[Frameworks] Film to digital photo to video on a JK

[Zach Poff]

I didn't have time at work to look back through my build documents, but
here are some answers to most of the questions from Chris: 

The general operation is as you describe. (Clarification: The projector
motor runs constantly during capture. It doesn't stop/start for each
frame since the intermittent projector movement handles that.) If the
software sees signs of a dropped frame, it will stop the projector and
warn the user, but there's no way to know for sure. I've been using it
for several years at about 4.15fps without many problems. (max speed
discovered via trial and error) 

I didn't get screen grabs of the other windows, but will try on Monday. 

Captures are 8bit, due to several factors: All inexpensive cameras with
HDMI live feeds were 8bit a few years ago when I built it. More
importantly, Max can't capture higher than 8bit anyway! 

The color values are all manual. We dialed in a custom WB setting on the
cam after tuning the LED control code, so if you pull the software RGB
sliders up together you'll get a pretty balanced grayscale. We use the
camera's picture modes to make the most of the 8bit signal: A
low-contrast profile for reversal and a high-contrast profile for neg. 

The Blackmagic capture boxes should work fine. Max is undergoing a
transition from Quicktime capture to AVFoundation so their capture code
was just re-written to directly grab from BMD devices. Haven't tried it
myself. For now I'm sticking with years-old Matrox drivers and the old
Quicktime capture code. If it aint broke... 

We're running it on a 2010 Mac Pro tower (sorry, forgot CPU specs) with
16GB RAM and an SSD for capture. Then we render onto a conventional HD.
Not a fast setup by today's standards, but it's a workhorse. 

The LED is a 40W RGB unit with multiple dies under a single lens. It
requires about 24v and we run it at way less than 40W. It's similar to
this one:
http://www.mouser.com/ProductDetail/LED-Engin/LZC-83MC00/?qs=sGAEpiMZZMtPzP3zsh8uzJaSIyo3FeiS
We can keep the enlarger lens at f5.6 or f8 for 90% of transfers, with
the option to open up if we run out of light. (The camera stays at its
lowest ISO.) 

We dim the LED channels with 3 hacked driver boards [1] that were
originally intended for little MR16 LED reflector bulbs, based on the
Powtech PT4115 chip. They keep constant-current and have a PWM input,
which we drive with the Arduino at a faster-than-usual PWM frequency to
avoid flicker. (I originally tried current-based dimming but there's not
enough accuracy in the low range for accurate color mixing.) 

The motor is a fancy Buehler gearhead unit with an integrated driver
that I got via surplus. No longer available anywhere. Any low speed,
high torque motor would work, via a PWM motor driver. 

I think the most important projector considerations are slot-loading,
gentle film handling, and enough room in the lens area to center your
enlarger lens without hitting the chassis. The Eiki's removable lens
mount was a huge help! Secondary factors would include belt-drive for
easy motor swap, and enough room in the lamphouse for the LED heatsink.
Eiki slot-loaders meet these criterion, and the back door swings open
for easy access too! 

100ft capture takes about 15min, then another 10ish to render. 

Max has a built-in scope [2] object (vectorscope, WFM, parade, histo).
They cost a fair bit of processing overhead, but it's certainly doable. 

Hope ity helps. I'll try to put this on my website next week. Even a
quick braindump is better than nothing! 

> Hi Zach,
> 
> First off thank you for your detailed and inspiring response! It helps to know about the shutter. If you have time to answer them, I have several questions and would greatly appreciate your feedback either here or off-list to help me further conceptualize my project. I must to say that I haven't worked in Max yet and I'm a little lost on a few principles that your system is based on. 
> 
> * The general interface/communication. >From what I can glean the camera is initialized into a video mode, then motor advances the film one frame, the arduino /+ PWM controller power on the LEDs once and TC Controller captures this event as a single frame in a video? Lather, rinse, repeat... * It'd be helpful to see screencaps of the capture and frame sensor settings just to get an idea of what other control your system affords
> 
> * At what bit depth are you capturing? 
> 
> * When the software checks the sprocket hole brightness do you use this to automatically configure the color space values?
> 
> * Would something like the Blackmagic Ultrastudio Mini suffice in place of the Matrox?
> 
> * Specs of the machine running this
> 
> * LED specs
> 
> * Motor specs
> 
> * Important characteristics of the projector? I'd assume an easily removable gate, no Kodak worm gear BS, so on... 
> 
> * Amount of time to capture 100' of film (~20' for capture only?)
> 
> * Could you theoretically implement a WFM or histogram into TC Controller?
 

Links:
------
[1]
http://www.dx.com/p/mr16-1-3w-650-700ma-constant-current-regulated-led-driver-8-40v-input-13557
[2] https://docs.cycling74.com/max7/maxobject/jit.scope
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