Part 2: Photography with Imre Z. Balint: Episode 2 – The Shutter

As promised, here is the supplemental post to accompany my video on YouTube. One of the major topics I'd like to address here is the interplay between the aperture and shutter, as the two go very much hand in hand.

But first, something that I didn't mention in my video is that shutter speed is measured in seconds or fractions of a second (for "usual" everyday type photography and not specialized work). For example, the majority of cameras (although this may depend on your specific model) will show a number like 60 to represent a shutter speed of 1/60th of a second. For long shutter speeds getting into whole seconds, this is usually shown as 2", which in this example means two seconds.

If you watched episode 1, then you learned that the aperture of a camera controls the amount of light that may pass through a lens by restricting it using an iris diaphragm. As for the shutter, it controls the duration of time that light may strike the sensor (or film). The combination of aperture and shutter speed is what provides you with the exposure you want (along with depth of field - DOF, which the aperture controls). Below are some general things to keep in mind about shutter speed and aperture:

• When the aperture is wide open (small f-numbers, small DOF), the shutter speed is faster as more light can pass through the lens.
• When the aperture is stopped down (big f-numbers, big DOF), the shutter speed is slower as less light can pass through the lens.
• The "A" setting or aperture priority mode allows the photographer to set the aperture to what they want specifically, and the camera's computer will figure out the appropriate shutter speed. I personally use this setting the most as I can control the DOF.
• The "S" setting or shutter priority mode (sometimes listed as Tv on some models for "time value") allows the photographer to set the shutter to a specific speed, and the camera's computer will figure out the appropriate aperture to use. The downside of this mode is that depending on the amount of available light, a proper exposure may not be possible (e.g. too little light in a dark room, shutter speed set too high, but the camera can't open the aperture any wider to let more light in, so the picture becomes under-exposed). On the other hand, a popular use of this is in sports photography where the shutter speed is set low enough to blur the background to give a sense of motion (e.g. a photographer follows a runner, so the runner is focused and sharp, but the background is a blur). Another example is at airshows where the photographer wants to get blurry propellers to show them in motion (more pleasing than to see blades standing still on an aircraft in flight!).
  
• In general, when shooting things like the night sky (e.g. for star trails and auroras), the camera is generally in full manual mode, and the aperture is set wide open (small f-number) and the shutter is set to many seconds... in some cases many minutes. This helps capture as much light as possible; DOF is irrelevant as stars are far enough away that lenses are set to focus to infinity. By the way, this is basic astro-photography, it only gets more complicated from here and more on that in the future.
  

And now for some links:

• http://www.wrotniak.net/photo/tech/fp-shutter.html
• http://en.wikipedia.org/wiki/Shutter_%28photography%29 - Shutters in general
• http://en.wikipedia.org/wiki/Focal-plane_shutter - Focal-plane shutter 
• http://en.wikipedia.org/wiki/Single-lens_reflex_camera - SLR in general (how light travels through one)
• http://en.wikipedia.org/wiki/Pentaprism and http://en.wikipedia.org/wiki/Pentamirror
  

Next week's episode will be about the sensitivity (ISO, digital noise, etc) of a camera. So remember to subscribe to my YouTube Channel to stay up-to-date with new videos, and bookmark this blog as well.