The Duclos Multi-Mount® is an interchangeable mount system that allows the user to quick swap between common lens mounts, in the field, with minimal tools or knowledge of lens design. It's certainly not a new concept... But Duclos has approached the interchangeable mount system with a high quality, reliable approach. Here, we'll go over the basics of how to swap the mount and adjust back-focus.
So switching the mount... It's as easy as spinning the knurled lock ring just below the mount flange. Rotate it counter clockwise until the mount disengages from the sub-mount. This lock ring keeps the mount pulled tight against the lens to ensure a secure, reliable fit with every mount. Once you've removed the mount you can attach a different mount. Every mount has a stainless steel plate at the bottom with a notch that interfaces with a pin on the Multi-Mount. This keeps the mount clocking true and prevents rotation once installed. Locate this slot and align it with the pin on the sub-mount, place the flange on the sub-mount and tighten the knurled lock ring. Some mounts such as Panavision will require tightening the lock ring before the pin and slot can engage but don't worry, they'll pair up.
Once the flange is in place and the lock ring is tightened, it's a good idea to give the lock ring a little tug with a rubber cord or jar opener to ensure it's as tight as possible. A simple power cord will do the trick (don't forget to unplug the power cord first). All-in-all this procedure should take a mere 60 seconds to remove and attach any combination of mounts. Easy.
The Multi-Mount is great but it isn't magical. You'll still need to adjust the back-focus when you switch between mounts. This is a common practice regardless of the interchangeable mount. There are many, many causes of back-focus imperfection such as transportation vibrations, temperature fluctuations, or simply settling materials. Most manufacturers use shims to adjust back focus which requires removing the mount and adding or removing shims to adjust the back-focus. These shims are usually offered in sizes as small as .0005". That's pretty small... For example, your average printer paper is .004". The smallest adjustment common in a cinema lens is 10x smaller than your average piece of printer paper. It's a very, very critical adjustment that must be maintained consistently and frequently. The Duclos Lenses Multi-Mount uses an internal adjustment accessed through a small slot at the rear of the sub mount.
There's no need to disassemble the lens to adjust back-focus. We recommend allowing a professional lens technician to calibrate back-focus properly but it's certainly not required if you have the tools necessary. If you purchased your lens from Duclos Lenses then you have two years of free maintenance which includes back-focus calibration - use it! Otherwise, here's a quick tutorial on back-focus adjustment. You'll need a .050" allen wrench, which is included with the Multi-Mount, and a good pair of eyes.
Start by loosening the three small setscrews at the rear of the sub mount with a .050" allen wrench. Two or three turns should do it, no need to remove the screws, just loosen them. Once those three set screws are loose, you can poke your .050" allen wrench through the slot at the base of the Multi-Mount to rotate the ring inside the Multi-Mount that adjusts back-focus. Most users won't have access to a test projector so we'll detail the adjustment procedure for use with a camera.
Set the camera up on a tripod or any stationary rig. Mount the lens on the camera and aim it at a detail rich subject - a focus chart, resolution chart, or if your name is Ketch, an Italian super model works well too. Set the distance between your camera and test chart at a convenient number that's available on the lens' focus scale. Usually 5 feet works well for most situations. If space is limited or if your monitor is small you'll want to be a bit closer to your subject. If you're unsure, just start with 5' and move forward or backward from there. Once you've taped out a distance set the lens to the telephoto end of the zoom. This is a must. You have to start at the telephoto end. Rack focus until your test chart is as sharp as possible. Don't worry about the focus scale yet. Once you've nailed focus, zoom to the wide end and you'll notice that your image may have softened a bit. Now, don't touch the focus ring on the lens. Adjust the back-focus ring at the rear of the Multi-Mount with your allen key, or any tool that fits in the slot and works well, until you get the sharpest image. Once you've chosen the sharpest setting with the back-focus ring, zoom back to the telephoto end and use the focus ring to obtain the sharpest image again. Repeat the above process a few more times until you can focus at the telephoto end and zoom to the wide end and the image looks sharp at both ends without adjustment. Now your back-focus is set properly. You can tighten down the three set screws at the rear of the sub mount with the .050" wrench. Not too tight, just enough to snug them.
All done! You'll want to do this often to make sure back-focus is calibrated. It's a quick procedure that can be done anywhere you can set up a camera. If you ever have any issues with your Multi-Mount, don't hesitate to contact a Duclos Lenses representative and we'll be glad to help you out however we can. Thanks!
Duclos Lenses has developed this product with the support and approval of the Original Lens Manufacturer. Therefor, the factory warranty is FULLY maintained. However, as part of our agreement with the Original Lens Manufacturer, we ask that you process all warranty repairs through Duclos Lenses should the need arise. This allows us to monitor the results of our products as well as provide valuable feedback to the Original Lens Manufacturer. For additional questions, warranty or general service, please contact firstname.lastname@example.org.