10 stop ND under expose?

badboy1984

badboy1984

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I've bought a 10 stop ND (Haida) not long ago and altho i do love the filter and it does give me the effect i want but i find it hard to nail the exposure on the final shot which leaves me something to post edit afterwards .......

I do the usual procedure first by composing the shot, getting the right exposure on a unfilter shot, focus etc then i screw on the 10 stop filter and calculate the 10 stop shutter speed by using the reading i get on a unfilter shot but the shot came out way under expose. i.e 1/30s i dailed in 30s but it came out way too dark on the subject, so i have put it to bulb mode and do a 60s exposure and it came out alright.

So far i gone through all the sample i take it seems the exposure is around 60sec to 90sec. The reading i get from camera is around 1/40 - 1/30 sec ish on iso 100 and aperture 16-22

Is it something i doing wrong or their shouldn't be a problem doing that long expose on day time? the concern i get is after i calculate the 10 stop shutter the exposure is way too under expose.
 
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theres also a good chance that your original shot would have underexposed - what meter mode are you using ? - if its evaluative the chances are that a bright sky will fool the meter and lead to under exposing your main subject anyway
 
I agree with both Dale and Pete here, check how many stops your filter actually is.

When you take your meter reading do you take the shot? I do and check the histogram to ensure the shot is exposed correctly before I use it as a baseline to calculate from, that way you can tweak the base exposure till it is correct, then add the 9.5 or 11 or however many stops on.

I wrote a blog piece this week on long exposures which includes a workflow for using a 10 stop ND filter if it is any help http://www.markmullenphotography.co.uk/blog/2012/8/long-exposure-photography---my-tips

(Mods, I hope it is OK linking to my blog, I hope it helps the OP, please delete if it is frowned upon)
 
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Cheers man, I will check the blog out when I go back home tonight. I do take the unfiltered shot first to check exposure and I use matrix metering.
 
try using spot reading from a foreground feature - either that or use a grad filter to balance the sky before taking your initial reading
 
cheers man. i give that a go at my garden before i heading out for more shots again :)
 
just done some testing, it appears my version of the haida 10 stop is a 11 stop ND. 60sec exposure i have to dail in 120sec to get it right.
 
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