After I dropped my lens, focus locks but images are blurry — what could be wrong?

Question

I have a Tamron 24-70 2.8 on a D610. I usually go for small apertures (F11 to 16) since I work with flashes on studio setups, my lens gives sharp images on those appertures but anything below F5.6 starts to get blurred even though AF locks on and MF shows me correct focus on the view finder. It is NOT a misfocusing issue on my part, since I have a Nikon 1.8 and is sharp as a knife at any aperture. Any guesses? I dropped my Tamron knee high but it didn't hit hard. I'm kinda lost.

Thanks!

Answer 1

If the drop knocked the optics in your lens out of proper alignment it will be most noticeable at the wider apertures. Narrower apertures that give greater depth of field can help mask misaligned lens elements.

You need to have the lens checked out and probably adjusted.

Based on personal experience: If you send it in, be sure to include some sample images that demonstrate the problem and also a detailed written description. Use images that show a clear focus target and also areas in front of and behind that target. I like shooting at a hash mark on a lined U.S. football field. By shooting at a low angle the detail in the grass around your target will show what areas are and are not in sharpest focus. Another good target is a sign posted to a chain link fence. Shoot one shot straight on perpendicular to the sign and another at about a 45° angle to the fence.

I've gotten lenses back that are much more correctly aligned when including such images than when only giving a written description.

Answer 2

If you know that you dropped the lens, and that the body can work properly with other lenses - I'd advise sending the lens and body into Nikon for calibration.

You really can't go wrong with ensuring that the two are paired together right. Its possible that the issue here isn't hardware related and is due to your technique and/or expectations. Without an example or more information I can't determine that though.

Answer 3

If the lens were made by Nikon, they might be willing to look at why the camera and lens aren't playing well together. But I think this sounds like an issue for Tamron to fix. That said, why don't you post some examples of the issue? It sounds like you don't usually use the lens wider open than f/11 or f/16. Are you sure that your eye hasn't just started to notice the lower quality of this lens (vs your Nikon f/1.8, which is presumably a "prime")? I do suspect your optics may have been knocked out of alignment, but I also wonder whether your "critical eye" hasn't improved. I've certainly had lenses I used until I became dissatisfied with the result.

Answer 4

Look very carefully at the leaves of your aperture to see if there is any oil on them which would interfere when stopping down to smaller apertures. Happened to me after dropping a lens.