Are there any of you engineer/mathematician types out there that can explain the calculations, the angles, the radius, adn the theory that make asymetric tilts work, such as those on the Sinar P2 and the Linhoff 6x9.

-- Kevin Kolosky (kjkolosky@kjkolosky.com), January 27, 2001

Answers

Asymmetric tilt is identical to axis tilt except that the line of fixed focus is now moved off center. No additional math involved.

-- Richard Ross (ross@hrl.com), January 27, 2001.

I am talking about designing one for my own use, not for using one I already have. Kevin

-- Kevin Kolosky (kjkolosky@kjkolosky.com), January 27, 2001.

Not much theory involved. Once you pick the axis of rotation, you just need a radius that gets the mechanism out of the way of the groundglass or lensboard. Decide on maximum tilt angle. From there on its designing the track/gearing to achieve the movement.

-- Glenn Kroeger (gkroeger@trinity.edu), January 27, 2001.

Glen there must be some theory (why they are better than another system) or they wouldn't be used. Kevin

-- Kevin Kolosky (kjkolosky@kjkolosky.com), January 27, 2001.

Kevin: It is not an issue of theory but of practicality.

Consider the rear standard. When you apply a tilt or swing, if the axis of that movement intersects the image area, objects along that axis will not change focus. For many cameras, those axes pass through the center of the groundglass, thus "center-tilt" designs. For base tilt cameras, the axis doesn't intersect the image area at all, so the entire image changes focus.

Sinar, to their credit, noticed that most people use a "two point" approach to focusing. They identify something in the lower portion of the image, and something in the upper portion of the image. By bringing these two areas into focus simultaneously, they arrive at the proper tilt to achieve the desired plane of focus. Sinar realized this was easier done if one of those areas didn't change focus as the standard was tilted, so they designed a system that placed the axis about 1/4 of the way into the image area. That seems to be a good place for it, but its not magic. They could have placed it farther into the image area, or closer to the edge, but where they placed it works pretty well.

There doesn't seem to be any advantage to asymmetric tilts on the front standard. Ideally, that axis should pass through one of the nodal points of the lens (I think the rear, but I could be wrong). Center tilt cameras come close, but each lens would need to be mounted in a custom board to achieve NO focus shift.

Many fine cameras, including the one I use, use base tilts. Everything shifts focus, but I just refocus as I tilt. Each system has advantages. Many base tilt cameras are yaw-free which is nice for architectural work.

Ultimately, any of the designs can achieve the same relative position of the lens and film, thus the same image. Its just a matter of convenience and what the operator is used to.

For many years, Sinar had a patent on asymmetric tilts. Now that the patent is expired, some other cameras include the option. But its still just a pragmatic, not a theoretical solution to focus plane management.

-- Glenn Kroeger (gkroeger@trinity.edu), January 28, 2001.

Kevin, what kind of photography are you planning on doing with your camera?

My experience is that where an assymetric design (and my experience with an assymetric design is strictly limited to working with Sinar P, P2, and C cameras --the Sinar F is a base tilt design) works best is in a high volume studio where you might be doing several set ups in a day and need to streamline the production process where ever possible; hence the need for (A) a yaw free design and (B) a system that speeds up the process of finding the best depth of field solution using a built in Scheimpflug calculator (the famed two point focusing system of the Sinar) and a built in hyperfocus calculator.

If you are doing field work, photographing architecture or making portraits, a camera that is yaw free (the tilt axis needs to be located below the swing axis) and rise in the focal plane may be the better solution.

Since most of the work I do falls into those categories, I found the Arca-Swiss design to be what works best for me.

Good luck to you on the project! I'll be interested to hear how it is moving along.

-- Ellis Vener (evphoto@insync.net), January 28, 2001.

Ellis and folks. I own and use a Sinar F1/F2 8 x 10, and I use the focusing system that is provided for that camera. But in looking at that P2 camera it seems to me that one could take that tilt design and transfer it rather easily into wood and use it on a field camera. I am not talking about machining in gears and etc so that it could be operated by turning a knob, but rather making it a tight fit with some sort of screw to stop its travel when everything is set up. Most of the field cameras I have looked at seem to have the base tilts such as my Sinar, and my thought is Why not incorporate the asymetric tilts if they are easier to use, and especially so if the patent has run out on them. Kevin

-- Kevin Kolosky (kjkolosky@kjkolosky.com), January 28, 2001.

Kevin:

Ebony and others are already doing this... see:

http://www.ebonycamera.com/asymmetrical%20movements.html

-- Glenn Kroeger (gkroeger@trinity.edu), January 28, 2001.

THANK YOU GLENN. JUST WHAT I WAS LOOKING FOR. AND THANK YOU TO EVERYONE ELSE AS WELL. kevin

-- Kevin Kolosky (kjkolosky@kjkolosky.com), January 28, 2001.

Now that I have looked at the Ebony site I wonder why this sort of camera cannot (is not) being built in the United States and at a price where people could redily afford it. I am a Chevy man (meaning I prefer to buy things made here and only buy things made everywhere else when the equivalent isn't made here. I know I know, overhead and profit. How about a bunch of large format lovers getting together and starting a company to build these things so that the profits come in the form of prices such that people can afford to buy them. Kevin

-- Kevin Kolosky (kjkolosky@kjkolosky.com), January 28, 2001.

According to the latest trade sources, sales of LF equipment are in decline, and I, for one, wouldn't put my own money into such a venture.
The current supposed resurgence of interest in LF is relative, and is still just a drop in the photographic ocean. Despite all the photography journals, and the trade, telling us that LF is alive and kicking, I personally don't see much evidence for it myself. Both Kodak and Fuji are showing their confidence in LF by reducing the sizes and emulsions available to LF users.
LF may be the 'in' format for top fashion photographers at the moment, but fashion, being fashion, is a fickle market that changes as the wind blows, and shouldn't be taken as any indicator of the future.
Personally, I think the LF equipment market has reached near saturation, with as many people selling up as are joining the LF ranks. I know that prices for some secondhand LF gear are at an all time low, in real terms, and even Nikon have gone against their own trend and actually reduced the price of their LF lenses.

If you want to pursue the dream of the 'perfect' LF camera, then go ahead, but I wouldn't plan on getting rich off of it. The market may be a lot smaller than many people would have you believe.

-- Pete Andrews (p.l.andrews@bham.ac.uk), January 29, 2001.

Greetings,

In addition to Pete's comments, I don't think there is such a thing as a perfect LF camera. It simply boils down to how one uses the camera and what "feels" natural for them. A person shooting landscapes and a person shooting tabletop will most likely use their cameras very differently, so there's no one shoe fits all.

Taken a step further, most manufacturers are not going to tool up to produce several different cameras for a relatively very small market. I don't see LF going away, but it's not going to be in the same genere as the mass market.

Regards,

-- Pete Caluori (pcaluori@hotmail.com), January 29, 2001.