Monday, 5 October 2015

Brief notes about night photography

Yesterday I published some night pictures of the rural complex "Los Espinillos". I've been watching them and I want share with you some of my conclusion and other open questions.

The first question is: What is the ideal combination of ISO and exposure time? I think it's a difficult question, without a unique answer.

For night photography you need a good camera because there are two factors implicated: the exposure time and the sensibility. If you want to take a picture in a bit of time, you need a great sensibility. A good camera supports high values of sensibilities, but more sensibility implies more noise. By the other hand, if you want to take the picture in a very long interval of time, you could have problems with the warming of the camera.

I have now a Nikon D7000. I think it's a good camera. It supports high sensibilities, but I prefer not to pass of ISO 200 or ISO 400. Usually, the warming is not a problem in this camera, so the technical limitations are less in this case than with other cameras.

With the light conditions of the last night, I had several options: I could shoot at ISO 100 for about twenty minutes, or I could shoot at ISO 400 for five minutes. What's better? In the first case I would have less noise, the clouds would be blurred, the stars would be lines in the sky, etc. In the second case I would have more noise , the clouds would be more defined  and the stars would be bright points.

I think the first question you have to answer is: What kind of sky would you like? Stars as lines or as points? Defined or blurred clouds? There isn't a "correct" answer. It's a subjective question, and it would depend of what you like in that moment, or what are de sky conditions then.

Personally, I like more the stars as points, but It usually implies more noise, so I chose the blurred clouds, making lines in the sky. This option is also interesting: you can play with those lines, and you can use them to compose. In the example picture, the lines seem to be rays flowing from the principal subject.

For stars as points, you should use exposure times lower than 30 seconds. By other hand, If you want very long star traces, you should compose several long exposure pictures (about 30 minutes each one).

Star traces (exposure time about 20 minutes)

In the light conditions of the last night, If you want to take a picture with a non-luminous principal subject and stars as points, and you aren't using external illumination, you only can use very high ISOs (~6400).

If you use a powerful continuous light the 30 seconds of exposition maybe you could to obtain interesting results with lower ISOs. But if you only have a little led torch, and you want show a ruin in the night, you only have two options: very long exposures or very high ISOs.

ISO 6400 is a guarantee of heavy noise. What about the middle term? The rule is that the amount of light have to be the same, i.e.:

"exposure time" x "ISO" ~ "amount of light"

20 s x ISO 6400 = 128000 (less than 129000, a little dark)
 258 s x ISO 500 = 129000
644 s x ISO 200 = 128800 (approx. 129000)

We can compare the noise at ISO 200 and ISO 500. In The second case the noise is "acceptable", but the quality is better at ISO 200.

After to watch all this, I think than night photography implies very long exposures. If you can't show stars as points (because of the noise), if you are working in very limited light conditions, I think you have not to fight versus it, but you have to power that. Maybe night photography has its own rules, and we must show those fantastic things that you can only watch with long exposures.

I think I will shoot at low ISOs and very long exposures next times. And you? What do you think?

Finally, I want to speak a little about artificial light in night photography. Watching my last series, I've thought about the paper of the external light in this kind of photography. I think the use of artificial light with intelligence could convert a normal picture in a very special surrealistic dream.

That's an example of use of artificial light as ambient light, with nothing special:

By other hand, this is a trying of intelligent use of artificial light: the lighted room.

The illumination of specific areas, increasing the message, could make that our picture be something very special.

The white balance is also very important at that point. The uses of several light colours, mixing cool and hot lights, makes the effect be much more interesting.

These have been my conclusions. What do you think? Are you agree? Have you got other opinions or ideas about it? Please, share them with us in comments below!

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