This is both good news and bad news for us lens addicts. Good news is that it's very cheap, often about $10 to $20 for a very good lens, and the bad news is that a lens that can't focus is not very useful. Fortunately, it's not difficult to add focusing capabilities to these lenses. In fact, it's more advantageous to roll your own. Why? depending on the helicoid you use, the lens can focus closer than what it's designed to. In part I of this series, We will talk about the materials you will need for the Helios-103 53mm f1.8 lens. The procedure for other lenses should be similar, but you probably need different sized filter combinations.
What you will need:
- A focus helicoid with a range of about 18-33mm (or 17-32mm, the more common and cheaper ones on eBay) with E-mount on one end, and 52mm opening on the other
- One 49mm filter ring (more about this later)
- One 52mm filter ring (more about this later)
- J-B Weld or J-B Kwik or any kind of epoxy that can bond with metal
- Helios-103 53mm f1.8 Kiev/Contax RF mount lens without focus helicoid
The helicoid I use, is the Yeenon 18-33mm M42-52mm. I have had this helicoid for more than a year and it has held up well with very regular use. The more common, and cheaper helicoid you can buy is the 17-32mm that almost everybody else sells. It's probably good enough to get started.
For filters, you will want to use the thinnest ones that you can get. As you can see, filters come in various thicknesses. The thinner ones gives you better chance of achieving infinity focus. When it comes to focusing, 1 mm means you can focus to infinity or not.
The trickiest part, is finding the right kind of 49mm and 52mm filters. The good news is that the 49mm filter ring will fit the lens almost perfectly, provided you have the right one. For 49mm filter, you will need one that the glass is fitted from the bottom, and for the 52mm filter, you will need one where the glass is fitted from the front. Below are pictures to help you understand what the heck I am talking about:
In the picture above, the filter on the right has the glass fitted from the top, and is held in place by a thin ring that screws on top of the glass. You will need the 52mm filter like this one. The filter on the left with glass fitted from the bottom. Note the space that extends from the rim where the glass sits on; this space is what stops the lens barrel from falling through on the 49mm filter and this is the reason why we need this kind of filter for the 49mm. To recap: 52mm filter needs to have the glass fitted from the top; 49mm filter needs the glass to be fitted from the bottom.
To remove the glass from the filter with top fitted glass, you turn the notches (circled in red) with a spanner wrench counterclockwise until the it comes off the filter. The picture below shows the filter with glass fitted from the bottom. The glass is usually held in place with a thin metal spring. Use something thin and small to prick the spring outwards to release it. If you do not see a spring, you will need to break the glass. The safe way to do this is to put the filter in a small plastic bag, and then break the glass pointy and heavy. This way the broken glass will be inside the bag.
The reason we have spent so much time talking about the filters is because if you don't have the right kind of filters, it would be difficult to focus to infinity with the 17-33mm focus helicoid.
Next time we will talk about how to test all the parts together to make sure you can focus the lens to infinity.