Extreme ND Filters
An ND filter reduces the amount of light entering the camera.
This principle can be used to produce smooth elegant images.
Attaching a 6-stop, 8-stop or even a 10-stop ND filter will allow
much longer shutter speeds - anything from 1 second to 30
seconds to 3 minutes.
Effects
1. Clouds appear to scud across the sky.
2. Waves and rivers blur.
3. Passers-by become transparent ghosts or even disappear
completely.
Note
1. You can stack filters to increase your stop value but air gaps
between stacked filters can lead to light leakage, flare and
reflections.
2. Many ND filters cannot block infrared so you may have to
tackle magenta colour casts, this is only an issue with digital
sensors, does not apply to 35mm cameras, check the
photoshop link in photography 101 to view 'How to remove
colour casts in Photoshop '.
3. Use ND filters only in outdoor and in daylight conditions, take
care in bright sunlight scenes as flare from bright elements like
water can cause sunspots on your final image.
4. Example camera settings, f/8 at 1/125 sec when 10 stop ND
filter added the shutter speed increases to 8 sec.
5. 30 seconds is the longest shutter speed in manual mode, for a
longer time then 30 seconds you will have to use bulb mode
and a remote shutter release.
6. Always position the ND filter closest to the lens, then followed
by a graduated ND filter or polarizing filter.
7. If using the slot in type filters i.e. lee or cokin, you can eliminate
glare and sun flares by placing a strip of gaffer tape along the
sides and top of the filter assembly. Gaffer tape leaves no
residue so is safe to use on photographic equipment which
is what it was designed for.
How to use your extreme filter
1. Compose your shot, leave the ND filter in the bag as it will only
block your view through the view finder.
2. Find a strong composition, simple and graphic.
3. Set your camera on a tripod.
4. Switch to aperture priority mode and choose a suitable aperture
say f/11 for landscapes.
5. Set your iso to 100 or 200.
6. Select RAW and JPEG from your camera menu.
7. If your are going to use a polarizing filter now is the time
to slide it into your filter holder and rotate to achieve
the desired amount of polarization, a polarizing
filter will give you a 2 stop light reduction so must
be attached for the initial exposure reading.
8. Depress the shutter button half way to activate the cameras
built in light meter and record the shutter speed.
9. Now switch to manual mode and set the same aperture value,
manually focus on the subject.
10. Convert the camera shutter speed using converter chart below.
11. Add in your ND graduated filter if you are going to use one in the
second slot and align it as required.
12. Now add your ND filter to the first slot beside the lens and cover
the viewfinder to prevent any light leakage also check the sides
of the filters to make sure no glare is hitting them, if so then shade
with your hand or gaffer tape, then activate the self timer or use a
cable release.
13. Take two photographs and check exposure and sharpness.