Here is my completed Rokinon 135 f/3.1 aperture mask...
This is the Tiffen 49mm filter retaining ring installed inside a 77mm - 49mm step down ring. The 77mm end thread into the Rokinon lens.
I then took a 77mm - 62mm step-down ring, flipped it over and glued it to the first step-down ring.
This exposes a 77mm male thread (not very useful, but I will probably find some use one day for it :-). But it also exposes a 62mm female thread (from the back, but the 62mm hole is 100% threaded, so it is actually usable that way).
With this, I could add 62mm camera accessories, like a 62mm threaded lens hood:
This hood has a front thread of 67mm, so I could piggy back a 67mm lens hood to further protect the lens from house lights.
Ah, but a 72mm lens cap came with the 67mm lens hood (a 67mm lens cap came with the 62mm lens hood), so now I also have a way to keep dust off of the Rokinon lens:
Here is the assembly installed on my Rokinon setup:
If you have very sharp eye, you will notice that the assembly does not screw directly into the Rokinon's 77mm filter thread. My Rokinon has a very shallow filter thread. If not careful, a filter does not thread fully in, and can fall off. What I did was to get a 77mm Tiffen filter (what would I do without the cheap Tiffen with junk glass? :-), and threw both the UV glass and the retaining ring away. When threaded into the Rokinon, it now provides a deep 77mm female thread for easy installation of 77mm stuff.
At a dark site, you probably won't need that extension 67mm lens hood and just use the 62mm hood and cap it with the 67mm lens cap that came with it.
If you are going to use a 55mm aperture, instead of my 49mm (I am not greedy, and always lean towards better stars :-), you may need to start with a 67mm lens hood. The 62mm hood on a 49.7mm aperture (the aperture of the 55mm Tiffen retainer ring) may be too narrow; or may not -- you just have to test it out to see if it starts creating aperture vinetting at the corners. You don't want any part of the lens hood to vignette and start generating diffraction spikes. (There are absolute crazies who add wires to their apertures to create spikes. Donno why such people exists.)
Hah, there is probably a 72mm lens hood that is thread in front for 77mm. That can then be a large lens hood that makes use of that unused 77mm male thread, ha ha. You can also find 77mm-77mm female to female adapters in the photography world (Amazon has a couple of them). When attached to the "useless" 77mm male thread, forms a 77mm female thread, which can actually be quite useful.
Chen
