Exposure Basics, lesson three?

Started Mar 18, 2013 | Discussions thread
Great Bustard
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Re: Quick correction.
In reply to Najinsky, Mar 21, 2013

Najinsky wrote:

Macx wrote:

I have a great respect for the problems you must face teaching beginners who come with cameras that might not even have basic aperture or shutter controls, etc. But why the bloody triangle? It really doesn't make sense. The only thing triangular about these three concepts is that there are three of them.

Yes it's as simple is that. Three settings that encompass the capture. A common way of showing something encompassed by three sides is a triangle. I didn't invent it, it's been around a long time and I happy to use it to convey the three related settings. It works for me, and it worked on the course.

If other people want to present it differently that's fine. But those graphs are attempting to show something else, the equivalence in exposure terms of different combinations of settings. That's fine too, if that's how you like to look at stuff.

But for the equivalent exposures, I simply show some photos, some of them with problems caused by the shutter speed too slow and some with the aperture too wide. Therefore including the notion that the scene may limit the range of equivalent exposures available to us. Then they practice it and see for themselves.

  • Wider aperture, more light on the sensor (less noise) and less DOF.
  • Narrower aperture, less light on the sensor (more noise) and more DOF.
  • Lower shutter speed, more light on the sensor (less noise) and more motion blur / camera shake.
  • Faster shutter speed, less light on the sensor (more noise) and less motion blur / camera shake.
  • Apertures at the very wide end (low f-ratios) often result in less sharpness (lens aberrations).
  • Apertures at the very narrow end (large f-ratios) often result in less sharpness (diffraction softening).
  • Lower ISO settings result in wider apertures, lower shutter speeds, and/or less flash power, or result in a darker photo for a given aperture, shutter speed and flash power.
  • Higher ISO settings result in narrower apertures, faster shutter speeds, and/or more flash power, or result in a brighter photo for a given aperture, shutter speed, and flash power.

In what way, then, is the "Exposure Triangle" useful in comparison?  That it shows a relationship between the numbers representing aperture, shutter speed, and ISO?  Why should a beginner care?  How does this relationship help them take a better photo?

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