45mm f1.8 for $200 in Canada only

Started Jun 14, 2013 | Discussions thread
viking79 Forum Pro • Posts: 14,147
Re: correction: use ephotozine.com or photozone.de for MTF if not found on DPR

Timmbits wrote:

Timmbits wrote:

However, while this other website agrees with the resolution and contrast findings, it contradicts the chromatic aberration data, and isn't too flattering. erphotoreview.com/wordpress/?p=3542

Is there something I am missing? Can anyone help explain?

Referring to my previous post, it's too late to edit it. I think I may have found why that site displays very bad CA data: he is photographing the CA line pattern at a slant, and the resulting bokeh is causing the severe distortion at edges. Click on the "Lon CA" tab to see what he is doing. This is the way to test DoF, but I haven't seen other sites do the CA that way, as measuring CA when in focus in center and out of focus at edges is NOT the way to do that.

What? I don't measure longitudinal CA on my site, I show it for reference. The Lateral CA in pixel width is measured on a flat chart. I don't know why ephotozine shows less.

You have to understand longitudinal and lateral CA are very different things. Lateral CA is from difference in magnification of the different colors and is very easy to correct out. Longitudinal CA is from different focal points for the different colors and more difficult to correct out, althought lightroom does include this feature now, but it doesn't always work well.

Very sorry if I caused any confusion - please disregard the link to the erphotoreview wordpress blog.

I'll prefer to use the data on ephotozine or on photozone.de in the future.

I generally get fairly consistent results with what they do, and I find my results accurate for what I get using the lenses.


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