Long exposures are a topic very dear to us, we have already written a practical guide to long exposures and today we will focus on one specific topic: long exposures during the daytime. Obviously what we said in the guide linked above remains valid, but we add some particular details useful when we shoot with strong light rather than at sunset or sunrise.
Recommended equipment for long exposures with strong light
Some tools are somewhat obvious, such as a (stable) tripod and the obvious camera and lens. We need to check that our camera can shoot for whatever length we choose, with the manual/bulb settings. We also recommend having a remote shutter release cable, which will be useful for setting precise shutter speeds and exceeding the 30″ limitation some cameras have.
ND filters for long daytime exposures
ND filters are essential as they decrease the amount of light that reaches the camera sensor and consequently allow you to lengthen the exposure times. Generally, we talk about ND8/ND64/ND1000 filters to indicate filters that reduce light by 3/6/10 stops respectively, but often these filters are used in more subtle light situations, such as sunrise and sunset. If we want to use such filters, even the strongest ND1000, in broad daylight we would not be able to obtain a long exposure of many seconds or minutes. Read more about the naming convention for ND filter.
Fortunately, there are “extreme” ND filters on the market with densities well above 10 stops, for example, NiSi has a 100×100 15 Stop ND32000 filter in the catalogue (also available in the 150x150mm and circular screw-in format) and a 100x100mm 20 Stop ND1000K filters. Square filters are considered essential by many amateur and professional photographers because they allow you to easily use more than one filter together (ND + GND filter + polariser).
If you have a holder like our V6 or V5 PRO, you can take long daytime exposures with polariser + ND (10, 11, 15 or 20 Stop) + any GND filter without mechanical vignetting problems even at 16/17mm on full-frame. And you still have a free slot, to use a second GND for example.
- 1300 seconds – f/1.8 – ISO 200
- Nikon D800
- Nikkor 20mm f/1.8
- NiSi V6 filter holder with Landscape Polariser
- NiSi ND1000K “Black Hole” 20 Stop
- CPL Landscape Polariser (included with NiSi V6)
- NiSi GND Hard 3 stops 100x100mm
The technique for daytime long exposure
The basic technique is practically identical to that shown in our step-by-step guide for Long Exposure, for your convenience we repeat the important steps below:
- After setting your composition, focus carefully. Being in the daytime you can do it simply with autofocus or by hand. If you have a very close foreground you may need to use hyperfocal, here you can find an in-depth analysis on focus in landscape photography. Once you have focused, make sure you have disabled Auto-Focus (AF, AF-S, AF-C or similar acronyms depending on the model of the camera) and that you are in manual focus (MF) mode. This way you will avoid camera attempts to change the focus after adding the ND.
- Take a test shot with polariser and GND, if required. Make sure you are satisfied with the exposure and make a note of the shutter speed. The test shot must be done in Manual or Aperture priority (A/Av), setting the required ISO, for the greatest dynamic range and least noise, and an optimal aperture for your lens, usually between f/8 and f/11 since the narrow aperture allows you to have the whole image in focus.
- Let’s assume that the test shot turned out well (i.e well exposed) with a shutter speed of 1/250″, now you can mount the ND filter, let’s say you want to start with the 10 stop (ND1000).
- Now you can calculate the new exposure time to compensate for 10 stops, you can use at least 3 methods:
- The first method consists in doubling the exposure time as many times as the stops absorbed by the filter, in this case we double 10 times. Starting from 1/250″ -> 1/125″ -> 1/60″ -> 1/30″ -> 1/15″ -> 1/8″ -> 1/4″ -> 1/2″ -> 1″ -> 2″ -> 4″
- We get the time in seconds by solving the fraction, 1/250″ is 0.004″, multiply by the ND value which in this case is 1000 (or 1024 to be precise): we still get 4 seconds of course (0.004 * 1000 = 4)
- The third method is to have a printed table or use an application (for example PhotoPills which also has many other functions) to keep always at hand.
- Now it’s time to set the resulting shutter speed and review the shot, if it is too dark we increase the time, if too bright, reduce it. There are always production tolerances and the ND filter may be slightly darker or lighter, but we can always adapt the time in a second shot. Also, remember that the light changes quickly, so keep that in mind if a lot of time passes between the test shot and the actual shot.
In the example above, the resulting time is only 4 seconds, but if we want to capture the movement of the clouds or maybe create architectural shots where people disappear or the shadows soften, we need a shutter speed from about 30″ to several minutes.
In this case, the use of a 15 or 20 stop filter is highly recommended. In the previous example, if we had used a 15 stop filter (ND32000) the resulting time would have been 128″ (2 minutes and 8 seconds), while with the 20 stop Black Hole ND filter the shot would have been 4000 seconds (1 hour, 6 minutes and 40 seconds), or only 30 minutes underexposing one stop (for example by opening the aperture 1 stop or increasing ISO).
The 20 stop is strongly recommended in situations of strong light when the starting shot is 1/500″ or more, to reach several minutes of exposure instead of hours!