LENS TESTING
You are looking at this file because you have some interest in checking the resolution of your lenses. The ability of a lens to resolve lines per millimeter (lpm) is not the only factor in lens quality. High resolution is only a necessary, but not sufficient, condition for lens quality. Contrast, distortion, flare, physical construction, etc. are all important factors. However, a lens that cannot produce decent LPM figures can never be a really good lens -- at least in my opinion.
Comments and/or questions should be emailed to me at "Z_Q-G.-U@COX.NET". I will try to respond to them individually unless the answers would be of wide interest, in which case I will post them as well.
The files listed below, which are available on this site, are scanned copies of the resolution chart and instructions published by Modern Photography, which stopped publishing nearly 15 years ago. In those years it was a competitor of Pop Photography. The lens testing kit contained original charts, instructions, and a loupe of about 26X power. I trust making copies of the instructions available is not deemed a copyright violation since the "owner magazine" no longer exits, and this is a labor of love and not profit.
To obtain actual lines per millemeter figures for your lenses you should follow the instructions exactly. While I base my test procedures on the instructions, I have modified and simplified them to facilitate my testing.
First, I include a known lens of high resolution in every test roll to serve as a benchmark. If the results for the benchmark lens are consistent across test rolls of film, then the balance of the tests on those rolls are probably valid. For me this lens is the 50/1.4AI which I shoot at 1.4 and 2. Note that in certain lighting conditions a very high shutter speed (1/8000?) might be necessary to test at 1.4 . Secondly, I use TMAX 100 developed in Dektol. Slow high resolution slide film is easier to use and read, but it is much more costly and time consuming than developing TMAX in my darkroom. I understand that Pop Photography is converting over to using Tech Pan film for its resolution tests. I have an old piece of masonite that I hang on my garage door. On it I have mounted the center chart and the two upper corner charts set the correct distances apart. I don't bother with the lower corner charts. All I do is hang the panel on the door, back up far enough so that the two corner charts appear in the corners of the viewfinder and then shoot. This places the lens sufficiently close to the exact distance from the chart that the instructions specify. My own experience is that a 20X loupe is barely sufficient for examining the charts. I normally use a 30X. I consider any lens that can resolve at the center the 0,1 group or smaller to be a sharp lens. Corners need to be at perhaps the -1,4 or smaller to be sharp there. I generally only test at max aperture and max+1 aperture since that is where nearly all my shooting is done.
Never test using AF, unless you are simply testing the camera's AF capability. Manually focus only. Use a MF camera if possible, since the bright focusing screens of a modern AF camera are not as precise. However, in the last year or so, I have gone to AF since my eyesight is not what it once was. Third, use a focusing magnifier if your camera allows its use. By doing all these things you are eliminating variables/factors that could distort the result. Even doing all this, I still end up with frames where the corners are resolving more LPM than the center, which means I have slightly misfocused the center and the curvature of field is making the corners appear at their sharpest.
Because the camera to target distance is rather short, I also set up two additional sets of corner charts and test at two other longer distances. The center chart remains in the center. Naturally, the groups that can be discerned with the loupe change the farther the test distance.
I scanned the resolution chart at 300 dpi. There are some flawed places in the scan, but I believe the result is of sufficient quality for the task at hand. It is set up so that if the image file is printed to an 8.5x11 paper size, the chart part of the page should be the correct size for the tests. The actual chart should be 4"x5" and is in the .gif format. The instructions are available only in TIFF. The TIFF format produces a cleaner and clearer output, and is a much smaller file than the JPEG format, and as such should download quicker.
You should download and print out at 300 dpi or higher RESCHT4.TIF (print at 4.5"x5.5") or RESCHRT3.GIF (print at 8"x10") and files TXTP1 - TXTP15.tif . Alternatively, download the AIRFORCECHART.jpg and print that. Note that some page numbers are missing.
txtp1.tif
txtp2.tif
txtp3.tif
txtp4.tif
txtp5.tif
txtp6.tif
txtp7.tif
txtp8.tif
txtp9.tif
txtp12.tif
txtp13.tif
txtp14.tif
txtp15.tif
reschrt3.gif
rescht4.gif
AIRFORCECHART.jpg
