Thursday, June 23, 2011

Rangefinder calibrations on 110B- part4

First system to be measured is RF parts.
We need to draw a rangefinder characteristic curve, to represent it's focus range. so there is a chart, focus distance in x-axis, and y-axis is the mirror moving range.
As we all agree, that Polaroid mass produced 110B cameras, so rangefinder part should  represent same character in every camera body, but after measuring so many rangefinders, I found out that they all have their own characters. Maybe the camera was for 3x4 instant film, no image enlargement required, so it tolerates for range variety, but it is intolerable if we use this rangefinder on 5x4 camera.

Each rangefinder on Byron will be measure their characteristic curve individually, record and draw in chart, for further matching their prime lens.

To quick finish this tedious job, I managed to use a laser beam to do the focus, no need to peek all the time, thus won't hurt my eyes too much.

The measuring result will be something like this.

Lens measuring is simple and straightforward, you mount the lens on a 5x4 camera, set it focus at infinity, then define this location as zero point. As we already know that 110B rail has 20.5mm moving range, so we should find out the focus range this lens has in 20.5mm rail movement.

Stick a simple ruler at the side of the rail, and a pin as a pointer, now you can focus object at different distance and record the rail movement.
The result should be as early post I made "Lens Curves".
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