# EF Lock * while using manual focus



## abik (Jul 8, 2014)

Hi guys, i am wondering what happens if i use manual focus how do i lock the exposure lets say i use TV or AV mode. can i still use the different metering modes? if yes how?


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## tirediron (Jul 8, 2014)

Focus and exposure are totally unrelated.  Manual/auto focus is set using (depending on your camera & lens) using either a menu-setting, a physical switch on the camera body or a switch on the lens.  This has NO effect at all on exposure which is set using either a menu setting or a 'Mode' dial, either on the top of the camera body, or via the top LCD on higher end bodies.  You can use any exposure mode you want in either manual or auto focus and one will have no effect on the other.  The specifics of setting each on your particular camera/lens, will be found in your manual(s).


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## dennybeall (Jul 8, 2014)

My Nikon does not see any relation between the two. In Av it will shoot a manually focused picture and it will just as happily shoot a very manually out of focus picture


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## KmH (Jul 8, 2014)

Nikon DSLR cameras do have a relationship between the AF system and the light metering system, but only when Spot metering mode is used.
Focus and metering remain separate functions though.

When using Spot metering the spot metered is concurrent with the selected AF point.

With all but Canon's top-of-the-line pro models, Canon DSLR camera Spot metering is done with only that portion of the viewfinder defined by the center AF point.
Focus and metering remain separate functions though.


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## TCampbell (Jul 8, 2014)

On a Canon body, the asterisk button (*) on the back will do an AE lock.  E.g. you can point the camera to what you'd like to "meter", press the AE lock button (the * button) and then recompose and shoot... but the camera will not re-meter when you recompose as long as you don't wait too long.  

There's an asterisk icon that you can see in the viewfinder (put your camera to your eye, press the '*' button and you'll see it appear.  Release all buttons and wait... while continuing to look through the viewfinder (it is also displayed on the back LCD if you have the exposure settings screen displayed) and you'll notice that it does eventually go out after several seconds of waiting (or immediately after you actually take the shot.)

Once you half-press the shutter (or anything that wakes up the metering system) you can press the AE lock and it'll remain until either (a) you take the shot or (b) you wait long enough for the metering system to go back to sleep (which is several seconds).  If for some reason you want to cancel the AE lock and don't want to wait out the 4-6 seconds for the camera to clear it on it's own (btw you can just force another AE lock too) you can just press the AF point selection button (usually immediately to the right of the '*' button) and this will force the camera to drop the AE lock immediately. 

See:  Canon DLC: Article: Using Auto Exposure (AE) Lock

Focus is independent of exposure metering *except* that some cameras will use it as part of intelligent tracking & recognition system (Canon iTR) when autofocus is enabled and you want to folio why subject in motion - the 1D X, for example, does this.   Since you specifically asked about manual focus -- there's generally no relationship.  BTW I say "generally" because sometimes there is.  If you use a long macro lens with the focus dialed all the way IN, "meter" and then run the focus all the way OUT and re-meter (without moving the camera at all) you'll notice the meter readings do actually change.  (A technical "nit" but I thought I'd throw it out there since the "there's no relation" is basically true 99% of the time but there are the rare exceptions to that generalization.)


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