Archived posting to the Leica Users Group, 2004/03/08
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>A friend bought a 10D and brought it over for a test drive. I downloaded a >test chart and we had at it. We posted two test charts about 2 meters >apart. I put a 50 Summicron lens on my R8 and he used a zoom with a top >range of 35 on his 10D (I am not sure what zoom it was). That gave >approximately the same coverage. We backed up so one chart was dead center >and the other one at the edge of the frame. Took a shot at f-8. I was >using Velvia and he saved his in the highest quality jpeg, one step below >Raw. He used manual focus as did I. We both used tripods and mirror >lock-up. We really wanted to do this outside, but it was raining and windy. >Couldn't wait as he was leaving the next day for two weeks vacation. Here >are the results of the target at the center of the frame. We shot at f-4, >5.6 and 8. I used the f-8 version because I thought it would compensate for >any focus problem a bit more than the rest. The light in the hallway was >quite dim and the exposures at f-8 are about 2 seconds for me and about 1 >second for him (ISO 50 vs 100) Aram I did some tests in the past comparing different lenses. Main problem is, always, to get the chart you are photographying exactly paralel at the film-or sensor- and this is achieved by using a bubble level and using a completely flat table and attaching the chart there. Secondly you need placing your camera so that the optical axis hits exactly the center of the chart. Otherwise the corners will have softness not due to the camera but to the lack of right centering. You need use the bubble level for leveling the camera and you need, too, be carefully lifting the camera in his tripod up to the exact place. It takes trully a lot of time. You need natural light if possible measured with a colormeter so that colors match and metering with incident light meter or bracketing but everytime you move the camera you need to check again the paralellism. Not an easy task. In the samples you showed us something went wrong with the 10D who, inferior to the Summicron, is not that bad. Do again. With these kind of tests some myths may collaps. Regards Felix - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html