
Posted: Sun Jul 26, 2020 5:50 am
Being you have a 2x3 Crown it has a side Rangefinder.
Kalart was the most common but a few Hugo Meyer do exists on Graflex Graphic cameras.
Now your camera was likely set up for a 101mm or 105mm lens and someone stuck a 90mm on it to make it complete. Focus scales were matched to a specific lens.
Lens are rarely their marked focal length. They are usually within 3mm either side of the nominal marking. The greater the divergence from the nominal value marked on the lens the greater the error at distance from infinity even if infinity is the same for both lens. A scale for a 101 that optically measured 99.5mm and a 101mm lens that optically measures 102mm the scale error will occur at 12 to 15 feet while a 101mm that optically measures 101.2mm will be off at 8 feet (roughly). The same holds true for a rangefinder calibrated for a lens.
The distance from the rear nodal point of the lens to the film plane is called the back focus. The rear nodal point of lens used on these cameras is at or near the aperture/shutter blades.
Loosen the screws on the infinity stops so that the stops move easily on the yoke. Use a jewelers screwdriver or similar.
With the camera on a sturdy tripod move the yoke forward from fully retracted .040 ± .010 inch and set the focus lock. With the lens wide open and the shutter open on T or locked open on B with a cable release. Focus the lens on an infinity target at least 5000 feet away on the ground glass using a good loupe. Lock the front standard. Measure from the ends of the yoke to the front standard on both sides. When both sides are the same distance from the end of the yoke and infinity is in sharp focus with the standard locked slide the infinity stops up to the front standard and tighten the front screw on both. (the stops must be in the up position) Unlock the front standard, slide it back, tighten the rear screws on the infinity stops, slide the front standard to the infinity stops, lock and verify that infinity is in sharp focus.
Next calibrate the rangefinder to the lens. The instructions are here
https://graflex.org/speed-graphic/kalart-adjustment.html and a better copy of the Kalart manual is available at
https://drive.google.com/file/d/0B1sPJkp-Mdghc0FwQkRuWEhFZEE/view?usp=sharing
The factory service manual for your Crown is
https://graflex.org/manuals/23-Pacemaker-Speed-and-Crown-Graphic.pdf