Zeiss Ikonta B (Pre War)
Rangefinder Out of Focus Evenly
(through all distances)
Problem: Camera produces sharp exposures when focused at known distances using the lens distance scale as a guide. When using the rangefinder to attempt focus, the setting is off a consistent amount at each distance.
* Caution!! If the amount of error in the rangefinder is large and not consistent throughout all distances, the below procedure will not probably not resolve the problem. See "Rangefinder Prisms Out of Adjustment" for such problems.
* Caution!! Be sure the shutter is not cocked. Set the focus on the lens to infinity. Set the shutter speed to B.
* Caution!! Have the proper small screwdrivers before attempting this repair. Use a tray, such as a TV tray, with a white towel placed in the tray. Remove all parts from the camera over this tray so any small pieces can be caught & seen if dropped!
* Caution!! Be sure you know how your camera is mis-aligned before beginning repair! Example: Does it indicate a focus of 15 meters when in reality the distance is 8 meters.
* Caution!! Caution!! If you do not have familiarity with small mechanical items and a lot of patience, do NOT attempt this repair! Please read through this entire article before attempting, and then make the decision whether to proceed at your own risk! I am NOT a camera repair man. I was in a position where I had trouble finding anyone I would trust that was willing to work on my camera and talked to some who had bad experiences with others attempting repair on their Zeiss camera.
--The following assumes that the camera front lens elements are in the correct helical. You either need a ground glass to check this or already have exposures from known distances while the lens was set to those distances. If the photos are tack sharp, the elements should be correct.
--Facing camera lens, remove the small screw at 4 O’clock & the other at 8 O’clock on the face plate.
--Facing camera lens and looking down onto the top of the lens, remove two screws at 12 O’clock on the top of the face plate.
--Remove the face plate. There is a lip on the plate at the 8 O’clock position. Therefore remove the faceplate by lifting from the 1 O’clock position of the plate (where your finger normally focuses the rangefinder) & carefully removing the plate from the camera.
* Caution!! The Face plate is extremely fragile & bends easily. You will know if this happen as the lens will focus with much more difficulty when the plate is replaced and the plate has been bent. Be careful!
--With the lens still at infinity and the camera on its back, slowly unscrew the lens counter-clockwise.
--Hold a slight even downward pressure on the lens gear to ensure it remains in full contact with the prism gear or the gear may slip and you will lose the original placement.
--Stop when you reach the point where the gear no longer contacts the lens and note the position of the tab. This is where the tab must be when you again screw on the front lens.
--Take some kind of marking material and mark matching spots on both the brass plate holding the prisms and the geared ring surrounding the lens. I used fingernail polish to make the marks then scribed a light line in the polish after it was dried to identify the exact position of the two pieces.
* Caution!! Do not move the focusing gear at all until this temporary mark has been made! This is the only way you will know the original position!
--Continue to slowly unscrew the lens. Note where the lens come free of the camera. The lens front must be in this same position when reassembling!
* Caution!! The lens must be in this same position when reassembling in order for the lens focusing point to be correct! You can actually engage the threads for the male/female mating of the two pieces from several different spots. Only one is correct!
--Remove the lens & set aside.
--It is now a matter of carefully lifting the large lens gear and moving the position one or two teeth. Remember that the lens focuses from infinity to close distance by moving counter clockwise. If the lens is still mis-aligned when assembled by a further distance on the lens then was the true distance, the gear must be moved counter clockwise.
* Caution!! This is trial & error. I would not go more then one or two teeth at a time. You should know upon reassembly if you went the correct direction by whether the focus is worse or better.
--Ensure that the tab on the large lens gear is rotated to the same position/location as when you unscrewed the lens. This means that the two alignment marks you made on the gear and the prism plate will be off (left or right) by the amount you moved or changed where the teeth engage.
--Replace the front lens starting from exactly the same position on the camera. As the lens is screwed on it will make contact with the tab and begin turning the gear as you continue to screw in the lens.
* Caution!! Remember to hold a slight even downward pressure on the lens gear as you are screwing in the lens so the gear will not ride over any of the engaged gears which would ruin the alignment between the lens gear and the prism gears.
* Caution!! The lens MUST stop at or near the infinity position as it did before you removed the lens. If this does not occur, then you have started the lens onto the camera from the wrong position and must remove the front lens and start over from there.
--Carefully place the faceplate back over the front lens and test the focus at all distances while holding the plate on with your fingers. (No need to have to remove the face plate screw again if you do not get satisfactory results.)
--If this does not result in proper alignment, try again to move the lens gear one or two teeth at at time, one direction or the other until resolved. When completed replace the screws that hold the faceplate on the camera.
Copyright: Bruce Varner 1972-2021