Performance Review of Panasonic GX 35-100mm f/2.8 Lens

Started Nov 12, 2012 | Discussions thread
OP William Castleman Regular Member • Posts: 480
Re: Performance Review of Panasonic GX 35-100mm f/2.8 Lens

Anders W wrote:

Thanks for your test! One question: According to one of your diagrams, the 75/1.8 does better at the edge than at the center across most of the aperture range. This doesn't seem credible. Have you accidentally mixed up the center and edge lines or what?

Thank you for asking about this.  I haven't had time to put up all of the methods used.  I reran the tests when I first saw the data.  I believe the higher edge MTF50 values on the 75 f/1.8 are due to two factors.  First, the 75 1.8 has excellent edge performance compared to other lenses tested.  However,  there is a testing artifact occurring.  I am using the enhanced ISO12233 resolution chart that has the improved lower contrast slanted edge in the center (about 10:1 contrast).  The edge slanted edge is the older style high contrast edge (40:1 contrast or greater).  It is probably over estimating edge performance.  I used to use the SFRplus chart for MFT50 testing, but switched back to the ISO12233 chart for this test because you can visually inspect the charts and see edge versus center performance and lateral chromatic aberration when it is occurring.

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William Castleman

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