Building a film scanner

[poita]

It was actually so many of you!

[poita]

I've started filling in some of the details in the first posts.

BTW, I'm old school, so have been using a PIC for controlling the LEDs. The PIC16F1937 has really precise timing, the jitter is down to 0.125us, but I am not up to speed on the newer microcontroller options out there, and I know most people won't be up with programming a PIC, so I'm open to suggestions here.

The PIC currently monitors pretty much everything, and can handle motor control and monitoring the LED temp sensor to keep colour accuracy, so keep that in mind if coming up with a replacement system.

[DoomBot]

Are you saying with a continuous scanner you can use RGB LEDS to flash each frame 3 times red, green, blue? I thought that was only for intermittent frame by frame.

[maksnew]

https://youtu.be/qSRMeLEZLRg

[poita]

https://youtu.be/qSRMeLEZLRg

Yeah, that is how many used to do it, with the trigger hooked up to a mouse button. It works, but the top speed is slow, and it is a bit kludgy. Now with cameras having a trigger input, it is no longer necessary.

Are you saying with a continuous scanner you can use RGB LEDS to flash each frame 3 times red, green, blue? I thought that was only for intermittent frame by frame.

No, but you can use the RGB LEDs to flash at different rates.
e.g. the blue might flash for 10ms, the red for 14ms, the green for 18ms. This allows you to adjust the exposure and light colour balance to suit the film stock, or the level of fade, or to suit the spectral response of the camera you are using.
If you design your LED source this way, it allows you to later use the same light source on an intermittent system, and do multiple exposures, or run the print through the scanner three times, and do a red, green and blue pass.

Either way, I recommend the RGB array vs a high CRI white LED, you get to control the colour balance, and the light frequency of each channel in a much more granular way.

[DoomBot]

Ah ok, i understand what your saying now, that makes more sense.
So how do you even know what to adjust the exposure and light colour balance to for a particular film stock, is there a reference chart for this?

[monks19]

Thanks Poita for your time and efforts. I started to lose all hope to build anything for a project like this. But someday, I will (or at least I will follow this guide).

[Valeyard]

CONTINUOUS SCANNER BUILD

A continuous scanner moves the film at a constant speed, rather than stopping and starting like a film projector does.
...

With modern cameras, this isn't much of an issue, their dynamic range is typically much wider than the range on a print, and $100,000 scanners like the ScanStation, the Spinner S (https://www.youtube.com/watch?v=NugH6zdXVmw) or even the $30,000 scanner like the BMD Cintel use this method, so very high-end results can be achieved. You can see by looking at those scanners that the film path is quite basic.

Thanks, now it finally makes sense to me why the BMD Cintel produces so much video noise on prints. Stopping the film at the gate instead of using a red lasers to read sprockets seems to produce much better results.

[BronzeTitan]

@ poita
Awesome thread and a great resource! Thanks!! 

added:
I wonder if you might keep in mind we "poor-pockets" (or in my case, "no pockets" ... blame my sculptor) and mention 2nd-level quality materials for an otherwise really good scanner?

[poita]

Well, what I have already outlined *is* the cheap version, for between two and three thousand dollars or so you will get identical results to the forty thousand euro Muller HDS+ film scanner (http://www.filmfabriek.nl), and similar results to the $100,000 ScanStation.

Same light source, better lens and same sensor, but with the ability to do 35mm.


But for the really low budgets (under a grand)...
If you want to go bargain basement, the cheapest, that is still worth bothering with is:
Get a broken projector (free or a few hundred dollars)
Take the LED light source out of a cheap photo scanner, or use a DC halogen light and a cold mirror: $30
Get a CompononS lens: $100 or cheaper second hand
Get a cheap machine vision camera: $465 https://www.ptgrey.com/chameleon3-32-mp-...sonyimx265
Get the magnet and hall effect sensor and related circuitry (resistor and vero board) : $10
Extension tubes and adaptors from ebay $30
Helical focuser or macro rail or bellows : $30 2nd hand

This will give close to professional level results for around $700 if you shop around and scrounge. You could get a cheaper camera, especially if you look at firewire 2nd hand, like an older Grasshopper model, or a slower 2nd hand astronomy camera, but the camera and lens and light source are where the quality is.
(e.g. A good one here for $329 https://www.ebay.com/itm/Point-Grey-GS3-...2654692999)

Basically, hook up the light, mount the lens on the camera, point it at the film gate, advance the frame and the magnet will trigger the camera to take a photo, rinse and repeat.