lens sharpness

[AlQ]

....at what point can you determine that a lens is bad and any fuzziness is due to the lens build and not human error?

Is there a way to quantitatively test the clarity and sharpness of a lens?

thanks!

[FallsCity]

This link might be helpful..

Finding the Sweet Spot

Instructs you how to find the sweet spot by taking multiple pictures, each at different apertures and seeing which is the sharpest.

[inkista]

Lens testing can be highly error prone, and not many people know how to do it right, which is why there's so much argument over results on websites on equipment "tests".

But basically, make sure you've eliminated any and all possible technique issues:

1). Have a well-lit target. Preferably one that's flat up against a vertical surface that you know the camera is perpendicular to (i.e., DoF and slanted surfaces and missing an AF target accounts for a lot of mistaken softness issues). Use a high-contrast target (printed material is usually very good).

2). Use a good, sturdy tripod. (Handholding camera shake thus eliminated). Remote and timer also good. Mirror lock-up if you're insanely paranoid about shake of any kind.

3). Test at all the full-stop aperture settings, not just wide open. (Most lenses display the most weakness wide open. That doesn't mean the lens is bad).

4). Manually focus the lens on the target using liveview and 10x magnification. This eliminates any AF system errors or AF system calibration errors from the equation.

If your lens still looks like crap after all this, then it's the lens, not the camera, and not technique. Typically, though, it won't be.