How do I recalibrate focus on an Argus C3 after reassembling the lens?
Asked 10/5/2022
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I restored an Argus C3 and had to disassemble the lens to clean dirt and debris from between the elements. After putting everything back together, photos are blurry at wide apertures. How can I set the camera back to proper infinity focus without shooting lots of test film?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
3y ago
2 Answers
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The Argus C3 is focused using the rangefinder.
These instructions are for rangefinder calibration.
Worth noting that by current expectations, the C3 may not be terribly sharp wide open. I mean if you are pixel peeping, don’t expect Sumicron results.
[edit] More Argus service manuals at Learn Camera Repair.
[edit] Typically a manual focus lens achieves infinity focus when the helicoid is fully retracted.
Which is to say infinity focus is when the lens helicoid is entirely unextended and closer than infinity focus is achieved by extending the lens in the helicoid.
However this assumes that the lens is the correct distance from the film plane and hence that any required shims are in place to provide the correct film to lens distance.
Originally by user95237. Source · Licensed CC BY-SA 4.0
user95237
3y ago
0
Generated from our catalog & community — verify before relying on it.
On an Argus C3, accurate focus depends on both the lens position and the rangefinder calibration.
A manual-focus lens normally reaches infinity when the helicoid is fully retracted, with closer focus obtained by extending it. So first make sure the lens was reassembled correctly and that infinity corresponds to the fully retracted helicoid position.
Also check that the lens sits at the correct distance from the film plane. If the camera originally used shims, they must be present and in the right place; otherwise infinity focus will be off even if the lens itself is assembled correctly.
Then calibrate the rangefinder so its infinity setting matches the actual lens focus. Service instructions/manuals for the Argus C3 can guide the adjustment procedure.
One more note: the C3 may simply not be very sharp wide open by modern standards, so some softness at maximum aperture can be normal. But if focus is consistently off, the likely causes are incorrect helicoid assembly, missing/incorrect shims, or rangefinder miscalibration.
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