So it’s been a LONG time since I started working on this - I bought an RGB LED light nearly two years ago, poked at it a bit, but then shelved it. ( Just bought me an Aputure MC. Looks like it is going to be a love affair. - #15 by Entropy512 )
I finally picked the project back up today, and finished a Python script that:
- Controls a Neewer RGB176 light - Amazon.com - sadly no longer available, so if anyone else wants to use this, hope that Neewer’s other RGB lights use the same BLE protocol. Amazon.com may be fully compatible protocol wise since it claims to be a refresh of what I have, but TBD
- Captures a red-only, green-only, and blue-only image and displays the maximum value for the captured CFA plane so that you can adjust the light intensity and shutter time.
–Suggested tuning is to have a segment of unexposed negative, and initially set all brightnesses to maximum. Adjust shutter speed until the dimmest channel is within range with some margin, then adjust the backlight brightnesses of the other channels to bring them into range - Merges those three planes into a single image and writes it as a DNG using the same techniques as my Python image conversion tools. Due to some small not-yet-implemented issues in tifffile, I save as a floating-point TIFF. An advantage of this is that I can stack multiple exposures if there’s ever a scenario where that might be beneficial, but so far this seems unlikely.
Right now the DNG color metadata recycles the camera’s. That’s not really valid for this use case. I don’t know if the best solution is to set the ColorMatrix so the primaries match the LED wavelengths, or set the RT filmneg tool to do all work in raw colorspace and also disable the camera input profile. Probably best would be to find a way to characterize the primaries of the film itself… No bueno if your shots are 25 years old. (Edit: Not necessarily! Current Gold 200 and recently-discontinued-but-datasheet-still-available Superia X-Tra 400 are really close matches to Gold 400 from the mid-late 1990s and “S-400” from the very late 1990s/early 2000s, and making a DCP profile using the published SSFs has AMAZING results.)
Current scripts are on github at GitHub - Entropy512/rgb_led_filmscan: RGB LED capture of film negatives, inspired by NateWeatherly on discuss.pixls.us
Edit: Also for reference, so far I’m using Amazon.com for holding my negatives, which has a built-in diffuser since the Neewer light’s diffuser isn’t so hot.