Ae-lock and Re-Compose

Started 3 months ago | Questions thread
alcelc
alcelc Forum Pro • Posts: 16,238
Re: Ae-lock and Re-Compose

Jcbailey wrote:

Autonerd wrote:

I believe (and I could be wrong, I'm more of an old-camera guy) AE lock should work as you are saying. Not sure what camera you have, but do you have to press or hold the AE Lock button to get it to work? (On old cameras you had to hold it.)

Also, how high are you allowing your ISO to go? If you've set a limit, it's possible you're just not getting enough light on the sensor. A room lit by artificial light has an exposure value of about EV5. At 1/200th of a second at ISO 3200, your aperture would need to be around f/2.2. Larger if the room is dimly lit.

It might help us here to see a sample pic with EXIF data or at least get your exposure/ISO settings.

Aaron

Still don’t understand it. It meters at 1/200 and I think my iso was 16000 shouldn’t it have got the light took the shot and it be bright?

That is the exposure your camera throught correct to expose for the light source. But when you want a brighter output to show the darker area away from the light, did you sure you don't need to increase exposure, e.g. 1/10" and ISO32000?

Why did it re-focus after pressing the shutter all the way down?

When you lock the exposure value, not sure which metering mode used, in case if spot or center weight metering (where highlight area is dominant of the metering area) was used, the meter reading would think the scene is bright so a right exposure ( naturally lower than need for a darker area) would be used. For your example was 1/200" & ISO16000.

When you do recompose, says pointed the cam towards the dark area, without AEL on highlight, the cam should take reading from the darker area of the room and so would use higher exposure for a brighter output ( just to say, 1/10" & ISO32000?) to show the detail of darker area better. Please note, the cost of brighter shadow area is the light will be over exposed.

However under AEL, the cam will use the exposure setting as taken from the bright area, hence you will get a darker (relative to taking reading from dark area) output but the light area will be well exposed.

For your case, if you are not looking forward to expose on the light source, e.g. wish to show the detail of the light bulb etc, do not lock AE on the light source.

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Albert
** Please forgive my typo error.
** Please feel free to download the original image I posted here and edit it as you like **

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