accuracy of timing - General Help and Assistance on using CHDK stable releases - CHDK Forum
« previous next »
Pages: [1]   Go Down

accuracy of timing

  • 6 Replies
  • 4968 Views
*

Offline walterjwhite

  • *
  • 8
accuracy of timing
« on: 27 / January / 2011, 16:20:25 »
Advertisements
Hi all,

I am using CHDK on a A540 and have a 60 - 70% accuracy with timing which is okay, but will cause jerky video once I stitch it together.

For instance, I have no pictures on 00 seconds, but this is what I do have: (also odd why this pattern is repeated)

02
04
08
10
14
16
20
24
26
30
32
36
38
42
46
48
52
54
58

I am using a simple sleep 2000.

Any ideas?

Walter
Logged
*

Offline SkyWalker9

  • ****
  • 301
  • SX20 IS (fw 1.02b)
Re: accuracy of timing
« Reply #1 on: 27 / January / 2011, 17:03:37 »
Quote from: walterjwhite on 27 / January / 2011, 16:20:25
I am using CHDK on a A540 and have a 60 - 70% accuracy with timing which is okay, but will cause jerky video once I stitch it together. For instance, I have no pictures on 00 seconds, but this is what I do have: (also odd why this pattern is repeated)

04  08  10  14  16  20  24  26  30  32  36  38  42  46  48  52  54  58

I am using a simple sleep 2000.
In order to determine what is causing this sequence we need to see the script. Please post the script you are using that is causing the re-occuring 2,4,2,4,2,4,4 pattern.
Logged
*

Offline reyalp

  • ******
  • 14128
Re: accuracy of timing
« Reply #2 on: 27 / January / 2011, 17:14:04 »
You should calculate your sleep time, rather than using a fixed time.

something like:
Code: [Select]
t1=get_tick_count()
shoot()
sleep(2000 - (get_tick_count() - t1)
If you are relying on autofocus on a variable scene, you may need to make additional adjustments to account for variation in AF time. With fixed focus, the above should be able to give you consistent intervals to within tens of milliseconds.

Of course, your interval also has to be longer than the maximum time the actual shot will take.
Logged
Don't forget what the H stands for.
*

Offline walterjwhite

  • *
  • 8
Re: accuracy of timing
« Reply #3 on: 28 / January / 2011, 10:37:35 »
I think I fixed the issue.  I used the get_tick_count found in another script to account for those differences.  I had already disabled the autofocus, so the only thing that would be dynamic would be the exposure time.  I should have been shooting a relatively stable scene.


Thanks,


Walter
Logged
*

Offline walterjwhite

  • *
  • 8
Re: accuracy of timing
« Reply #4 on: 30 / January / 2011, 12:21:19 »
Hi,

This my revised script ... I am still having issues with every once and a while, it will miss a picture:



@title Intervalometer
i=2000

set_focus 4500
set_aflock 1

while 1 do
   a=get_tick_count
   shoot
   b=get_tick_count
   
   c=a - b + i
   
   if c < 0 then c = 0
   sleep c
wend



Walter
Logged
*

Offline reyalp

  • ******
  • 14128
Re: accuracy of timing
« Reply #5 on: 30 / January / 2011, 14:57:14 »
What mode are you shooting in ? In some of the auto modes, the camera will refuse to shoot if it thinks are too wrong.

Are you shooting raw or DNG ?  If so, the saving time might exceed your 2 second interval.

Have you verified that the set_focus and set_aflock are doing what you expect ?
Logged
Don't forget what the H stands for.
*

Offline fudgey

  • *****
  • 1705
  • a570is
Re: accuracy of timing
« Reply #6 on: 30 / January / 2011, 15:07:01 »
Quote from: reyalp on 30 / January / 2011, 14:57:14
Are you shooting raw or DNG ?  If so, the saving time might exceed your 2 second interval.

Maybe in some circumstances exposure + focus + shoot + JPEG encoding + saving could exceed even 2 seconds (low light, JPEG scaling enabled, slow SD card, lots of photos on card, delay of creating a new DCIM subdirectory to SD card, ...).

And the obvious: did you disable photo review?
Logged
Pages: [1]   Go Up
« previous next »
 

Related Topics


SimplePortal © 2008-2014, SimplePortal