I've had the B+W 10 stop 3.0 ND filter for a few months now and thought I would give it a whirl on a recent trip to NZ. In retrospect I should have played with it before I left or even researched other peoples experiences, needless to say I had mixed results. Since then I've studied up and thought I would share some tips that may help you get better results.

First up how I use the filter. Before you even put the ND filter on follow these steps:

• put your camera on a tripod :) you are going to be shooting upwards of 10s so this is a must.
• compose the shot, if you are using this filter it's likely you want to show some sort of motion blur, include clouds, water, crowds or something that moves and juxtapose this with something static.
• set focus and switch to manual, I wouldn't rely on auto focus through the filter.
• set the white balance (the camera has no chance once the filters on) or put a white card in the first shot to set the WB in post.
• correctly expose the scene, setting the aperture and shutter speed (for the scene without the filter at this stage).
• take a test shot and check histogram (re do previous step if unhappy).

Note: setting the white balance isn't as important if shooting in RAW but is a must otherwise.

Put the filter on!

• stop down the exposure 10 stops (for my camera this is 30 clicks of the shutter speed wheel as each increment is a third of a stop - make sure you are going the correct way!).
• go for it, check histogram, correct accordingly.

At 17mm on a full frame camera I noticed the filter vignetted quite a bit so be mindful of this. When you get your photos into post you are likely to have to do a lot of colour correction, first correct the white balance. Colours still look way out? You've either got colour cast caused by your filter (I can say from experience the drop in Formatt (Hi-Tech) filters are bad for this, tisk tisk not again Formatt?) or infrared contamination (images lack contrast, appears 'muddy').

Here is a shot taken at Craters of the Moon, Taupo, New Zealand. Straight out of the camera you can see it looks muddy and the white balance is all off:

After some colour correction in Adobe RAW we get:

Converting to black and white and processing in Photoshop the end result is a far more contrasty shot where colour is not an issue:

IR contamination the good the bad and the ugly:

• foliage (leaves, grass etc.) come out bright, can be a good look in b&w, leaves reflect IR so they don't burn in the sun!
• Blue sky's appear darker, good thing
• Rocks and sand absorb IR, can look muddy and lack contrast
• the sea absorbs all IR, ok to shoot

There are a couple of options to minimise IR contamination.

• The use of an additional hot mirror filter to block IR (I've never tried this so can comment on its effectiveness)
• Shoot the sea to minimise IR
• Don't shot long exposures!
• Shot long exposures as well as short ones and blend in PS