Karl Williams

As some of you know, I make considerable use of the NDx1000 filter to enable me to shoot long exposures in normal light with a view to producing images like these:

A number of you have asked me about this filter (what they are, where they can be purchased, how they are used etc.) so I thought it might be useful if I wrote a few details down.

Most of you will be familiar with the use of neutral density filters, which are essentially “sunglasses for cameras” in that their sole purpose is to reduce the amount of light passing through the lens. The most common types are the NDx2, NDx4 and NDx8 filters which reduce the light by factors of 2 (1 stop), 4 (2 stops) and 8 (3 stops) and are readily available from camera shops and online suppliers. Although these can be used in any combination to produce a combined effect of anything up to NDx64 (6 stops), stacking is not generally recommended because of the problems of vignetting with anything approaching a standard or wide-angle focal length. Apart from anything else, a bit of common sense, and a rudimentary knowledge of optics, suggests that one layer of filtration is better than 3!

The NDx1000 filter (approximately 10 stops) is, as far as I’m aware, only produced by one manufacturer (B+W) and is available as the B+W ND-110(3.0) filter. It is not generally available from high street camera shops but can be purchased online in the UK from Warehouse Express. Because of its comparative rarity, however, it tends to be (occasionally) in short supply and it is expensive. Currently, the cost of a 77mm filter (which fits the Canon 10-22mm zoom and the Sigma 10-20mm zoom) is £79.99 from Warehouse Express .. so it’s something you need to think seriously about before committing yourself. If you’re anything like me, your camera bag and computer are full of expensive gadgets and software which, at the time, you couldn’t possibly live without but which, in hindsight, you could all too easily live without!

As far as the use of the filter goes, the major problem arises from the fact that it is so dark that it has all the light transmission properties of a lens cap .. you can see the sun through it, but that’s about it! Not only can you not see through it, neither can your autofocus gizmo and, given the sort of exposure times you’ll be dealing with (100+ secs), your “live view” screen will struggle as well. This means that all your composing, focussing and exposure measurement have to be done before you put the filter on the lens, and a wee bit of calculation has to be done to convert the “unfiltered” shutter speed to the “filtered” shutter speed. OK, it’s a bit of a bind but into every life a little rain must fall, as they say .. the end result is well worth it.

So .. on to the nitty gritty. Here’s what to do:

1. CHECK YOUR BATTERY .. believe me, you do NOT want it going tits up in the middle of a long exposure!

2. Remove the standard UV or protection filter from the lens (if you want to avoid the possibility of vignetting when the ND filter is on), set the lens to “manual focus”, set the exposure programme to “manual” and set the camera up on the tripod.

3. Do the “composing and focussing” bit and adjust the aperture until you get “correct” exposure with a shutter speed of 1/10 sec (bear with me, there’s a reason for this);

4. Put the filter on the lens!

5. Cover up the eyepiece (some cameras come with a wee rubber eyepiece mask for this purpose) to avoid stray light leaking through the eyepiece onto the sensor.

6. Activate your “live view” facility. Yeah, I know I told you it would be virtually useless but you’ll see enough to know that light is getting through to the sensor. Apart from anything else, it locks up the mirror (at least it does on my Canon) and that’s always good practice for tripod shots.

7. Connect up your cable release, set the shutter speed to BULB and expose for 100 secs (which is 1000×1/10 .. now you can see the reason for choosing an easy “unfiltered” shutter speed). For those of you new to long exposures, the time will count off on your LCD screen .. so there’s no need for all this “1 potato, 2 potato, 3 potato ..” stuff we used to do in the old days.

8. Check the result; if it’s under-exposed (as it may well be, in my experience), increase the exposure time by half a stop (multiply by 1½ ) or a full stop (multiply by 2) as appropriate and re-shoot. Ignore the warm tone of the result .. this is something which is an inherent feature of the filter and can easily corrected at the processing stage.

9. If you’re planning to take bracketed shots for subsequent HDR processing (as was the case in both of the above shots), take further exposures at 4 times the exposure time in steps 7/8 and at ¼ that time. Do the latter one still on the BULB setting .. it’s easier than resetting the camera and a fraction of a second either way will make damn all difference.

Finally, some rememberable “unfiltered/filtered” exposure conversions if the light is too bright (in step 3) to get an “unfiltered” exposure of 1/10 sec:

1/15 sec ~ 60 secs (more or less)
1/20 sec ~ 50 secs (exactly)
1/30 sec ~ 30 secs (more or less)

GOOD LUCK!

_{LATE AMENDMENT: I’ve added an extra step, which I’d forgotten in the original: putting the filter on the lens! “FOF (forgetful old fart) syndrome” strikes again!}