Quote Originally Posted by canoli


wondering if you can help me choose a ND filter...I'll be out in Big Sur next month, and the coast is generally very sunny once the fog burns off. I've never used a ND filter, so anything you can tell me will be helpful.


I'll be using a 40D and the 17-40, 70-200 2.8 IS and the 50 1.4. I have a good tripod, cable release.


I'm leaning toward the square filters with a 2-stop factor. But do I need a holder as well, or do you generally just hand-hold the filter in front of the lens?


Do you have any sample pictures (with EXIF) that'll represent what you're trying to accomplish? For example:


f/22, ISO 50, 1/15th:





I had the 85/1.2 with me, and tried some shots with it, but I had no ability to get thin DoF at the same time as motion blur - I think wide open I was getting 1/5000th at ISO 100 (if not ISO 50).


If I wanted f/1.2, ISO 50, 1/8th, I'd have needed 8 stops of aperture change and one stop of shutter change, so I'd need a 9-stop filter to get those specs. I'd probably end up with a 10-stop filter and ISO 100 (which I wouldn't be complaining about) to get there.


You might want slow water/surf blurs, so you may not care about thin DoF (but might want to get closer to f/11 to avoid diffraction effects, so that's two stops). You'll want to confirm the minimum aperture of your lens (i.e. the 85/1.2 only goes down to f/16, whereas I think I have a lens that'll go to f/32). You'll want to determine the shutter speed you want, and work the math from there.


I haven't bought ND filters yet, as I don't feel like I have the disposable cash to buy a full set, and rarely have a strong desire to have one. That said, I figure I'll get something along the lines of 1, 2, 4, and 8 stops, knowing that I can stack no more than one filter and get most combinations from 1 to 12 stops (I'd be missing 7 and 11 stops, oh well). Given normal product lines, I suspect I'll be looking at the 1, 2, 3, 6, and 10-stop models, which would give me everything from 1 to 16 stops (except for 14 and 15 stops) with no more than 2 filters at a time.