I recently purchased a used Canon 55-250mm IS lens and it works nicely at 55mm(even with lower shutter speed, and f/4 aperture), but turns out quite blurry at longer focal lengths, even with a shutter speed of 1/800, f/11 and while mounted on a tripod. I'm not sure if this is a user error, or something wrong with the lens. Any ideas?
Your lens is damaged.
- One of your images (shown below) exhibits an abnormal amount of spherical aberration. It is not the kind of softness you would get when out of focus. Also, notice that the bricks on the left side are significantly softer than the right side, which indicates decentering. Both of these indicate that one or more lens elements have been thrown off their correct position, most likely due to impact or shock (e.g. being dropped). (Note that dust spots are visible in your image which indicate that your camera's sensor needs to be cleaned.)
- Your lens needs to be repaired or replaced. Considering the low cost of the lens, the latter is probably the more economical option. I have personally dealt with this issue with a similar lens for the Pentax K system. See: Pentax DA L 55-300mm lens very soft--is it broken?
I think @ths is right, and you probably need to try to repair the lens. However, before you do that, the following might solve your problem, or at the very least will mean you've tried everything before you try a repair/replacement.
- On the tripod, is image stabilization turned off? I doubt this will make significant difference, but may be asked when taking for repair.
- Is autofocus turned on, on both the lens and body (if applicable)? If set to manual focus, the camera will obviously take the photograph regardless.
- Is focus mode set to continuous tracking? That is, if you keep the shutter release half pressed does the camera continue to focus even as it is moved?
- Are the front and lens elements clean?
These might be a bit basic, but just mean you have everything covered if you try to take your lens back.
Based on personal experience, I'd say the 55-250 is best from 55-135mm and then the performance does drop off from there to 250mm. But having said that, the samples you posted indicated you are not getting close to the potential of this lens when performing properly. If there are no other issues present that could cause your photos to be blurry, then it appears there is a problem with your lens.
The following photos were taken with an EOS Rebel XTi (400D) and an EF-S 55-250mm f/4-5.6 IS II lens. They were resized to 1152x768.
ISO 800, 1/100 sec, f/5.6, 250mm
ISO 200, 1/800 sec, f/10, 250mm
When the full resolution version of the second photo is viewed at 100% there is some softness on the right edge of objects and people that are the same distance from the camera as the subjects that are clear. The AF was aimed at about the fifth row down from the top (the folks just in front of the guy in the white shirt). There is much less of the edge softness on the left edge of the frame.