My modular system includes the following components:
- Focus helicoids
- Extension tubes
- Filter rings, mostly 52mm and 55mm
- step-up/step-down rings
My most often used helicoids - 2x Vivitar Macro 2X teleconverter and the 18-33mm M42-M52 Yeenon
The next question is the mounting type of these helicoids. Most common is M42-M42, which means the mount (male side) of the helicoid has a M42 mount, and the opening (female side) that accepts the lens, is also M42. Other types include M42-M52 (52mm opening), M68-M68, and other more specialized types. Personally, I find the M42 opening a bit restrictive, for two reasons: 1) Some of my lenses have large diameters but have short flange distance and the lens needs to go inside the helicoid to achieve infinity focus, so I need an opening as large as possible, and 2) You will need a lot of M42-52mm, M42-55mm, M42-62mm, step-up rings to mount the lenses to the helicoid. This could get expensive if you have lot of lenses. I have a couple hundreds junk filters of all sizes, and I am not kidding you, I accumulated these filters many years ago from the Henry's Outlet store, like I knew what I was going to do with them :) I would prefer not having to buy anything if possible. Did I mention that I am cheap? So I ended up with the M42-M52 helicoids.
But, it's up to you which one to buy. M42-M42 are sometimes 50% cheaper than an M42-M52, probably because they don't sell as many as the M42-M42. For long lenses, you probably want a longer helicoid, like the 35-90mm, or roll your own with the Vivitar 2X macro teleconverter like I have done.
I made my own focus helicoids from the Vivitar 2X Macro teleconverters, for two reasons. First, I am cheap. I can often buy one of these at the camera show for $10 to $15, and now I have 5 or 6 of them in various mounts, but it doesn't matter what mount it is as the mount will be removed anyway. Second, these Vivitar teleconverters are extremely well made and focuses very smoothly. If you have ever used the cheap 17-32mm or 12-17mm helicoids, you know how bad they are. Lots of play and the workmanship leaves much to be desired. Even my 18-33mm Yeenon helicoid, which is much better than the average, is starting to get a bit loosy. The Vivitars, on the other hand, are rock solid. There is a limitation, of course. These teleconverters are about twice as long as the standard 17-33mm, so they are not good for short lenses, unless the lens can go inside the helicoid. That's the reason I use them mostly for long lenses.
I also make the Vivitar helicoids stackable. Most long lenses have very long minimum focus distance, which sometimes up to 10 meters (33 feet) for 300mm+ lenses. A single focus helicoid just isn't enough to get them focus closer, and that's why I sometimes stack two Vivitar helicoids together for the longer lenses, and often get them to focus closer than 3 feet for a 7 or 8 inch lens. For even longer lenses, you can even use three of them together.
How do I make the Vivitars stackable? Very simple. Remove the mount completely, and epoxy a 62mm filter ring on it. Depending how I use it, I will use either a 55mm-62mm step-up ring, to connect to another Vivitar helicoid, or a 42mm-62mm step-up ring, plus a M42-E-mount adapter if I want to use it by itself on the camera. All these rings add a bit of thickness to the helicoid, but it's a small price to pay for versatility. I will have another post at the end of this series with more details on the Vivitar helicoid.
After you have decided on the helicoid, you will then need to get a thin M42 to E-mount adapter, like this one I reviewed, but I bought two more from eBay that's cheaper (around $8 each shipped) and they fit as good, if not better than the Yeenon. They are 1mm thick, so it's perfect to connect the M42-mount helicoid to your camera. Too bad I don't see the 1mm M42 adapters for M4/3; there is a 5mm one, which I bought, but it's quite a bit limited as it increases the overall thickness of the helicoid. when mounted to the camera.
On part IV, we will talk about extension tubes.