Nikkor 24-85mm F2.8-F4 AF-D Lens test

This lens first appealed to me most because of it’s speed and allround abilities; having F2.8 available at 24mm and being able to go to 85mm with F4 makes this a very usefull lens within this range.
I’ve always been satisfied with this lens for day-time photography, but cleary preferred my 80-200mm F2.8 when shooting at the 80mm range. The 24-85mm AF-D is just not that sharp.
In order to see whether this lens is usable for astrophotography and if so, at what settings I decided to do an easy test which you can do at home.

Put the lens to the test

Using a test chart I took many photo’s from the tripod on all the possible F-stops at 24mm (lens wide open), 50mm and 85mm.
Here are the results at each focal length for the fastest F-stop possible;

24mm F2.8

50mm F3.5

85mm F4

We can clearly see the lens suffering from severe barrel distortion at 24mm and some pincushion distortion at 85mm. This goes along with a huge difference in sharpness at the corners/edges and the center. Strangely enough the right side of the image is much sharper than the center especially at 24mm. This might be a defect of my version of the lens, but in any case we can clearly see this lens is not providing a flat field that is sharp in all corners.
The following image clearly shows this:
Center sharpness

The lens is the sharpest at F4 at all focal lengths so it seems, and is the sharpest at 85mm.
Center sharpness at F4

Nikkor 24-85mm F2.8-F4 AF-D for Astrophotography

I’ve used this lens only once for astrophotography, so I haven’t a lot material available yet on different settings for comparison. But this image is clearly confirming the things I noticed in the test above.
Cygnus widefield
This image was taken with the Nikkor 24-85mm F2.8-F4 AF-D and used at 75mm F8.

We can see that this image is not nicely flat and sharp in all corners. Furthermore there is some heavy coma visible.
Cygnus widefield corner areas

On the plus side; the colors are good and there is not much chromatic abberation visible.

Conclusion on Nikkor 24-85mm F2.8-F4 AF

This lens lacks real sharpness and is not flat throughout the field of view. The lens seems sharpest at 85mm F4, but has some pincushion distortion at that focal length. My Nikkor 80-200mm F2.8 is definatly performing better at 80mm so I wont be using this lens for that focal length.
At 50mm this lens might be suitable for astrophotography, but I suspect that my Nikkor 50mm F1.8 is probably better for this. I will test this out in the field when I get the chance.
At 24mm I think this lens has to much distortion to be usable.
I will update this post when I have more test material from the field.

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