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Zoom intervalometer

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Zoom intervalometer
« on: 12 / July / 2015, 10:30:03 »
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Hello programming wizards, I have an sx40 and am looking to write a zoom intervalometer script with the following functionality:

- lock the focus and exposure at start so it doesn't calculate it for every frame and conserve battery life
- get the number of zoom steps and set the start zoom
- specify a frame interval after which the zoom step is increased or decreased
e.g. start zoom 0; every 24 frames increase zoom level +1
e.g. start zoom 30; every 48 frames decrease zoom level -1
- switch off screen after few frames to conserve battery life

The idea is after that when I build the timelapse to have it zooming as smoothly as possible.

I'm trying to jumble up a few scripts but am failing miserably. I would be very grateful if someone can help me out with this. I will answer any questions and clarify any issues with the above requisites.
Thank yo very much

Re: Zoom intervalometer
« Reply #1 on: 12 / July / 2015, 11:45:39 »
Here you go.

Edit : attached script removed. Updated version posted later in this thread.
« Last Edit: 13 / July / 2015, 10:07:39 by waterwingz »
Ported :   A1200    SD940   G10    Powershot N    G16

Re: Zoom intervalometer
« Reply #2 on: 12 / July / 2015, 13:19:17 »
Thank you, Waterwingz! I will test as soon as I get back home and load it on the camera and will report back.

Re: Zoom intervalometer
« Reply #3 on: 12 / July / 2015, 18:14:03 »
Hello again, I had the chance to test it and have the following to report:

- the zoom step functionality works great advancing both at zoom out and zoom in

Issues (might be camera related):
- the first frame at each zoom level is underexposed (looking at the script that might be the nd filter?) - all the rest at the same zoom level are ok and the focus seems locked
- the camera refocuses and there is a slight delay when it moves to the next zoom level

A solution:
- is it possible to lock the autofocus at the start so it doesn't refocus throughout the zoom range? (which will solve the two issues)

Thanks again


Re: Zoom intervalometer
« Reply #4 on: 12 / July / 2015, 18:19:11 »
One extra thought. Can a global ND filter be set at the beginning as well which doesn't change throughout the image sequence? this way on bright days a slower speed and open aperture can be selected in manual mode and reduce flicker in the resulting timelapse video.

I suppose that wouldn't work if the ND filter is simply simulated by a closed down aperture but it's worth asking.

Thanks

Re: Zoom intervalometer
« Reply #5 on: 12 / July / 2015, 19:24:32 »
Issues (might be camera related):
- the first frame at each zoom level is underexposed (looking at the script that might be the nd filter?)
That's possible if you were shooting outdoors.  Easy enough to fix - I'll post an update a bit later today.

Quote
- the camera refocuses and there is a slight delay when it moves to the next zoom level
A solution:  is it possible to lock the autofocus at the start so it doesn't refocus throughout the zoom range? (which will solve the two issues)
The script does a refocus and resets the exposure after every zoom step on purpose.  I think it has to do that or your shots will be out of focus and incorrectly exposed?

Can a global ND filter be set at the beginning as well which doesn't change throughout the image sequence? this way on bright days a slower speed and open aperture can be selected in manual mode and reduce flicker in the resulting timelapse video.
I suppose that wouldn't work if the ND filter is simply simulated by a closed down aperture but it's worth asking.
Almost all Canon Powershots have a real ND filter (typically adding about 3 f-stops when inserted).   I'm not sure I understand how using it to get slower speed and a wider aperture will reduce flicker in the final timelapse though.
« Last Edit: 12 / July / 2015, 19:26:35 by waterwingz »
Ported :   A1200    SD940   G10    Powershot N    G16

Re: Zoom intervalometer
« Reply #6 on: 13 / July / 2015, 00:07:29 »
- the first frame at each zoom level is underexposed (looking at the script that might be the nd
Updated script attached.

The ND filter should now be handled properly (i.e. if the first shot after each zoom change uses the filter then the subsequent shots at that zoom position will too.)

I also cleaned up the timing so that each shot happens at the specified interval,  even when zoom step & refocus & set exposure is required in between shots.

Edit : attached script removed and reposted later in this thread
« Last Edit: 13 / July / 2015, 10:06:40 by waterwingz »
Ported :   A1200    SD940   G10    Powershot N    G16

Re: Zoom intervalometer
« Reply #7 on: 13 / July / 2015, 06:56:30 »
Thanks Waterwingz, you are a star.

Quote
I'm not sure I understand how using it to get slower speed and a wider aperture will reduce flicker in the final timelapse though.

After experimenting with other intervalometers I discovered that I achieved the least amount of flickering/ most consistent exposure results across frames with the widest aperture and a shutter speed under 1/200. These settings can allow for shooting in bright days if there is a built in ND filter which can be set prior to shooting.

