>Working late in the lab again! I’m trying to detect the film sprocket holes for my DIY cine film scanning project and in the process finding out quite a lot about photo-transistors. The plan is to mount one of these into my film transport mechanism to give feedback to the stepper motor. With some great support from Archie over at PC-control.co.uk I’ve made a little circuit to test the sensors and measure the high and low voltages they give.
By placing a bit of card or some white super8 film leader next to the sensors I had the circuit tuned quite well (using the salvaged Epson printer proximity sensor) to the point where I thought this to be a viable route… However, tests with actual film strips gave a very curious result… Though seemingly black to the naked eye, movie film seems to have little or no opacity when seen by the phototransistor.
Realising that the Epson photo diode/phototransistor device uses infrared light, I thought I’d take a look an infrared look at some movie film with my miniDV camera in nightshot mode…
Bingo! The cine film is pretty much transparent under IR lighting. There’s no way an IR photosensor will detect the sprocket holes when the film base itself is rendered almost completely transparent. I’ll be looking at sensors in the visible light range next…
(Also of interest here, notice how the film looks so scratched under IR lighting; some film scanners use just such an IR pass to enable infrared cleaning of scanned images.)
>This grey and blue thing might not look like much, but it’s my very first Windows application! The StepForward and StepBackward buttons tell my StepperBee card to move the stepper motor forwards and backwards. A strip of Super8 film sitting in my DIY film transport moves accordingly… Up until now, I’ve always been sending instructions to the StepperBee using the controller application that came with the board, so this represents a fairly dramatic development. For a long time I’ve wanted to make things and control them from the PC, so this is a real first.
To produce this exciting code, I downloaded Microsoft VisualBasic 2008 Express Edition, then pasted in the code found at the StepperBee website.
Unfortunately the middle ‘Snapshot’ button doesn’t do anything yet. Triggering the Sumix camera and saving the images was something I hoped to do within the Sumix camera application, but this doesn’t seem to be possible. I think the camera will have to be triggered by my application somehow, and I suspect that a whole other can of worms lies therein.
Next up also I need to find out more about the optical proximity sensor I’ve recovered from an old Epson printer… can this be hooked up to one of the StepperBee’s input channels and if so, how accurately might it pick up on the tiny film sprocket holes? Stay tuned…
>Up late again… Still trying to finish the short film ‘TXT Island’ hopefully JUST in time for submission to the
Rushes Soho Shorts Festival 2009. 2 days time now… Russell over at Shrooty is taking care of the music/sound and doing sterling work too. A few wee picture fixes, a few more renders, then the submission DVD could just make the closing date…
Here’s The Sumix camera in DIY cine scanner mode. The lightbox and big tripod are rather cumbersome but temporary necessities. The stepper motor here does advance the film, but unfortunately a random amount each time! Still, both stepper motor and camera are under USB control from the PC. A milestone of sorts but redesign of film transport needed.
Another early 90s Super8 cine frame. I’ve got a stepper motor advancing the film under the camera now, but the drive is uneven, so not much use yet for any automated capturing. Making a film advance mechanism is proving to be a VERY demanding task indeed!
This image is captured at 1280×1024 using Sumix 150M monochrome camera with macro lens tubes, Super8 film backlit by lightbox. Some DeNoise and Levels applied in After Effects.
Above is one of the Super8 frames (seen in previous post) imaged by the monochrome Sumix 150M camera. The 35mm lens with 60mm worth of extension tubes lets the image fill the frame. The end of lens is about 30mm away from the subject; again this is shot on lightbox. Some Photoshop de-noise and levels applied.
Until I try combining three RGB filtered images or buy a colour USB camera like this one here… maybe I’ll just have to colour these in by hand 🙂
I’m back scratching the 8mm itch again… This still taken with canon350d, standard 18-55mm kit lens and Raynox macro adaptor attached. Super8 film strip is backlit by lightbox and held flat with edge of plastic ruler (note the millimetre markings).
These frames happen to be some peacenik badges on a stall at the Beverley Rainbow festival, Humberside circa 1990.