AF thru a chain link fence

Started May 24, 2012 | Discussions
jonikon
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AF thru a chain link fence
May 24, 2012

While visiting a wildlife part recently, I had the opportunity to test my D7000's AF while shooting through a chain link fence. What This is what I discovered .

  • Unless there was more than one wire inside the AF box, the camera would ignore the wire and focus on the subject. If two wires were inside the box, it was impossible to achieve focus on anything other than the wire.

  • AF-C seemed to favor the moving animal over the static fence.

  • The AF box was quite accurate in determining the point of focus at the time of exposure , but would sometimes display an incorrect point of focus when viewing the focus point after the shot.

Here are some of my test photos taken through the fence.

I purposefully focused on a cross in the fence wire here.

I wish I could post these with the focus points shown. Anybody know how to do that?
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Deleted1929
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Re: AF thru a chain link fence
In reply to jonikon, May 24, 2012

One time to reach for manual focus is when you've something between you and the subject. You can still use focus confirmation but you avoid the AF system switching to something it finds more interesting ( or having to coax it to the right depth in the first place ). I think a lot of people regard manual focus as some kind of hangover from the old days before AF, whereas I think of it as just one more option.

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StephenG

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Kerry Pierce
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Re: AF thru a chain link fence
In reply to jonikon, May 24, 2012

Looks to me like your shooting position is too far away from the fence.

You should put the fence well within the lens' minimum focus distance, but not right up against the fence. Most of the time, the fence will be completely OOF and unseen, if you're close enough to it. That way, not only will the camera not focus on the fence, the fence will disappear from the photo.

Kerry

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jonikon
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Re: AF thru a chain link fence
In reply to Kerry Pierce, May 25, 2012

Kerry Pierce wrote:

Looks to me like your shooting position is too far away from the fence.

You should put the fence well within the lens' minimum focus distance, but not right up against the fence. Most of the time, the fence will be completely OOF and unseen, if you're close enough to it. That way, not only will the camera not focus on the fence, the fence will disappear from the photo.

Kerry

Good idea Kerry, but the big cat cages had low barriers a few feet away from the fence that you must stay behind so people can't stick their fingers in the cages, and have them chomped off!

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Ray63129
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Re: AF thru a chain link fence
In reply to jonikon, May 25, 2012

Also going to a larger aperature (small DOF)(maybe f/3.5) will help keep the fense from being so fisible.

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jonikon
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UPDATED with Action photos thru a chain link fence
In reply to jonikon, May 25, 2012

Besides the static shots closer to the fence, I found I could get good AF through the fence at some distance while shooting action, if I used AF-C, 3D tracking. BTW, I found manual focus to be useless in this situation.

These shots are all cropped and since they were all shot from the same location, I have included the uncropped version of the first image to give you some perspective.
Lens used: Nikon 18-105

I normally don't keep photos of animals behind a fence or bars as I find the fences totally distracting and even a a bit disturbing. But in this case I think these may be worth keeping, since the big cats really seemed to be enjoying this little exercise, even though they are fenced in. BTW, these photos were shot at the Out of Africa Wildlife Park in Arizona, USA who claim that although the animals are socialized to humans, they are not trained performers. From what I could see, the animals seem to be treated very well, and have lots of room for exercise. Much more so than in a typical zoo anyways.

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RP McMurphy
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Re: AF thru a chain link fence
In reply to jonikon, May 25, 2012

AF set to closest point focus? Dynamic area?

Dont understand why for a difficult shot people think the camera knows what you want to focus on - either correct it manually (eyes dont matter you have a green light focus confirmation or use AFS and focus and recompose if necessary - in those pics it's not necessary to recompose as your target was mainly in the centre

9, 21, 51 point etc means that the camera has to check all those points and try and figure out what you want to take a picture of - if there was ever a time to help the camera out then this is the time

Dynamic range focus closest point etc works well for BIF because they are the cloest object to the camera but if you have more automatic settings and soemthing between you and what you want to focus on then give the camera a pointer and take control

no need to go to the min focussing distance to focus past the wires, all the AF systems in Nikons can cope with this with the correct setting - AFS centre point, aquire focus (lock if you wish and recompose) and shoot

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RP McMurphy
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Re: AF thru a chain link fence
In reply to RP McMurphy, May 25, 2012

Also it seems that you may also have shutter button still activated as AF on so when you take the shot it re-centres

Try to acquire focus with button half depressed and then click

But with adjustment of 22 it maybe acquiring correct focus and your corrections have screwed it up

My advice for fine tune is not to change it unless you know what you are doing and with respect I am not sure that if you are having such difficulty in figuring out what went wrong you could adjust that with confidence - no offence meant here

Fine tune set to zero and try again with a similar target with AFS only - do you get a focussed shot. Then try AFC with the centre point only- aquire focus and see if camera tracks

Try this before you ask the camera to figure it out for you and then build up from there, seeing what auto aquisition works and whether it's acquiring closest point focus

All that before you fine tune a lens - cant see you have a hope to figure what went wrong if the lens is so far out of tune - it's possible it is needing adjustment but it's unlikely this much and other areas should be verified firstly before changing that

Try all of that first - then try on a tripod with live view - figure out if you are in full control of the settings before assuming the hardware is at fault would be my recommendation

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RP McMurphy
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Re: AF thru a chain link fence
In reply to RP McMurphy, May 25, 2012

Sorry for even more...

You say you wouldn't be able to track the animal manually because of eyesight - as said there is a green light to tell you when it is in focus - but that shot could be taken easily with manual focus

You are at f9 with a 105mm (=160mm) it can move around plenty and still be in focus - you'd only need to be there or thereabouts with focus at those distances

Also if it's a macro 105mm then the focus limiter should also help - no?

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stuntmonkey
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Re: AF thru a chain link fence
In reply to jonikon, May 25, 2012

jonikon wrote:

  • Unless there was more than one wire inside the AF box, the camera would ignore the wire and focus on the subject. If two wires were inside the box, it was impossible to achieve focus on anything other than the wire.

Not to nit, but in plain English, that translates as "The AF will focus on the thing that is closest to you" However, I do know what you mean.

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