How do you test lens sharpness?

The best test is a picture of a duck.

Fresh baked bread is an excellent test subject when dealing with sharpness. If you bread gets smushed, you aren't all that sharp.

Failing that....stick with ole Doc Klepper's advice...makes the most sense.

tange1 wrote in post #2146495
I'm just curious but how do you test if a lens is decently sharp? I just got a 28-135mm IS USM from a friend and it seems great but I just wonder how sharp it is in comparison to my kit lens?

I do testing similar to that done by photozone. My software and targets are available but the software requires a programe called Matlab to run. Alternatively you can by a copy of Imatest that photozone use. These methods give you actual number to compare and are very consistant is done with reasonable care.

The simple old test was to tape a peice of news print against the wall and shoot that. Things to observe doing this.

Shoot at constant magnification.
Make sure the camera back (sensor) and target are parallel.
Shoot every stop from wide open to f16.
Use a tripod and mirror lockup with a cable release or the 5 second timer to remove vibrations.
Repeat the test at least 3 times with a new AF action each time and use the sharpest one as AF accuracy has a random element.
Ensure all shots have the same post processing.
Examin at 100% to determin relative sharpness.

fslshooter wrote in post #2147485
Here's an easy way to test for sharpness. Mount a yardstick with easily readable numbers on it at a 45 degree angle either vertically or horizontally from where you shoot. Use center point focus, focus on the number 18, shoot then view the image on your computer monitor. If #18 is perfectly focused then the lens is sharp. If any other number is in better focus than #18 then the focus is off.

This is not a test for sharpness, it is a not very good or reliable way of checking the AF accuracy. There are better method for both.

I agree with Doc. The best test is to go out, take a bunch of pix, and see how it performs. I don't take pictures of batteries, rulers, test patterns, etc. See how it performs in the real world.