DSLR Concepts: The watered down basics

For as long as I can remember, I have been a point-and-shoot enthusiast. After using a bridge (SuperZoom) camera for a long time, I finally upgraded to a DSLR.

When I upgraded to a DSLR, I started learning about the various aspects of DSLR photography. I read many blogs, websites, and books that attempted to explain the basics. In my humble opinion, however, all these sources were a little too technical when it came to explaining one concept – exposure.

After reading the definitions from various sources, I would always come away with a few questions:

  • What does exposure really mean?
  • What is the relationship between aperture, shutter speed, and ISO?
  • Do I really need to understand these concepts to take good photos?

For a person who has been taking photos for over a decade now, I found these concepts intriguing. I found a lot of technical explanations online for aperture, shutter speed, and ISO. But just like exposure, I found nothing that tied them all together in an extremely simple manner.

This blog post is my attempt at explaining the basic concept of exposure, as I understand it today.

What is Exposure?

A photo is all about light. Exposure is nothing but the quantity of light that is used to create a photo in a camera.

Before going into aperture, shutter speed and ISO, let us try to understand what one must do to fill 1 bucket of water. (Huh?)

Let’s assume you have the following three items to fill 1 bucket of water:

A pipe that carries water.

A valve that opens and closes.

A bucket of a certain size.

For the sake of simplicity, let’s say you could fill 1 bucket with the following parameters:

Use a pipe of 10-inch diameter.

Open the valve for 10 seconds.

Use a bucket of a 10-liter capacity.

It’s simple isn’t it?

Let’s compare the idea of filling 1 bucket of water to the concepts of photography:

Pipe = Aperture (the diameter of the opening that allows light into the camera)

Valve = Shutter (can be opened for a pre-defined number of seconds)

Size of the bucket = ISO (time taken to fill the bucket; smaller the bucket, the faster it fills up).

So, based on how much water you want, you can fill 1 bucket of water in any of the following ways:

  • Use a 10-inch pipe, open the valve for 10 seconds, and fill a bucket of 10 liters.
  • Use a 5-inch pipe, open the valve for 10 seconds, and fill a bucket of 5 liters.
  • Use a 10-inch pipe, open the valve for 5 seconds, and fill a bucket of 5 liters.

Water vs. Light

The world of DSLR photography with light is not different from filling water in a bucket. You can create a photo by adjusting any of the following parameters to adjust the quantity of light used to create a photo because:

Exposure = Aperture + Shutter Speed + ISO

  • Aperture: Increase the Aperture for more light and decrease it for less light.
  • Shutter Speed: Decrease the Shutter Speed (shutter stays open for a longer duration) for more light and increase the Shutter Speed (shutter stays open for a shorter duration) for less light.
  • ISO: ISO defines how sensitive the sensor is to light. In the older non-digital camera days, films were used to take photos. A term called film-speed was used define how soon the photo was created on the film when light fell on it. A 100 film-speed was less sensitive and 200 film-speed was more sensitive to light. With DSLRs, the term called ISO is used to define how sensitive the sensor is to light. The higher the ISO setting on your camera, the more sensitive it is to light.

Theoretically, you could increase one parameter and decrease the others to ensure that the same quantity of light creates the digital image.

Here are a few examples of a candle photographed with different settings:

1) Auto Mode:

2) High ISO (More Sensitive to Light): Aperture f5.6, Shutter Speed 1/125 second, ISO 1600

3) High Shutter Speed (Less Light): Aperture f5.6, Shutter Speed 1/1000 second, ISO 100

4) Low Shutter Speed (More Light): Aperture f5.6, Shutter Speed 1/5 second, ISO 100

4) Low Aperture (Less Light): Aperture f16, Shutter Speed 1/125 second, ISO 100

If you are using a DSLR in Auto mode, a good way to see the values for Aperture, Shutter Speed and ISO is to view the properties of the photo. Better still, you can adjust these parameters to see what effect this has on a photo.

You don’t really need to know these concepts to take a good photo in Auto mode. However, to upgrade from a point-and-shoot mode to a serious hobbyist mode, these concepts are extremely useful. There is so much more you can do in composing the photo if you know how these concepts (Aperture, Shutter Speed and ISO) work together to bring a ‘Digital Photo’ into existence!

Stay tuned for future blog posts on other photography concepts like f-stop, crop factor, and lenses.

To see my photos, visit my Photography Blog.


9 thoughts on “DSLR Concepts: The watered down basics

    • Thank you Hari. The purpose of this post was basically for a non-technical user who is migrating from a point-and-shoot to a DSLR. The camera is a Canon 60D with 18-200mm IS lens.

    • Thanks Hari. I also read that the background blur (Depth of Field) is directly proportional to Sensor Size. Check http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm

      To quote “As sensor size increases, the depth of field will decrease for a given aperture (when filling the frame with a subject of the same size and distance). This is because larger sensors require one to get closer to their subject, or to use a longer focal length in order to fill the frame with that subject. This means that one has to use progressively smaller aperture sizes in order to maintain the same depth of field on larger sensors.”

  1. excellent write up Sri. Will check on this when i upgrade to one (DSLR) myself. Right now, playing around with a Nikon P500, which I think’s a good mid-point between point-and-shoot and DSLR.

  2. Ok checked it out…good writeup. But where can I find resources to try and optimize what I can do with Superzoom (thanks for letting me know the category of my camera!!). So for instance, I have been playing with Aperture and Shutter speed, right…I feel a slight frustration that I can’t really go too fine-grained on it. I guess I need to accept it. But anyway, my idea is to get an understanding of the range of things I can do with my P500. Where to go? Any pointers will be HUGELY appreciated.

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