As a result of the recent CHDK script for dummies thread, I've thought that it could be a good idea to share my intervalometer script here. There's nothing new in it, you can find all the information needed to write it in the CHDK wiki page. But it took me some time to find it out, and I've thought that it could help others beginning with CHDK scripts.
I'm using a Powershot A570IS with the CHDK Allbest build v51. That's important because some points in the script are DIGIC III specific (but adapting it to DIGIC II cams would be easy).

This is the script that I'm using:


@title KAP vpiorno 3.3
@param a Interval (Secs)
@default a 10
@param b Secs until 1st shoot
@default b 20
@param c Turn off display (0=no, 1=yes)
@default c 1

t=get_tick_count
if a<10 then a=10
d=a*1000
if b<15 then b=15
s=t+((b-(15/10))*1000)

rem Blue LED blinking to check if script is running
for x=1 to 8
set_led 9 1
sleep 50
set_led 9 0
sleep 50
next x

rem Turning off LCD display
get_prop 105 e
if c<>0 & e<>2 then
for n=0 to (2-e)
click "display"
next n
endif

goto "shoot"

:shoot
if get_tick_count<s then goto "shoot"
s=s+d
shoot
goto "shoot"

end


When I wrote the script, I had three points in mind to deal with. First, I wanted a good synchronization between shooting and servo movements (controlled by aurico or camremote). The first intervalometer script I used employed the “sleep” function to time shoots. This works shooting, “sleeping” for x seconds, and shooting again. The problem with this approach is that the interval between shots is not x, but x plus shooting time. And shooting time isn't negligible, and even worst, isn't always the same. You can check this, as I did, running one of this scripts with your cam pointed to a stopwatch. You'll see an accumulated delay that will cause that some shoots take place during servo movements. To avoid that, I used the get_tick_count function, which allows shooting at precise intervals defined by the internal camera clock. My intervalometer now passes the stopwatch test!

Other point I was trying to solve was finding an easy way to turn off the LCD display. As you know, when CHDK is loaded, camera buttons don't play its normal functions. So, if you want to turn off the LCD to save batteries during flight, you have to do it first and then load CHDK and script blindly, which is a bit inconvenient. In my script, I get the LCD state with the get_prop function, and then I turn it off with the click display function. The value for the get_prop function is specific for digic III cams, you need to change it for digic II.

Finally, I use the set_led function to let one of the leds blink (the blue one, in my case). This way I can be sure that the script is running. This led is bright enough to see it blinking under sunlight, if you look the camera closely.

As you can see, there's nothing in my script that you couldn't do in other ways, but I find it very convenient to use. I hope some of you could find this useful.

Thanks for that. Will try it out.
Michael.

Thanks for that Vincente, very very useful for me. I knew about the timing issue from reading the wiki but it has not really been an issue with what I've been doing up to now but may be in the future. What is a real bonus is the LCD shut down. This is a cracking feature as it will save power without doubt. Using my A640 it was easy just to close the moveable LCD screen itself. but on my G7 the LCD screen is fixed.

BTW the trend of camera manufacturers starting to use fixed LCD screens is a pain. To my mind one of the creative features allowed by the digital camera is the ability to position the camera in awkward situations and still be able to see and take a picture. By fixing that feature they are in effect stifling that spontaneous creativity. For KAP it is not an issue as we are unable to view anyway but I use the same cameras underground and it does become an issue. I get round it by using a small viewing screen but its just more gear to hawk around.

I'm glad you liked the script.

@Wicherd: I can't understand your off topic comment. I'm limited by my english, I'm afraid. What should be the role of that little mirror?

Fantastic script, Vincente! I would have used this yesterday, if I had it! Now I have it for the next time I need it. Thanks very much for sharing it!

I will be using this in very low wind conditions with my SD870 and gent360 on a Brooxes AutoKAP rig. Until recently, I used the gent360 with an infrared capable Pentax Optio. Now the gent360 will continue to rotate my servo and pause, and the intervalometer will trigger the SD870 at the appropriate time.

If you want to shoot at intervals of less than 10 seconds, the statement: if a<10 then a=10 needs to be edited. I have changed it to: if a<5 then a=5, and also changed the default interval to 5.

The display off part of the script doesn't work with the SD870, since this camera doesn't have a dedicated display button. There is a way to make it work by adding some statements into the shoot loop in the script, and I have tried it, but the LCD comes on for a split second between shots. I can't believe that turning the LCD on and off hundreds of times each KAP session could be good for the camera, so I think I'll just continue to use the plug in the AV jack.

The blinking LED also doesn't work with the SD870, probably because of differences between the A series cameras and the SD cameras. I set the camera's shutter sound to its loudest, which lets me know that the camera is taking photos. This feature also seems to use very little battery power.

Vicente, I just did a test of 20 shots and they are 5 seconds apart according to the EXIF data, which rounds to the closest second only. I just tried to synchronize it with my gent360, which I thought was rotating my pan servo at 5 second intervals. It looks like the servo interval is more like 4.25 seconds. When I try to modify the script to set a 4.25 second triggering interval, the camera freezes.

Michael, you're right. With the help of the CHDK forum I've solved my 6 seconds limit problem. I'm a bit ashamed, it was something really silly: just setting the review time to "Off" in the camera menu. Now I can get intervals under 4 seconds.

Regarding a 4.25 seconds interval, I don´t know how you have modified the script, but one possibility is that I think that CHDK scripts only admit integer variables. Try the following code. It works in my camera, and I get intervals around 4.25 seconds.


@title ms intervalometer
@param a Interval (ms)
@default a 4250

t=get_tick_count

goto "shoot"

:shoot
if get_tick_count<t then goto "shoot"
t=t+a
shoot
goto "shoot"

end


Broox, you're wright, probably all this scripting effort is a bit exagerated. But I enjoy it. Those who don't like spending time in this kind of things will be happier following your advice and shooting with their control systems.

Just an aside on Brooks comment. I sometimes wish the Gent-360 had a longer delay between pan and shoot or simply took the picture just prior to rotating. My light rigs have a torsion mode that seems to last a little longer than the delay. I don't see the script as an easy solution (synchronizing sounds like a lot of work) -- just saying this might be a reason some people want a bit more control in separating the two.

Thanks for the "display off" discussion!

Hi Folks,
CHDK allows a min intervall of ~ 3 secs (in the needed KAP resolution) even I was also able to shoot 2 secs intervals in low res for time-lap videos.
(and this minimum time depends on several circumstances - speed of card, manual Focus set or set to infinity ......)

But Broox's proposal ist the only right one:
let the control device do the shutter for you !!! then your camera is totally sychronized
Additional to the devices Broox told you, there is also another solution:

The new AuRiCo also supports direct connection of a USB cable to control the shutter via CHDK (works down to 2 secs)

Interested ?
ask me ( engels.p@-online.de ) or Broox .....

Good news, I found the command “set_backlight 0” on the chdk wiki page. This will shut off the LCD to save energy during long flights :-)

.....ready to fly now.

Ron