Lesson 2.3: The Shutter... and the Aperture.. and the Sensor...

You've now framed and focussed on your prey... let's talk about the eye...

What one has to realize is that the human eye is constantly framing and focussing on the scene.. and the relevant neurons take the instant signal back to the brain, which processes the scene..

The amazing part is that the brain does not constantly add the information the eye provides over time.. if it did, the images would keep adding up on top of each other and would slowly become an all white blur.. the brain somehow separates images over time and we therefore see an unchanging scene..

Its a little complicated but if you think about it, it is quite amazing...

The SLR camera on the other hand has no such feature.. if it sees light from the same image, no matter how dark, for long enough, it will fade into white...

A video camera on the other hand does not have this problem, exactly because it knows that every x milli-seconds it is taking a new photo...

Before going ahead, refer to the section on the Lens as an adder of light.

So some basics on the hardware:
1. The shutter decides the volume of light that can get in.  The longer it is open, the more volume of light that gets in.  This is determined by the shutter speed.
2. The aperture/lens-system is like the iris/lens.  The wider it is open and the bigger the lens, the more orders of light that can get in.  This is the f-number.
2. The sensor is like the retina.  The more sensitive it is, the better it can resolve what the aperture let in.  This is the ISO rating.

The perfect picture is simply a combination of how much light you let in, how accurately your aperture/lens system can replicate the image, and how well your sensor can resolve what was let in.

You see something with your eyes.  You feel something.  Your camera tries to capture it and show it to someone.  The other person feels something.

Communication.  That is the basic purpose of photography.

Lesson 2.3: The Focus... and the AF

So now the Ah moment is done... you have used a lens of some kind, looked through it, zoomed and framed exactly what caused the Ah... and its time to focus...

A frame is a 2-D window or boundary extruded into infinity. You need one more plane to fix the subject in this long extrusion. This is where you focus.

For example consider the following:


Usually within the lens system, there are a set of singlets that move to zoom and frame. Another set of singlets control the focus. So on a lens you should see a zoom ring and a focus ring (when you're running on manual) both moving different element sets.

There are several cool auto-focus technologies and its fascinating how they work, but then I promised this would not be a technical site. Essentially, the AF system shoots out an infra-red or a red beam (not to interfere with the surrounding light) and uses the reflection of this beam to measure focus.

The beauty of an SLR camera is that you see what the lens sees. So if you see a clear image of something you like, so does the lens.

There are still cooler systems that track the movement of your eye and then focus on a subject within the frame.

Lesson 2.2: The Frame and Zoom

A zoom lens allows you to frame distant objects without getting too close.

Imagine the following scenarios...

1. Borrowed from a friend who is an amazing shot...


2. From a recent holiday we took:


How would you think these photos were taken. I doubt that the bird perched and posed for Garmia to take a photo or the two gentlemen posed just for me...

The first thing to note is the framing in both pictures. Only the subjects of interest are in. Everything else is out. This is key.

The bird sitting on a rock. The two gentlemen are talking. Thats it.

Subjects are sensitive. You can't get too close to fill the lens with the subject. You need to be far away.

So.. once again.. you've decided on the ah moment.. I want to capture this bird sitting on this rock. You see the frame in your head.

Shit.. I can't get closer.. so then you take out your zoom lens, turn the knob until you see exactly the frame you want from a distance that is comfortable for the subject.

A zoom lens allows you to frame distant objects without getting too close. End of story.

Lesson 2.1: The Lens as an Adder

Taking a photograph sometimes requires a good mix of cold mechanics and a lot of warm emotions... emotions we spoke about.. lets go a little deeper into the mechanics...

A key question that we need to answer first is: What is the purpose of the lens in a camera?

A lens is an 'Adder of Light'. I was shocked when one of the optical designers in my first company told me this. The explanation is simple and complex at the same time.

The first thing to understand is that a photograph and a scene are all about edges. There are boundaries and the contrast between the boundaries makes the composition.

Everytime there is an edge, light bouncing off that edge (depending on how fine and narrow that edge is) is scattered. There is a complex theory to explain what happens afterwards, and here is a good picture to remember (taken from a UBC, Canada website):



The center spot would be the '0-order', next to it on both sides are the 1st order, and so on to infinity. All these infinite orders 'added together' would result in the orginal slit or edge that created this pattern.

