Gecko-Cam IMS OLPF


It would be almost unthinkable for a rental house to not have a good lens test projector. It helps decipher the optical characteristics of your lens: geometry, aberrations, and focus.

But what happens when you use the same lens on a film camera and then a digital camera? Most digital cameras use an OLPF (Optical Low Pass Filter) in front of the sensor to reduce moiré effects. It’s usually birefringent crystal and works by slightly separating each ray of light into two or four rays that are slightly offset.

Birefringent crystal showing double refraction. Photo: APN MJM.

Birefringent crystal showing double refraction. Photo: APN MJM.

OLPFs are not standardized. They come in different thicknesses and grades of “diffusion.” In fact, you can swap OLPFs on RED Epic cameras.

The universal standard for flange focal depth of a PL mount camera and lens in the film days was 52 mm (give or take to compensate for amount of play in the gate). But if you have a filter between the rear element and image plane, the depth is increased by 1/3 the thickness of the filter. So, you have to adjust the depth of the camera’s lens mount accordingly to ensure accurate focus marks.

The Gecko-Cam lens projector, seen at many of the worlds largest rental houses, have an Interchangeable Mount System (IMS). It lets you to use different types of mounts on a variety of lenses for digital cinema and TV production.

 Gecko-Cam IMS mounts with OLPF for PL, Canon EF and Nikon F.

Gecko-Cam IMS mounts with OLPF for PL, Canon EF and Nikon F.

Now Gecko-Cam provides IMS mounts with and without OLPFs built in. This lets you see how the lens performance might differ on analog cameras compared to digital cameras. (Some day cine cameras will have sensors dense enough that OLPFs may no longer be needed, or are cancelled out, as we’re seeing on the latest Canon, Sony and Nikon digital cameras, but that’s another story.)

PL Mount: OLPF unscrews easily

PL Mount: OLPF unscrews easily

Gecko-Cam’s new IMS mounts come with 2 different OLPF filter thicknesses: 2.5 mm and 3 mm. They can be differentiated by the color of the rubber O-ring around the barrel.

Red: 2.5mm OLPF (Flange Focal Depth of 52.90mm)

Blue: 3 mm OLPF (FFD: 53.06 mm)

No O-ring: No OLPF (FFD: 52.00 mm)

Gecko-Cam was founded in Munich in 2002 by a band of ARRI alumni and cine service wizards. They make and sell collimators, lens test projectors, flange depth measuring tools, specialized lens and camera service tools. Gecko-Cam also distributes Wooden Camera, Element Technica, Tangohead, V-Bag, Bluestar, and many others. Gecko-Cam repairs and modifies equipment, services most lenses (even ARRI Macros), and has been a RED Certified Service Center since January 2011.

Gecko Cam will be at NAB in Booths C8530 and C8430.

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