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Topics - natschil

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General Chat / Digitalising slide-film with magic lantern
« on: June 20, 2020, 10:51:42 AM »
I've been working on a machine for digitalising slide film for a while, and it has reached a point where it is working very well, so I thought I would share

Here is a video of the machine in action https://drive.google.com/file/d/1HwVwULBRlTh9yDRKbw87FjLXRVLTpz3j/view


I'm using an EOS M, together with a modification of ML where I've mapped certain PTP commands to take a picture and adjust exposure times. Because slide film has such a high dynamic range, a single exposure time would not have worked well. I therefore look at the histogram and adjust exposure for each image. If the image is still too dark, I increase the exposure time, take another picture, and then combine both pictures with the enfuse utility. The lens is a 100mm Canon FD macro lens, together with some teleconverters.

I've digitalised several thousand pictures at this point, here is one https://drive.google.com/file/d/1cbxvvk_QhnVmxhfcxLwNyc8-gOdHBt_e/view?usp=sharing

What is slowing things down quite a bit is that setting the exposure time isn't instantaneous. A large chunk of time is spent waiting just to be sure that the exposure being set has been set. Nevertheless, the whole thing is still *much* faster than using a slide film scanner that scans the slide "line by line". The sharpness of the images is limited by the grain of the slides.

This project would not have been possible without ML, thanks a lot to everyone who has worked on ML over the years!

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General Development / Custom PTP commands (on EOS M)
« on: September 25, 2019, 11:19:52 AM »
First of all: thank you for making magic lantern, it is incredibly useful and I couldn't imagine buying a camera that doesn't support it.

I'm trying to build a setup for digitalizing old slide film. I have an  EOS-M (original) running Magic Lantern, and  a slide projector that I've modified so that I can now easily step through slides. I've bought an old manual focus macro lens, for which I intend to build a mechanism for autofocussing via a computer and an electric motor. My only problem: it seems like the EOS-M does not work well with certain ptp commands. So I've decided to write my own ptp handler that does the things I need. I essentially need only (a) a way to trigger taking pictures from my laptop. (b) a way to get a small piece of the live view (for focussing) to the laptop.

I've successfully compiled the ptp code, and written a "Hello-World" handler with which I can communicate with the camera. This works. However, it seems like the camera goes into some kind of ptp-lockup-mode whenever it is plugged into usb, which means that lens_take_picture() doesn't work - the picture gets taken only once the usb cable is unplugged. This is kind of annoying. I am able to take pictures in bulb mode, but doing take_pulb_pic(1) results in a very long exposure, and takes so long that the ptp call times out.

Before I start trying to reverse-engineer the EOS-M firmware in the manner of https://research.checkpoint.com/say-cheese-ransomware-ing-a-dslr-camera/, I was wondering if anyone here could offer some suggestions/insight. I'm aware that I could work around (a) by audio remote shot/IR remote and (b) by doing some kind of focus-checking on-camera and filming the live-view with a  webcam, but both of those approaches are *very* hacky and I feel like there must be a more elegant way to do this via ptp.

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