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Looking for advice on focus and zoom control

motion control focus control zoom control camera rig dslr canon 70d remote control

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#1 Clara Pais

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Posted 09 June 2015 - 09:34 AM

Looking for advice on how to program controlled focus and zoom on a Canon 70D, though open to suggestions on other DSLRs and HD cameras.

 

I want to program the camera to zoom in from a wide shot to a close up very slowly for 15 mins, stay on the close up for a few minutes then zoom back to the wide shot again in 15 mins, remaining always in focus. This is not for a time-lapse, it will be a continuous shot. Is it possible to do this with a DSLR? What kind of equipment would I need?

 

Would love to hear from someone who has done something like this!


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#2 Stuart Brereton

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Posted 09 June 2015 - 02:11 PM

You'd need to have the focus set to manual on the lens, and some sort of remotely controlled zoom motor. You'd also need a dSLR capable of shooting continuously for over 30 minutes, which most can't.


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#3 Satsuki Murashige

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Posted 09 June 2015 - 06:47 PM

You will also need a zoom lens that is parfocal, meaning that it is designed to stay in focus while zooming. There are very few Canon EF zooms that are parfocal because it adds to the cost and is not required for stills shooting with autofocus. The 24-105mm f4 would be one, mainly because of the slow maximum aperture. The 24-70 f2.8 and 70-200 f2.8 are supposed to be, but in my experience they are not 90% of the time. I would try to figure out what focal length range you need first, then start looking for lenses to match.

The reason most DSLRs stop recording after 29 minutes is that their manufacturers would be taxed at a higher rate for import/export due to being newly classified as video cameras. Keeping the recording time below 30 minutes at a time lets them avoid this. So your best bet is to either hide a cut at some point in the shot with a wipe and edit two shots together, record to a Prores recorder with HDMI input like a Pix240 or Atomos Ninja without rolling the camera, or use a video camera which can record a single take longer than 30 minutes.

For the zoom motor, I would look into motion control timelapse systems. The usual manually controlled zoom motor systems like the Preston Microforce are great for smooth motion but are not slow enough to stretch the zoom over 15 minutes. More like 1-2 minutes. You will also want a system where you can program Bézier curves to gradually slow the zoom speed since the magnification increases progressively as the focal length gets longer. Otherwise it will look like your zoom is happening faster and faster as you reach the end of the lens, and vice versa for the zoom out.
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#4 Clara Pais

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Posted 11 June 2015 - 08:52 AM

Thank you both for your replies. Thank you especially Satsuki Murashige, the kind of detail in your reply was exactly what I was hoping for. I will look into your suggestions, hopefully I can find a zoom control that can be slow enough!


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