Here is a new interesting application for the FRSP feature: 3D scanning of real objects, via the method of photogrammetry (
https://en.wikipedia.org/wiki/Comparison_of_photogrammetry_software). Basically, one has to take hundreds of pictures of the object from different angles, and use a smart software which would find and match features across the photos, and fit a model to it (3D model of the object + the camera positions + the model of the camera and lens).
Here is my simple setup for taking pictures (of small objects; the purpose is to reproduce objects using my 3D printer):
- a rotating platform driven by a stepper motor (1600 steps per full rotation);
- home photostudio lighting (two large softboxes and reflectors) using speedlights triggered by a single RF controller;
- camera (Canon 6D) on a tripod pointing at a small object sitting in the middle of the rotating platform, taking photos of the object at regular intervals (say every 2s - using the intervalometer feature of ML).
It all works pretty well, except that I don't wont to burn the shutter of my 6D for this stuff. It takes at least ~50 shots per object to build a model, and likely a few times more to also incorporate focus stacking into this (so probably ~250 shots per scan). FRSP would fit nicely here - if I could make it work with my setup.
At the very least, I need to have my flashes go off every time the intervalometer takes a FRSP photo. I saw reading the light from the camera LED suggested in this thread as the solution for this problem - can anyone give a reference to a page where this is discussed in detail? I couldn't find details in this thread. Specifically, I need to know if there is a lag between the LED flash and the actual FRSP exposure. If there is no lag, I can use a simple photodiode circuitry to do the trick, but with a lag I'll likely resort to using a microcontroller.
The first post in this thread mentions that when FRSP is used with intervalometer, the shortest possible time interval is ~10 seconds. Is it still the case, specifically for 6D? Ideally, I'd like to use a 2s interval.
Has anyone tried Advanced Intervalometer module with FRSP? Will it work? My idea is to take continuous photos of the rotating object over the course of a few full rotations, while slowly shifting the focus from the foreground to the background of the object. My hope is that one doesn't need to do a bunch of focus stacking before running the photogrammetry software (this will significantly complicate the process); instead, one would just slowly vary the focal point while taking hundreds photos of the rotating object, and let the photogrammetry software find and match all the sharp features of the photos, which at the end should recover the whole extent of the object.
