Arca Swiss brainbox manual

[Bart Langenaken]

I bought an Arca Swiss brainbox and I'm looking for a manual. Anybody??

Bart

[Frank Petronio]

Ok, I'm curious and can't wait for the punchline. What the hell is a brainbox?

[Ellis Vener]

The Brainbox is a calculator that slides on the monorail behind the rear function carrier (RFC) and is used to detemine the optimum f-stop for a given spread between the near point you want in focus and the far point you also want in focus -- in short it is a hyper-focal focus point calculator. The way it works is you focus on the near point you want in focus and slide the brainbox up to the How hard can something be to light if you have a crane, a generator that can light a small town and a soft box the size of my house?

so that it just touches the RFC. You then focus, using the RFC, on your far point and push the button on the side on the side of the Brainbox. a spring loaded arm in the Brainbox moves forward and makes contact with the RFC in its new position. there is a millimeter ruler on the top of the Brainbox and also scales for different formats from from 6x9 to 8x10 (the different scales are necessary because of the different standards for what is considered sharp on the different formats -- 6x9cm images images need for critical focusing requirements than 4x5 which in turn need a tight consideration of what is "sharp' than 5x7 or 8x10) . For a given format you determine the optimum f-stop and then focus back t ohalfthe measure distance ( for example: If the spread is 10mm you'd back the rear standard up so the reading on the millimeter scale on the Brainbox is 5mm).

The Brainbox actually works quite nicely. And works much more quickly than it has taken you to read this far.

My question for Bart is: where did you find one? Did you buy it new or used? I don't think Arca-Swiss has made them in years and my understanding from my conversation with Martin Vogt at Arca-Swiss is that I have the last one that was made.

[Tom Westbrook]

Any chance either of you can post a photo of it? Sounds like a very cool accessory. Maybe it could be made into a DIY project? I'm picturing a clamp-on slide rule kind of gizmo.

[David Karp]

Tom,

John Sexton gave his workshop participants a note card with a chart containing much the same information for 4x5 and 8x10 formats. Just focus on the near and far points, split the difference, and refer to the chart for the f/stop. He gave f/stops for critical focus and "acceptable focus" for each format. I transferred the 4x5 information to a smaller card and carry it with me whenever I am photographing. I try to use the "critical" focus column, and the system works great for me. It may take slightly longer to use this procedure than a Brainbox, but I doubt that it is substantially longer.

Regarding the Brainbox, you might want to find out what level of sharpness the manufacturer finds acceptable. Joe Englander said that for the Sinar calculator, acceptable sharpness is set for a 2X enlargement, which is perfect for studio catalog photography, but perhaps not for other applications. See this article http://www.englander-workshops.com/documents/depth.pdf (http://www.englander-workshops.com/documents/depth.pdf). Also, check out Tuan's article on the subject: http://www.largeformatphotography.info/fstop.html#ref (http://www.largeformatphotography.info/fstop.html#ref).

If I recall properly, Sexton's 4x5 table closely correlates with the figures in Tuan's article.

[David Karp]

Tom,

I forgot to add that Tuan has a link in the article I referenced above to a DIY project for a calculator. The example is for an A-S F-Line camera.

[David Karp]

Oops. Here is the link: http://www.largeformatphotography.info/dofknob/#example (http://www.largeformatphotography.info/dofknob/#example).

[Tom Westbrook]

I do have that chart in my camera bag (somewhere). But, a quick little slide thing like Ellis describes avoids having to focus, stare at the tiny tick marks on a black rail under the dark cloth to see where the carrier is (harder on the Arca since the rear carrier is invariably sitting right on top of the nearest number), then try to remember the measurement while you refocus, find where the carrier is now under the dark cloth, then subtract and find the darned chart in your bag...

Maybe the depth of field scale mentioned on the Home Page at http://www.largeformatphotography.info/dofknob/ (http://www.largeformatphotography.info/dofknob/) would work almost as well, though, except I'd still have to remember that 1 or 2 digit number for about a 10 seconds--some days that's harder than it really should be ;^)

[Dominique Cesari]

I put three photographs of my Brainbox at :
http://perso.club-internet.fr/cesarigd/textephot/brainbox.htm (http://perso.club-internet.fr/cesarigd/textephot/brainbox.htm)

[Ellis Vener]

Joe Englander said that for the Sinar calculator, acceptable sharpness is set for a 2X enlargement, which is perfect for studio catalog photography...

When I owned a Sinar C (Sinar P rear standard and F front standard) I always used the 6x9cm format scale instead of the 4x5 scale. This worked very well for work ranging from studio tabletop "product" photography to landscapes and cityscapes being reproduced at virtually every scale from 1/4 page or smaller to mural size prints.

[David Karp]

Ellis,

Thanks for the great suggestion. It is one of those things that cause you to wonder: "Why didn't I think of that?" Thanks for the benefit of your experience. I am going to try it with the calculator on my Cambo 45 SF.