It is currently Fri Sep 18, 2020 3:11 pm




Post new topic Reply to topic  [ 8 posts ] 
 Constant Motion vs Motion Intervals 
Author Message
User avatar

Joined: Wed Mar 16, 2011 2:58 pm
Posts: 1348
Location: Denver, Colorado
Post Constant Motion vs Motion Intervals
What is everyone else doing with this?

My timelapse robot works on a move->stop->shoot->repeat format.

it works pretty well, i had always assumed this was the correct way to do this, but it can be a bit tricky sometimes, and i am constantly working on my system making adjustments, tweaks, or redesigns.

I saw a mention that some people use a dolly with constant movement.

What do you use, and why? What benefits are there?


I think one of the reasons i went with a move-shoot-move-shoot setup is because i plan to bring my astrophotography into my time-lapses, and if im running 30 second exposures i should probably have the camera sitting still while it shoots.

Am i making this more complicated than it needs to be?


Im aiming to build another timelapse dolly out of 80/20 aluminum, which will be more of a traditional slide mechanism. Im wondering if i should just leave the move-shoot-move to Speedy 2.2 and go with constant movement on my new rig.

_________________
http://www.BioLapse.com
http://www.TheChronosProject.com


Wed Apr 27, 2011 9:11 am
Profile
User avatar

Joined: Tue Jul 08, 2008 12:36 pm
Posts: 1787
Location: Antarctica/California/New Zealand
Post Re: Constant Motion vs Motion Intervals
Advantages for move-shoot move:
-Sharp pictures, good if you want to do any layering in post
-Sharp pictures mean good stills for still photo displays
-If you have a bump in your rail/mechanism it is easier to fix in post with motion tracking software (this is also the case with short exposure times on constant movement).

Advantages for constant movement:
-Slight motion blur will make the video look a whole lot nicer, read up about how they used the (then) revolutionary "Go Motion" instead of "Stop Motion" in Empire Strikes Back.
-Much simpler mechanisms for motion control, much less likely to have mechanical issues.

Basically the same effect as move-shoot-move can be obtained by using short exposures on a constant movement system, unless you are looking at long exposure night shots.
Move shoot move is also great to have if you want to venture into stop motion animation areas.
It basically comes down to personal preference.
You can't go too far wrong with the Dynamic Perception controller though for the best of both worlds at a bargain price.
(No, Jay is not giving me kick backs :lol: )

_________________
Anthony Powell
"Antarctica: A Year On Ice" Feature Film
Vimeo Youtube Photos
Twitter Instagram Google+
Facebook Facebook Movie Page


Wed Apr 27, 2011 2:23 pm
Profile

Joined: Mon Jul 19, 2010 1:52 pm
Posts: 72
Post Re: Constant Motion vs Motion Intervals
A question back to Antz: with DC motors one sort of can do both : constant power (PWM) -> constant speed. Start/stop (MX2) -> shoot/move/shoot. Although I don't like the latter with DC motors it seems to work well enough for the purpose. Not sure how the MX2 blocks the dolly from sliding when not horizontal as there is nothing to hold the motor when there is no power and there is no feedback.

BUT with stepper motors the story is a bit different or should I say the opposite. These create discrete steps by default (which you have to make smaller via very expensive gearboxes or use microstepping) but I think I read that if you want to create a sort of constant motion with steppers it doesn't work as well, certainly not when not geared down or using microstepping.

I am still pondering on what motor solution to go for that will work well for both video and TL movement (the former much faster of course). I am edging towards steppers because I don't fancy all the calibration issues with the MX2/DP motor. Also, steppers have a quite large dynamic range which would suit the dual purpose, much more so than DC motors.


Fri Apr 29, 2011 6:28 am
Profile

Joined: Mon Apr 04, 2011 5:21 pm
Posts: 340
Post Re: Constant Motion vs Motion Intervals
lenny4d wrote:
A question back to Antz: with DC motors one sort of can do both : constant power (PWM) -> constant speed. Start/stop (MX2) -> shoot/move/shoot. Although I don't like the latter with DC motors it seems to work well enough for the purpose. Not sure how the MX2 blocks the dolly from sliding when not horizontal as there is nothing to hold the motor when there is no power and there is no feedback.


