Building a smart (light sensitive) intervalometer

[harryprayiv]

Hi guys, I usually just read posts around here. But, I figured I have a worthwhile question. So, here it goes. Also, I have read the other posts concerning this topic, but I assumed this might be different enough to get it's own mention. Here goes.

 

So, I have been using the TTL Tobin Time Lapse Motor for the past few days and although it's a pretty cool little motor, I find myself wanting to work with something a little better (specifically in the accuracy department as far as exposure time, automatic shutter compensation and other things). See, this motor only shoots at 3/4 of a second exposures in normal mode (which is far too slow for some daylight conditions) if I am to want the exposures to not suddenly JUMP to another setting mid-shot (my alternative would be to sit by the camera for hours and slowly chnage the F-stop in regular increments....NO WAY!

Now, my school also has a Thing M motor that I have used on previous instances, but even that is still not up to the standard that I am used to (it has the speed ramp function, but is not battery powered and I'd have to program these ramps in advance, which would require an identical light situation a whole day ahead of time for me to program the meter readings into a ramp).

 

I have been working with in-camera intervalometer's in my Bauer C107XL Super 8'sand I love the way they work...I only wish that the camera would compensate for exposure with shutter speed rather than F-stop changes. As it is, the Bauer doesn't allow me to do a sunset and then keep the camera on to do a time lapse of the stars and moon after sunset (I know that this would be hard taking the star's movement at night into account, but I kind of want to see that streaking effect). The cool thing about the Bauer is that it can actually do an exposure ramp because it's reacting to the light in the frame.

 

In conclusion, what I am asking is.....is there a way to build a homemade intervalometer that can be hooked to my Bolex, to a light meter (maybe the Sekonic L508), and/or computer that calculates shutter speed in any light where I could just keep the lense on the camera at a set F-stop? or am I just barking up the wrong tree??

[harryprayiv]

If this question perhaps sounded too involved for anyone, I am even looing for weblinks for plans. Sorry to get so complex on my only question...I have a tendency to do that.

[Mister X]

I trust that you've seen this web-page:

 

Densitometer & Intervalometer projects

[harryprayiv]

HI. Yeah I had seen that page. The only thing is, he doesn't go into enough detail about anything. He doesn't even talk about the device's light sensitivity even though it seems to be built into the device, I need to find some schematics for a device that actually explains everything. I don't care if I have to pay for it...I just don't wnat to pay how mcuh one of the devices actually would cost from a company that makes stuff for the motion picture industry because everything's over priced when the people who manufacture and sell that stuff come into the picture.

[Rachel Oliver]

You could get a Kern Switar POE zoom lens for the H16, it's got a built in auto metre! I set up a shot that lasted 3 days with this and a Tobin TTL...... Although this is moving Fstops as opposed to exposure times for light compensation. Just a thought

[harryprayiv]

You know, I was actually using that very same lense in this particular instance. I didn't know that it did that, but I had a suspicion that it might. Only thing is, opening up the lense to no matter what would make it so I could smoothly capture a sunset and then some stars in the same shot....cause no matter how much I open the lens at the speed that the TTL Tobin works at which is .75 s/frame, I need control over the exposure time because of the extreme differences in light between high noon on a sunny day and stars at night. I'd like my depth of field to stay constant too. Anyway, thanks for the info on that particular zoom lense. It will remain an option for the future.

-Harry

[Sam Wells]

HSo, I have been using the TTL Tobin Time Lapse Motor for the past few days and although it's a pretty cool little motor, I find myself wanting to work with something a little better (specifically in the accuracy department as far as exposure time, automatic shutter compensation and other things).

Really ? How much inaccuracy did you find in exposure time ? In both normal and seconds mode, what, ? I'm curious. (the other things I'm not concerned about).

 

There's the Norris LPC 90, a bit up the price scale......

 

-Sam

[harryprayiv]

I mean, the exposure time is accurate, but you do have to know where you ar eon the dial, which is impossible unless you test the motor with a stopwatch before you load film. I also would like to be able to control the amount of time in between each exposure AND how long the exposure takes. Right now, I can eaither have normal exposure at any increment I want, really (it is really hard to accurately set the intervals...especially as the times get higher between each exposure because you have to hand turn a knob with no detents to set the time...this always requires adjustment, so I'd say that a 50 minute interval would take at least 100 minutes to set correclty if you're lucky and/or fussy like me). Anyway, The TTl Tobin doesn't really offer as much control of everything as I need. It's a great little device if you're planning on standing next to it and changing the F stop all day, but working in diverse situations that are connected isn't really realistic. I hope any of this helps in giving you a clear comparison of what I want and what I am dealing with. Thanks. Also, I've never heard of the intervalometer that you mentioned..does it have the ability to control the shutter time? I'd be verey interested in it (probably more interested in using schematics of it to build my own) if it does.

[Sam Wells]

http://www.norrisfilmproducts.com

 

I'm not sure they're gonna send you schematics, though :o

 

-Sam

[harryprayiv]

Thank you kindly, Sam. I'm gonna try and contact them and figure out if any Sekonic meters can be hooked to that as well. The only thing is, the website says that the motor only goes down to 1 second exposures....which might not be quick enough for my needs....it's kind of sad how specific my needs are....I just don't want to have to bring the camera down 5 stops (with a combination of F stop compensation and ND filters) before I even start shooting. You know? Plus, I'll learn a lot building my own.

 

Before, I was thinking about building a light sensitive eye onto the box, so I could have control of the exposure based on what the eye reads, but now, I am thinking that if I get a Sekonic L 608, I could use that so that I know it's precise.....I mean, who can build their own light meter? I certainly don't think I can at this point!

