I've been having sharpness issues with recent bird captures, and then realized we've been having a very grey winter. I usually use Aperture Priority with a fairly fast (500+) shutter speed. My lens is a
Nikon 55-200mm f/4-5.6G ED AF-S DX Autofocus Zoom Lens. Does the 4-5.6 mean that my aperture is limited to those two openings? If so, then I need another lens with lower (more open) aperture settings.
Wondering if this is a wear and tear issue, and might be worth taking some control shots under different conditions with the same settings (& tripod etc). 4-5.6 refers to the maximum aperture for the lens, which decreases as you zoom in.
For this kind of lens brightness of scene is very important to get great clarity. In this winter cloudy atmosphere is just not possible with lower ISO. With high ISO you will loose on clarity (noise). I think that you use 200 mm what makes image even more soft. For birds photography is best to start with minimum 300 mm and 2.8 aperture.Zoom lens with 2.8 on all extend is the best. With your lens you will get best results on very bright day.
A variable aperture lens like you 55-200 is lens which has a different maximum aperture depending on the focal lenght.
In your case the the 55-200 will allow f4 at 55mm and only f5.6 at 200mm.
This might no seem like a lot, but it drops your shutter speed one stop at 200mm.
Example: you have a bird several meters in front of you (your exposure settings are for the bird, not the background).
Let's presume at 55mm your correct exposure for the bird would be f4 at 1/500th of a second.
At 200mm (you want to have a close up shot of the bird, right?) your exposure would then be f5.6 at 1/250th of a second since your lens can't do f4 at 200mm. With a shutter speed of 1/250 you'll probably have motion blur. Those birds just won't sit still enough.
To counteract this you will then have to bump up your ISO one stop (from 200 to 400, let's say) to have again your desired shutter speed of 1/500th of a second to freeze the birds motion.
Depending on the light available and your camera's sensor this can be quite tricky.
If you have the budget, use "constant aperture" lenses (most quality zoom lenses are f2.8 or f4). You can then have an aperture of f4 throughout the entire zoom range of the lens. They are much more predictable and easier to use, especially in low light conditions.
Hope this helps.
Thanks for all of the information. I appreciate your generosity. Got a good tripod (Manfrotto) for Christmas, don't have external flash units yet, probably for my birthday in Sept. the next lens, probably not until 2014. Until then I'll wait for sunny days to try the bird captures.