A special feature of Canon New FD lenses is that their aperture remains fixed at a value as long as they are not attached to a camera.
The aperture blades cannot then be moved and checking the optics and aperture blades with an LED lamp is only possible to a limited extent.
“Aperture key”
While looking for a solution on how to get my New FD lenses to not block their aperture blades, I came across my spare parts box.
Why should I invent something that already exists?
The bayonet ring of a Canon FD camera should be ideal for my purpose.
When you place a New FD lens on the bayonet ring on the camera, the aperture is unlocked and can be closed by the camera or with the stop-down button.
So all I have to do is remove a bayonet ring from an abandoned Canon FD camera and have what I need: an "aperture key" to move the aperture blades to check for oil contamination.
Or let it completely open and check the lens with the LED lamp.
To do this, I chose an already dismantled Canon T90, which, as it turned out, offered tough resistance.
An ideal “aperture key” for easy-to-handle screwing.
It just needs to be disassembled.
Stubborn resistance of the screws
Simply unscrewing the bayonet ring from the mirror box couldn't do it.
Because the four screws responsible for this are (presumably) fixed with epoxy resin, which is extremely strong:
Since the resin covers the screw head profile, the screwdriver does not grip.
So I went through the known escalation levels
Acetone didn't do anything:
Using the Dremel Versatip I was able to melt the coating off and use a probe to scrape it away enough to get two screws out with the screwdriver:
But there was still stubborn resistance.
The remaining two screws resist removal.
Using the Dremel and a tungsten carbide cutter with an egg tip, I milled off the screw heads and cut out the upper part of the holes in the bayonet ring:
After a few rounds of milling, the ring fell from the mirror case onto the table.
I used the Dremel to work away any remaining sharp burrs around the milled out areas.
Complete:
The "aperture key" can be easily gripped on the two remaining extensions.
Using the two new indentations created by milling the "aperture key" can also be easily screwed into tighter FD lens bayonets:
In the basic position, that is after screwing the ring into the lens bayonet, the aperture is open. The aperture blades can be closed to the set aperture value using the aperture lever (opposite the red dot). The aperture is adjusted using the aperture ring on the lens.
So I should be well prepared for the upcoming round of inspections of my FD lenses
+++
All information provided without guarantee and use at your own risk.
The aperture blades cannot then be moved and checking the optics and aperture blades with an LED lamp is only possible to a limited extent.
“Aperture key”
While looking for a solution on how to get my New FD lenses to not block their aperture blades, I came across my spare parts box.
Why should I invent something that already exists?
The bayonet ring of a Canon FD camera should be ideal for my purpose.
When you place a New FD lens on the bayonet ring on the camera, the aperture is unlocked and can be closed by the camera or with the stop-down button.
So all I have to do is remove a bayonet ring from an abandoned Canon FD camera and have what I need: an "aperture key" to move the aperture blades to check for oil contamination.
Or let it completely open and check the lens with the LED lamp.
To do this, I chose an already dismantled Canon T90, which, as it turned out, offered tough resistance.
An ideal “aperture key” for easy-to-handle screwing.
It just needs to be disassembled.
Stubborn resistance of the screws
Simply unscrewing the bayonet ring from the mirror box couldn't do it.
Because the four screws responsible for this are (presumably) fixed with epoxy resin, which is extremely strong:
Since the resin covers the screw head profile, the screwdriver does not grip.
So I went through the known escalation levels
Acetone didn't do anything:
Using the Dremel Versatip I was able to melt the coating off and use a probe to scrape it away enough to get two screws out with the screwdriver:
But there was still stubborn resistance.
The remaining two screws resist removal.
Using the Dremel and a tungsten carbide cutter with an egg tip, I milled off the screw heads and cut out the upper part of the holes in the bayonet ring:
After a few rounds of milling, the ring fell from the mirror case onto the table.
I used the Dremel to work away any remaining sharp burrs around the milled out areas.
Complete:
The "aperture key" can be easily gripped on the two remaining extensions.
Using the two new indentations created by milling the "aperture key" can also be easily screwed into tighter FD lens bayonets:
In the basic position, that is after screwing the ring into the lens bayonet, the aperture is open. The aperture blades can be closed to the set aperture value using the aperture lever (opposite the red dot). The aperture is adjusted using the aperture ring on the lens.
So I should be well prepared for the upcoming round of inspections of my FD lenses
+++
All information provided without guarantee and use at your own risk.
Last edited:
