Camera support for use of unchipped manual lenses

H. G. Dietz

Department of Electrical and Computer Engineering
Center for Visualization & Virtual Environments
University of Kentucky, Lexington, KY 40506-0046

Original February 22, 2020

This document should be cited using something like the bibtex entry:

author={Henry Gordon Dietz},
title={{Camera support for use of unchipped manual lenses}},
institution={University of Kentucky},
howpublished={Aggregate.Org online technical report},

The Paper

The primary publication decribing this work is "Camera support for use of unchipped manual lenses," by Henry Dietz and presented as a poster at IS&T Electronic Imaging 2020. A preprint version is posted here.

The 3D-Printable QR Coded Lenscaps

We have posted the customizer model generator for 3D-Printed Screw-In Front Lenscaps With Optional QR Code. Note that the QR code requires some contrast to work well, so you may want to change filament to a different color, or use paint or a marker, to give the QR code pattern higher contrast.


The source code for gmfl.lua, the CHDK "guess my focal length" demonstration application, is posted here.

The parameters are:

Sampling time in seconds. How long should it monitor motion before making the focal length guess?
How many zoom steps to use for calibration. The camera is queried to determine how many zoom steps it supports, and that range is divided into this number of equally-spaced zoom positions to calibrate on. Note that zoom steps don't necessarily have an obvious correspondence to focal lengths, so the actual focal lengths used might not be equally spaced.
Motion granularity is used to determine how many motion-detection boxes to fragment the live view image into. The number specified states the number of live view pixels per motion detection box -- the default is 10.
Light threshold sets the motion detection threshold. The default level, 12, is a good general-purpose choice, but very contrasty or very flat or very dim lighting may produce better results with a different threshold value.

The Aggregate. The only thing set in stone is our name.