ND Filter or Stop Down on Exposure Compensation?

[neuroanatomist]

Yes, 0.9 is a 3-stop reduction. In my experience, 2 stops may not be sufficient, especially at f/1.2 (even if you are stopping down the aperture a little for more DOF). Consider - if ISO100 and 1/4000 shutter speed is over-exposed, and you want to keep the same aperture and the ISO is already on the floor, adding a 3-stop ND filter will take you to 1/500 shutter for the same overexposure - i.e. you've got a lot of latitude to darken when 1/4000 at ISO100 is overexposed. If that's under-exposed, you can bump the shutter or the ISO one stop and you're set. More likely, with an f/1.2 lens, you'll run into a situation where 3 stops is not enough - in that case, you'll either need to stack the ND and CPL for 5 stops, or consider a stronger ND (next in the B+W lineup is the 1.8, 6 stops).



In the 72mm filter diameter, the B+W 0.6 (102) is about half the cost of the 0.9 (103) - $40 vs. $80 - and I expect that accounts for the 0.6 being 'the most popular'. Personally, I prefer the 0.9 because if I want 2 stops I can use the CPL (rotated so it doesn't polarize, if necessary).


Have you considered the expensive option of the Singh-Ray variable ND filter? Basically CPL and linear polarizer stacked, meaning you can go from about 2 stops to completely black (8 stops in practice). It's 77mm so you'd need a step-up ring (and be unable to use the lens hood), but with larger diameter vignetting wouldn't be an issue.


Vignetting might not be an issue anyway - what body are you using? If it's a crop body, with an L lens you will probably not see much vignetting even with stacked filters.

[waving_odd]

If that's under-exposed, you can bump the shutter or the ISO one stop and you're set.

That's a good point!

In the 72mm filter diameter, the B+W 0.6 (102) is about half the cost of the 0.9 (103) - $40 vs. $80 - and I expect that accounts for the 0.6 being 'the most popular'.

Another good point. And I suspect that many other users are also using it for f/1.8 (popular for Nikkor and Canon's glasses) or even f/2. Then 0.6 might be enough... Just my 2 cents...

Have you considered the expensive option of the Singh-Ray variable ND filter?

With $400 (filter + step-up ring), I rather save up another 1 grand to get 50mm f/1.2 L. []

Vignetting might not be an issue anyway - what body are you using? If it's a crop body, with an L lens you will probably not see much vignetting even with stacked filters.

I switch using it between 5D2 and 40D. But since my 24-70 needs the full frame more than this 85mm, I think you hit the bull eye that the vignetting might not be an issue as they are cropped out in the first place.