LRTimelapse Forum

Full Version: How to calculate moving distance on slider?
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Is there a formula to calculate the distance which the slider should move between shoots in order to create a smooth timelapse?


That depends on many factors: Focal length, distance to foreground, Sensor size, movement of other axis if any etc...
I'd recommend to not starting to calculate those things but just make some test shots. Compare two shots on the screen, if you see a significant difference, the step is too large.
As a rule of thumb: if you do 500 images on an 80cm rail, which is set up close to the ground for some foreground, this should be fine.
Very interesting question. I would love to see some formula or spreadsheet where you could input all the factors Gunther mentioned and get a starting point for the number of images per rail length.

Gunther, do you have a rule of thumb for a setup in about 1m height, with foreground objects 3-5m away, using a wide angle lens (in the range 14mm to 24mm), no movement of other axis, FF sensor, output in 4K 30FPS? Would 500 images in 120cm rail length be a good starting point?
I never set up my slider so high if I don't have to... And also there is no true or false for that... If just depends on the look you want to create. I'd suggest that you just make a test setup!
I will definitely make a test setup. I just wanted to get some ideas about useful starting points.

If you always put the slider low to the ground with foreground objects close by, how do you deal with the limited DOF? Even if you stop down to f/11 (which sometimes is not the best idea for other reasons) and use an ultra-wide-angle lens you either get a sharp foreground or a sharp background but not both. Therefore my idea would be to raise the slider slightly to get some additional distance between the lens and the ground and in addition to extend the distance to the closest foreground object and manage that way to get both foreground and background within DOF.
Often I like the look of a blurred foreground, it draws the attention of the viewer to the background where the action takes place. But of course, it depends.
I avoid closing the aperture too much to avoid dust spots on the sensor getting visible in the shots.