Barn owl (but DOF problem between IR/no IR mode)

[Dodutils]

For some weeks I found rejection balls (don't know if it is correct name as I am not english native) on the ground in my barn produced by some owl, so I checked upside and located a girder were I guessed it could come time to time (looking all the sh*t it left on the girder was easy to guess ;-)

So I decided to setup a camera up there (got to climb 6 meters with a ladder), but the 3.6mm standard lens of my camera produced too large field of view picture and too small owl, so I replaced the lens with a 12mm
but I noticed a problem I never had to face, the difference between IR and no IR mode that ruins the focus when DOF is very thin (12mm at 2.5m distance = very thin DOF so focus must be set precisely).

If I set focus at night (IR) pciture is out of focus daylight and if I set focus daylight then picture is out of focus IR mode so I guess I will have to put two cameras side by side each one with the right focus...

Anyway, here is the beauty focus set to IR mode.

Owl

• Dodutils
• Feb 3, 2019
• 1

 

[tangent]

The only solution I'm aware of would be a varifocal camera (which may not always focus right), or a box camera with auto back focus (ABF).

 

[Dodutils]

The only solution I'm aware of would be a varifocal camera (which may not always focus right), or a box camera with auto back focus (ABF).

sure but ... to expensive for my need and I am not even sure the owl will stay here for a long time ;-)

 

[tangent]

Another option you might have some fun with would be loading CHDK on an old Canon digital camera rigged to a constant power source.
You can automatically take pictures on motion among many other things.

I gotten some nice pictures of fox kits and some other wildlife this way.

 

[Dodutils]

Another option you might have some fun with would be loading CHDK on an old Canon digital camera rigged to a constant power source.
You can automatically take pictures on motion among many other things.

I gotten some nice pictures of fox kits and some other wildlife this way.

I want to video to be streamed and do not want to climb the ladder every day so as I do have a lot of small low priced chinese cameras (I use a lot of them at counrty house) I will add a second one side by side.

But for "real" wild life capture I am starting a project with an ESP32 microcontroller and a OV2640 camera and an IR detector all running on battery.

 

[alastairstevenson]

A dumb question, for which apologies ...
Was the 12mm lens you used an 'IR corrected' type?
These can be slightly more expensive - but they aim to maintain the focus when used on the whole spectrum from visible to infra-red.
Usually stamped 'IR' on the side of the lens.

 

[Dodutils]

A dumb question, for which apologies ...
Was the 12mm lens you used an 'IR corrected' type?
These can be slightly more expensive - but they aim to maintain the focus when used on the whole spectrum from visible to infra-red.
Usually stamped 'IR' on the side of the lens.

I do have many lens from 2.8 to 16mm I know some have this "IR" written, will check next week when back to country house but may be I will step back to a 8mm to get deeper DOF and be less affected by this IR focus effect.

But I thought the "IR" was only there to say lens was not filtering IR.

 

[alastairstevenson]

You might be right about the meaning of IR on the side of the lens, now I think I about it.
But you do get IR-corrected lenses that aim to maintain focus when also used with IR light.

 

[Dodutils]

You might be right about the meaning of IR on the side of the lens, now I think I about it.
But you do get IR-corrected lenses that aim to maintain focus when also used with IR light.

good to know I will check for it

 

[pozzello]

I try to focus my converted fixed lenses at night. that way, night is guaranteed to be sharp,
and while daytime may be not-so sharp, i find it more forgiving due to the extra light available. ymmv.

Another (more complex) solution is to find a focus point somewhere in between the ideal daytime and ideal night-time focus points,
(ie, neither is 'perfect', but both are acceptable)
which means several focusing sessions and marking the lens to keep track of where the 'other' best focal point is.

But yes, some lenses are better at this than others (less spread between ideal day & night focus points)...

 

[Fastb]

when the camera switches to IR mode, the IR cut filter moves out of the optical path. A click can be heard in the camera.
So the optical path is different, from "Day" to "Night" mode. The different optical path affects focus.
These threads will provide more info:
Any Dahua cams WITHOUT the focus bug?
Infrared focus shift - explanation

Fastb