Camera support for use of unchipped manual lenses

H. G. Dietz
http://aggregate.org/hankd/

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: 

@techreport{manlens20200222,
author={Henry Gordon Dietz},
title={{Camera support for use of unchipped manual lenses}},
month={February},
day={22},
year={2020},
institution={University of Kentucky},
howpublished={Aggregate.Org online technical report},
URL={http://aggregate.org/DIT/MANLENS/}
}

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.

Software

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

The parameters are:

s
Sampling time in seconds. How long should it monitor motion before making the focal length guess?
z
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.
s
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.
l
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.

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