500:1 gear ratio makes it near impossible for the shaft to move the motor... I'd also say the proof is in the pudding: This was shot entirely in MSM: http://www.vimeo.com/18475474 You can only notice the move shoot falling apart in one shot where I screwed up and by having it moving too far per shot with the lens literally inches from the foreground (low shot beach shot over ice melt stream). Otherwise it's pretty damn hard to see any lack of smoothness even though there is the added challenge of ramped moves in MSM.

lenny4d wrote:
BUT with stepper motors the story is a bit different or should I say the opposite. These create discrete steps by default (which you have to make smaller via very expensive gearboxes or use microstepping) but I think I read that if you want to create a sort of constant motion with steppers it doesn't work as well, certainly not when not geared down or using microstepping.


That's a myth. Steppers can produce silky smooth constant motion. They just need to be controlled properly. I've seen it with my own eyes

lenny4d wrote:
I am still pondering on what motor solution to go for that will work well for both video and TL movement (the former much faster of course). I am edging towards steppers because I don't fancy all the calibration issues with the MX2/DP motor.


I suppose I see it a different way... You can get amazing shots out of our system, two of three most popular videos on Vimeo were created with Stage Zero without calibration issues. All you need to do is get out there and shoot. It only takes a little bit of experience and a creative mindset. I've said this over and over: I chose the belt on our system for a specific reason... The distance between the teeth is a good general rule of thumb for distance per shot. If you have objects super-super close then slow it down a bit, if your foreground is at a good distance away you can get more aggressive. I have NEVER calibrated my system! I've only adjusted the min-pulse setting to get a little better performance out of super slow continuous speeds. Granted you can't get perfect repeat moves but it was never intended for that, it's intended to get uncompromising motion timelapse on a budget. Pardon my pomp but we destroyed that goal and now we're looking to new goals. =)

lenny4d wrote:
Also, steppers have a quite large dynamic range which would suit the dual purpose, much more so than DC motors.


Exactly! That's why we're working hard on our graphic GUI and highly sophisticated 32 'node' daisy chain-able stepper systems that will be able to hit a mark on the nose, do repeat motion and much more. :lol:


Fri Apr 29, 2011 9:50 am
Profile

Joined: Mon Apr 04, 2011 5:21 pm
Posts: 340
Post Re: Constant Motion vs Motion Intervals
Ps. I just got off the phone with the infamous Survivor timelapse guys... They absolutely love MSM on the DP system. ;)


Fri Apr 29, 2011 10:17 am
Profile
User avatar

Joined: Tue Jul 08, 2008 12:36 pm
Posts: 1787
Location: Antarctica/California/New Zealand
Post Re: Constant Motion vs Motion Intervals
I'd agree with everything Jay says.
It boils down to if you need repeatability, or precise preset points, you need steppers.
For the systems I use, once I got familiar with them after only a couple of shots, I am now able to set up and get the shot I want virtually every time with ease, just a matter of being familiar with your set-up and how it performs. I'll normally have a shot going in under 10 minutes.
Down the road I will be looking towards a fully programmable system that can hit a mark, focus point, and exact camera angle at multiple points, which would require a stepper system, but anything commercially available in this category right now is ridiculously priced, and I don't have the time to build it myself.

_________________
Anthony Powell
"Antarctica: A Year On Ice" Feature Film
Vimeo Youtube Photos
Twitter Instagram Google+
Facebook Facebook Movie Page


Fri Apr 29, 2011 1:28 pm
Profile
User avatar

Joined: Sun Jan 31, 2010 12:47 pm
Posts: 116
Location: UK
Post Re: Constant Motion vs Motion Intervals
Antz wrote:
anything commercially available in this category right now is ridiculously priced


Priced for the market I guess. Definitely big ticket items.
Cough... Marc Roberts... cough.


Fri Apr 29, 2011 3:35 pm
Profile

Joined: Mon Jul 19, 2010 1:52 pm
Posts: 72
Post Re: Constant Motion vs Motion Intervals
thanks for the feedback temp-milapse, of course I "know" (from the videos etc etc) that the DP system is a rather nice system, not only performance but also engineering wise. Fabulous work!. Ok, got it the 500:1 blocking. Thanks for demystifying the stepper-continuous motion myth.

Also from all the videos & posts on the Merlin head I know that's the one I want to go for. I am posting the spec on the system I am putting together in a different thread. I know I could buy the DP system or the motion timer, but it's fun to build yourself & have a hobby not to mention $$.


Sat Apr 30, 2011 2:39 pm
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 8 posts ] 


Who is online

Users browsing this forum: No registered users and 8 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB © phpBB Group.
Designed by Vjacheslav Trushkin for Free Forums/DivisionCore. pozycjonowanie