Homemade Minolta 16-II “Distance” Lens/Filter

Monday, April 20th, ©2009 Marcus Brooks
Minolta 16-II with DIY Yellow Distance Lens

Minolta 16-II with DIY Lens/Filter

Netizen Linghai Chen noticed that my old microfilm page says I used a “homemade yellow distance lens” with my Minolta 16-II camera. He wants to know how I made such a lens.

I thought you’d never ask!

For those just tuning in: In the 1960’s, there was a popular “spy” camera called the Minolta 16-II. Its lens was tack-sharp but just a bit myopic, with its focus fixed at about 3 meters. You could adjust the f stop (lens aperture) to vary the depth of focus, but to get a sharp landscape photo you had to stop all the way down to f/16.

To make the camera more usable, Minolta offered slide-on lens filters. Lenses #1 and #2 had plus diopters for close-up work. The #0 “distance” lens had a slight minus diopter, which provided sharp landscape images at any f stop.

Nowadays, you can find a #0 lens for the 16-II at any store that sells hen’s teeth. In fact, the original distance lens is at least as rare and almost as desirable as Minolta 16 cartridges (which are another story). Since I couldn’t find one, I decided to make one for myself.

Minolta 16-II DOF Chart (Including -0.25 diopter)

Minolta 16-II Depth-of-Focus Chart (Including -0.25 diopter)

Making the Lens

The closest available match to the Minolta #0 lens is a -0.25 diopter eyeglass lens. On the 16-II, this won’t quite focus to infinity at f/2.8, but it’s close. I included a -0.25 diopter bar when I made my graphical DOF/exposure guide for the 16-II (detail shown above). You can use that as a focusing guide for this lens.

Here’s how I made the lens:

  1. Make friends with an optician.
  2. Purchase from said friend a tintable plastic -0.25 (negative 1/4) diopter eyeglass lens blank. (He’s not supposed to sell these without a prescription, so gentle persuasion may be required.) If I do this again I’ll try anti-scratch plastic, but it might not be so easy to tint.
  3. Cover both sides of the blank with masking tape to prevent scratches if you slip.
  4. With a cutting wheel on a rotary tool (e.g., Dremel), carefully cut Minolta-lens-sized chunks out of the blank. I made the cut under flowing water, but don’t electrocute yourself! (Use a flex-shaft attachment and keep the motor housing dry. If possible, use a GFCI-protected outlet or a cordless tool.)
  5. Lens Mount Detail (with Minolta #1 for Comparison)

    DIY Lens Mount (with Minolta #1 for Comparison)

  6. Carefully grind the back of each lens flat only around the perimeter (mostly at the corners). This makes mounting the lens easier.
  7. Remove the masking tape. If you want to color the lens, do it now (see below).
  8. With patience, pliers, and the cut-off wheel, fashion a lens mount out of thin brass or soda can aluminum (see photo). I couldn’t fashion leaf springs that small, so my mount uses a snug friction fit.
  9. Carefully epoxy the frame to the lens (super glue might fog the plastic).

From my blank, I got one “prime” lens (cut from the center) and four “off-center” lenses that I consider “seconds.” (They might be just fine, but I suspect they could have some prism distortion.)

Coloring the Lens

For your first attempt, dye each lens separately before gluing on its frame. That way you can try different shades of color, or even different colors. Later you might want to dye the whole blank first if you decide to make lenses wholesale for friends, etc.

  1. Mix up a strong, hot batch of RIT fabric dye. I used #42, Straw Yellow. (Conveniently, 42 is also the answer to life, the universe, etc., among other things.)
  2. Soak the lens in the dye, pulling it out now and then to check its color. The longer it soaks, the darker it gets. I don’t recall exactly how long it takes; the plastic I used got dark pretty quickly.
  3. When the color looks right, rinse, dry, and mount the lens.

BTW: Using RIT fabric dye is a standard modeling trick for tinting cowls and canopies. It works on most clear plastics that I’ve tried, but I’d be careful to specify tintable plastic when you get lenses.

I chose darkish yellow as most useful for outdoor B&W photography; it darkens a blue sky a bit and helps clouds stand out. Deeper, redder shades have a more drastic effect, and will also darken foliage some. Add a stop or two to the exposure, more for darker filters.

Green is also a popular B&W filter. With a bit of extra exposure it makes foliage look lighter, and it should also darken the sky a bit. It’s mostly used to darken pale skin tones for portraiture. This isn’t so useful in a distance lens, but why not try making a green +1.5 or +2 diopter lens for portraits?

Offhand, I can’t tell if the #1 and #2 16-II lenses are +1 and +2 diopters. (Wouldn’t that be too easy?) But they seem to be focused in the same ballpark.

I don’t want to get into filtration for color film, except for one idea. A dark neutral density close-up lens/filter (i.e., using black dye and a +2 or higher diopter) might be handy in bright sunlight. The ND would let you set a wider aperture to get the blurred background that’s favored for flower close-ups. I’ll let you figure out the focal ranges!

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8 Responses to “Homemade Minolta 16-II “Distance” Lens/Filter”

  1. David Foy says:

    Marcus, glad to see you’re still at it. David Foy

  2. marcus says:

    Hi David! Glad to hear from you. I haven’t shot any film in a while because of various disruptions, but someday…

    I have been trying to chip away at some to-dos on my “cameos” page. I still come across subminis in movies now and then, mostly old movies!

  3. Hah, that’s awesome – Creativity is required with something like this I guess. Mind telling us the name of your optician friend? 😉

  4. marcus says:

    Frankly, that was so long ago I’ve forgotten! It was one of those passing friendships; cash passed his way, lenses passed mine.

  5. Thanks for sharing, say, do you have a twitter to follow?

  6. marcus says:

    No twitter as yet. Things I want to share tend to run into the hundreds of words, so I blog instead. I don’t imagine many of my day-to-day activities would hold any interest, even if I felt like sharing them.

  7. cesar orlando jurado jaramillo says:

    DONDE PUEDO ENCONTRAR PELICULA PARA MINOLTA 1 6

  8. marcus says:

    Perdona mi Google-traducida en español.

    Trate de fuentes figuran en esta lista
    http://www.subclub.org/sponsors/sponsors.htm

    En los EE.UU., Ebay, a veces tiene edad Minolta 16 películas. Mantenga siempre el cartucho. Puede ser recargado.

    (Briefly in my native English: for Minolta 16 film, try the sponsors at subclub.org. In the US, Ebay sometimes has old Minolta 16 film. Always keep the cartridge. It can be reloaded.)

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