50mm f1.4 possible problem

lizzard_nyc

HI all,
I am not tech savy at all, and know in my heart that I really never will be, so please, use small words.

My old 50mm f1.4 for my Canon broke, it refused to AFabout 3 months ago, went and traded it in at Adorama, and got another copy. I've used it since then but recently I'm just not happy with it, nothing seems tack sharp, but between switching lenses and cameras lately, I didn't really notice it too much.
My brother borrowed the lens for shooting a parade w/ me and he also came back w/ many shots that were blurred (a higher number than usualy he said, but he's also not used to shooting w/ a 1.4 lens and was using it at pretty close to 1.4 and 1.8, which could be the problem).

My question is this.

How do I test a lens? in small words please.
I want to know if it's user error or lens error.

thank you,
Liz

ziggy53

lizzard_nyc wrote: »

... many shots that were blurred ...

"Blur" can be synonymous to "soft/out-of-focus", or blur can be something else entirely. Links to sample images, full resolution and full EXIF, would be extremely helpful in a proper diagnosis of the problem.

lizzard_nyc wrote: »

... My question is this.

How do I test a lens? ...

When I test a new lens I often choose a few different subjects for comparison:

1) A brick wall, shot straight on and squared with, using a tripod. This is a pretty good test for front-focus, back-focus, field curvature and vignetting issues. If a camera/lens combination does not focus accurately in this test, something needs to be serviced. Make sure to test at least twice MFD (minimum focus distance) from the wall.

2) A fence line or similar, shot at an angle to the subject. Put a singular strong-contrast target on the top of the middle post and use a single focus point in the camera to focus against the target. This shows focus accuracy and/or how easily distracting for/aft objects influence AF accuracy (compared to the above wall shot). It also shows bokeh tendencies at different aperture settings.

3) A focus target/chart like in the following:

http://regex.info/blog/photo-tech/focus-chart

I do recommend testing these charts at twice minimum focus distance or greater. Most lenses, especially most zoom lenses, do not do their best at MFD. True macro lenses are the major exception.

4) A US stop sign, or similar very high contrast signage, both centered and off center and to the side and/or corner. This can show chromatic errors and off-axis errors.

5) A spectral highlight at night. (Point source ideally, but a street light at some distance will do.) Try to avoid "blooming" of the source but allow some white clipping. This shows internal reflections and dispersion problems. Again, test both in the center and with the subject at the sides or corners.

6) Now just shoot "typical" subjects for your use of the lens(es). It's important that the lens perform correctly for your intended uses.

Feel free to use JPGs and just give image links or directory links, but any significant issues and comparisons you may want to add inline to a post describing particular issues. These may be crops and display 100 percent if you wish. 100 percent crops aren't really fair unless you intend to print "very" large, but it can be easier to display comparisons for examination and to demonstrate problems.