Ae-lock and Re-Compose

Started 3 months ago | Questions thread
PhotoTeach2 Forum Pro • Posts: 12,516
Re: Ae-lock and Re-Compose

Jcbailey wrote:

Bill Ferris wrote:

Jcbailey wrote:

I'm confused on how AE-lock works. I was adivsed and also tried this. Walk into a room point at what i want to capture, lock the exposure with AE-lock. re-compose and take the shot. in theory the shot should have the same exposure as when i locked it. I don't see this.

Did you read this reply to one of your previous threads?

I second the suggestion to READ this again ...

for example. i went into a dark room and found some light. i metered the light and my Shutter was at 1/200 to see if it was right i metered the dark spot and it was 1/60. so i Ae-locked the 1/200 from the light locked it re-composed and the shot came out dark.

Because it set the exposure to render the (bright/white) "light" as a GRAY, making the rest of the scene even darker. (as explained below)

Spot-Metering MUST be read from a (average-reflectance) GRAY, unless you use either + or - EC (Exposure-Compensation).  +2 if white and +3 if a light-source

Metering off the light in the dark room would have set the exposure & lightness of the scene 1 to 2 stops below optimal. When metering in a space to use as a reference for exposure and ISO settings, it's best to find a surface that's middle gray in tonality. If that's not available, if very dark or very light are what's available, you'll need to dial-in exposure compensation to compensate for metering off surfaces that are 1 to 2 stops off middle gray.

my camera focused again while i pressed the shutter all the way down and took whatever shot it wanted. I was in AV mode with a fixed iso.

What happend?

As for the autofocus, were you in single-shot mode or continuous AF? Also, was your camera setup so the shutter release button activated autofocus or so a button on the back side of the camera activated AF?

Last one was spot metering i think. this one was evaluative and AE-lock.

AE (and AF) lock can be custom set differently in different cameras.

Evaluative-Metering is designed to be used as a POINT & SHOOT camera since it is designed to already make the (intelligent) calculations for you.  Often it works very well, but I personally like to make my own decisions, BUT ... that is hard to do in Evaluative because you don't know what decisions it has already done.

So Average/Center-Weighted or Spot is better to ensure your own preference.

BUT ... Spot-Metering REQUIRES you to fully understand EC and understand you MUST use it (correctly) when (spot) metering from either a light or dark area.

+1 or +2 if white (and +3 if a light "source").

-1 or -2 if dark for black.

Thanks for the reply though

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