Time Lapse Tutorial: A1 – What is Day & Night

In this article and the few coming ones, I will try to help the reader to visualize and imagine Time as a light chart. Understanding where you are and where you will be on that chart, in my opinion, is crucial for creating efficient time lapses, with lesser guesswork and within the capabilities and limitations of one’s camera.

One of the keys to understanding most types of flows is by being aware of flow’s dynamics over time. That does not apply only to time lapse but rather to absolutely any passage from any point A to any point B, and any displacement results to Time.

Since the case here is with a photography-based medium, photography deals with light, so I’ll be addressing light dynamics over time.
(Note: we will assume here that we are shooting on Planet Earth)

As with the self-rotating, around-the-Sun-revolving, axis-switching, and quasi-spherical Planet Earth we have what we call a Day. In our system we only have one significant source of light, that is a star known as the Sun, whereas other stars/suns are far, to an extent that we can consider their light effect as mathematically negligible. A Day is when a point on Earth is exposed to direct Sun light, a Night when it is not exposed.

A convention that has been used for a while now, assumes that the Earth spins around its own axis in a fixed 24-hour known as 1 Day (both night and day), and that spinning Earth revolves around the Sun (let’s round the values) in 365 days. So no matter what, Day+Night = constant 24 Hours.

Given that Light was one of the earliest Man’s perceptions and later-on references, we are going to use the simple vocabulary of Light to draw a chart of light variance in a 24-hour time frame.

If we are to describe Light starting from midnight, we follow this trend: too dark, dark, getting brighter, bright, getting darker and dark. To my knowledge, this is the same everywhere on our planet except that each of these terms changes in duration depending on geographical location. These fluctuations are due to seasons and how close to poles one is, i.e. how far from the Equator.

timelapse_adsrIn sound synthesis, there is something very well defined, yet very describing and highly analogous, with the day/night phenomenon, after all, sound is waveform variation over time. That is called an Envelope. The envelope consists of 4 attributes/parameters abbreviated as ASDR, Attack-Sustain-Decay-Release. What are these? I am going to drop the decay from the analogy for simplification purposes.

Attack is the time it takes to reach a given point, amplitude, intensity, loudness, etc.
Sustain is a plateau, it is the duration and intensity of staying or holding the peak reached in attack.
Release is the time needed to reach back the total silence; silence to sound is what dark is to light.

IMG_5846Let’s go back to the Day/Night, most cameras have a light meter that measures the quantity of light, this helps the camera and the shooter to decide what setting to choose in order to achieve the wanted image, or an image that he/she considers optimal. The light meter is built around LDR photoelectric components. Briefly, the camera’s light sensor outputs a measurement that is relatively rendered into the light indicators one see in the viewfinder.

Again for simplification, let’s assume that a densely clouded moonless night with electricity outage, or a lens with a lens cap, is the darkest it can get; while a close up with a telephoto pointed to the Sun, though not recommended, is the brightest one can reach, again that applies on Planet Earth.
Most cameras have a Light Value ranging from -2.7 to 17, noting that one relies on trial and error or experience when shooting in light values below -2.7, as the camera’s light meter becomes obsolete when pointing to shutter-speeds longer than 2 seconds.

Back to our sound analogy, night is silence, dawn till sunshine is attack, the whole day is “sustain”, and sunset is “release”, and the next night is silence again, but it can not be not too silent if the moon is around.

Now let’s say that total dark/silence is zero (0) and full true noon in summer/maximum loudness is ten (10).

What changes around seasons and location on earth?

Equinox (equal-night) is when the night and day durations are equal, it happens twice a year in large zones of the Earth.
Later the duration of night progresses and day regresses, and vice versa to the day in which the difference of durations peaks and these are the “Winter/Vernal” and “Summer/Estival” Solstices (sol=sun stice/stance=stand, and when one stands he/she is on his/her highest).

Given a fixed location on Earth, on the same day of the calendar, day/night duration difference varies the farther we go from the equator toward the North or South Pole.

So with this extreme simplification, one can start to visualize the behavior of a day. It is fundamental in time-lapsing to realize the position of your start time and your end time of the day’s approximate chart or plot. The farther B is from A, the more skills, techniques, attempts are needed. Remember before beginning any sequence try to imagine where your intended time lapse falls on the chart.

I will go deeper in each of the zones, and talk about more complex fluctuations to compute, moon rises, sporadic cloud coverage, densely clouded days with eventuality of Sun penetration, etc. subject to the response and feedback on the articles.

An average day, somewhere not extreme in the World

This chart shows a “typical” day. Moderate light intensity, not a significant differential in daytime/night duration

A Short winter day, same location

This is a very short winter day, you notice is the light intensity is much lower, the night is long. On any given day. At one geographical location the durations vary from shorter or longer, with latitude, the two extremes are the Equator and the Poles (refer to the Goodreads Tab)

A long summer day, same location

This is a very long summer day, you notice is the light intensity is much higher and daytime significantly longer than night, the night is very short. On any given day. At one geographical location the durations vary from shorter or longer, with latitude, the two extremes are the Equator and the Poles (refer to the Goodreads Tab)

24+ Hours Transitional Time Lapse

In this video, on the bottom left you can see the camera setting varying. Try to notice the ISO value ramping on both twilights.
and next to it you can see the histogram of each frame. (the horizontal axis of a histogram refers to the scope/range/gamut of light in one frame and the verticals show the intensity of each horizontal sample.) The camera used is a Nikon D2x, This camera reads no negative light values. This time lapse is shot at A- Aperture priority, f:8 with the primitive AutoISO on. (Beirut-Lebanon 02 June 2012)

1689105_603226419745210_43941412_nAs an example, in this plot, on the left is “earlier” and the right is “later”, the yellow line is the variation of light over a relatively short period. One could intuitively deduce that it is in the after noon (the line sloping direction) and 4 intermittent cloud passages happened, while the first cloud passage ( the first “Valley” in the plot) was dense and remained for a longer duration than the 3 other clouds obfuscating the Sun. With experience one could deduce the camera direction from this chart.

In this graph you see (in orange) the variation of light value over a full 48 hours, as recorded by the camera. The blue plot is the the ISO value which was on AutoISO.Camera being used is a Nikon D3300 with an 18-55 kit lens.

This graph is a “zoom” in time from the previous graph. It is the twilight (starting from last seen Sun disk to total darkness. Horizontally, left is before and right is after. Since the light intensity (gray line) is sloping down that means that this twilight is Dusk (dawn is almost the same but mirrored. The yellow highlight zone is where the AutoISO was performing the stepped ramp from ISO 100 to ISO 1600

Another “time-zoom” into the previously mentioned yellow highlighted timespan. Here you see in red, the ISO value changes from ISO 100 to ISO 100. Now the too technical part of this chart (you can skip): the camera is shooting at fixed 30 seconds interval. the camera is D3300 that shares the AutoISO mechanics with all pre-Nikon D4s camera. The ISO switching threshold is a maximum of 1 second. It was upgraded to a maximum of 30 seconds in D4s. All points in the yellow zone are combinations of shutter speed of 1 second with increasing ISO that saturates on: 1s, ISO 1600, and after this point longer exposure time at ISO 1600 are used.
Given the expanded threshold of the D4s, this ramp can go smoother and longer in time. That could be showcased in a full article.

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