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Flange Focal Distance Range

Michael Panfeld

Michael Panfeld

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Hi: does anybody know what the range will be in mm for the new internal backfocus mechanism destined for the EPIC/Sacrlet? The Canon EF's FFD is 44mm, the PL's is 52, which at a minimum is 8mm of travel. I am asking because I am thinking about designing mounts or adatptors for OCT19 (61mm), BNCR (61.5mm), on down to Canon FD (42mm). Any insight on the mount or focus mechanism specs would be appreciated? Thanks
 
Michael, the real question is how much depth is there between the mounting surface, where the flange plate of the mount attaches, and the OLPF or other outer-most optical element within the camera. The actual sensor block range of travel is probably very small, probably < 2~3mm. Proper FFD for each mount type is achieved by creating a mount system that sets the mount at the proper FFD. The mounts attach via 4 bolts, unless something has changed.

Theoretically, you should be able to remove one mount, like the PL mount for example, and replace it with a Canon mount in a matter of a couple minutes and should not need to adjust the sensor block. But if you do need to adjust, the sensor block adjustment is there.
 
.001mm?

.001mm?

Irmeli R said:
that would require the mating surfaces to be ground to 0.001mm precision and then not coated by paint. i doubt this will be done but then again adjusting the back focus with the internal actuators should not take long.
Click to expand...
I find it pretty funny when people say .001mm. Considering that human hair on average is .030mm. First Denz "skips" a zero with their claim of .001mm precision and now this(please, nothing personal) I've designed dozens of gadgets and would never dare claim this kind of precision. ANY dirt, oxidation or invisible spec of dust will throw that out the door.....
Rant over!!!
 
there is (much) more to it

there is (much) more to it

Irmeli R said:
you're right jacek..but even a 0.01mm precision requires the contacting surfaces not to be anodized or painted, but ground or high precision machined like this hard front:
Click to expand...
Irmeli,
With all due respect
Its all a bit more complicated than that:
Hard anodize builds up material- up to .003"(.075mm)
Some better anodizers can control that to a degree but you'll need to spec it for them.
Regular- non hard anodizing will remove or build .0002-3"(.007mm) depending on the place that is doing it (the etching, etc.)
When you spec a BB finish that will actually build up to .0005" depending on finish spec'd
Really even .01mm will require bare metal finish-no treatment for consistant results. Everything else is just marketing spiel....
 
Sorry

Sorry

Haven't read your post carefully.
 
Jeff Kilgroe said:
The actual sensor block range of travel is probably very small, probably < 2~3mm.
Click to expand...

Jeff, that is my very point. The Canon EF mount, which RED says will be one if the available mounts, has a 44mm FFD. The Canon FD mounted lenses have a 42mm FFD. So, if there is that 2-3mm range of lens block travel, then I might be able to add a cheap $30 FD to EF mount to my FD lenses and use them on the EPIC/Scarlett's EF mount by setting the backfocus. Waaalaaa! A whole new set of lens choices (Canon FDs produce fantastically rich images).

The question that needs to be answered in order to know if I can do that is: exactly how much range will the sensor block have and what is its range of travel relative to the theoretical FFD "zero" point. In other words, will the sensor block have +/- 1.5mm (for a total of 3mm of travel) relative to FFD "zero", or perhaps +.5mm and - 2.5mm (for that same 3mm range), etc... Maybe the range will be +/-2mm or maybe just +/-1mm. Anybody know?

Also, how does RED plan on having the sensor block stay in the same plane as it travels along that 3mm of travel? I mean wouldn't wear and or elasticity of the chain, belt or whatever mechanical connection exists bewteen the (I am assuming) 3 or 4 threaded posts knock the block out of plane very quickly with .00000 etc mm of tolerance?

Thoughts?
 
I'd be stunned if there wasn't a worm gear or rack of sme sort in there. But you have this all wrong in thinking about the range of travel -- it really doesn't have to be that long. Each lens mount will come mounted to a flat plate of metal which is what is mounted to the camera face. Between the lens mount and the metal plate there can be a variety of thicknesses of a collar to get the mounts to a correct depth. So start with a design that gets the metal plate as close to the optical low pass filter as makes sense and then shim plate out all the mounts from there. then the sensor travel is only needed to correct for imprecision in the mounts, not for the actual differences in the distances between them.
 
Exactly what Mitch said.

The guys at RED have also maintained that mounts can be swapped in the field and in just a few minutes. Only 4 bolts -- as clearly seen in all the renders and prototype photos. While precise back focus is desirable, there is some room for error and fluctuations. After all, there is a margin of error every time you mount a lens and lock it into place, whether it's a PL mount, Nikon, Canon, etc..

The backfocus adjustment on the new DSMC brains supposedly has a multi-axis capability for factory and service-center corrections. There is a mechanical user adjustment as well that moves the sensor block forward or back along the optical path. The total range of adjustment for this is at most 2 to 3 mm, or so I would think.
 
ALLSTAR OCT-19 adapter

ALLSTAR OCT-19 adapter

Michael - I just received ALLSTAR's OCT-19 adapter. See http://www.reduser.net/forum/showthread.php?p=686638#post686638. You own a great set of lenses! I wish I had a Super Baltar 20mm. - John

Michael Panfeld said:
Hi: does anybody know what the range will be in mm for the new internal backfocus mechanism destined for the EPIC/Sacrlet? The Canon EF's FFD is 44mm, the PL's is 52, which at a minimum is 8mm of travel. I am asking because I am thinking about designing mounts or adatptors for OCT19 (61mm), BNCR (61.5mm), on down to Canon FD (42mm). Any insight on the mount or focus mechanism specs would be appreciated? Thanks
Click to expand...
 
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