Re: Questions/opinions about variable-density optical audio track recording.
- From: "Ken Hart" <kwhart1@xxxxxxxxxxx>
- Date: Tue, 22 Apr 2008 03:58:39 GMT
"Green Xenon [Radium]" <glucegen1@xxxxxxxxxx> wrote in message
news:480d373e$0$30207$4c368faf@xxxxxxxxxxxxxxxxx
Hi:This is completely out of my area, but I'll throw out some ideas/concepts.
I am not asking homework questions. The questions are out of my interest
in variable-density film audio.
My favorite analog audio storage medium consist of the optical equivalent
of magnetic tape. It is similar to the optical tracks of old analog B&W
films -- except without the video or any images. My optical tape records
audio optically on a tape using variable-density encoding [not
variable-area] and is monaural. As with any photography, the tape must not
be exposed to light before recording or development and must not be
exposed to extraneous light [light other than the optical audio signal]
during or before recording/development. Such exposure will corrupt the
film. After recording. The film is developed using photographic chemicals.
This tape is like a reel-to-reel [i.e. not a cassette] film using optics
and chemistry instead of magnetism.
What characteristics in the film material itself [e.g. the chemicals
within the film, "grains", etc. etc.] determines the audio quality [e.g.
the bandwidth, dynamic range, SNR, clipping point, treble response, etc.
etc.] of a VD track?
Based on your comments, the audio output depends on the density of the
exposed film. Film does not always have straight-line response to light.
Additionally, the developing process may not always cause a straight-line
density response. For example, if a particular audio tone goes from 10% to
90% electronically, the film's response may be 10% to 50%. Additionally, the
developement may move the film's response so that the final result might be
30% to 100%. You have to consider the base density of the film, and the
contrast of the film.
As for the characteristics of the film, a finer grain film will allow a
quicker change in density, allowing a higher frequency sound to be recorded
for a given speed of transport.
If I've completely missed the mark of your post, please re-read my first
sentence!
.
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