Response to Anders W and a few comments re E-M1 and A7

Started Dec 23, 2013 | Discussions thread
seachicken2000 Veteran Member • Posts: 3,228
Re: Whose humbug?

Anders W wrote:

Have now checked out your RAWs by means of RawDigger and get a value of about 1.9 EV (just like Photozone) for the NEX-7 and about 1.8 EV for the NEX-F3. I was not super careful when I took the measures but I think these values are unlikely to be off by more than one unit in the first decimal. So a tad less vignetting with the F3 but only a tad. The F3 image is also a tad brigher overall, which may at least partly explain your initial impression.


I get slightly different values, but not off by more than one from yours: 1.7EV (NEX-F3) and 2EV (NEX-7) from RawDigger using the green channel.

I also took a sequence of NEX-7 images increasing the exposure (as with the NEX-F3), and found the corners overtook the center levels between 2 and 2.3EV. The vignetting profile on DXO's NEX-7 test at 10mm f/8 shows 2.3EV at the 100% field position, so this kind of fits with both photozone and DXO.

The intervals I get are 1.3~1.7 for the NEX-F3, and 2~2.3 for the NEX-7. The values were on the upper end of first and the lower end of the second, so I believe this is consistent with the RawDigger figures.

What I still find unexplained is that even though the lens seems to have an image circle much wider than APS-C (from the images taken with the A7r), the vignetting seems larger than expected and increases sharply towards the corners on the APS-C bodies. One explanation might be that even the NEX-F3 is pixel vignetting, and the A7r with its offset microlenses improves on this. I plan to upgrade to the A7r when the price settles down, and I will try the same experiment again and see if anything changes.

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