These tests are from the Swedish magazine Aktuell Fotografi. They started MTF lens tests in 1990 at the optical lab at Hasselblad.

The tests are done at 10 cycles/mm ("contrast"), 20 cycles/mm and 40 cycles/mm ("sharpness"). Both tangential and radial MTF values (0 - 1) are read at 0, 3, 6, 9, 12, 15, 18 and 21 mm off the optical axis. A MTF value of 1 equals a 100% transfered contrast which is impossible. Very good lenses have MTF values over 0.80. For some lenses the values drop to almost zero in corners wide open. Each lens is measured at f/4 and f/8.

A rating is calculated based on all data but with a weighing system.

• 10 c/mm = 57%, 20 c/mm = 29% and 40 c/mm = 14%
  
• Data between center (0) and corner (21) are weighed with decreasing weights from center to corner.
  
• f/8 = 67% and f/4 = 33%

This rating system is weighted for "contrast", center and stopped down. The same system is used for all lenses. You can directly compare a zoom lens to a fast prime lens. You can also compare 35mm lenses with medium format lenses. Becuase of the larger image circle, medium format lenses have lower ratings than 35mm lenses. But since these images need less enlargements, the final picture will be better.

The rating system was designed to give numbers between 0 and 5. The mean value of these ratings are around 4. Most good prime lenses have ratings over 4. Really bad zooms have under 2. Note that a lens with a rating of 0 would still produce an acceptable (in small prints) but soft image.
These tests include only sharpness/contrast, not vignetting, distortion, centering etc that is included in some other tests, e.g. CDI or ColorFoto.

The data is collected by Olle Bjernulf.