Fixed focus for time lapse interval with Ixus 850 IS?

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Fixed focus for time lapse interval with Ixus 850 IS?
« on: 30 / April / 2015, 12:57:34 »
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Dear all,

I am using a Canon Ixus 850 IS with a self-written basic script to take pictures for a time lapse of around three month. After two weeks and more than a thousand pics I figured out that only half of the pictures are in focus.

The focus issue does neither match with the aperture (the camera has two apertures of 2.8 and 7.1 and by default selects automatically depending on available light), the scene brightness nor with anything else I am able to reconstruct.

To avoid exactly these kind of focus problems my script consists of the following, reduced to the very basic:

Code: [Select]
rem preparation

print "Lock autofocus"
set_aflock 1
sleep 500

print "Set focus to infinity"
set_prop 11 3
set_focus 65535
sleep 3000

print "Take a test shot"
shoot
sleep 3000


rem shooting

goto "shoot"

:shoot

  press "shoot_half"
  sleep 500
  if get_bv96 > -505 then
   press "shoot_full_only"
   sleep 100
  release "shoot_full"
  sleep 15*60*1000
  goto "shoot"


Does anyone know how to really set the fixed focus, ideally to infinity and with an aperture of 7.1 all the time?

Thanks a lot,
Ben

Re: Fixed focus for time lapse interval with Ixus 850 IS?
« Reply #1 on: 30 / April / 2015, 13:37:16 »
the camera has two apertures of 2.8 and 7.1
Actually,  it only has one aperature (f2.8 when zoomed wide).   The f7.1 is achieved  by inserting a neutral density filter into the light path.

Quote
Does anyone know how to really set the fixed focus, ideally to infinity and with an aperture of 7.1 all the time?
What you have written should work for your camera.  However, you could try using set_mf( ) rather than set_aflock ()
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