Old vintage soviet lenses, with Helios being one of the most popular and cheap options, have gained their specific place in photographers gear sets. They are simple, glass and metal build, and pretty sharp despite of their age. Most of those old lenses were made with M42 screw mount, making them a pretty universal lens for different camera brands.
But some of those Helios (and not only them) have a special aperture pin, allowing automatic aperture actuation of compatible camera bodies. The problem is that this pin haven’t been used by almost all cameras. And when you try to mount Helios lens onto your camera, you can use only the lowest aperture setting (wide open), because the aperture pin will not be pressed when taking a shot.
Some M42 to other bayonets adapters have a special flange to block this pin, but they are not available for all the cameras. And some of such adapters will not allow you to focus on infinity.
But there is one simple trick that will allow you to use full manual aperture setting control on any camera body.
Required kit and equipment:
• Helios lens (with aperture pin)
• flat head (slotted) screwdriver
• working surface (I’ve used a mouse pad)
• some tubing (or a nut, collar, etc.)
• knife (or other tool that will allow you to make a pin block)
Step 1: Unscrewing the back plate
Place your lens in a secure position (in order to keep it in place when unscrewing the bolts), select the appropriately sized screwdriver and unscrew four small bolts. Keep them in a box (or other container) to avoid accidental loss.
Step 2: Removal of a back (bayonet) plate
Remove the back (bayonet) plate from the lens. But keep it down to keep the pin in the back plate.
Step 3: Making a pin block
Take a pin, select your option to make a block (in my case I’ve opted for pen refill). Cut a small piece of tubing (or other option) – approximately 1.5-2 mm. This size should be enough to keep the pin suppressed.
Step 4: Assembly
Place the bin with its block into the back plate and install the plate back to the lens.
Screw in all the 4 bolts.
As a result, the aperture pin will be always “pressed” and you will gain the full manual control over the aperture settings.
It is a pretty simple and very useful method if you want to squeeze all the juice from your Helios lens.
If you know any other method, please share it with us in the comments below.