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Lesson Five: Balance – ISO

ISO  ~ known in the past as ASA is the camera’s film-speed and is the third variable in the balance of a proper exposure.

Film speed was used in the past to allow for better camera performance in different and difficult light, and has adapted itself to the digital age to give us one more level of control in the hunt for the perfect exposure.

You will most always use a low ISO (200-400) in order to reap the quality rewards, and only bump up to your camera’s minimum good quality ISO (800-1000 usually) to gain some extra play with the available ambient light. ISO is directly linked to light and unlike Aperture and Shutter Speed it has only one function in exposure. ~  It will give you a boost to light sensitivity in your exposure for each interval it is raised.

Although it does nothing to your composition besides light sensitivity; it does have a secondary effect on the photo. Quality does degrade as you boost the ISO. First you see some acceptable grain, then tolerable grain, then unacceptable grain and in the end, colour banding.

ISO performance varies from camera to camera, and is always a topic of new feature sheets as breakthroughs are made in the science of digital ISO  all the time.  In the near future sensors will be able to provide usable photos in very low light situations without a flash.

Have a look at how ISO affects quality as it is boosted. It is more apparent in darker conditions like low light and night-scapes.

Using ISO to your advantage can open up some creative options that might elude you as well.  Sometimes you need an extra couple of stops to get the detail you need in a photo. You can usually live with a little grain in your photo if it means you nail the shot. My camera (Nikon D-700) preforms acceptably well into the iso 1600 range and if I have to go to iso 2000 I will.

ISO boosting is great when you have your Aperture and Shutter Speed set and don’t want to touch it because the composition would change undesirably. If you start out with your camera on iso 400, you have a bit of room up and down to play with if you run into the need for more or less light.

Together with Aperture and Shutter Speed, proper ISO setting is crucial to to the perfect exposure.
If you are to tame light, you must know where the ISO control is on your camera and keep it at the top of your mind as you compose your photo.

The next lesson will deal with Light. and how we can tame light with light.
Using ambient against itself and making light with flashes and strobes. This is where things get interesting.


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