AE Lock

[DueyDooDah]

I have an EOS 30D and need a bit of help in understanding AE Lock.

While trying to take a picture of a white piece of paper (which turns out an ugly shade of brown) I am attempting to lock exposure on a gray card prior to the shot. The problem lies in the short period of time the lock lasts (about 4 seconds) until everything resets. Let me see if I'm doing this correctly:

I press the shutter button halfway down, focusing on the gray card. I then can then release the shutter button and press the * button or just press the * button while still holding down the shutter button. I expect the lock to remain until I again press the * button(?), but this is not what happens. After the 4 seconds, I have to recompose. This is not always convenient.

Am I doing something wrong or do I just need to be quicker?

 

[ukcatfan]

Just switch to manual mode and adjust to the correct exposure.

Kevin

 

[DueyDooDah]

Yes, that's a good way to fix this specific problem but I'm trying to learn to use the AE Lock feature so I am hoping that someone can answer my original question.

 

[boBQuincy]

I have a 30D and checked the manual (and tried what it showed).
Once you press the shutter button halfway and then press AE lock it locks in the exposure for as long as you hold the shutter button halfway *or* for a few seconds after you release the shutter button.

If the white paper is an ugly brown the white balance might be off, it should be an ugly gray. Here is a useful place for exposure compensation, set it to +2, meter on the white paper, and take the photo. It should be a lot better, but still not quite right.

According to the Zone System white paper is about 3 to 4 stops brighter than a gray card, depending on if you want any texture to show.

 

[AndrewWG]

I tried this with my 30D on my last WDW trip and was very unsuccessful. I now see that I didn't hold the shutter halfway down. I didn't give it much thought at the time, but now I'll be trying again.

 

[MarkBarbieri]

I set Custom Function 4 to 2 (AE Lock/AF) and set the focus mode to AI Server. That way pushing the * button makes the camera AF and letting go locks focus. Pushing the shutter button halfway locks exposure until released. The FEL button is used to lock flash exposure. I think you press it and it's good for 16 seconds, but I'm not quite sure about that.

 

[0bli0]

when you were exposing for the grey card, were you attempting to correct white balance (to turn the white paper from brown to white), or get the proper exposure? grey cards can be used for both. when you were focussed on the grey card - what type of metering were you using? if you were using average or weighted average, how much of the card was visible and how did it compare to the scene with the white paper?

if you want to quickly learn the best way to understand how AE works, take a shot of someone where you're exposing for their face and let some sky leak in. you'll see the sky is very white or light grey in the photo. now if you point the camera at the sky and use the AE lock button (you will see the * in the viewfinder for as long as the lock applies - which is as long as you keep half-pressing the shutter), you can then take the same original photo of the person and you'll see the sky is nice and blue, however the face may be a bit dark.

i have a small reflector which is grey on one side and white on the other. i generally only use it when shooting manual for portraits or something similar (and to compare exposure to my gossen 6) and i'm not concerned with a blown-out sky. i do use the AE lock whenever the scene calls for it and i generally use the my hand as an exposure guide. i use the darker back side of my hand if i want to preserve shadow detail or the lighter palm if i want to more evenly expose (it depends on the scene).

if you were looking to keep the white paper white, i'd shoot it raw and then correct in Aperture. you might want to double check to see that you havent changed the default white balance.

 

[Groucho]

Why not just do a little exposure compensation?

And like others have said, white balance will affect the color; if you're getting a brown tint, it'll still be there even with exposure lock.

 

[skr8pn]

Yes, that's a good way to fix this specific problem but I'm trying to learn to use the AE Lock feature so I am hoping that someone can answer my original question.

I have to say, once I learned this nifty little function I love it. Just growing my small arsenol of things to use for better pictures. It's really good to take one with the AE locked then another not locked so the camera adjust automatically. Big difference in the pics. If I can find some I'll try to post for comparison.