Over the weekend I started playing with my "new"
Vivitar 120-600mm F5.6-F8.
Conditions were windy and I don't have a tripod made especially for heavy lenses (Sirui T-025X) so results might not be as good as I'd wish. Still, the lens delivers pretty good results.
Since I already have a Pentax 60-250 F4 (a vastly superior lens) my main interest is at the tele end, near 600mm. I mostly tested there.
First comment, purple fringing is strong with this lens, as is to be expected. Luckily, it's also easy to correct via post-processing.
Second, the focus ring is superb, very smooth, easy to operate and precise.
Third, using ES and 10 second timer help to prevent vibrations, but I'm not convinced that it wouldn't be better to use SR instead. I'll have to try.
It's possible to click images to see full-res versions.
My first pair of samples shows the same image, the first being a JPEG straight out of camera, the second the same with PF removed, some clarity and vibrance added. Image shot at F8. Subject about 15 feet from camera (near the closest focus distance).
Unmodified
Modified
The second series looks to see if there's a significant drop in resolution as we zoom in, going from 250, to roughly 400, to 600. All at F8. Subject about 25 feet from camera. All images cropped to 100% magnification, which explains the different FOV.
250mm
400mm
600
The third compares (different composition, same distance) the same subject at F8 and F16. Subject about 30 feet from camera.
F8
F16
The last shows the detail that's possible to capture with a distant subject (about 200 feet, roughly). Shot at F8, and cropped to 100%.