Anamorphic Chop Shop – Kowa B&H Minimum Focus Mod

November 20, 2016

Stepping up from last week, here’s how to achieve closer focus natively with your Kowa B&H. I also explain how stretch varies across the focus range. I believe this process can be applied to other vintage projection lenses.


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Tito Ferradans here for Episode 3 of the Kowa month. Today’s mod is a little more elaborate than last week’s Edge Blackening. Also introduced by James Price, today we’ll be slashing minimum focus a tad closer.

The Kowa B&H is an amazing projection lens and, until quite recently, a double-focus setup. That means relying heavily on diopters for close focus. The Kowa isn’t too bad, at 5ft or 1.5m for minimum focus, but it would be nice to go closer.

What we’re gonna need for today is:

  • Kowa B&H (or Elmo II)
  • a tiny screwdriver
  • needle nose pliers
  • a file

Before we start, some useful info. Projection lenses vary their stretch factor across their focus range. I’ll come back to this subject in the future. For now, here’s a comparison of the Kowa focused at infinity (6’6″, using a +0.5 diopter), and at original minimum focus (4’8″ for me).

The nominal stretch factor is only valid for infinity. At minimum focus we come down to around 1.8x. Single focus solutions fix this, as the anamorphic block stays focused at infinity – hence, it has constant stretch. Not everyone can afford a single focus solution though.

I believe this is a process that, like the previous tutorial, can be applied to other lenses such as Kowas 8Z and 16H. I couldn’t check by myself. If you’re able to do it, please let me know!

The first step is to get to the core of the lens. Using the screwdriver, loosen these three tiny screws on the front of the Kowa.

Now get a grip and rotate the front ring out. This will set the body’s glove free and you can spin it out all the way through the back. Welcome to Greaseland.

You will find three little brass tabs around the lens. As you move the front element back and forth, notice these tabs are the focus limiters. The front marks infinity, the back is for minimum focus. At minimum focus you can see a gap between the front element and the body. The goal is to eliminate this gap. Not all Kowas have such gap. Two of my three Kowas had it.

Sometimes you might find a tab with a longer back part. If that’s the case, you can simply take out the longer tab and enjoy shorter minimum focus. This process is easily reversible because you can restore the lens back to normal by simply putting the tab back. Not my case.

Take out each brass tab by removing their screws. They’re tough. DO NOT PROCEED IF YOU’RE UNSURE ABOUT PERMANENTLY MODDING YOUR LENS. In an ideal world, instead of the file and pliers we would have the tab held by a vise and a fine metal saw to do the cut. Too bad I don’t live in an ideal world. Using the pliers, snap one end of each tab to make them shorter. File the cut clean.

By cutting them we change how far the front element can travel and eliminate that pesky gap. Screw all the tabs back with he short part facing the back of the Kowa. I had a longer tab in all my lenses. It turned out to be the key to infinity focus. The top of it is just a tad higher than the others so, when I tested without it, I could focus way past infinity and that is no good. Cut it shorter too and put it back in place.

If you change your mind AFTER cutting the tabs, the best you can do is rotate one of them 180 degrees, restoring the original minimum focus stopper, while the others hold for infinity.

Reassemble the lens. When you put back the glove, there’s a chance that the Kowa’s focus markings won’t match. Let’s fix it. Loosen these three screws around the markings skirt. This allows it to rotate. Focus to infinity. Adjust the markings, tighten back the screws.

Time for testing. Here’s our previous minimum focus, at 4’8″. Here’s the new one, at 3’8″. The stretch factor has been further decreased to 1.7x.

On James’ tests he was able to come down to 2’8″, and stretch dropped to 1.55x. Nothing comes without a “Price”.

Since we’re already in the subject of price, I’m gonna take a moment to thank James for the effort of putting all the data on the forum and then clarifying my many questions through detailed messages. Thank you, sir, you are an inspiration!

Now, if you’re still watching and had the guts to do the mod, please let me know how it went on the comments! Subscribe if you haven’t yet, because next week we’ll be improving the Kowa’s optical performance with a highly recommended tune up that you can do by yourself. See you then! Ferradans out.