The catch here is that this is what the camera sees. Your eye has processed it, added the light, and your brain tells you there is an edge. But the camera can only see this. The lens then takes these and puts them back together and shrinks them so they fit onto a 35mm film array.

Thats the reason you need a lens. Without the lens, you would just see a blur of lines...

Now if you had an infinitely big lens, you could capture all the infinite orders and get the perfect sum. But then you would also need an infinite amount of money. So we try to capture as many orders as our wallets can afford.

Of course the complexity is that in a given composition there is not just a single edge and a single color (or wavelength of light) but several edges and several colors. So the lens has to not only manage adding one edge, but several edges at several wavelengths.. its one of the hardest things to design and typically a 'lens' that you see will have atleast 10 single lenses (singlets) to correct various problems it faces.. chromatic abberations.. colors not lining up.. edge distortions (the pin cushion effect).. etc... lens design is a really fun job!!

Here is a good picture from the following website




So I hope the next time you look through a lens, you can imagine all the interactions of light that go on in front and appreciate how the lens is able to put it all back together for you.

LESSON 2: The role of a camera...

Philosophy is one thing.. it is the Why... but without a How, life would be hard...

We hopefully agree that we want to capture a singular moment into a little piece of paper or a image on a screen somewhere... there are the following things that need to happen...

A scene.. light bounces off that scene and enters your lens... the lens focuses the light onto the film plane through a little opening or an aperture.. you see the moment and click.... a little shutter opens and the film behind the shutter captures the light using some chemistry or electronics.. as the case might be... and if you happen to click at the right thing at exactly the right moment.. you are lucky enough to capture the emotion you wanted...

The camera is then doing the following things for you:
1. Framing precisely what and only what caused the 'Oh' moment...
2. Focussing on precisely what caused the 'Oh' moment...
3. Allowing a certain amount of light in
4. Capturing the light on a film or array...

LESSON 1: What's a good photo...?

This has to be the first thing that all of of us need to calibrate.. but here is my first Lemma:

Lemma 1: A good photo is something that connects emotionally with you..

Now this is really important.. since a lot of people jump immediately into framing, lighting, focus.. etc etc... its all bull shit.. a good photo like a good piece of art is something that connects with you... it reminds you of a past experience or a future potential... it makes a new pattern in your mind... and so on...

That is the reason for the photo to exist... here is one of the better photos I've taken with my iPhone...



Its something I happened to see on my way to work one morning.. I whipped out my iPhone and got it.. I claim this is a good photo for several reasons... and a lot of other people also liked it for what I assume is several other reasons...

EXERCISE 1: Find any 5 photos that you like and try to explain to yourself why you like these photos... what was the first thing that went through your mind when you saw them.. hopefully it wasn't framing...

So again.. a good photo creates an emotion within you... a good photo that you take therefore is a way of capturing an emotion that you feel at that moment using a camera and film... or a jpeg.. I really cannot over emphasize this point... photography is about communication... communication with a larger and very diverse audience...

Some people might say.. I just want to make a record of my baby or my travels... but the purpose there is to capture the emotions you feel at the time to enjoy them when you are old and in a chair... the purpose of that photo is to capture what you felt at that time...

EXERCISE 2: With the 5 photos you identified earlier, write down the emotions you felt when you saw them...

Photography and me...

I got my first camera at the age of 14 or 15.. a Kodak point and shoot.. It survived until I was about 20.... where it got left behind in a Toilet in O'Hare airport in Chicago...

That was really depressing, since I lost the last pictures I took before I left India... and I was a grad student with no money.. so I saved for a year and got myself a Pentax point and shoot for something like $125... it was a really great buy in 1998.. now I didn't know much about cameras, but I really liked to take pictures.. didn't know anything about landscapes, potraits, or lighting.. or lenses... but I took a lot of photos...

Since then I graduated to a Canon Elan II, bought a telephoto lens, took tons of more photos.. worked with optical equipment managers for several years building much more complex lenses and auto-focus systems than the ones I used.. and got more and more interested in the art of capturing light...

I remember how amazed I was at learning stuff about the camera... and as I tried to learn, I found websites and books that were sometimes too basic and sometimes too technical...

I've decided therefore to make a little 'learn photography my way' lesson with this blog... it is meant for people who are just about to start.. know nothing about physics or light.... but appreciate and want to take photographs... all I need from you is curiousity...