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FORBES70 65mm Motion Camera adapter prototype
  • muntusmuntus

    From the same brain that brought us Dog Schidt Optiks, Richard Gale has designed the FORBES70, a working prototype 65mm digital camera. Here's a link to where he discuses the basic design and shows examples of focal lengths with various medium format lenses:

    It's basically a box with a medium format mount on the front and some ground glass and a Black Magic Pocket Cinema Camera inside. This is a gross oversimplification of the design, but those are the broad strokes. It also has 6 stops of internal ND. Although the camera is not capturing as many pixels as some of the higher budget large sensor offerings, I find the larger format visually pleasing.

    Another link to some colored footage:

    Since it's being captured with Cinema DNG format, you should be able to get the image exactly how you want it.

  • 8 Replies sorted by
  • jazzroyjazzroy

    I like the test images but I don't get the point. The advantage of medium format is the sensor size, much more then the lenses, so why putting medium format lenses on a BMPCC sensor?

  • PsycoPsyco

    I think they are using an optical system (like a speedbooster) to compress the 65mm frame to the super16 sensor - but I'm not sure.

    Pictures look very nice.

  • robertGLrobertGL

    seems absolutely pointless

  • muntusmuntus

    @Psyco I think that's exactly what it is. Basically, making the super16 sensor behave as if it was a 65mm camera.

    @jazzroy I certainly think you're right. The advantage of the medium format size is the sensor size. What the Forbes seems to be doing is using the medium format front end as an imager that the Black Magic focuses on, much like the old 35mm adapters did for camcorders back before dslr video. With the 35mm adapters, there was no increase of resolution because the camcorders were still using small sensors, but the images were more pleasing because of the 35mm front end.

  • CFreakCFreak

    More dog sheite… I mean Dog Schidt.

  • tupptupp

    @jazzroy & @robertGL You can't see the "point" in the images? Look at the footage shot with the 40mm lens.

    @Psyco & @muntus: Yes. The Forbes 70 essentially is a fancy medium format DOF adapter that utilizes a BMPCC to capture the images.

    Other than probably being the only medium format DOF adapter in existence, the Forbes 70 is unique in how the optics behind the focal plane are highly optimized for the BMPCC's Super16 sensor.

  • jazzroyjazzroy

    @tupp I looked at the footage and that's why I think it's pointless. Althought I like the focus behaviour forcing a 65mm image to a 16mm sensor is a demanding task for the optics, and the result is blurry detail around the side edges of the picture.

    And I don't like it or think it can be used professionaly except for the artistic look.

    Why 16mm? Couldn't he go for APS-C or even FF with a 5D? That would have much more sense.

  • tupptupp

    @jazzroy Let's not jump to conclusions as to why the edges are soft in the posted test footage. Such an effect is optional, as shown by the edge-to-center sharpness in this earlier Forbes 70 footage:

    In the later narrated video posted by the OP, I think that Richard Gale explains that he was trying six stops of ND, and that he compensated in the exposure by opening the aperture behind the focal plane. The soft edges were evidently caused by opening that aperture so excessively. Gale mentioned elsewhere that the soft edges could have also been compounded by an improper alignment adjustment in that behind-the-focal-plane optical chain.

    In regards to "forcing" a medium format image onto a Super16 sensor, again, the Forbes 70 is essentially a medium format DOF adapter. You could replace the optimized behind-the-focal-plane optical chain with a simple macro lens, and you would get the same basic effect -- just with less efficiency (and perhaps without the soft-edge option). So, it is not necessarily a "demanding task," as any camera with such a common lens could be used, regardless of the sensor size.

    I can't speak for Gale, but I would guess that he chose the BMPCC because, when he first built the Forbes 70 a few years ago, it was the best quality camera at size that wouldn't require making a cumbersome housing for the unit.

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