How many people would like a B4 mount 35mm adaptor

[Phil Bloom]

Is there a market for an affordable alternative to the pro 35?

[Bob Hart]

It might become a parallel market pretty much llike what has happened with the alternative adaptors currently in the Mini35 product space - I purposely say product space not marketplace because the alternatives have created their own, a sort of Henry Ford analogy if you will.

You could have it tomorrow if Quyen stuck a correctly positioned B4 mount on back of his existing 50mm Minolta based relay arrangement in place of the mount for JVC or Canon flip models.

The available field-of-view onto the groundglass is sufficiently confined for a 2/3" CCD. I've tried it, albeit with a JVC KY-F50 camera head, a LETUS35 FLIP for XL and bits and pieces all gaffataped and lackybanded to a piece of wood.

I guess a good little reason why it has not happened is that B4 mount cameras are a little expensive to be experimenting with and who would likely loan their 750 or 900 for the experimentation?

If the older B4 mount Betacams are the same as modern B4 mount cameras in terms of flange to focal plane etc., then one of these would be a viable test bed.

Dennis? 50mm Nikon f1.4, bring it forward of "in-air" flange about 5mm - 8mm, gaffer it in or on the back of your new flip/Brevis, sit it on a housebrick in front of a Cinealta on a benchtop. Plug in the monitor, power up, stand in front and smile. Looking forward to your test grabs.

[Jon Wolding]

I hope to pick up an HPX500 in the next 8 months... and I'd love to be able to quickchange to an adapter.

[Dennis Wood]

Bob, you're an intuitive fellow. We're on it already :-)

[Igor Babic]

Bob, is there then a problem with 3ccd color alignment?

[Bob Hart]

Igor.


That is something I cannot predict. Any adaptor relay even to a 2/3" CCD based on a 35mm still-camera lens will only be using the centre portion of that lens and hopefully, at 50mm focal length, a relatively small angle of incidence upon the CCDs. The "in air" flange to focal plane distance of the B4 ENG lenses and the Nikon F mount lenses differs by only a few millmetres.

P+S Technik use a custom relay lens and another sweet optic they call a field lens, just behind the groundglass on the Pro35.

It is obviously the gold standard and has a gold standard price to go with it.

My own rough testing was done on a JVC KY-F50 which is 1996 SD technology, not HD, although it is good for 700 lines in its specification sheet. The LETUS35 I tried it on was a XL flip version with the Minolta still-camera lens relay. This also has a close-up lens glued on front.

Quyen also uses on this version, a single element biconvex close-up lens reversed as a condenser about 15mm behind the groundglass. I have seen asymmetric colour fringing on the XL1 footage I shot during a music video.

This suggests centricity or angular alignment of the relay optics, the dioptre on front and the condenser is off. This does not surprise me given three known points of compliance in the path, the Canon mount itself, the junction between the bridge tube to relay lens, bridge tube to rear of flip enclosure. One trusts the centricity and angular alignment was good during initial build before shipping.

If the effect is caused by the relay lens itself, I would expect a second more symmetrical pattern of fringing imposed over the artifacts an inaccurate path would cause although it might not be readily visible if it is weak by comparison.

I think with alternative adaptors, precise centricity of all optical elements on the optical axis will have very much more to do with it than the actual optical performance of the relay lenses themselves.

A flip path complicates the achievement of centricity and angular alignment. If either or both are off, rainbows can occur.

Build qualities will have to be much improved for alternative adaptor performance to meet the requirements of the 2/3" cameras, professional standards the users aspire to and their clients demand. Quyen' and Dennis' move to CNC machined metal casework for their flip enclosures is a welcome step. With the quality move, a higher cost for the adaptor may be expected to accompany the greater care needed to achieve those qualities in the initial build and maintain them for the working life of the appliance.