65mm Filter Size?

Since the URSA Cine 17K 65mm will not have internal ND the next option is external. However, this raises an important question: Are 4x5.65 filters too small for the coverage? Do you need to go to 6x6 filters for this camera?

As I haven't shot 65mm film in the past, nor have I had the opportunity to work with the Alexa 65, this becomes and important question. Obviously you need lenses that cover 65mm size. But when using a matte box and filters what size is needed?

Remember the Cine 65 camera sensor has a sensor that is 50.808 mm horizontally and has a diagonal 55.9 mm.

65mm is just medium format lenses. 4x5.65 filters are fine.

101mm X 143.51mm = 4x5.65

Well, I think it's possible that wide enough lenses could see the edge of a 4x5.65 matte box. But I'm not 100% sure about that.

I know with 4x4 and wider than 16mm on Super 35 you easily see the side edges. So 16mm on VistaVision/Full-Frame you definitely will see the edge with 4x4. I know for sure that 4x5.65 is safe with 16mm on VistaVision/Full-Frame, but once you start going wider I'm not too sure since I have never gone wider than 16mm on VistaVision/Full-Frame.

Either way, it sounds like the good news is 4x5.65 is safe. But wanted to be absolutely certain.

I think the game plan was to release the Cine 65 late this year, so I would imagine that we’ll know the filter limitations as the camera is ready to ship.

I know with 4x4 and wider than 16mm on Super 35 you easily see the side edges. So 16mm on VistaVision/Full-Frame you definitely will see the edge with 4x4. I know for sure that 4x5.65 is safe with 16mm on VistaVision/Full-Frame, but once you start going wider I'm not too sure since I have never gone wider than 16mm on VistaVision/Full-Frame.

The format is ultimately less important than the size of the front element, Tim. Some very wide angle lenses; on even smaller formats can be testing. For example the J11/HJ11 B4 wide angle lenes have an extremely large front element, larger I would dare say than some telephoto FF lenses; the Chroizel Matte box I had where I could use both 4x4 and 4x5.65; rarely if ever needed even the larger size, so what Shaheed says makes perfect sense.

There’s no limitation.

Only the size of the lens you’re putting on it.

I have a set of converted Mamiya 645 primes. They’re smaller than a lot of 135 format lenses.

My existing NDs work just fine.

JB

There’s no limitation.

Only the size of the lens you’re putting on it.

I have a set of converted Mamiya 645 primes. They’re smaller than a lot of 135 format lenses.

My existing NDs work just fine.

JB

Thanks JB! I guess this really is lens dependent. Can't wait to see footage from the camera!

Some of my old LF stills lenses have much smaller filters. Including lenses that cover an 11x14 sheet of film.

What matters is angle of view AKA the wider you go the bigger the issue. How far from the front the filter is placed. If the filter is 1metre from the lens you'd need a huge filter. If it's almost touching the lens you need something just bigger than the lens.

It's simple enough to draw a triangle . The point inside the lens is one corner. The distance from that to the filter gives you to the two sides. That's enough to figure out how big you need.