Quote
The script does a refocus and resets the exposure after every zoom step on purpose.  I think it has to do that or your shots will be out of focus and incorrectly exposed?
This one is also connected to the previous observations. When the focus and exposure are locked at the first frame i achieve more consistent results in terms of flicker and timing. I also gain a significant battery life increase.  With more or less consistent lighting this is rarely a problem. And even with sunsets a bit of underexposure at the end can be tweaked in Premiere if you boost the midtones.

Now with the zoom there is the issue of changing maximum aperture as you move across the zoom range. But if i manually lock the exposure to the maximum at the zoom then this is remedied and again should give more consistent exposure results.

The focus is a bit trickier when you get beyond a certain value as your focus plane becomes thinner. But if you know what you want to focus on you can dial it in the camera (approximately) while in manual focus. This is something that will require more testing though.
However most general scenes will call for focus at infinity and a small travel across the zoom. A locked focus will be easy to set up and where you have moving objects the camera wouldn't search to focus between frames/zoom levels and produce random results.

e.g. settings could be

Lock focus at start [ ]
Lock exposure/shutter speed & aperture at start [ ]
Set ND filter level [ n ]

Essentially more manual control would be a bit more work setting up initially but would produce better more consistent results.

I will test the current version and report.

Thanks


Re: Zoom intervalometer
« Reply #8 on: 13 / July / 2015, 09:40:57 »
After experimenting with other intervalometers I discovered that I achieved the least amount of flickering/ most consistent exposure results across frames with the widest aperture and a shutter speed under 1/200. These settings can allow for shooting in bright days if there is a built in ND filter which can be set prior to shooting.
So if I try to find a scientific explanation for this,  I suppose it's possible that the actual shutter speed is more consistent when it is lower.  If there is a slight variation due to mechanical issues or camera timing,  it might be more pronounced at faster speeds.  Normally you would not notice that with a single exposure but an intervalometer shooting the same scene repetitively would make it more visible?   

I don't have an explanation for why widest aperture helps though.

Quote
The focus is a bit trickier when you get beyond a certain value as your focus plane becomes thinner. But if you know what you want to focus on you can dial it in the camera (approximately) while in manual focus. This is something that will require more testing though. However most general scenes will call for focus at infinity and a small travel across the zoom.
From my many and long experiments with setting manual focus at infinity with CHDK,   I'm not convinced that you can change the lens position (i.e. zoom) and have the focus point not change.   If you were originally focussed at infinity then the depth of field for these little cameras might hide that.   

Quote
e.g. settings could be
Lock focus at start [ ]
Lock exposure/shutter speed & aperture at start [ ]
Set ND filter level [ n ]
Essentially more manual control would be a bit more work setting up initially but would produce better more consistent results.
Easy enought to add.  I'll be interested to hear if it makes a big difference.

Quote
I will test the current version and report.
I think that I did not quite get the ND filter fix right in the v2 version of the script.  V3 is attached.
« Last Edit: 13 / July / 2015, 10:05:04 by waterwingz »
Ported :   A1200    SD940   G10    Powershot N    G16

Re: Zoom intervalometer
« Reply #9 on: 13 / July / 2015, 10:59:51 »
Yes, i think your reasoning for the shutter speed is right. Even though the camera has an electronic shutter with higher speeds it can introduce slight variations which become noticeable as flickers when you put the frames together at 24fps.  At slower speeds it gets the timing right most of the time.

For the aperture i believe it has to do with the fluctuations of the physical iris opening mechanism. It is less prone to variation if the iris is kept wide open. This is jut a guess though based on reading info regarding timelapses done with DSLRs and their bigger lenses/irises.

Now, if CHDK has the possibility to actually keep the iris open all the time and only use the electronic shutter to record the frame then I reckon that would completely eliminate variation due to slight differences in the iris opening from frame to frame.

Quote
From my many and long experiments with setting manual focus at infinity with CHDK,   I'm not convinced that you can change the lens position (i.e. zoom) and have the focus point not change.   If you were originally focussed at infinity then the depth of field for these little cameras might hide that.   
A note before the report: the SX40 I am using has a M mode where I choose the speed and aperture and also a manual focus setting which I use in the testing. I think this overrides the script's settings but it still takes exposure and focus measurements when it moves between zoom levels.

Issues I found when testing now the latest version 3:

- the first frame at a zoom level is still under-exposed compared to the rest at that same zoom level


- when I put the timer at 2 seconds between frames when it moves to the next zoom level and takes measurements the delay becomes 4 or 5 seconds then within the same zoom level it is 2 seconds (you can see what i mean in the attachment)

Thanks again for following up on this.

 

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