Focus Trap
Sat 09-Jan-21 04:33 PM
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#1. "RE: Focus Trap" | In response to Reply # 0
Sun 10-Jan-21 01:16 PMMike,
I haven't tried this since one of my film camera's supported it. I would guess that you set shutter release to focus priority. Can you confirm that and tell us about your other settings and approach, and what your goal for capture is? Thanks.Brett
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#2. "RE: Focus Trap" | In response to Reply # 1
Sun 10-Jan-21 04:30 PMThe Z cameras require an extra step for Trap Focus.
Set Custom Setting #A8 to AF-ON only.
Set AF-ON, Out-of-focus release, sub-option to DisableVisit my Nikonians gallery.
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#3. "RE: Focus Trap" | In response to Reply # 0
Sun 10-Jan-21 07:33 PM
Last summer during the “great lockdown” I spent some time using a Sabre LIDAR unit to photograph Bluebirds nesting in my nest box.
https://cognisys-inc.com/triggering-systems/sabre/sabre-1.html
I used a 300mm and 600mm, one issue was of course the DOF. AT 15 to 20 feet, and f8 the DOF is only a couple inches or less. So while sitting here contemplating the state of the world trying to figure out how to get more DOF it occurred to me that I have an 85mm PCE lens, and could set up a focus trap, Position the lens much closer to the subject, and adjust the tilt to increase my vertical DOF. Setting up a little test using the lens align tools I found that I could get 7 to 8 inch DOF (vertical) at 30 inches distance from the subject @ f8 using the tilt. Not so much on the horizontal plane. Then I really don’t care about the DOF above and below the subject. (At least at this point, you never know).
Since then I have learned, that a manual focus lens can not be used for focus trap. That means I will have to use the Sabre unit for the trigger for the 85 PCE. However on testing and attempting to set up the focus trap I was using a 70-200 f2.8 Fl lens. I could not get it to work. It would still cycle ever few seconds, and take out of focus images as seen in the last image.
I think one issue is is settled, it will not work in continuous H, only in Single. Even though A1 is set to focus release. Thats a bummer, that mean you have to sit there and set the shutter after each release, and there is no possibility of getting multiple shots as the bird flies through the plane of focus.
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https://cognisys-inc.com/triggering-systems/sabre/sabre-1.html
I used a 300mm and 600mm, one issue was of course the DOF. AT 15 to 20 feet, and f8 the DOF is only a couple inches or less. So while sitting here contemplating the state of the world trying to figure out how to get more DOF it occurred to me that I have an 85mm PCE lens, and could set up a focus trap, Position the lens much closer to the subject, and adjust the tilt to increase my vertical DOF. Setting up a little test using the lens align tools I found that I could get 7 to 8 inch DOF (vertical) at 30 inches distance from the subject @ f8 using the tilt. Not so much on the horizontal plane. Then I really don’t care about the DOF above and below the subject. (At least at this point, you never know).
Since then I have learned, that a manual focus lens can not be used for focus trap. That means I will have to use the Sabre unit for the trigger for the 85 PCE. However on testing and attempting to set up the focus trap I was using a 70-200 f2.8 Fl lens. I could not get it to work. It would still cycle ever few seconds, and take out of focus images as seen in the last image.
I think one issue is is settled, it will not work in continuous H, only in Single. Even though A1 is set to focus release. Thats a bummer, that mean you have to sit there and set the shutter after each release, and there is no possibility of getting multiple shots as the bird flies through the plane of focus.





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#5. "RE: Focus Trap" | In response to Reply # 3
Mon 11-Jan-21 12:49 PMThis seems to work for me.
I did not use AF-C mode
A2 - Focus
A7 - AF-ON only & out-of-focus release - disable
Release Mode - L or H
Single-point AF
Set focus point.
Activate shutter button
Move an object into focus...
camera takes multiple images at the rate specified by the release rate
To me this seems to be consistent with what I thought "Trap Focus" meant.
There is a specific focus point (that does not change)
when something is in focus the shutter releases.
With AF-C mode the thought (I suppose) is that the camera will change the focus as needed.
However this is not what appears to happen. The camera takes multiple images while the focus process is occurring resulting in out of focus images. Even though the release mode is focus.
Since AF-C changes the focus point this seems (to me) to be inconsistent with the definition of trap focus.
Where the focus point remains constant and an object moves into that point.Visit my gallery.
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#6. "RE: Focus Trap" | In response to Reply # 5
Mon 11-Jan-21 03:26 PMI decided to try it one more time. Setting it up I had the same problem. Holding the shutter down for 4 or 5 second the shutter would start to cycle, at maybe 5 sec intervals. Reading your reply I decided to change to AF-S mode, I was in AF-C. Although its suppose to work in either. After switching to AF-S everything worked as advertised. My first thought was OK I guess it won't work in AF-C mode even though the auto focus is separate from the shutter release. I switched back to AF-C mode, and it seems to work ok, it no longer cycles the shutter. So that is good, thanks for the push. I was hoping to use this in conjunction with my 85mm PCE lens to capture some inflight birds taking advantage of the adjustable DOF. It appears that it does not work with manual focus lens even though they give an in/out of focus indication. Thanks for you time. Now its time to back to the drawing board for plan B.
MikeVisit my Nikonians gallery.
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