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Add framelines section

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Matt McWilliams 2022-07-26 15:21:37 -04:00
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NOTES_ON_OPTICAL_PRINTER_TECHNIQUE.md
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@ -271,4 +271,33 @@ Step contact printing, such as by bipacking in the optical printer camera, is a
It must give exposures which are exact 1:1, but there is then some
shrinkage in processing.
Optical printing with the aimframe method compensates for processing shrinkage.
Shrinkage errors are too small to matter with simple printers.
Shrinkage errors are too small to matter with simple printers.
## SAMEFRAME
A strip of identical frames, shot in the optical printer camera, is cut in two and registered in both the printer gate (upright, emulsion away from lens) and the camera gate (as it was shot).
The coincidence of details of image and sameframe is viewed through an opening in the rear of a special pressure plate.
A prismatic gate focuser may be substituted for the pressure plate, but only the most positive registration systems will be unaffected by this.
Only the most solid optical printers will allow loading the camera without disturbing the setup.
The sameframe method does not compensate for processing shrinkage.
## FRAMELINES
If the camera which made the original film had a frameline
much higher or lower than that of the printer camera, then
the vertical adjustment of the lens should deviate from the
aimframe setup, to compensate for this.
Otherwise the print will have a very thick, or even a double frameline.
Sometimes the sole reason for optical printing is to adjust the height of the frameline of an original film shot with a wayward camera. Sometimes it is to simulate such film.
Then the printer camera must have its frameline adjusted.
For a Bolex this is a simple claw exchange (revertible).
To make a frameline adjustment, if the reflex viewfinder is well-set, then even if it does not view the full frame, the vertical adjustment can be made until the upper frameline just appears, then until the lower frameline just appears, and the two adjustments averaged.
If the reflex viewfinder is untrustworthy, then a camera gate focuser can be used.
Or this method: register in the printer gate a bipack of the original with any file shot in the printer camera.
Determine how much vertical adjustment separates their framelines.
Make that puch adjustment to the aimframe setup.
The framelines of the original can always be eliminated from the print by setting the magnification slightly greater than 1.