ND Filter or Stop Down on Exposure Compensation?

[waving_odd]

I am really happy with the bokeh of the 85 f/1.2 L II. However, f/1.2 could be subject to over-exposure if using outdoor, even if I change to use lowest ISO and very fast shutter speed.


So should I get a ND filter to stop down? If so, what Attenuation Factor should I get?


How about stop down on Exposure Compensation?


Any other suggestions?


Thanks in advance!

[Daniel Browning]

So should I get a ND filter to stop down?

Yes.

If so, what Attenuation Factor should I get?

I find that 0.9 is usually enough to get the shutter speed down to 1/4000 or so.

How about stop down on Exposure Compensation?

That wont do anything if your shutter speed is already as fast as it can go.

[neuroanatomist]

[Exposure compensation] wont do anything if your shutter speed is already as fast as it can go.... your ISO is already set as low as possible.

So yes, you need an ND filter. Note that a circular polarizer gives about a 2-stop reduction, and if necessary (on an 85mm lens) you can stack filters as long as the mounts are reasonably thin. With an L lens, you'll definitely want a high-quality filter, such as B+W MRC or the higher-end Hoya filters.

[waving_odd]

Thanks Daniel and neuroanatomist.

I find that 0.9 is usually enough to get the shutter speed down to 1/4000 or so.

So 0.9 is 3 stop reduction. Would the reduction be too much by your experience? Heard froma well known online filter reseller that B+W's 0.6 is the most popular ND filter in photographic work. So is 2 stop a more popular choice?

Note that a circular polarizer gives about a 2-stop reduction, and if necessary (on an 85mm lens) you can stack filters as long as the mounts are reasonably thin

That's exactly my concern too. Currently there is a B+W XS-Pro UV 010 on my 85mm glass. It's thin -- 3mm. But since they don't have CPL nor ND on XS-Pro slim mount yet, I could only stack another regular F-Pro (5mm) CPL/ND on it. Of course I can take away the UV to avoid stacking. But it's really inconvenient. []

[Daniel Browning]

Would the reduction be too much by your experience?

Not for me.

Heard froma well known online filter reseller that B+W's 0.6 is the most popular ND filter in photographic work. So is 2 stop a more popular choice?

That makes sense.

Currently there is a B+W XS-Pro UV 010 on my 85mm glass

Be aware that flare and glare is increased by having a UV filter (no matter how good the coatings are).

Of course I can take away the UV to avoid stacking. But it's really inconvenient. [img]/emoticons/emotion-6.gif[/img]

I definitely suggest removing the UV when you use ND, otherwise the flare will be even worse.

[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.