Archived posting to the Leica Users Group, 1996/05/20
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Lens tests...The Air Force resolution tarkets were mentioned --the ones adapted by Modern Photography Magazine many moons ago. Actually, it was about 1960 or so that Modern made a lens test set up using copies of the Air Force resolution targets. I know about this because I did it. The test procedure was spearheaded by Ben Sherman, Burt Keppler, and Ed Meyers (me). I had the original Air Force target made into a fine negative, from which we contact printed (by vacuum, I believe) the target prints. They were all high contrast at that time. The array was placed on a wall and test were made at about 25X (when possible) the focal-length distance. For long lenses I did it closer and adjusted the reading results. Panatomic-X film was used, processed in Kodak Microdol-X developer. I read the negs with a high-quality 20X microscope. Oh yes, the test exposures were made without the camera shutter. I used the on/off light switch to prevent shutter shake. Interpretation of the resolution targets, sometimes, could go one step higher, or lower. We usually gave the benefit of doubt and chose the better reading. Much can be said about resolution with high-contrast targets being the wrong way to go. At that time it was the one and only, until it became more scientific. But I remember the following: Sometimes Leitz lenses would score thru the roof, as I believe, at that time Leitz had very high resolution, but not-so-high contrast. Zeiss lenses had not as good resolution, at times, but very high contrast. Nikkor lenses seemed to go the Zeiss way with high contrast. Therefore, sometimes Nikkors didn't even pass the resolution test, and I had to ask for another sample--that that didn't always pass. Yet the Nikkors made very sharp photographs. It's all different now. Leica has much higher contrast than it had in the old days. The early Summar had good resolution but is very low in contrast. I still have an unscratched one. Many funny things happened while testing lenses in those days. Too much to write down at this time. But get me started in a room of people and it would be an entertaining evening. Ed Meyers