Nocticron Transmission = Poor.

Started Apr 18, 2014 | Discussions thread
kenw Veteran Member • Posts: 5,342
Re: Other fast lenses really not much better

Anders W wrote:

I checked my 12/2 and 20/1.7 using methods somewhat similar to yours: shooting the same small patch of the wall in the center and in all four corners and then checking the RAW levels via RawDigger, but taking into account where the corners of the frame are actually located after software-correction. I get a figure just above one EV worth of vignetting with both lenses wide open. Lenstip reports 1.49 EV for the 12 and 1.65 EV for the 20, so it seems they are indeed overestimating things, although the overestimate is not quite as large in these two cases as in the one you examined.

DxOMark reports about 1.1 EV for the 12, which fits well with my measurements. For the 20, however, they report about 1.6 EV for version I of the lens (the one I have) and even more than that (1.7 or 1.8) for version II, which is 0.5 EV or more in excess of my results. It looks like their results are based on some kind of curve-fitting (if you look at "profiles"). I wonder if that plays a part here.

Photozone reports about 1.3 EV for the 12 and 1.5 EV for the 20. Again a bit too much. SLR Gear has about 0.7 EV for the 12 and about 1 EV for the 20. So their estimates appear to be a bit too low.

Weird that we don't seem to have reliable results from any of the major lens testing sites with regard to vignetting. Doesn't seem like the most complicated thing to measure.

Yes, I've always naively thought that vignetting would be pretty easy to measure with the possible exception of camera model variability with very large aperture lenses due to different off axis response. I compared LensTip, photozone and DxO for a few lenses just as you did and was equally perplexed.

Thanks for sharing your results!
Ken W
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