Tuesday, January 19, 2010

Distance Scale is not so correct.....

I received feedback from Raymond who told me that "the focus scale, the ground glass and the rangefinder did not agree on the focus distance." That brings me curiosity how precise the RF on 110B? I never doubt about the distance scale that camera shows me, until this time.
So I managed to measure the REAL distance scale that read out from ground glass panel. After some cameras were measured, a curve plotted to represent the relationship of focus distance and the rail movement.
Black curve represents the measure I made from ground glass, the blue curve is what distance scale on camera marked.

The curve tells me some facts that I should let all of the polaroid 110A/B owners to know, that is "the distance scale on camera is IN-CORRECT"!!
How surprise! I did trust the credits of Polaroid, their reputations of the quality control on productions......., but I should check before that!!
The curve tells me that 127mm lens actually can not focus as close as 3 feet, like  the distance scale shows, 3.6ft (110cm) is the nearest distance that camera can focus.
And the curve tells me more, that the distance scale is somewhat correct from infinity to about 5 feet, and then incorrect increase when focus closer.
BEWARE!!!
I should re-mark the distance scale on Byron.

(afternoon the same day Added...)
I received a mail, James from US told me that 'Actually Polaroid did make the distance scale inaccurate on purpose. What they did was based on ordinary people who are not aware 'focal plane', estimating distance between subject and the front end of lens, not knowing that real focus is on 'focal plane', about 20cm behind the lens, thus Polaroid marked the scale a little bit shorter, to compensate the common errors. When subject is far out of 5feet, that 20cm error won't bother anything, but if subject is very close, say 4feet (120cm), that 20cm deliberated shortage then become obvious! That is exactly what my curve shows me!!

And Mr.James pointed out that '110B camera was made in a closed system, that is, fixed lens, so as long as the range finder is coupled with the lens, no matter how the distance scale marked, it won't bring errors, but Byron now makes its range finder an open system, not only coupled with one lens only, and it also becomes reference for other lenses, for un-coupled setting, that makes distance scale in-correct.'
Thanks James, your explanation released me, bring back my faith to Polaroid!
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