different in between base tilts & axial tilts

[exitnine]

hi everybody...

i have a stupid and simple question, oh well, sound like it anyway, so i won't b e shy to ask this, the question is what the different in between base tilts & ax ial tilts. i know right now different manufactories make different model 4x5 ca mera, and they have different tilts, like base tilts and axial tilts, which one i should choose from and which are those tilts for?

or can anyone direct me to some web site to find out more of this, many many tha nks...

thanks for your times and info.

jack jackngan@gis.net

[Glenn Kroeger]

Ultimately, there is no difference. Both can achieve the same final lens-film geometry. Base tilts are often more compact, and are used on field cameras and folding cameras. Center tilts are used on some field cameras and many monorails.

Center tilts can make tilts and swings easier. This is because the image is not thrown completely out of focus as the swings and tilts are applied. This works best when the nodal point of the lens and the film plane align with the tilt and swing axes. Even on many center tilt cameras, this alignment is not achieved so some focus shift occurs.

Focus shift is much greater with base tilts. With practice, you can learn to refocus as you tilt and work nearly as fast as with center tilts.

[Ellis Vener]

Actually there can be a major difference. Because a combination tilt and swing m ovement will induce yaw in a system (jargon for: the front and rear planes of the camera can no longer be parallel even on one line with each other) it is oft en desirable to have a camera that has a yaw free design. This requires that the tilt pivot be below the swing pivot. This requires a base tilt or a modified base til t camera, such as are found on the Arca Swiss, Sinar, one or two of the Linhof studio monorail cameras (not the Technikardan unless you tilt it on its side), a nd the big studio cameras from Horseman and maybe Toyo, and maybe a couple of others I don't know about. Not all base tilt cameras are yaw free! For exampl e the old Sinar Norma, the old Arca Swiss Basic, many of the flatbed unfolding cameras like the Linhof Technika, Toyo 45 series, and the Canham DLC. Mostly the need for a yaw free design is found in studio applications such as product photography. i have also found it handy when shooting architecture.

[Steve Pfaff]

Very good Ellis. Let me try to give our friend Jack an example. Suppose you are photographing a diagonal row of bottles. You want a view from somewhat above, but your camera doesnt have enough rear rise to allow you to keep the monorail (bed) level. So you tilt the whole camera forward. Now you have the angle of view you want, but your bottles are converging at the bottom because your film plane is no longer vertical. Fine, you tilt the film place back till its vertical. Now you want to get the whole row in focus so you swing the back. Opssince your rear standard is still tilted forward, when you rotate it for the swing, one side rises slightly and the other falls slightly. Now your bottles appear tipped. You might be able to correct this by tipping the whole camera, buta better way is to have the swing pivot above the tilt pivot. This way when you tilt the back up to vertical, the swing pivot becomes horizontal again and the problem goes away. I dont know why this is called "yaw". It doesnt seem to have much to do with the notion of yaw in aviation. Hope this helps. Its a minor problem, but it is there. On the other hand, Glenn is correct; axis tilts are often easier and quicker to work with. P.S. The Horseman catalog of a couple of years back has some diagrams of this, with pictures of what happens. Maybe you can get your hands on one.

[Glenn Kroeger]

OK Ellis...you win! I was avoiding getting into yaw. No question that yaw-free is an advantage... but you can still ultimately achieve the same geometry with a yaw-full camera by tilting the camera so that the rear standard is level, since the lensboard doesn't care how its oriented when all is said and done. And if Jack is mainly going for landscape, yaw is a really minor issue.

Ultimately, Jack, you need to play around with one or both type systems to get a first hand feel for the difference... diagrams only go so far. In an ideal world, I would prefer axial tilts but I live just fine with base tilts and no yaw.

[Bob Salomon]

A yaw free camera is simply one where the tilt point is at the same place as the swing or below the swing point.

That means that any camera that is yaw prone, regardless of it's type of movement, is yaw free when used on its side and any yaw free camera when used on its side becomes yaw prone.

basically with a center tilt camera, since there is no or minimal image shift, yaw is not a factor. With a base tilt camera it can become a major factor since there is an image shift when base tilts are used and the yaw may make it impossible to reposition the object on the ground glass as desired without changing the camera's position relative to the object. This changes the perspective of the shot.

[Doug Paramore]

Jack: The guys are right that yaw is a factor for working in the studio or even some architectural photography and some cameras are definately easier to work with in the studio. For field use, however, my preference is for a camera with front axis tilts and back base tilts. I find it a lot faster to use in landscape photography. A combination of front axis tilts and base tilts is great for getting everything into focus. Also, if you focus in a little with the back and tilt it back to get the closeup stuff in focus it gives a little more image size boost to the foreground, which I prefer for many scenes. One of the easiest to work with this way is with the Linhof disign, where the back is mounted on rods. You can almost tie the camera in a knot and still make the scene look like you want it. Doug