I'm working with a young lady who wants to learn more about controlling her camera. One of our first lessons was to focus on how changing the aperture affects the depth of field in an image. First, I must say that I was surprised that she was quite comfortable working in Manual mode! "I was shooting in Auto then just switched to Manual and, well, it just made sense," she said to me! Wow! That doesn't happen for everyone, so let's just say that - let's call her Siobhan (that's NOT her name) because I love to say 'Siobhan' ("she vaan") - Siobhan gets it! So, she's been shooting in Manual and understands that the idea is to set your aperture and then your shutter speed - or vice versa - until the index needle points to "0." However, what she doesn't (no, we're past lesson one, so we'll say 'didn't') understand is why she changes one or the other (aperture or shutter speed).
OK, so you've got the scene, right? I'm asking Siobhan to take shots of a row of balls all lined up in a container and each ball marked with a number with her center of focus on the ball in in the middle. (see this post: http://www.infotor.com/blog/creative-modes-aperture-priority-and-depth-of-field) We start with her aperture set at f/16, a small aperture opening, so all of the balls should be in focus, since a small aperture (less light) creates a deep depth of field. Right? You with me here? Siobhan adjusts her shutter speed (remember, we’re working in Manual now) until the index needle points to 0. She takes the shot. Looks at the result. I tell her to move to f/11, the next larger (in area of light) aperture opening, i.e., twice as much light now coming through the lens, and she does. Her Manual exposure index shows she is -1 stop underexposed. Hmmmm? I think. Oh, that’s right she’s in Manual not Aperture Priority, as I would normally have my beginning students use (where the camera would just automatically change the shutter speed to make up the wider aperture setting). I tell Siobhan, “OK, -1 stop underexposed. What do you need to do to your shutter speed or ISO to compensate, to bring the pointer back up to the zero?” With some prodding, we get to the fact that she needs to slow down her shutter speed by one full stop (http://www.infotor.com/blog/flash-friday-know-your-full-stops-for-aperture-shutter-speed-iso-and-flash-power/). So, for example, if the camera saw that 1/125 was the correct shutter speed before, Siobhan has to slow down the shutter speed one full stop or 1/60. She did this. And so it continued as we worked our way down the aperture range.
At one point, Siobhan turned to me and said, “Oh, you mean three clicks!” I stared. What? “So, I just need to turn the shutter control wheel (usually the wheel on top of your camera) or the aperture control wheel (in Manual mode, usually the rear wheel or the top wheel in combination with pressing a rear camera button) three clicks to change it one full stop,” she said, intently. I thought about that. Of course! Siobhan was correct. Her camera (by default) is set to 1/3 increments between full stops (1/2 increments is the alternative - a menu setting). So, by clicking from f/5.6 to f/4, Siobhan went f/5.6 to f/5.0 {1 click], f/5.0 to f/4.5 [2 clicks], and then f.4.5 to f/4 [3 clicks). Three clicks! Brialliant! No math! (To be able to read the chart above more easily, click on it to display a larger version.)
So, the lesson from Siobhan: assuming you are on a full stop aperture or shutter speed setting, three clicks of the appropriate dial wheel either way will move you from one full stop to the next full stop (up or down)! Cool! Thanks, Siobhan!
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