High ISO Preview (HIP)

Night photography requires long exposures. That requires patience, don't strain it by waiting unnecessarily long. Here is a practical guide to determine your exposure time in a matter of seconds, rather than minutes.

What's an exposure stop again?

A "stop" of exposure is twice or half the light. If you double or half the exposure time, you get twice or half the light. Likewise, if you double or half the ISO sensitivity of your DSLR sensor, you get twice or half the light. You can use both of them to compensate for each other. If you double/triple... the ISO sensitivity, you can half/third the exposure time to get the very same exposure, i.e. amount of light.

Exposure time: -1 stop yields half the light

ISO: +1 stop yields twice the light

Used at the same time, they compensate for each other.

High ISO Preview

Here is how to do it:

1) Set your camera to ISO 6400 and figure out correct exposure. This looses only seconds: 1” (too low), 2” (still low), 4” (over): 3” is the right exposure! - This cost you 10 seconds to figure out correct exposure.

2) For each exposure, review your RGB histogram and the blinkies, make sure you expose as much "to the right" as you can, without blowing out too many highlights. Trade off between sacrifical and desired highlights.

3) Now re-adjust sensitivity back to ISO 100 and change the exposure time to the number you just determined in minutes (3 minutes)

Noise doesn’t matter, all you want is figure out the histogram! You can even take the camera off the tripod and do hand-held preview shots to figure out the best composition. It doesn't matter that the image is blurry from shake, but it gives you a good idea of how the composition looks like.

Here's an example: I did a HIP and figured out that I need 2 seconds at ISO 6400, then switched to ISO 100 and exposed for 2 minutes:

The first image is nothing to brag about, it's noisy as hell, the ripples on the water make it very busy, but it has the correct exposure (and, of course, I chose the composition first, including f/11 to have everything sharp from foreground to clouds). The second, final image is a real night photo: smooth, soothing, beautiful colors, great shadows of the poles sticking out, the water is smoothed out, the clouds are moving, we are capturing the element of time! And it took only seconds to figure out the correct exposure time.

Summary Table

Use the below table to give you guidance on what settings to use. Some cameras have 200 as their lowest (=native) ISO setting, some cameras have ISO 50. Choose the case with your camera's base ISO:

Download this table, print it, cut it out, tape it to your tripod leg using clear packaging tape!

Older cameras may not have the sensitivity range shown above for 6 stops difference. My old Nikon D200 started at ISO 200 and went only to ISO 3200 (4 stops), so I had to use the rule that 4s at ISO 3200 meant 1 min at ISO 200. A 10s HIP, for example, would have meant 2.5 min exposure time at ISO 200. A bit of math, but not that difficult once you figured it out.

And, of course, you can use aperture as part of this as well. F-stops aren't as intuitive, you'll need to learn them, but here are the most common full-stop apertures:

2.8 - 4.0 - 5.6 - 8 - 11 - 16 - 22

I configured my camera such that aperture changes happen in 1/2 stops, that way I know I need two clicks on the dial for one stop, which helps do this in complete darkness.


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