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 Post subject: Thought I understood focus until....
PostPosted: Mon Sep 16, 2013 8:55 pm 
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Joined: Mon May 07, 2012 8:28 am
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Location: Raleigh, NC
I now have a program that shows me where my focus points are! :oops:

Of course, I always set my focus point on the eye (when doing portraits) so tonight, I did a little test. Set my focus point on the eye "snap" - set it on the eye again, held shutter down half way to lock focus (from all I've read in the NYIP literature as well as my camera manual) re-composed the shot keeping shutter button half way and "snap", took another picture thinking my focus point was locked on my subjects eye but when I bring it up on my screen, the focus point moved from the eye to the nose!

Is there something I'm missing here? Maybe I'm misunderstanding the concept of lock focus. I have my camera set in AF-C mode but also tried the AF-A (Auto Servo) and AF-S (Single Servo) to see if that was the issue.

I'm stumped!

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 Post subject: Re: Thought I understood focus until....
PostPosted: Mon Sep 16, 2013 9:15 pm 
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AF-C focusing mode does not allow focus & recompose. I suggest the following test. Set your camera to AF-S mode and focus on something. Then recompose on something that is definitely out of focus, something really close. The focusing plane should remain where you originally focused even though the focusing point moved. The software only shows which focusing point locked the focus and where it is on the frame. It does not show where you originally focused before recomposing. I hope it makes sense. Ask if it does not.

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 Post subject: Re: Thought I understood focus until....
PostPosted: Tue Sep 17, 2013 6:06 am 
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Do you have back button focus option? It changes your world. Click the back button where you want focus and keep it held down while you recompose and click shutter button to take shot.

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 Post subject: Re: Thought I understood focus until....
PostPosted: Tue Sep 17, 2013 9:04 am 
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Location: Massachusetts
Link explaining differences of Nikon focus modes.......
What is the difference between AF-A, AF-S, AF-C and MF focus modes on Nikon camera's

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Last edited by Mark Farrell on Tue Sep 17, 2013 9:51 am, edited 1 time in total.

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 Post subject: Re: Thought I understood focus until....
PostPosted: Tue Sep 17, 2013 9:31 am 
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Mark Farrell wrote:

AF-S locks the focus as long as the shutter button is held halfway down (or back button held for BBF).
AF-C is continuous focusing, tries to track what you focused on, but I believe it only works if the subject is moving toward or away from the camera, not left or right.
AF-A is automatic, the camera tries to determine if AF-S or AF-C is better.
MF is manual focus.

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 Post subject: Re: Thought I understood focus until....
PostPosted: Tue Sep 17, 2013 3:32 pm 
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Location: Raleigh, NC
Thank you all for your help & tips!

Donna: Yes, I have Back Button focus and learned about it a few weeks back. Thought it was a great function but honestly, it's just as easy to hold the shutter button down half way to focus.

This is a new camera for me so I'm still getting a feel for all it's bells & whistles! I even was able to download the manual via my SmartPhone so it's literally in the palm of my hand! ;D

I guess I thought the focus points would stay as I "re-composed" but it doesn't seem that is the case from what Oleg has described. That's kind of what threw me off...I was expecting to see the focus point on my monitor where I originally placed it (on the eye) in my re-composed shot. Does that make any sense?? :lol:

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 Post subject: Re: Thought I understood focus until....
PostPosted: Tue Sep 17, 2013 5:40 pm 
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ALSchmidt wrote:
Thank you all for your help & tips!

Donna: Yes, I have Back Button focus and learned about it a few weeks back. Thought it was a great function but honestly, it's just as easy to hold the shutter button down half way to focus.

This is a new camera for me so I'm still getting a feel for all it's bells & whistles! I even was able to download the manual via my SmartPhone so it's literally in the palm of my hand! ;D

I guess I thought the focus points would stay as I "re-composed" but it doesn't seem that is the case from what Oleg has described. That's kind of what threw me off...I was expecting to see the focus point on my monitor where I originally placed it (on the eye) in my re-composed shot. Does that make any sense?? :lol:


I recommend the Backup Focus Button configuration. There's too many things going on with the shutter button held down half way such as exposure. Best to separate them out. The option is there for a reason. It may take some getting used to, but eliminates the focus point issue. You focus once and shoot until the focus point must change. Just my two cents. :)

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 Post subject: Re: Thought I understood focus until....
PostPosted: Tue Sep 17, 2013 6:37 pm 
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Joined: Fri Dec 23, 2011 10:16 am
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Location: Houston, Texas
I have my auto focus set to continuous on my back button. This way if I am holding my back button down I am getting continuous auto focus. I can set my focus with the back button, release the back button and I can re-frame to my heart's content and then shoot. I got my wife really mad at me with this though because I didn't tell her how to use the back button and most of her shots that day were out of focus.

Back button auto focus can be a bit awkward at first but I will set every camera I get to use it. There are, however many who feel this is not a good way to go because of not being careful about the focal plane and the focus can be off when you reframe.

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 Post subject: Re: Thought I understood focus until....
PostPosted: Tue Sep 17, 2013 11:15 pm 
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Joined: Mon May 07, 2012 8:28 am
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Location: Raleigh, NC
Steve Batson wrote:
ALSchmidt wrote:
Thank you all for your help & tips!

Donna: Yes, I have Back Button focus and learned about it a few weeks back. Thought it was a great function but honestly, it's just as easy to hold the shutter button down half way to focus.

This is a new camera for me so I'm still getting a feel for all it's bells & whistles! I even was able to download the manual via my SmartPhone so it's literally in the palm of my hand! ;D

I guess I thought the focus points would stay as I "re-composed" but it doesn't seem that is the case from what Oleg has described. That's kind of what threw me off...I was expecting to see the focus point on my monitor where I originally placed it (on the eye) in my re-composed shot. Does that make any sense?? :lol:


I recommend the Backup Focus Button configuration. There's too many things going on with the shutter button held down half way such as exposure. Best to separate them out. The option is there for a reason. It may take some getting used to, but eliminates the focus point issue. You focus once and shoot until the focus point must change. Just my two cents. :)


Good points! Will consider trying it to see if it's something I can adjust to better. Still have a lot more to get use to with the new camera first.

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 Post subject: Re: Thought I understood focus until....
PostPosted: Fri Sep 20, 2013 12:26 am 
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Joined: Tue Jan 27, 2009 3:58 am
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Let me see if I have the scenario correct.

You focus on the eyes, get your shot and that shot is okay. You refocus on the eyes and then, keeping the shutter pressed half way, recompose\reframe the shot, expecting the focus to be locked, and the focus seems to have moved from the eyes to the nose.

Since there is one good shot and assuming that you're focusing the same way for the second shot, the camera seems to be focusing on what you think it is. There are two things that can be happening for the second shot to be off. The one everyone seems to be talking about is having the wrong focusing mode set and, given what Oleg said about the mode you are using, that is probably what's happening.

Something else that could be happening that I haven't seen mentioned is the distance between you and the subject has changed and the eyes are now at the edge of, or outside of, the DOF. This could show up when shooting something like a headshot and to blur the background you might have a combination of large aperture and you're shooting in close. Both the aperture and camera\subject distance reduce the DOF and it wouldn't take much of a change in distance to move the focal plane from where the eyes are to, like here, the nose.

Vance

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