help required re 550d AE lock

mik0m

mik0m

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mick
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Hope someone can offer a beginer a little help here.

Having got a copy of Understanding Exposure I have been experimenting with the AE lock on my Canon 550.

However after trying it for a while i have noticed that now on all modes apart from Manual the exposure indicator does not shift from dead centre when in AV or TV. It stays dead centre whether I aim the camera at deep shadow or bright light.

Now as far as I know all I have done is try to lock exposure (spot metering selected) by pressing the small button beneath the asterick symbol on the top of the camera body ( the AE lock button ..I hope)..the asterick symbol appears in the viewfinder when in AV and TV mode but not in M but appears to have no effect on the exposure indication given .... eg perfect centre.

I have tried clearing the camera settings but with no luck..the situation remains as above.

If anyone has any suggestions what I have done wrong they would be most welcome here.

Thanks
 
Exposure lock is for the auto modes, in manual you set the exposure on how you want to meter and leave it at that.
 
Are you locking it when metering off a shadow/highlight or am I misunderstanding what your saying?

Basically the lightmeter assumes that whatever you meter off will be approximately 18% grey (in theory, most are actually calibrated to about 14% grey but thats another topic) so if you meter off something darker then the camera will overexpose and render it grey. Likewise if you meter off something whiter than 18% grey then the camera will render it as grey by underexposure.
Is that what your trying to get at?

If thats what your trying to do, spot meter off the brightest part of what your photographing, lock the exposure and use exposure compensation to overexpose the image +1.5 to +2 stops. This technique is called 'highlight priority metering' technically as your metering to preserve the highlights. The image may come out too dark, you can correct that in editing. (This is how I do it when shooting slide film which is similar to digital regarding exposure, e.g metering to preserve highlights etc, with negative film its actually the opposite, you meter off the shadows and use EC for -1.5 to -2.0 stops, this usually overexposes the image but you get beautiful dynamic range and you can get away with up to +3 stops with negative film before highlight detail is lost)

Looking at the manual for your camera it appears that it doesn't give any indication of difference in exposure to what has been locked similar to in the manual mode, not all cameras do as the idea of AE lock is that its what you've selected. One of my AF cameras (Minolta Dynax 5) does when using the manual mode or spot metering by using the exposure compensation scale to indicate the difference in exposure between what the camera thinks is the correct exposure and what your using by manual selection or AE lock.
 
s162216 said:
Are you locking it when metering off a shadow/highlight or am I misunderstanding what your saying?

Basically the lightmeter assumes that whatever you meter off will be approximately 18% grey (in theory, most are actually calibrated to about 14% grey but thats another topic) so if you meter off something darker then the camera will overexpose and render it grey. Likewise if you meter off something whiter than 18% grey then the camera will render it as grey by underexposure.
Is that what your trying to get at?

If thats what your trying to do, spot meter off the brightest part of what your photographing, lock the exposure and use exposure compensation to overexpose the image +1.5 to +2 stops. This technique is called 'highlight priority metering' technically as your metering to preserve the highlights. The image may come out too dark, you can correct that in editing. (This is how I do it when shooting slide film which is similar to digital regarding exposure, e.g metering to preserve highlights etc, with negative film its actually the opposite, you meter off the shadows and use EC for -1.5 to -2.0 stops, this usually overexposes the image but you get beautiful dynamic range and you can get away with up to +3 stops with negative film before highlight detail is lost)

Looking at the manual for your camera it appears that it doesn't give any indication of difference in exposure to what has been locked similar to in the manual mode, not all cameras do as the idea of AE lock is that its what you've selected. One of my AF cameras (Minolta Dynax 5) does when using the manual mode or spot metering by using the exposure compensation scale to indicate the difference in exposure between what the camera thinks is the correct exposure and what your using by manual selection or AE lock.
Click to expand...

AE Lock does NOTHING in Manual mode, There's some great info in there re some complex stuff that the OP is a long way from though.:)

I've just looked at the Manual for this camera to help you -sheesh - who writes these. Why wouldn't it tell you what AE Lock does properly in relation to other modes.:razz:

When in Manual mode, you choose the area you want to meter and then set your aperture / shutter speed to suit that area.

AE Lock is for when you're in an auto mode and you need to set your exposure from an area that wouldn't be the automatic one for the scene you've selected. So you 'lock' the exposure prior to shooting.
 
Essentially what I was trying to say above in a bit of a more compact form! :)
 
Thank you for your help.... I realise I need to read more....

Am I misunderstanding something very basic then like the exposure meter in the viewfinder is not supposed to indicate anything other than dead centre when in an auto mode as the camera is automatically settig correct exposure and is continually updating the settings as the camera is moved?

So if in say AV mode if I want to overide the camera I turn to exposure compensation to over or under expose?

If so no wonder your confused....

And you are right about the manual ....nightmare to read never mind understand
 
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Yes the auto mode will adjust the camera settings to keep to the centre of the meter, that's why you need to understand what it's reading. You can override its readings either by exp lock or exp compensation.

Or shoot manual, whereby you can lock in the settings you want in a more rigid way.
 
Best guide to checking exposure is by using the histogram and blinkies then compensate/adjust accordingly

Unfortunately you won't find much mention of them in Understanding Exposure :thumbsdown:
 
thanks for all your comments and help much appreciated helps lighten the darkness so to speak
 
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