Exposure Basics, lesson three?

Started Mar 18, 2013 | Discussions thread
Najinsky
Veteran MemberPosts: 4,597
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Re: Quick correction.
In reply to Great Bustard, Mar 21, 2013

Great Bustard wrote:

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?

You may have seen that I have now made quite a number of post. I fear that if you haven't picked it up by now, I'm not going to be the one to do it for you. But I'll try, one more time, just for you.

The exposure triangle is useful in overcoming the new student's fear of the camera controls. At the introductory level of the students I was teaching, most had a fear that they didn't know what the camera controls were or how to use them. Most were shooting auto, all were shooting JPEG, even though some had DSLRs.

I would say to the students, when you shoot the camera in auto, the camera is making decisions for you about three key settings for you. What we're going to do is learn what those settings are, and what they mean to the camera. We'll learn how they impact your images so that we can begin to make our own decisions about those settings so we can start capturing the images we want.

This diagram shows you the three settings the camera is deciding for you (cue the exposure triangle diagram). Lets look at each one in turn.

This, and only this is the purpose of the exposure triangle (as I used it). And as stated, again with a slightly busier version, including the common numbers used for those setting, as a recap aid once we have covered and practiced changing each of the settings.

You can sit there all day, and ask me questions all day about why the triangle doesn't predict stock market prices and football scores or even those questions relating to photography. The answer will remain the same. I don't use it to try to explain those things. Only to help overcome their fear of the camera controls, in a way that relates to what the camera is already doing when the shoot on auto. And then to confirm those three settings are now understood sufficiently to start building on.

-Najinsky

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