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compuwar
Jul 22, 2008, 07:19 PM
This has been discussed in a recent filter thread and in a prior thread. Last week I was experimenting with a Kodak Wratten ND 4.00 100cmx100cm filter. The ND4 gives 13 1/3 stops of negative exposure value. My D2x apparently meters through the prism, not the lens, so I underexposed this first real test shot by a stop and a half or so guestimating the bulb setting (around 30 secs.) Therefore, I had to set a black and white point in Capture NX to bring it back to spec- I'm not sure if that or the ND filter are responsible for the Kodachrome look, more detailed testing will figure that out in the future.

There was traffic on the highway, additionally, I circumnavigated the camera while counting out the seconds, passing in front of the lens once.

I'm fairly confident that this lens will allow me to get most people out of a crowded scene for a project I want to do.



compuwar
Jul 22, 2008, 08:05 PM
Actually, I think it was the second picture where I circumnavigated the camera. Traffic was light, but several cars passed, this is a 54 second exposure, again white and black points set in CaptureNX. 20-35mm vignettes some at 20mm, even on APS-C.

Westside guy
Jul 22, 2008, 09:14 PM
That's pretty cool how well that works.

I also don't see any trace of a color cast either (I'd asked about that on that other thread).

compuwar
Jul 23, 2008, 05:45 AM
That's pretty cool how well that works.

I also don't see any trace of a color cast either (I'd asked about that on that other thread).

Yeah, exposure wasn't good (I didn't calculate exposure, I ballparked but it wasn't too far off, and I'm very pleased with the results. It was a real PITA trying to even find an ND4, but I'm glad I got it, and while I wasn't sure sub minute exposures would be useful to me, I'm quite happy with the first tests and will try to do some more testing before going on to shoot some real subjects. I expect next time I'll shoot some non-filtered tests for coparison (though it won't help compare the long exposure changes) and actually calculate exposure rather than just guessing it (though on bulb, I'm still doing "one-one-thousand," "two one-thousand..."

I don't usually walk in front of the lens, but I figured traffic was sparse enough that it was a good test- and the results are impressive.