BetterPhoto Q&A
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Sharon Barberee		Can someone explain what this graph means.... I found this test on my Sigma Lens but am totally confused as to what it is saying Photodo test result: 3,9 Effective focal length: 72 - 193 mm Weighted MTF for 70 mm: f2,8 0,73, f4 0,76, f8 0,75 Weighted MTF for 135 mm: f2,8 0,76, f4 0,84, f8 0,87 Weighted MTF for 200 mm: f2,8 0,78, f4 0,81, f8 0,81 Average Weighted MTF: 0,81 Grade: 3,9 Weighted MTF 10 lp/mm: 0,89 Weighted MTF 20 lp/mm: 0,77 Weighted MTF 40 lp/mm: 0,54 Max distortion: -2,22% - 3,79% To love this question, log in above October 05, 2005

Uyen		Hi Sharon, Did you mean to post the MTF charts from photodo here and they didn't appear? All that's showing up is some text. The clearest explanation on how to read these charts I've found is this: http://www.luminous-landscape.com/tutorials/understanding-series/understanding-mtf.shtml In the photodo charts, the test results are presented a bit differently than the charts in this article, but still it's a place to start. To love this comment, log in above October 05, 2005

Jon Close		The link to luminous-landscape is a good one. Additionally, at the bottom of the photodo page is a link to their own explanation, "Understanding the MTF graphs, numbers and ratings" To love this comment, log in above October 05, 2005

Sharon Barberee		Hi again, Yeah that was what I meant to do but it didnt cooperate. After ALOT of reading I think I have figured out the charts, altho I am not schooled on the tech stuff....Thanks alot !!!!!!!!!! To love this comment, log in above October 06, 2005

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