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Back button focus with Canon 7d Marki: Metering problems and explanation of focus and meteer

iris
Enthusiast

Wrestling with understanding of how the focus and metering actually work once you've set up a continuous "back button focus"...I have the first tracking AF situation chosen from the cutsom menu and have tried using the shutter button for  AE locking only  or meter only....but I am having trouble with  metering....While holding down the continuos AF button as I have moved it to the locatio offered in the custom menu...I still use the wheel on the top of the camera to meter....Is this correct?   When shooting with continuous AF, holding the back button as chosen frojm the custom menu...is the focus area always going to be over the center metering area.....?    If you shoot this way, is your image always going to be in the center of your frame...????  YOu may be able to physical move your lens around to follow a hockey player of bird...but is your focus area (whatever one you chose as your default) going to always sit over the metering area in the center of the lens?  Perhaps I don't understand the way the word "Tracking is used"

 

 

. I have chosen the "expanded focus" for my default focus.

 

I have watched video after YOu tube video and ccan't find one that actually shows what is going on inside the view finder?

 

 

6 REPLIES 6

Waddizzle
Legend

You're wrestling with multiple issues at once, when they are, in fact, separate issues.  The AF system is the most complex.

 

http://www.learn.usa.canon.com/resources/articles/2014/eos7dmk2_afGuidebook.shtml

 

The AI SERVO mode of the Auto-Focus system in the 7D2 is one of Canon's most complex.  I suggest setting it up with the default settings, so that you can get a basic understanding of what is occurring with AF Assist Points.  Post back with specific questions.

 

Back Button Focus is pretty straight forward.  I do not use it lock in exposures.  I use it to engage, or disengage, the AF tracking system.  I hold BBF to engage AF, and release the BBF button to disengage it.  .By separating out the AF from the shutter, I can take pictures faster without having to wait for the camera to lock/track focus on a subject.  I will frequently use ONE SHOT mode to get a confirmation beep, and a AF point flash in the viewfinder.

 

I am not very good at moving the camera and tracking a subject, especially with super telephoto focal lengths.  Tracking birds in flight is art that I may never master.  But, setting up a big lens on a tripod and pre-focusing it on a part of the field where I anticipate the action to go is easy to do.  Being familiar with the DOF of your lens is the key.

 

I rarely use exposure lock when I am hand holding the camera shooting sports, or the occasional bird, mainly because I am shooting under widely varying lighting condition, in Continuous Shooting drive mode.  I am also using AI SERVO mode, when I do.  Under those conditions, I am typcially shooting in Manual shooting mode, with ISO set to AUTO.  I try not to let the camera adjust more than one leg of the exposure triangle at a time.

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"The right mouse button is your friend."

Waddizzle
Legend

"I have the first tracking AF situation chosen from the cutsom menu and have tried using the shutter button for  AE locking only  or meter only....but I am having trouble with  metering...."

 

Assuming that your finger is not accidentally hitting the <*>, AE lock, button, which is next to <AF-ON>, the camera behaves differently depending upon the focus mode.  In ONE SHOT mode, the camera locks focus and exposure when it beeps, and stays that way until you release the shutter button and re-acquire focus.  In AI SERVO mode, the camera will continuously update focus on a moving subject, as well as updating exposure.

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"While holding down the continuos AF button as I have moved it to the locatio offered in the custom menu...I still use the wheel on the top of the camera to meter....Is this correct??

 

Not sure what you mean by moving it to a location in the custom menu.  Holding down the <AF-ON> button, will give you different results, depending upon the focus mode that you have selected.  Depending upon the shooting mode [M, Av, Tv, P} the camera's main wheel will behave differently.  In Manual mode, the main wheel will normally adjust shutter speed, although this can be changed through custom programming.

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"When shooting with continuous AF, holding the back button as chosen frojm the custom menu...is the focus area always going to be over the center metering area.....? "

 

I will assume that you mean AI SERVO mode.  The initial focus area will be the default AF point that you have selected.  The default factory setting is the center AF point, which I suggest to always use.  Depending upon the settings you have selected in the AF menus, the camera can track a subject as it moves through viewfinder by using AF Assist points.

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" If you shoot this way [AI SERVO], is your image always going to be in the center of your frame...????  "

 

No, your subject will not always be dead center in the frame, which is why the camera is able to use AF Assist points.  The camera can lose tracking of the subject for a number of reasons, including the subject moving far enough to the edge, outside of the AF area in the viewfinder, where the active AF points can no longer track it.

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"You may be able to physical move your lens around to follow a hockey player [or a] bird...but is your focus area (whatever one you chose as your default) going to always sit over the metering area in the center of the lens?"

 

Depending upon your shooting mode, the focus area could be just the center AF point, are varying combinations of all of the AF points in the camera.  The default factory setting, when shooting in Manual mode, is the just the center AF point, without any active AF Assist points.

 

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"The right mouse button is your friend."

diverhank
Authority

Focusing and metering, as you might know, are two separate things.  You should keep everything (including metering) as part of the shutter button push – just remove the focusing function -  to the back button.

 

Unless you are doing spot metering, the above will work very well and I recommend against spot focusing for BIF…you will never be precise enough to do spot on a moving bird – just use the default metering option which is the evaluative metering.  For BIF, you should use Tv mode or Av mode but not manual.  That way, for most cameras, including your 7D1, you can take advantage of the exposure compensation to get the bird exposure right (instead of spot metering).

 

Regarding autofocus…your 7D1 has 19 focus points.  The default is in the middle and you can move it around.  The initial focus point starts where you put the focus point initially.  There is a nice guide Canon puts together…I’ll let you read that.

 

https://www.learn.usa.canon.com/app/pdfs/quickguides/CDLC_EOS7D_AF_Modes_QuickGuide.pdf

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The Custom  Functions Menu doesn't offer JUST a focus option alone that I can tell.....it offers "AFspot +metering", or "Spot Metering" or * (which I believe is AE lock).......I guess I'm missing something here?

 


@iris wrote:

The Custom  Functions Menu doesn't offer JUST a focus option alone that I can tell.....it offers "AFspot +metering", or "Spot Metering" or * (which I believe is AE lock).......I guess I'm missing something here?


I might have given you some bum info.  What I have set for mine was:

 

Back button (AF On) = AF (metering and AF Start)

Shutter Button = Metering

 

While I don't really need metering, the option above equates to just AF start because before I shoot, by depressing the shutter button, I'm taking another metering, overriding the old one done by the Back Button.  Hope this makes sense.  This has served me well in my BIF shooting.  When you have a chance, click on my Flickr link and choose the Birds In Flight (BIF) album to take a look at the kinds of pictures I took with this setting.

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Diverhank's photos on Flickr

iris
Enthusiast

Do I understand correctly that if I move focus to the back button, I don't have to "do" anything to what was and is still the shutter button.....I ask this because when you go into the Custom menu to change your AF/metering to the AF-on button on the back it also offers changes to the orginal shutter button setup incluidng the original AF/Meterein or only Metering or  *........but you shouldn't choose any of those RIGHT.....just leaave it allone and the SHutter Button is just the shutter button?????

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