Exposure exposed!

My brother-in-law, bought an Olympus EP2 and kit lens and he asked me- What is exposure? Great question!

Well, it is hard to explain in technical jargons but let’s start with the understanding of the exposure triangle (I took this term from Bryan Peterson). The exposure triangle is about the 3 variables that affect exposure which is Aperture, Shutter Speed and ISO (light sensitivity). And at the heart of the exposure triangle is the light meter sensitivity (ISO). An image that is well exposed looks right, not too bright and not too dark.

Well, let me try to explain exposure using a water tap metaphor like the following.
Light = water
Aperture =Tap opening that control the water flow.
Shutter Speed = Time control on how long to keep the tap on
Right exposure = Full Bucket of water (to the brim)
ISO = number of water tap with the same tap opening/ and time to fill up the bucket
Noise = level of disturbance to the water surface resulting in more bubbles and noise.

Let’s, start and imagine.
You want to fill up a water bucket (full, not more and not less) with the least amount of noise so that you do not wake Sheena (my little gilr) up. You have a choice to select how much to turn the tap (Aperture) and the choice of how long (shutter speed) to keep the water flowing. Of course you can decide on how many tap (ISO) with the same tap setting to fill up the bucket at the same time.

So that is the concept of exposure! A balancing act to achieve the right exposure with the desired creative effect.

Let me explain more. When the tap is turned more (Aperture is larger) more water will flow into the bucket and so it takes less time (fast shutter) to fill up the bucket. Likewise if you run the tap longer (shutter speed slower), you need a smaller tap opening (aperture) so that you still get the same amount of water into the bucket.

What about ISO, well if you have many taps (high ISO) running at the same time and with the same tap aperture/time combo setting it will need less time to fill up the bucket but the result could be with water bubbles (noise). This is not good because you might wake Sheena up and she will cause havoc! It is a balancing act and the essence is to keep the noise low and at the same time balancing the other variables to get the right/creative exposure. Do you know that there are at least 6 exposures combo that can give you the tecnically correct exposure but there is only 1 or 2 creative exposure.

This is where you change the variables in the exposure triangle to convey motion (shutter speed control) or subject inclusion/isolation (aperture control) in your images. Happy experimenting. "CLICK"