Recently I found great project for simplifying photo film digitalising.
VL53L0X is used here to determine beginning and end of film roll.
I would like to completely automate this process but I need to solve next question:
How to measure distance between film exposures (X value) to precisely calculate dx value for the motor to scroll to the next frame? Taking into consideration that this distance could be different per shooting format and even camera manufacturer.
Ideally I would like to write program which will scroll first exposure to the center of a film carrier and I should be able to calculate frame width and distance between exposures to perfectly center every frame.
So I wondering, is there a sensor that could measure these gaps of non exposed film? Also it should be more or less fast, otherwise it's better to write simple mobile app to enter these values.
johnerrington:
Cant you use the perforations to ientify the position? - that is what they are for.
Actually, not really. They are used for moving film inside a camera. Also they are don’t exist on 120 film format.
For now I ordered GY-2561 TSL2561 sensor. Once I print everything I will share results.
Yes, and in a film projector for placing the frame correctly - which is why in the "old days" you got a bit of frame jitter on films if the perforations were worn.
However - an alternative. An optical mouse detects movement very nicely - perhaps you could strip one and repurpose it to measure the movement?
You would probably still need to recalibrate by finding the gap between frames - which might not be so easy if you had a series of very pale frames.
johnerrington:
You would probably still need to recalibrate by finding the gap between frames - which might not be so easy if you had a series of very pale frames.
That's true, I've been thinking about it and decided that I can scroll film forward for Y mm trying to find pattern. Otherwise device will switch into semi manual mode.
I've looked into using a mouse it seems complicated. However your "manual " mode got me thinking. If you use an accurate transport mechanism - stepper motor or rotary encoder - then you just need to move the same distance each time once you have identified the frame spacing.
wsnake:
Actually, not really. They are used for moving film inside a camera.
The sprocket holes should match the film frame exactly as the sprocket typically does one turn per frame.
This means that when sprocket holes are present they are a really good way to measure frames.
Without sprocket holes you may be better off just having presents for common frame sizes and determine
the feed-distances by trial and error (or even measurement
Finding the initial frame though is still an issue...
That's where the pre-set distances come in. As per your comment #5, a frame is a frame. Know the start of the first frame (easy to see), know the size of the frame (known based on film type and camera), and you can automatically move the film to whichever frame you want.
120 film format (mostly used by me) don't have perforation at all.
Two rubber rollers can solve that. It will allow you to move the film a specific distance reliably.
Standards cover only exposure dimensions, so I can 100% rely on exposure width by format and hardcode it.
So I need to find a way to determine exact distance between frames regardless of film format.
So all you need to know is what camera made the exposure (look at the label, or at the film - measure by hand maybe), when installing the film into the device you align the start of film with a marker, and off you go. There are only a finite number of cameras around, so not that hard to have a pre-programmed list of frame sizes.
Actually, generic photo resistor is pretty precise! I put it into pen cap with 1mm hole. Measured delta values for non exposed film and hardcoded it for PoC purposes. In prod version initial value could be easily calculated. Please checkout video. IMG_4684.mov - Google Drive
Currently I'm going to wait for 3D printed parts for the carrier and then will steadily attach photo resistor with "curtains" closely to a film surface to limit incoming light in order to increase accuracy.
