The first truly popular photographs were daguerreotypes, incredibly long exposures that required people to remain still for the duration of the exposure while their image was recorded onto a surface of polished silver coated in silver halide particles.
Although photographic technology has improved a lot since then, long exposure photography has remained popular, both for it’s necessity when shooting in low light levels, as well as for it’s ability to interpret reality differently.
Long exposures stretch out the moment that a photograph was taken until reality takes on a surreal twist in the image. Running water becomes a blurred silky substance, raging oceans turn into calm pools of mercury, and the stars above us, which seem static to the naked eye, are transformed into bright trails that arc across the sky.
It is an art form in itself, and images with a long exposure can make the viewer see the world in a different way.
One of the reasons I enjoy long exposures is it’s ability to remove texture from certain parts of the image like the ocean, and concentrate the eye on the textures and structures of another part. A wooden pier structure for example, or rocks on a beach.
The most important tools for long exposures are a steady tripod to hold the camera still during the exposure, and a cable release, so the shutter can be tripped without touching (and possibly moving) the camera.
A Bulb facility on the camera is essential as it allows you to choose when to close the shutter, and also makes exposures longer than 30 seconds possible. Mirror lock up is also nice, but not available in every camera.
The easiest way to create long exposure images is to shoot after the sun has set, close down the aperture as much as possible, and then take a meter reading from the foreground.
This can be done by either spot metering various parts of the foreground and calculating an average, or more simply by filling the viewfinder with foreground using matrix or evaluative metering. Depending on light levels, you can get exposures of up to 30 second in the afterglow of sunset or pre- dawn glow of sunrise.
It’s important to remember at these times that although it may not look it to our eyes, the sky is still much brighter than the earth and will need to be filtered using a neutral density graduated filter.
The simple way to calculate which strength of ND graduated filter to use is to now point your camera at the sky, filling the viewfinder and noting how many stops brighter than your foreground exposure it is.
I always try to ensure that my images don’t exceed more than 5 stops of exposure range, that’s two or three stops either side of my base exposure. If the sky is 5 stops brighter than my base exposure than either a 2 or a 3 stop ND graduated filter will bring it back into that 5 stop latitude, depending on how dark I want the sky to be.
However, often the best light and most colourful skies happen just before sunset, and in those cases it can be impossible to get shutter speeds of longer than a second, even with the aperture closed right down.
Is it possible to get long exposure at that time?
Actually, there are neutral density filters available from both Hoya and B+W which cut out the light by 9 or 10 stops respectively, enabling long exposures to be shot even in bright daylight.
Using them can be tricky at first, but there are certain techniques which can help a lot.
The shot above was taken on the Amazon river, and I wanted to pull the eye to the colour and texture of the rope, whilst still capturing the sunset. Although the sun was obscured by clouds, it was still far too bright to get a long enough exposure without using a strong ND filter, so I chose to use a 9 stop Hoya ND400.
One of the problems in using these kind of filters is that once they are screwed onto the lens, you can no longer see through the viewfinder, so all composition, metering and placement of graduated filters has to be done first.
In this case I metered the pier and river first, making sure all of it could be captured within a range of 5 stops. This was my base exposure. I then measured the sky to see how many stops of ND grad filter I would need to balance the sky’s brightness and bring it into my exposure range. The sky was 5 stops brighter, so I used a Lee 3 stop graduated filter with a hard graduation across the sky, sliding it into the filter holder until it was in the place where I wanted it.
At this point I still didn’t have the 9 stop Hoya filter on my lens, so to make sure the graduated filter stayed in the correct place on the image I carefully removed the entire holder with the graduated filter still in place, and then screwed the Hoya ND400 onto the front of the lens. I then replaced the entire graduated filter holder, again, being careful not to move the grad filter in it’s rails.
So now the camera was filtered correctly, but I still had to recalculate the exposure to take the 9 stop filter into account.
Exposures work by doubling or halving the amount of light onto the sensor, so in terms of shutter speeds you either need to double the shutter time to increase exposure by a stop, or half it to reduce the exposure by a stop.
As I’d added a 9 stop filter, I needed to add another nine stops to the base exposure I’d measured before putting the filter on. The base exposure was 1/4 second, so doubling that exposure 9 times gave me an exposure time of 2 minutes.
For example: 1/4 second – 1/2second – 1 second – 2 seconds – 4 seconds – 8 seconds – 15 seconds – 30 seconds – 1 minute – 2 minutes.
All that remained to do was open the shutter with the cable release, and sit and wait while the exposure was made, being careful not to move too much as the pier I was on was actually floating and I didn’t want to disturb it in the water and blur the image.
After a little over two minutes I clicked the shutter closed and saw what I had captured.
In some cases, placing the graduated filters can be tricky. In the shot below, taken just after sunrise, I needed to have the grad filters sloping at an angle so they didn’t cover the rocks.
The problem here is that it’s impossible to see through the lens with the 9 stop ND filter on, and practically impossible to remember exactly what angle the graduated filters were at. If they aren’t rotated correctly then there will be a gap between the cliff tops and the sky which would be brighter than the rest of the sky and look terrible.
In this situation I did everything as described above, the only difference that I was also using a polarizer to eliminate reflected highlights in the water. This also meant that the corner of the filter holder would be visible in the shot, so I zoomed in a little to stop this happening.
After all the filters were on, instead of adding 9 stops of exposure to the base reading by increasing shutter time, I added it by opening the aperture up as much as I could (2 and a half stops) and by increasing the ISO speed to 1600 (4 stops).
This gave me a very grainy image with limited depth of, field, and it was also underexposed by 2 and a half stops, but most importantly it allowed me to take a fast exposure with the 9 stop filter on in order check the ND graduated filters were in the right place. I repeated this a couple of times, adjusting the ND grads after each shot until I was satisfied with the filter placement.
When I was happy that they were in the right place, I put the ISO and aperture back at their original settings of ISO100 and f9 respectively, and then added the 9 stops of exposure to the shutter time, again giving me an exposure time of 2 minutes.
This time I had nowhere to sit while I waited for the image to expose as I was knee deep in water and hoping that the waves would remain calm and not move the tripod.
The final thing to bear in mind with long exposure photography is that images will often be more noisy than shorter exposures, especially in the shadows. Different people with different cameras have their own ways of dealing with this. Some prefer not to use the in-camera noise suppression and turn it off, cleaning any noise up later in post processing, but I personally keep it turned on.
Shooting in RAW rather than JPEG gives a lot of advantages, not least the ability to clean image noise more effectively in post processing. I use a plug-in called Neat Image which is pretty effective at cleaning noise without losing detail, especially when done on a duplicated layer in Photoshop so the exact amount of reduction can be dialed in using the opacity slider in the Layers palette.
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