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Tobin Time lapse questions


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#1 Damien Bhatti

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Posted 29 August 2008 - 01:10 PM

Hello there -

What is the shutter speed of the TTL(or bolex) when the animation mode is set (using the animation shutter release) I suspect its different from just using a shutter release cable on its own?

Thanks
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#2 Dominic Alt

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Posted 29 August 2008 - 02:04 PM

What is the shutter speed of the TTL(or bolex) when the animation mode is set (using the animation shutter release) I suspect its different from just using a shutter release cable on its own?

That's an easy one. It's limited to a single speed, 3/8th second. You never have to worry about what shutter speed is most appropriate! Because you can't change it.

Oh, and it's a wild speed. Hopefully, you won't get flicker.

As far as just using the single-frame release on the Bolex, that is 1/30th of second, when the I-T knob or lever is in the "I" position.
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#3 Damien Bhatti

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Posted 29 August 2008 - 02:35 PM

That's an easy one. It's limited to a single speed, 3/8th second. You never have to worry about what shutter speed is most appropriate! Because you can't change it.

Oh, and it's a wild speed. Hopefully, you won't get flicker.

As far as just using the single-frame release on the Bolex, that is 1/30th of second, when the I-T knob or lever is in the "I" position.



Hi thanks for quick response. Do you get flicker using a house hold lighting set up with tunsten bulbs bought at a hardware store? Also do you have to disengage the motor to manually advance the " camera mechanism with a rewind crank so the wider end of the pin, and the red dot, are uppermost"

I take it you do?/ does the camera need to be wound down completely as well before installing it?
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#4 Damien Bhatti

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Posted 29 August 2008 - 02:50 PM

In the instructions it says that the widest part of the pin stops uppermost, but the larger groove on my motor is the opposite, it rests at the bottom after 1 revolution. Should I just fit the pin the opposite way around suggested? Thanks,
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#5 Damien Bhatti

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Posted 29 August 2008 - 03:11 PM

well success hopefully, but 3/8ths of a second seems mightily slow! I was looking at the shutter going around. hmmm...
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#6 Arnis Hagendorfs

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Posted 29 August 2008 - 04:56 PM

I just made that mistake and got every thing totally overexposed. If you measure exposure at 1/30 you need to compensate 5 stops or use ND 1.5 filter. I made plants growing shoots using light special light for plants, no flickering.
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#7 Nick Mulder

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Posted 29 August 2008 - 04:57 PM

Near on most Bolexes that have the 1:1 shaft will also have the variable shutter - you can use this to decrease the exposure time...

The smaller the shutter gets the more the relative slop in the mechanism can(will) become a factor in your exposure, thats why Bolex don't register beyond '1' on the scale (which is one stop, halving the angle) - but you can use much smaller angles by eye-balling in and taping down the lever

Welcome to under/overexposed slit-scan rolling shutter fun
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#8 Nick Mulder

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Posted 29 August 2008 - 05:06 PM

I just made that mistake and got every thing totally overexposed. If you measure exposure at 1/30 you need to compensate 5 stops or use ND 1.5 filter. I made plants growing shoots using light special light for plants, no flickering.


Sorry to be the nerd - and I hope my calcs are correct - but the difference between 1/30 and 3/8 is 3.5 stops, around 8 filter factors or 0.9 and a bit ND.

ND 1.5 filter is either too much or too little for either 3.5 and 5 stops (using both scales)

Edited by Nick Mulder, 29 August 2008 - 05:07 PM.

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#9 Arnis Hagendorfs

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Posted 29 August 2008 - 06:02 PM

You are right, sorry, 5 stops if measure 1/50 as normal 24 fps, as I understand.
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#10 Damien Bhatti

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Posted 29 August 2008 - 06:11 PM

Near on most Bolexes that have the 1:1 shaft will also have the variable shutter - you can use this to decrease the exposure time...

The smaller the shutter gets the more the relative slop in the mechanism can(will) become a factor in your exposure, thats why Bolex don't register beyond '1' on the scale (which is one stop, halving the angle) - but you can use much smaller angles by eye-balling in and taping down the lever

Welcome to under/overexposed slit-scan rolling shutter fun


Alright, so I take it this is a tricky way of shortening the exposure time. Would it be best just to put on a ND. 0.9 for practicalities sake and read at 1/30th through the meter?

Is it a bad idea to leave the shutter at 3/8ths and go by that on your meter? (i imagine this posits a basic answer!)
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#11 Dominic Alt

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Posted 29 August 2008 - 06:18 PM

Hi thanks for quick response. Do you get flicker using a house hold lighting set up with tunsten bulbs bought at a hardware store? Also do you have to disengage the motor to manually advance the " camera mechanism with a rewind crank so the wider end of the pin, and the red dot, are uppermost"

Last question first, yes, you must disengage the motor to manually rotate a Bolex.

First question: as to when you'll get flicker, that is unpredictable. Depends on many factors. So...

I would recommend shooting a test, especially if you are going to use the variable shutter to cut exposure time. While shooting the test, you can fire off some single-frames with the spring shutter. You get a nice fast shutter speed. If there are no problems in the test, then you can animate with confidence.

I actually gave the wrong shutter speed. 3/8 second is the "adapted" shutter speed compensating for the prism. The gearmotor takes ("about") 1 and 1/3 seconds to make a full turn, giving a shutter speed (assuming a 133 degree shutter) of (133/360) * 1.33 = 1/2 second.

So the true shutter speed is 1/2 second. Yes, that is very slow!
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#12 Damien Bhatti

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Posted 30 August 2008 - 05:28 AM

Last question first, yes, you must disengage the motor to manually rotate a Bolex.

First question: as to when you'll get flicker, that is unpredictable. Depends on many factors. So...

I would recommend shooting a test, especially if you are going to use the variable shutter to cut exposure time. While shooting the test, you can fire off some single-frames with the spring shutter. You get a nice fast shutter speed. If there are no problems in the test, then you can animate with confidence.

I actually gave the wrong shutter speed. 3/8 second is the "adapted" shutter speed compensating for the prism. The gearmotor takes ("about") 1 and 1/3 seconds to make a full turn, giving a shutter speed (assuming a 133 degree shutter) of (133/360) * 1.33 = 1/2 second.

So the true shutter speed is 1/2 second. Yes, that is very slow!


I do not think that I am going to use the variable shutter to cut exposure time, as it sounds a bit to tricky and I really need to start shooting as soon as possible.

So, what are the main disadvantages over, say, stopping down approx vs variable shutter to cut exposure time?

I suppose that the slightest of movements would create quite alot of blur.

Thanks
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#13 Clive Tobin

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Posted 23 October 2008 - 06:59 PM

You are right, sorry, 5 stops if measure 1/50 as normal 24 fps, as I understand.

The 5 stops that I am talking about in the instruction manual is the difference between shooting with the TTL time lapse motor, versus normal filming at 24 FPS which is effectively about 1/80 second.

The instructions are furnished with each new TTL motor, and they are also posted on the website at http://www.tobincine...com/page30.html .

The 3/8 second (or about 32/80 second) is ideal for stop motion work as it makes your 100 watt bulb equivalent to 3200 watts. The relatively slow motor speed enables the motor to stop quickly enough using dynamic (electrical) braking instead of a mechanical stop, so the TTL motor should work reliably for a very long time.
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Visual Products

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