Test Basis:

To compare lens sharpness and focusing accuracy between the Nikon E990 v1.1 and Nikon E4500 v.1.1 with my digiscoping setup of Swarovski AT80HD and custom made mount.

Configuration:

The dummy bird was approx. 10 meters away from setup. Both the cameras were set for Aperture Priority. The Nikon 4500 was zoomed until f4.0 was obtained to match f4.0 at maximum zoom in the 990. Obviously, by doing so, we can see there is no correlation to zoom factor as the images differs slightly in sizes which makes the 4500 lens slower. Cameras shutter speed were around 1/50 secs. and triggered via a mechanical remote release. Center-weighted metering with 0.0 and -0.3 EV compensation. In addition, the cameras were set to Auto white balance, Single shot, Full Fine, Normal image adjustment, Normal image sharpening.

I made equidistant markings like this IIIIIIIII with a Casio Labeler and taped that to the focusing barrel of the spotting scope to ensure repeatability of test and accuracy of focus shifting of 1 mark left and right of approx. 1 mm. The reason I did this was to compensate for any focusing error and see if the cameras can still focus.

Photographs shown are as was taken i.e. no levelling and no unsharp masking. All that was done was resizing to 640 x 480, text added and flattened with Photoshop and saved at high setting of about 9.

Comment:
It is quite obvious from the results below that the Nikon 4500 is not compatible with my equipment or my eyes. I could not get a reasonably sharp photos from the 4500 no matter what I tried. It could be this particular camera, I don't really know.

Comparison photo of 3 Megapixels Nikon 990 (2048 X 1536 pixels) overlaid on 4 Megapixels Nikon 4500 (2272 X 1704 pixels)