I am a new GND filter user, and I am having a little bit of trouble with my Genustech 10-stop ND filter. It seems when I use it and stop it down 7, 8, 9 or to the maximum, there are uneven shadows cast over my image.
I am using the filter with a Canon 35L and a 72 to 77mm stepup ring. I have done a fair amount of experimentation and most of my results are coming out the same. The only idea I have (which I would appreciate confirmed, if possible,) is that the step up ring is somehow interfering.
Here are four test images to demonstrate the problem I am having.
Yeah. That's the nature of the beast. You're really dealing with two polarizing filters in front of your lens, and the further you go in your ND, the more likely you are to see that. I bought a Genus VND and returned it the next day - both for that and for how much detail the filter took away from the image, which was considerable. In my opinion, you're better off with fixed ND filters.
Yes, as Peter says, that is a problem common to, as far as I know, all variable ND filters. In my experience they are usable to about 5 stops before the uneven density becomes obvious. If variability up to 5 stops meets your needs, then you may still find it convenient. But to get beyond that, and especially in the 9 to 10 stop range, you will be much happier with a regular ND.
Thanks everyone. I am having better luck stopping down to 8 or 9, rather than to the max. I appreciate the input—thanks for helping me understand my new toy :P
