This episode was brought to you by Skillshare Despite what I say on this channel, human
vision is quite amazing - we may not have the sharpest vision, or the best colour vision,
or the best night vision of the animal kingdom, but we do have a remarkable balance of all
three - a jack of all trades if you will.
However, because we are mostly diurnal animals, our night vision is certainly the weakest.
So, I was wondering, when compared to the average camera, how does our eyesight deal
with low light conditions?
[Intro by Caro Waro & Cristina de Manuel]
Our eyes can cope with over a million-fold
change in brightness from broad daylight to a pitch black night, and coping with and adapting
to changing levels of light variation is one of the eye’s most important jobs.
There are several ways our eyes let us see better in the dark.
Firstly, our pupil can widen, allowing more light to pass through.
However, our pupils are only able to dilate from 1 millimeter up to 8 millimetres, which
isn’t really enough to let in the amount of light required to transition from a brightly
lit scene to a starry night.
Most of the magic that enables us to see at night happens in the retina.
This process is known as dark adaptation.
Firstly, there is a switchover from cones to rods.
Cones are photosensitive cells which respond best in high light levels and they send colour
information to the brain, whereas the rods are also sensitive at a much wider range of
light levels - especially lower ones, and this is actually why our vision is generally in black
and white in low light conditions.
To complete dark adaptation, the rods in the retina must fully regenerate.
When a photoreceptor is stimulated by light, a compound called rhodopsin is photobleached
in response.
In cones, it takes around 10 minutes for the pigment to regenerate, and in rods, up to
30 minutes - which is why it generally takes around half an hour to fully adjust to a dark
room.
The horizontal cells which connect photoreceptors downstream together also send information
back to the photoreceptors so they can adjust their sensitivity accordingly, and this means
that small changes in light levels that would be normally imperceptible in broad daylight
are detected and fully perceptible under low light conditions.
Now, that’s about it when it comes to dark adaptation in humans because we don’t have
the other fancy adaptations that other nocturnal animals have for low light environments, such
as tapetums or spatial or temporal summation.
So, how do cameras operate?
Well, there are a few things that work quite similarly to our own vision.
We can open the aperture of a camera to let more light in onto the sensor, and we can
also raise the ISO, which increases the sensitivity of the sensor.
Both of these would be the equivalent of dilating our pupils and undergoing dark adaptation.
However, even when increasing ISO as far as possible and opening the aperture as wide
as it will go, the resulting picture of a night sky will probably be a lot blacker that
what you can see in real life.
But fortunately, there are a few other things you can do with your camera to make it perform a little
bit better in low light, the main one being to decrease the shutter speed.
This allows an image to expose on the sensor for longer.
So for example, these pictures here took between 8 and 15 seconds to take - and believe it
or not, they were taken at midnight!
And, to be honest, I have to say that getting an updated image every 10 seconds is *anything*
but practical in real life but they can capture a great level of detail and can also be used
for artistic purposes, such as to denote the passing of time, or for creative purposes.
However, as well as taking longer to photograph, the other downside of low light photography
is that it tends to have a lot more noise.
Cranking up the ISO increases sensor noise, and exposing images on the sensor for longer
than a couple of seconds creates thermal noise as the sensor heats up.
There are, however, a few ways around this.
It is generally possible to reduce the appearance of ISO noise in post-production, and you can
reduce the degree of thermal noise in-camera using a setting called the long exposure noise
reduction or LENR setting.
If you activate this setting after taking a photo, the camera will take a second picture
with the shutter closed for the same amount of time, meaning you will have a dark picture
with a thermal noise imaged on it, which can be subtracted from the original photo taken.
Whilst it does double the amount of time it takes to take a photo, it does render a much
cleaner image.
So, as to who performs better in low light, our eyes or a run of the mill camera, it depends
on what you want.
If what you want is to navigate quickly and detect objects and do everything fast, human
vision wins out.
But, if you’re after detail and colour information, then camera is probably the way to go.
And, fun fact before I head off, the sky pictures you saw in today’s episode as you might
have been able to guess I took myself, I'm quite proud of them, they were from the Perseid
Meteor shower in mid-August.
I took them following Ian Norman’s course on skillshare, who is an astrophotographer
I really, really admire and compared to theclueless Inés from a year ago, I’m really pleased
with how they turned out.
Skillshare is an online learning community with over 16000 classes, and if you know me,
you know that with every video I make I always try to challenge myself to try out a new photography
or editing technique, and honestly, over the past couple of months I’ve been trying out
a few new things from skillshare, from subtle animation things, to improving my timelapses
to this long exposure photography - I'm trying hyperlapses next!
So if you’re like me and you like learning new things and pushing yourself creatively,
the first 500 people to click the link in the description will get a 2 month free trial
on skillshare.
After that, membership starts at 10 dollars per month, but, if you discover during your
trial that it’s not for you, you can cancel, there is no risk or obligation to continue
with it! and as always thank you so much for watching
me and I’ll see you in the next one!
Bye!
[Art & Animation: Caro Waro & Cristina de Manuel]
[Music: Thastor & CryoSleepKitten] [Hosting, Script, Editing: Inés Dawson]
[Translated into {language} by {your name}]