For black and white night photography to be successful, it helps to think in black and white because the eye perceives things differently at night to during the day and you need to be able to compensate.
Although the colour temperature for night shots is actually the same as for daylight, the difficulty in believing this is because objects at night usually look blueish to the human eye.
Normal vision is called photopic vision which means the human eye uses cones to sense light. The eye is working in photopic mode during daylight. During photopic vision three types of cone receptors in the eye are used to sense light as three colours, red, green and blue.
Night vision is called scotopic vision which means the human eye uses rods to sense light. Scotopic vision cannot perceive colours and records light in terms of black, white and grey. But importantly, the sensitivity range of the rods makes the eye more sensitive to blue light at night.
Above: Black and White Photo of a Bench in Elizabeth Park in West Hartford, Connecticut, at Night by Sage Ross
Canon Digital Rebel XTi, 1/20 sec, f/1.8, ISO 1600, lens focal length 50 mm
Mesopic vision means a combination of both photopic and scotopic and predominates at dawn and dusk or in urban areas that are dimly lit. The combination of the higher total sensitivity of the rods in the eye for the blue range with the color perception of the cones results in a very strong appearance of bluish colours around dawn or other low levels of light. Mesopic vision is what most of us use at night as there is so much 'light pollution' nowadays.
Above: A Performer at 2007 Buskerfest in Toronto, Canada by Darren Tse
Canon EOS Digital Rebel XT, 1/5 sec, f/5, ISO 800, lens focal length 38 mm
So it's important to realise that in black and white night photography, what you are seeing is not exactly what the camera will record. You have to learn 'black and white thinking' to allow you to make informed choices as that beautiful blue night scene will look different in the final black and white shot.
This is potentially a problem if you are shooting in colour and converting to black and white afterwards in Photoshop. More about this further down the page.
As if dealing with mesopic vision wasn't enough, there is another problem that awaits you in black and white night photography and that is a thing called 'reciprocity failure'. This only occurs with film and it is more pronounced with black and white film than colour film.
Above: The Eiffel Tower at Night During the 1900 Exposition by William Herman Rau (American, 1855-1920)
The term reciprocity failure means that with long exposures, the film becomes less sensitive to light and results become unpredictable. This particularly occurs with long exposures such as those needed in the low-level light conditions that you usually have to work with in black and white night photography. Kodak Tri-X and Ilford HP5 and FP4 films work well at night but Ilford films in general have a greater tendency towards reciprocity failure.
Reciprocity failure doesn't happen with digital cameras but there is another problem then which is that digital noise increases with the longer exposures. The answer is to use a tripod and keep the exposure as short as possible.
A 4-second exposure is much better than a 16-second exposure but then you will have to choose a wider aperture so depth of field will be smaller and more of the background will be out of focus. This could be a plus of course, depending on your intentions.
Also keep the ISO as low as possible, 200 or less, as the noise on many digital cameras increases rapidly about 400 and up. In my experience, Canon make the best cameras for dealing with noise. With Canon cameras you can shoot at quite high ISOs but keep the level of noise down to an acceptable level.
If you are shooting digital, your camera will record light of three different colours, red, green and blue, on a scale of 0 up to 255. The three readings combine to give a single reading for each dot on your sensor. Since each colour has a possibility of 256 readings, the total number of possibilities in a single pixel is 256 x 256 x 256 which is more than 16 million possibilities - so many colours!
If you set your digital camera to record in black and white, it ignores these possibilities and just records the strength of the light on a scale from 0 to 255. Pure black is 0 and pure white is 255 and everything else is shades of grey. In other words, by setting the camera to black and white rather than colour, you have just thrown away most of the 16 million possibilities and opted for 256 possibilities.
If, on the other hand, you shoot in colour, you can convert to grey-scale later in Photoshop with a huge range of subtlety available due to the camera having captured all that 'extra' information.
If you do decide to record in colour and convert afterwards, don't make the mistake of converting your images using the desaturate option under the image/adjustments menu as results will be much better using the channel mixer. Just check the 'monochrome' box and play about with the sliders. Provided you make sure that the values add up to 100, the lightness won't alter - unless you like a particular effect of course.
If you enjoyed this article on black and white night photography, consider taking some shots of the moon next time you are out at night. Click the following link if you would like to read photography tips for making moon photographs.
And here's a couple of other articles which might also interest you:
Seeing in the Dark: A Guide to Night Photography
Seeing the Unseen - How to Photograph Landscapes at Night
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