mengwei11 said:
Sorry, I might have made a mistake. All my cameras are set that way (AE lock linked to AF lock) forgot it is a conscious option after so long. The rest are right. Apologize for the mistake.
New to cs... Evaluative metering
- Thread starter mengwei11
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Sorry, I might have made a mistake. All my cameras are set that way (AE lock linked to AF lock) forgot it is a conscious option after so long. The rest are right. Apologize for the mistake.
I using a 50D. by default when you had chosen a focus point and you half-depress shutter, you lock both focus and exposure. Of course you can change that in custom function.
As for evaluative metering, in simple english :- means it's Canon metering design to guess what's your main subject. It goes by dividing it into zones and try to expose the main subject correctly.
If you're using spot metering, then most likely you would want to keep the exposure when recomposing, since the subject you spot meter on will be the exposure you want to achieve (e.g. the main subject or a 18% grey card). So in this case locking AE while half press shutter release is ok.
On the other hand, if you're using evaluative metering, let's say you're using center focusing point. You focus on the subject with it at the center, and then recompose to place it at the thirds. Now imagine the background to one side of the subject is dark while the other side is bright. By recomposing, you have now shifted the subject and hence either more light or less light (depending which side you're shifting) enters the camera. If in this case you lock the AE while focusing, the final exposure after recomposing will be incorrect.
Yes you're right, for Canon camera this is the case, as long as you're in One Shot AF and evaluative metering. See here.
On the other hand in Nikon cameras, the default for exposure lock at half press shutter is off, and it needs to be specifically turned on in custom menu. So different manufacturer does it differently. But I do find Nikon's more logical not to lock the AE in matrix metering due to the reason given above.
Ok I've been experimenting and this is my layman findings. I think most of u have been explaining this to me, just that I need to sort of articulate it back so that I understand.
Using evaluative metering
- with my 50d where u focus lock is also where you meter lock. The *lock has no effect on evaluative
- when I focus lock / meter lock on the subject, the exposure is locked. Hence if I focused on sky, but then recomposed where a dark tree is in the picture, the picture is underexposed (becos the camera has locked an exposure to compensate for the bright sky)
Using spot metering
- this is where the * ae lock makes a difference. But it only makes a difference if your focus point and metering point is different! (which is not what a lot of mags and people say!)
- if your focus point and metering point is the same, when u half depress the shutter to lock focus, exposure is already locked, so no need to depress *
- but if u want to meter for say the sky, then u *ae lock at the sky, recompose and focus on subject and fire off. The picture will have the exposure based on the sky. I know this is a lousy example, and I'm wondering now, when would ae lock be useful.
Ok I think I understand now. Sorry for being slow.
Using evaluative metering
- with my 50d where u focus lock is also where you meter lock. The *lock has no effect on evaluative
- when I focus lock / meter lock on the subject, the exposure is locked. Hence if I focused on sky, but then recomposed where a dark tree is in the picture, the picture is underexposed (becos the camera has locked an exposure to compensate for the bright sky)
Using spot metering
- this is where the * ae lock makes a difference. But it only makes a difference if your focus point and metering point is different! (which is not what a lot of mags and people say!)
- if your focus point and metering point is the same, when u half depress the shutter to lock focus, exposure is already locked, so no need to depress *
- but if u want to meter for say the sky, then u *ae lock at the sky, recompose and focus on subject and fire off. The picture will have the exposure based on the sky. I know this is a lousy example, and I'm wondering now, when would ae lock be useful.
Ok I think I understand now. Sorry for being slow.
the way I am understanding your post, is different from what ziploc stated in post #43.
He's saying that the AE-lock feature is useful when paired with evaluative metering, not spot metering.
Actually I meant it the other way round, meaning pairing AE lock with spot (or center weighted) metering is more desirable, and not so with evaluative.
I remember reading this mentioned specifically in one of the Nikon manual (regarding not to lock AE when using matrix metering)... but I can't remember which one. I owned an F90, F5, Fuji S2 (D80) before, and now the Fuji S5 (D200), so it must be one of them... :bsmilie: The older manual has better explanation regarding the matrix metering as well, with pictures as illustration (think it was the F90).
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ziploc said:Actually I meant it the other way round, meaning paring with spot (or center weighted) metering is more desirable, and not so with evaluative.
I remember reading this mentioned specifically in one of the Nikon manual (regarding not to lock AE when using matrix metering)... but I can't remember which one. I owned an F90, F5, Fuji S2 (D80) before, and now the Fuji S5 (D200), so it must be one of them... :bsmilie: The older manual has better explanation regarding the matrix metering as well, with pictures as illustration (think it was the F90).
In canon the ae lock has no effect in evaluative. I'm so happy I sort of understand now.
oh?Actually I meant it the other way round, meaning pairing AE lock with spot (or center weighted) metering is more desirable, and not so with evaluative.
I remember reading this mentioned specifically in one of the Nikon manual (regarding not to lock AE when using matrix metering)... but I can't remember which one. I owned an F90, F5, Fuji S2 (D80) before, and now the Fuji S5 (D200), so it must be one of them... :bsmilie: The older manual has better explanation regarding the matrix metering as well, with pictures as illustration (think it was the F90).
I kinda agreed with your earlier point of view
To me, when using spot or center-weighted metering, it makes sense to couple metering and exposure-lock together with a single half-press of the shutter release. I would use this when capturing a portrait, for example.
Both accurate focus and exposure on my subject are most important to me, even though I would re-compose to have the subject at an intersection of the thirds for example.
It's good when shooting backlit subjects when using Spot or Center-Weighted Metering in conjunction with Spot or Center AF
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Diavonex said:It's good when shooting backlit subjects when using Spot or Center-Weighted Metering
That's what I thought. But it doesn't seem to be the case. Subject against backlit background. U set to spot meter. U focus on subject, the exposure is locked. UNLESS you want to meter for the backlit, but focus on the subject, but I don't understand why you will do that.
If the subject is off-center, you lock exposure and focus, recompose and shoot. Subject will be correctly exposed and focused.
TS is asking for the merits of de-coupling the focus and exposure locks.
Yours is the perfect example of when it is a good idea to couple the focus and exposure together
TS is asking for the merits of de-coupling the focus and exposure locks.
Yours is the perfect example of when it is a good idea to couple the focus and exposure together
I've edit my reply:
It should be using Spot or Center-Weighted Metering in conjunction with Spot or Center AF.
I'm confused liao
Seems to have gone off on a tangent. Will stop here before I confuse myself further :sweat:
Seems to have gone off on a tangent. Will stop here before I confuse myself further :sweat:
You'd do that if you want to shoot a silhouette with a nicely exposed sunset in the background (for example). Need to meter on the sky, but focus on the silhouette. Something like this:
If the camera tried to meter to retain some details in the silhouette (the subject in focus), the sky would be blown out, or at least overexposed and the mood would be completely different.
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