How does EC actually work?

I have been shooting in AV for the past few months but when we were on a mini vacation two weeks ago now, a few situations came up where it wasn't working so I tried manual mode. I'll be honest, I had no idea how easy it is. I shot manual years ago with an old (even back then) Minolta film camera. It was so old it didn't have either a hot shoe or through the lens light metering. I had no problem with the settings back then. Of course, you couldn't select ISO: you had to change your film.

So my question: when in AV mode and using the EC dial control on the top left of the camera, what does the camera actually do? In manual mode, you change one of the three variables and the EC isn't even available. Which of the variables does the camera change when you adjust the dial of the EC wheel in the other modes? I've looked in several G12 books I have and it isn't explained in any detail. They all say it will lighten or darken the photo, that's it. Is there any way to ask the camera software to lean toward one of the 3 variables (ISO, shutter speed and aperture) when it makes its decision? Is it selected depending on your mode choice, i.e., if in AV, would it adjust either the ISO or shutter speed other than the aperture?

I like manual a lot, but since I got my flash, I will still use AV in low light situations where flash is appropriate.

Thanks for your assistance,

Kim

EC adjusts whichever parameter you HAVEN'T chosen to control; In Tv, it will adjust your aperture and in Av it will adjust your shutter speed. If you are using Auto ISO in either mode, it will adjust the ISO first and then move to the appropriate item (which is one of the reasons I dislike Auto ISO).

In P, it will adjust both settings (aperture/shutter) to the next, appropriate exposure pairing, up or down.

thx, Eric....

That was a very clear explanation. I was hoping it was something like that. I guess if you are in AV and already at the widest aperture, EC will then start changing the shutter speed if more light is needed.

I never use auto ISO for some reason. I guess I'm use to selecting ISO from the film days and now with digital it's so easy, why make it auto?

thanks again for your explanation,

Kim

Phoenixkh wrote in post #13285470
thx, Eric....

That was a very clear explanation. I was hoping it was something like that. I guess if you are in AV and already at the widest aperture, EC will then start changing the shutter speed if more light is needed.
...

Happy to be able to help. But to be clear, in Av mode, EC will always only change shutter speed, regardless of whether you are at max aperture or not. You are the only one that will change the aperture there. Similarly, in Tv, it will never change your shutter speed.

If the G12 is like the Rebels, it's interesting to note that you select the "other" parameter for Manual mode as well. If the default for Manual is selecting shutter speed (I forget, honestly) then pressing A/v will let you adjust the other parameter.

Here's how I think about EC: Without an exposure compensation setting (and assuming ISO is manually set), the camera will meter the scene according to its programming - which assumes the overall scene matches 18% gray.

It will still meter the scene the same way when you dial in EC, but now you're forcing it to expose the scene with that much alteration (in stops) to the second parameter. If you set EC to +1 stop in Av mode, you get one stop less of shutter speed. +1 stop in shutter priority will open the aperture one stop (assuming you aren't at the limit already).

Of course you could say that maybe the camera meters differently with EC added (I haven't read how it is set up), but for practical purposes it doesn't matter - a change to the target metering versus having the same metering adjusted is just a matter of semantics; use whatever understanding makes the most sense.

Here's something you might enjoy. Play with this in Av, Tv, P, and Manual modes.

Let's say you are in Av mode. Compose a shot and then Half-press the shutter. Now press the '*' button (upper right). This is AE Lock. Generally it is used for getting an Auto Exposure on a certain subject or part of the frame, and then re-composing the shot. Then you half-press, proceed to full-press, and you have your finely tuned shot. (there are similar uses of the '*' button to lock-in a flash exposure setting, and a couple other handy uses)

The reason I bring it up though is that pressing '*' button displays an indicator of what combination of Aperature and Shutter-speed the camera has decided on (for that metered exposure).

A couple practical uses for this (besides re-composing the shot):
a) while you have that indicator displayed, you can rotate the Control Dial and see what other combinations of Aperature & Speed -- yield the same exposure.
b) you can mentally note the range of settings, then switch to Manual mode and play within that range, or go out of that range to get the image you want.
c) In Manual mode and with that indicator displayed, when you rotate the Control Dial -- only ONE of the settings is changed and you can immediately see the results (brighter/darker) on the LCD scene as you effectively altered the exposure. Press the '+/-' button (1 o'clock pos.) to toggle over to the "other" setting. By "setting" I mean Aperature or Shutter-speed. Hit '+/-' again to toggle back to control of the other. Use the Control Dial: The indicator will hold Aperature in a fixed position while Shutter-speed 'slider' moves left and right. Toggle '+/-', and Shutter-speed is fixed... Aperature slider moves. Cool. Further: As you do this, look at the vertical 'exposure level' indicator on the right... shows under- and over- exposure. I think this is similar to the Ev adjust scale, but with an extended range. (Pressing '*' again resets exposure back within 'normal' range <---- do try this!)

I have used these methods to relearn some photography, and to settle-in to what the G camera can do.

You should read the guide on Exposure Lock etc. -- once you press the '*', you can actually cancel that operation by pressing most buttons and if you did not expect that it could be frustrating. Also, remember you have several metering options in the Functions/Set area.

I did "experiments" in exposure and flash compensation with my G9 in P, Av and Tv modes, see http://lightdescriptio​n.blogspot.com …l/exposure%20co​mpensation . Although now obvious, this was eye opening to me at the time. I'm pretty sure that all the G series use the same logic. (Best to read those blog posts in reverse order.)

You all have been very helpful to me. I have a whole list of things to try now. These forums are very fun and informative.

thanks again,

Kim