Originally posted by uccemebug Lowell, are you saying you think you can test for the bokeh issue and/or the light falloff issue?
I can't say that I can test bokeh, any better than anyone else, but for light fall off, anyone with a K mount or M42 lens with F1.4 aperture can do this.
It is really simple. In fact, I do a similar test with my lenses now.
I shoot against a uniformly lit block wall, to test metering, and I have published the curve for my K50F1.4 lens many times on my *istD, K10D and K7D. All that is needed is to take the same setup and as opposed to checking exposure accuracy at each aperture, letting the camera pick the shutter the metering thinks it needs, take the lens at one metered point, (I would recommend between F4-5.6) and then change both aperture and shutter to match that exposure setting, across all apertures.
The problem is that sometimes F1.4 is just so bright that you don't have the range to take the shot because you are above 1/4000. but any way, you get the idea.
you can then measure in any good photo editor the greyscale value of the central portion of the frame. this may or may not change over the exposure range, and that change will be due to 1 of 3 specific things. Either shutter speed error, aperture error, or the behavior of the sensor as a function of the angle of incidence of the light. The other key indicator of sensor issues is not in the middle of the frame where the light hitting the sensor is highly accute, but at the corners. The issue of deep well sensors is largely a cause of vignetting. So a real indicator of this may be to measure not just the central portion of the frame, but the corners, and compare them. I do not knwo wat editor people use, but I use PSP X3 and it can measure either the entire scene or just the selection window, for greyscale values. Therefore when I do tests I use the selection window and select an approximate 10% area box in the middle. I have done checks when others have posted, on the corners also to show vignetting.
I am willing to bet that there will be much more issue with respect to lens accuracy, especially aperture, than with any other measureable issue. My gut feel is that Fast lenses might be a little "optimistic" in the nomenclature of the lens. Remember there is marketing involved here as well.
The fact is, every one should do a test with their kit to measure at least exposure accuracy with each lens/camera combo any way. Just to understand how it behaves.
Here is a copy of the Metering errors for my cameras with the K50F1.4 attached
You need to know that between roughly 25 and 230 greyscale value on the histogram, that the change in greyscale is almost linear in terms of EV with a 1EV change being about 45 greyscale. I measured this by changing shutter speed up and down with a fixed aperture and the same block wall target.