be useful for a birder with a budget.
You're correct about losing resolution and image quality, and I should have mentioned it. I just hope that people don't think that they're going to have the magnification of a real 2000mm lens just because they have a smaller sensor in their camera.
Remember folks, "equivalency" in lens terminology is all about field of view and nothing more!
I tried to search for examples of long lens photography, and came across the following collection by Ari Hazeghi of various raptors. He appears to favor the Canon EOS 1D Mark IV, and a 840 mm lens-- probably a 600mm f/4L IS II USM lens with a 1.4x teleconverter.
That's a $5300 body, and a $11500 lens, and probably a damn good tripod. But the images are amazing.
So that's what's possible at that focal length. Compared to that, the P90 looks like a very cheap imitation. Maybe it's useful in the right hands, but for most people it's just a gimmick.