[Sam Wells]

Says the exposure time goes as short as 1/16 sec, with intervals of one sec.

 

You may have to use some ND with existing rigs.

 

(and / or use slow film, pull process etc)

 

The issue of tying to a spot meter still raises issues of re-rating the stock, if you should not want what the meter is aimed at exposed at mid grey, and so on..

 

-Sam

[harryprayiv]

Says the exposure time goes as short as 1/16 sec, with intervals of one sec.

 

You may have to use some ND with existing rigs.

 

(and / or use slow film, pull process etc)

 

The issue of tying to a spot meter still raises issues of re-rating the stock, if you should not want what the meter is aimed at exposed at mid grey, and so on..

 

-Sam

Says the exposure time goes as short as 1/16 sec, with intervals of one sec.

 

You may have to use some ND with existing rigs.

 

(and / or use slow film, pull process etc)

 

The issue of tying to a spot meter still raises issues of re-rating the stock, if you should not want what the meter is aimed at exposed at mid grey, and so on..

 

-Sam

Thanks. I hadn't seen that it went down to 1/16 of a second. I saw the 1 second thing and, well you know. That motor and control unit is damn expensive though! Anyway, I was thinking that if I am going to be using it for landscape's, I might consider using a lumasphere type exposure since I want the whole light to be averaged. I mean, in an ideal situation, I would be standing next to the camera with a computer with programmed exposure ramps that could be adjusted to the shutter speed...but the chellenge of that is it's sheer tediousness.

 

 

I often dream about what technology can do....

It would be interesting if someone could build a motion controlled meter that could be programmed to move around what would be the camera's frame in time with the camera, hooked to a motor that could control the exposure time. Then, the exposure could move to what you're choosing to highlight in accordance with your program. You could then program in a actual color value (computer compensation for the subject not being medium gray).

 

For now, I need to find the motors with that have variable speeds that can be precisely controlled with an external device. Undoubtedly, I need to learn about the HC11 chip that was mentioned in the first link.....is there any kinds of chips like that one, but with extra processing power? Basically, I am thinking about changing schools.....right now, I go to an art school, but I think I have the mind/interest to be in an electrical engineering school.

[harryprayiv]

Oh yeah and also, I was thinking that I wanted to put a gray card in front of the light meter, but then I got to thinking that this might actually just end up being odd because the gray will undoubtedly fade in the sun...There's so much to think about....it's making me insane...and I like it.

Thanks again, Sam and all.

[Guest NCSProducts]

I mean, the exposure time is accurate, but you do have to know where you are on the dial, which is impossible unless you test the motor with a stopwatch before you load film. I also would like to be able to control the amount of time in between each exposure AND how long the exposure takes. Right now, I can eaither have normal exposure at any increment I want, really (it is really hard to accurately set the intervals...especially as the times get higher between each exposure because you have to hand turn a knob with no detents to set the time...this always requires adjustment, so I'd say that a 50 minute interval would take at least 100 minutes to set correclty if you're lucky and/or fussy like me).

The TCS time lapse motor is very primitive and limiting. :(

The premier company for intervalometers (and camera motors in general) is NCS Products. :)

 

NCS has two styles of Bolex intervalometers, the TimeFlow series, which work with the internal spring, and the Revolution series, which drives the 8:1 shaft (and also let you shoot sync).

 

More expensive then the TCS motor, but considering how much more advanced, a much better value! Select shutter speed and interval independently and with digital precision! Automatic shutoff, delay before filming, all kinds of features. If you click on the links below, you can read and download the product manuals. Both product lines have more advanced features then even the $4K Norris.

 

Ok, before this starts sounding like a product plug, B) let me try to answer the original question of controlling exposure duration via ambient light. To do that, you do need the $4K Norris motor. Someday, I will incorporate an ambient light sensor into the NCS Products intervalometers, but it's not available yet.

 

- Dom, in sunny New York.

Chief Engineer, NCS Products.

 

NCS Products Home Page

TimeFlow Intervalometers for Bolex

Revolution Time Lapse + Sync for Bolex

[harryprayiv]

Hi guys. Here I am, a year later and I am close to figuring it out! I am going to use the Thing -M animation motor and make my own control unit with a PIC chip and some C programmed by me. The minimum shutter time is .12 of a second...I think this is ideal for night shooting...also, I may give it the option of repetitive, programmable shutters (back and forth, back and forth on one frame in the dark until something exposes!) Here's somethingh I wrote about the brain....

 

? Thing-I? replacement controller for the Thing-M Animation Motor

Description: I reverse engineered the output of the Thing-M?s control unit for the purposes of making my own output unit that can also send the motor the proper signal. The control unit will be sensitive to changes in ambient light intensity through a Sekonic L558C-ish lumisphere. The annoying thing is, the L558 doesn't have a data output port, so I have to invest in a VERY expensive photo cell and lumisphere.

 

The brain will use the photo cell's resistance information to calculate a shutter speed for each repetition of the exposure. In this way, it can create time-lapse images with zero-flicker and perfectly uniform negative density...even well into the night, allowing the exposure of stars if necessary.

- runs on a pic chip

- has a 555 timer circuit

- lets you input the t-stop and film ASA that you are using with a telephone-keypad

- receives light intensity information from an external photo cell or light meter (if equipped with an output signal)

- computes the appropriate exposure time of the shutter

- included a capping shutter mechanism to minimize shutter light leak in long delays

- allows one to set the desired frame rate and manually override the shutter speed if necessary

- runs on a DC battery for days

- control the Thing-M's motor, the 4023-820 with identical torque to the original thing-m brain

- no changes in depth of field

- completely programmable

Edited March 31, 2005 by demesisx