I wanted to make more time-lapse videos of the magnetic putty doing other tricks. For this I decided to also add some new features to the time-lapse controller, namely the ability to dynamically increase and decrease the rate at which the pictures were taken.
The reason I wanted this functionality is that sometimes things happen more quickly and sometimes more slowly, so being able to adjust the shutter rate seemed like it would allow more interesting videos to be created. It was not particularly difficult to implement this and the resulting code can be found here:
Version 0.2 of the Arduino time-lapse controller sketch.
With these new features I am firmly beyond the abilities of the built in time-lapse function of the D300 camera, so now there is at last a good motive to build an external time-lapse controller (in addition to the fun of it).
I made use of the new functionality while recording three new videos of strands of magnetic putty being pulled up towards a magnet. The result can be seen below.
I still am not sure what causes the flickering in the videos as I supply the LED light from a lab power supply set up to function as a constant current source. The only other light source in the room is my computer monitor which is aimed away from the scene.
Hi Per
I’m just getting into time-lapse photography, and I read somewhere on the internet that the blades of the aperture do move on electronic lenses during each exposure. The aperture goes from fully open to the set f/stop every time the shutter is activated. The way round this is apparently to set the aperture and then unlock the lens and slightly turn it to break the contacts. alternatively a fully manual lens with an aperture ring shouldn’t do this. Let me know if this helps?
Cheers
Iain
Hi Iain
Thanks for your comment.
I am pretty sure you are right about the aperture changing from wide open to whatever it shall be at each exposure on an SLR camera. For one thing, the aperture needs to be maximally open for auto focus to work well (or at all) and one usually wants as bright a picture as possible in the view finder.
Thanks to your tips, I googled the issue and found this:
http://www.diyphotography.net/preventing-time-lapse-flicker-caused-mechanical-inconsistencies/
Rotating the lens slightly seems to work fine on my D300 (it does not prevent taking pictures), so this should get rid of the aperture jitter. Apparently, it is not only the diaphragm that can jitter, but also the shutter. The solution to the shutter jitter seems to be to use slow shutter speeds, so the aperture and ISO (and lighting) needs to be adjusted to get a slow shutter.
Looking back at the time lapse in this blog post, I was apparently already using a slow shutter speed (1/10 s), so it was probably mostly the aperture jitter that you mention that played tricks on me. Thanks for bringing it up!
I will rotate the lens or use a lens with manual aperture setting (I actually have an old 35-70 mm lens where the aperture can be set manually) next time I do a time lapse. Thanks again.
Per