Time Lapse Shutter Speeds

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djembeplay

Well-known member
Hey guys. Ive been thinking about this lately after reading through Barry's DVX book for the first time. More a question of theory I suppose, why does he recommend a shutter speed of 1/4 cycles per second for 2 frame per second fast motion? I am not arguing it but trying to understand it visually. I see the shutter closing 4 times in one second... say between frame 6, 12, 18, and 24. Now we are going to speed it up to only take frame 12 and 24 or 6 and 18. So why would we specifically want that shutter speed? Also, this question most likely due to some inherent lack of my fundamental understanding of shutter speed, if the shutter closes at frame 6 and 18 and we end up using frame 7 and 19 for some odd reason when we apply our time lapse in post... wouldnt this be the same as if the shutter had only been open for one frame... equating to a frame exposure if we had used a 1/24 shutter speed? Lookin forward to the responses here... Be well-

Tejay
 
It doesn't work that way. If you're using the slow shutter speed then you get duplicate frames recorded in the data stream. So at 1/4 shutter speed, you'll get four distinct unique frames per second. The camera continues to buffer up the frames until the shutter speed is finished, performing what they call "frame accumulation". Then it writes the frames to tape, and continues writing that same frame until the next one is ready.

So when you use 1/4 - sec to simulate 2fps, each frame gets written on the tape 12 times. All 12 of those frames are identical, and you only need one, so you throw away 11 and keep the one.
 
Ahh... I can see much clearer now. But the water is still a blight bit murky. I dont understand why there would be 12 distinct frames with a 1/4 'slow shutter.' I understand the concept of the camera buffering for a quarter second then writing duplicate frames... but why would it not be 6 duplicate frames with a 1/4 shutter speed shooting 24p? Hope you see my reply and thanks a bunch for the help Barry. I learned a ton about the DVX and all cameras in general from recently reading your DVX book. Be well-

Tejay
 
Oh ok I get it. So... I think this should be my last question on this topic. I guess I was looking at the 1/4 shutter speed as something mathematical with strict borders for editing in post (such as 40% playback on 60i for smooth slow-mo). But what I am getting now (besides a broader understanding of how the DVX handles shutter speeds) is that any shutter speed will work for any time lapse speed... but these numbers (like 1/4 shutter for 2p) are just recommended speeds for playback that, once sped-up in post, yield images that are not too blurry but not too choppy... Am I off the mark? Thanks-

T
 
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