ND Filters

mercphoto

I want to make sure I'm getting the right filter. I'm in need of a neutral density filter. Sunday I made a shot at 1/2 second shutter. At ISO 100 the camera was blinking f/22, which meant the exposure needed an aperture smaller than my lens would close down to. I put on a circular polarizer simply to cut out one stop of light and it still flashed. I took the shots anyway. I cut 1.25 stops of exposure out in the raw converter and its still a tad over-exposed. So that looks like 2.5 stops of light too much. Correct?

I went looking at ND filters and it seems an ND4 is good for two stops and I didn't see anything (yet) more severe than that. Do I stack ND filters? Any other tricks I should know of? Thanks.

Pupator

Sounds to me that you're on the right track in every way. Stacking is fine but I seem to remember reading that you stop a bit more light with 2 +2 filters than with 1 +4. I don't know how valid that is, but it made sense to me at the time.

mercphoto

Pupator wrote:

Sounds to me that you're on the right track in every way.

What I wanted to hear before I spent $$$. I have found a B+W 3-stop filter and will probably get that.

ziggy53

This from Adorama:

"B&W Neutral Density filters are available in most sizes and in the following strengths:
· .3 (2X) Reduces the light one f-stop.
· .6 (4X) Reduces the light two f-stops.
· .9 (8X) Reduces the light three f-stops.
· 1.8 (64X) Reduces the light six f-stops
· 3.0 (ten f-stops) & 4.0 (seventeen f-stops) are for astronomical and sun studies."

Example:

http://www.adorama.com/BW67ND1X.html

TylerW

Hrmph. Bought an ND2 a couple of weeks ago from calumet after asking for a two stop ND. Sales clerk insisted that ND2 = 2 stops of light after I quizzically asked about it, since it looked a little light to be a full two stops.

Hopefully I still have the recipt.