This manual covers the basic installation and operation of your Letus Extreme / Economy 35mm adapter. Please note that the Letus35 Extreme will be used as an example in this manual. The majority of instructions are interchangeable with the Letus35 Economy. Any differences between the two will be noted.

Basic Letus35 Extreme / Economy Setup:

1. Initial Preperation
   Use the included Allen wrench to loosen the set screws holding the threaded ring on the rear of the adapter. Back the screws out far enough to allow the ring to spin freely on the adapter without coming off. A single turn of each screw should be plenty.
   • The Letus35 Extreme / Economy can be attached to your camera with or without rails. We highly recommend the use of rails espescially when using the Extreme.
   • Letus35 Extreme Only - If you are using a rail support with your adapter make sure that the rail mount bracket is fastned to the bottom of the adapter. Use the included screw to attach the bracket to the lower front of the adapter
2. Attaching the Letus35 Extreme / Economy to the camera filter threads.
   • If you are NOT using a rail support you will need to hold the adapter with one hand while you spin the ring (loosened in step 1) with the other hand.
   • Letus35 Extreme Only - If you are using a rail support you will have to first slide the adapter onto the rails and then up against the filter threads.
   With the threads of the adapter carefully aligned with the threads of the camera, slowly turn the ring in a clockwise direction until the ring is securely fastened on the camera. Do not over tighten as you can damage the filter threads on your camera.
3. Aligning the view
   
   • If you are NOT using a rail support: With your camera turned on and completely zoomed out adjust the adapter until the Ground Glass (GG) is squarely centered. When the GG is centered re-tighten the screws on the thread ring that you loosened in step 1.
   • If you are using a rail support, you can tighten the screws on the ring once the ring is fully threaded onto the camera. The ground glass (GG) should already be centered in your image with no further adjustment needed.
4. Zooming in
   Without attaching a lens to the adapter, turn your camera on and point it toward a bright white area that fills the entire frame. This can be the sky or a brightly lit white card / wall. Make sure your Letus Extreme / Economy is turned OFF and zoom in completely on the ground glass (GG) of the adapter. Depending on the brightness of the object you may need to use the camera's internal neutral density (ND) filters and adjust the iris until you can clearly see the specs / grain of the GG. If it is still too bright, attach the SLR lens and close it down until you can see the grain.
5. Setting the focus
   Once you are zoomed in on the ground glass and can see the grain clearly, use the auto focus function of your camera and let the camera focus on the ground glass element. Once it has settled on a focus point, switch to manual focus and lock this focus setting down. (Depending on your camera, you may need to use gaffer tape to lock / tape the focus ring in place.)
6. Filling the frame
   You can now zoom back out until the GG fills the frame completely without any vignetting. Lock this position down and take note of your zoom number for future setup reference.
7. Attach your 35mm lens
   If you have not done so already, attach your 35mm SLR lens to the lens mount of your Letus Extreme / Economy.
8. Power on
   Turn on the Letus35 Extreme / Economy using the LED switch. Point your camera at a white card to white balance your camera.
9. Shoot
   You are all set!

Advanced Letus35 Extreme / Economy Setup:

Changing Lens Mounts:

1. On the front of the adapter there is an interchangeable lens mount that will allow you to use different brands of lenses. This mount is held in place by three set screws.
2. To change the mount, remove your 35mm lens, loosen the set screws, and pull out the mount.
3. Replace the mount with the one desired, and re-tighten the three screws.

Measuring Focus:

1. The Letus35 Extreme comes pre-marked with the film plane on the side of the adapter. This is where all measurements for focus should be taken from.
2. If you are using the adapter with the Letus rail mount bracket, you can use the back side of this mount to attach your tape measure to for accurate focus measurements. The back of the bracket aligns with the image plane of the adapter.

Back Focus Adjustment:

**The back focus for your lens mount is factory pre-set, so it should not need adjusting.**

1. Setup your camera with the Letus35 Extreme / Economy using the preceding instructions, and attach a 50mm lens. (Any lens will do, but a 50mm is the most helpful.)
2. Place a Siemens star in front of the lens at a predetermined distance. It will be more helpful to have the distance be closer to the lens, and that the distance corresponds to a marking on the 35mm lens (4 feet or 1 meter is a beginning point). To determine the distance the star is at, you will need to measure from the film plane out to the star. (See above for how to measure focus.)
3. Using the SLR lens, turn it until it reads the distance that the Siemens star is at. (4 feet / 1 meter for example.) The image should be in focus at this point. If the image is not in focus, you will need to adjust the back focus.
4. To adjust the back focus of the adapter, keep every thing set up as it is currently. Hold the lens with one hand to prevent it from falling out of the adapter. Gently loosen the screws holding the lens mount in the Extreme / Economy.
5. Once the lens mount is loosened, gently and slowly pull the lens mount forward in 1mm increments. Each time you make an adjustment, watch the resulting image (preferbly on a preview monitor). You will reach a point where the image will be in focus at the reading marked on the lens. Once you have found this location, tighten the lens mount screws.
6. Make sure that when you are tightening the lens mount screws that the lens mount is square with the adapter. If it is not perfectly square, you may find that parts of your resulting image are not in focus when other parts are.
7. Now that your lens is set correctly you can double check it by setting the star at different distances, measuring it, and then setting the lens accordingly. The measurements should hold up through this process. If it doesn’t, then you need to adjust the back focus some more.