Exposure Part I : Theory

canon-eos.jpg At moments when work is pretty darned draining with no signs of sleeping it is time to focus on my undeniable obsessions, this time photography. I consider myself an ameture photographer as I have got lot to learn but I love to share all that I have learned. Though I mostly recommend to rely on your intuition for your utopia experiences a little bit of theory always enhance the adventure.

So today I am gonna share what I know about camera exposure, theory. (Note: I am referring to DSLR cameras which allow us to control the lightning, shutter speed and aperture size). So what is exposure? A photograph is all about lights. Hence, the quality and details depend on how the light is captured. If too much light is captured the image is darken considerable, while when relatively little light is captured the image is too dim. Exposure is how much light is captured in order to get the image.

In capturing any photograph our first concentration must be on the image, second on the varying brightnesses. An image with the same brightness everywhere would be dull and uninteresting – just a splotch of black, gray or white. So when we are dealing with exposure the only question is “how much?” Too little exposure, important parts of the image will be lost while too much exposure will result in total darkness. The external factors influencing these remains the brightness and the reflective characteristics of the subject and the environment.

As we are dealing with light when more light enters the camera it will result in an image that is darker. So what we need to find out is how much light will make the image neither too dark or too light. The correct amount of light have to be correctly and accurately measured to get a perfect shot.

There are two ways we can control this. First we can control the intensity (brightness) or the amount of light entering the camera (aperture size). Second we can control the amount of time it takes for light to enter the camera (shutter speed).

Think of this as filling a bucket with water. The amount of water winding up in the bucket depends on how fast the water was running and how long it was allowed to flow. If you want to fill the bucket to a specific depth, we can do so by either running the water rapidly for a short time or by running it slower for a prolong time. Either way, the bucket will have the same amount of water, the right amount that we wanted.

In photography the rate of flow of light is called intensity and hence the formula becomes.


So looking at the formula if we have less light then we must allow more time to get the same exposure. Or if we have less time, then we can increase the intensity. However, there are many combinations of time and intensity that can give the same exposure, which are called equivalent exposures. In theory equivalent exposures are of same image quality however there are artistic considerations.

So how does a SLR camera control exposure so we can selectively correct the exposure to our hearts desire. Come back soon to find out!

  1. #1 by nass on January 10, 2007 - 9:15 am

    man, why don’t u submit ur blog to http://mvblogs.org? U have some great articles here which I think many ppl out there would find interesting.

  2. #2 by nass on January 10, 2007 - 9:19 am

    i’m also into photography, but i only use my phone’s camera 🙂

    you’d wanna check this page that I made: http://feedosphere.blogspot.com

  3. #3 by am on January 10, 2007 - 4:32 pm

    intresting blog dude…yaa i havnt seen ur blog around mvblogs…better submit.. 🙂

  4. #4 by Yusuf on January 11, 2007 - 4:26 pm

    thanks… I am currently travelin n will check later… In rush 4got camera… damn… checking blog on opera mini…


  5. #5 by Pete on June 12, 2008 - 2:55 am


    I’m a professional photographer and what you seem to keep in your head I have written on paper :).
    Well written introduction to exposure. I found your blog while I was researching my new optics.

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