Axis or base tilts ???greenspun.com : LUSENET : Large format photography : One Thread
I've been reading about the different "types of tilts" available on field and view cameras but am still unclear as to what the differences are. One article on this site suggests that you may wish to adjust focus (one of the steps) by using the base or the axis tilt method. Is there a way to tell which tilt adjustment is which on a camera ? I presently have a Calumet C400 and also a Prinzdorff field camera which I am comparing to attempt to see if there is a difference. I also have read that cameras like the Ebony and Sinar have asymmetrical tilts and was wondering if anybody could offer a simple laymans explanation on what this does ? Thanks for any help that you may offer.
-- GreyWolf (email@example.com), December 31, 2000
Grey Wolf: Your Calumet C400 has axis tilts. Can't remember what the Prinzdorff has. Haven't seen one in years. The axis tilts are at the center of the lens or back, base tilts are at the bottom. I prefer axis tilts for the lens and base tilts for the back. With lens axis tilts, less refocusing is needed when the lens is tilted. I prefer base tilts for the back for the same reason. When the camera is tilted down and focused into the scene, the back can be tilted to the rear to straighten verticles and bring the foreground into focus a little easier than having to move the whole standard. Either will work, but that is my preference. The Sinar tilts around the base, but it slides in the tilting mechanism to keep the lens and back in the same place. It is kinda what you get used to, as both systems can be set up quickly with practice.
-- Doug Paramore (firstname.lastname@example.org), January 01, 2001.
Grey, the base tilts are usually designed to be yaw free...yaw only comes into play when using front tilt and swing simultaneously. If the pivot point of the tilt is below the swing point, then the camera is yaw free, and has base tilt. The benefit of this is, you do not have to continual adjust one of the two movements when changing the other. If the tilt point is just slightly above swing point, then the camera is not yaw free, but still has base tilt. In landscape shooting, Yaw is a very rare occurence, and in my opinon the loss of axis or assymtrical tilts is not worth the benefits of yaw free.
Axis tilts are just that, they tilt on a given axis, some cameras have fixed axis tilts which are usually at the center of the lens, (hence the name lens axis tilt) which is ideal, while other cameras such as Horseman L series has variable axis tilt, the user slects at what axis the lens will be tilted from.
Doug, I am confused about what you write. I do understand that rear tilt will alter the perspective, however, wont it also throw the film way out of the plane of sharp focus? If you pointed the camera downwards and kept the standards paralell, you would have converging verticals, but the plane of sharp focus will be exactly on the film plane. Now if you use rear tilt to rid the converging verticals, the plane of sharp focus still lies paralell to the front standard, but yet the back is tilted moving the film way out of the plane of sharp focus. At the very center of the film it should be fine, but at the top and bottom it would far exceed the allowance that Depth of Focus would permit, regardless of the f stop shot at? Can you, or anyone else, explain how this works? I see this written in view camera books, but it never addresses how this focus shortcoming is overcome? thanks
-- Bill Glickman (email@example.com), January 01, 2001.
Note to Bill: When setting up the shot with the camera pointed down slightly and a lot of foreground included, you make the initial focus point the more distant point, such as the horizon or distant mountains, etc. When you tilt the back to get the foreground in focus, you will find the back is just about verticle. If you have verticles that are critical, you may need to touch up the fine focus with front tilt, but most times not as stopping down takes care of the tiny bit of refocus needed. Tilting the back means that the top of the back is being moved away from the nearest object, in effect giving more bellows extension as if you were focusing on a closer object. In use, it is very quick to do and only needs minor refocus after making the movement. It also makes the foreground objects slightly larger, which I find desirable in most instances. If you look at the camera from the side, you will that the back, lens and plane of focus intersect as they should. Play with your camera a little and you can see on the ground glass what is happening. The same thing can be done with axis tilts on the back, but you have to refocus a bit more. Hope this help,
-- Doug Paramore (firstname.lastname@example.org), January 01, 2001.
The Sinar assymetrical tilts and swings (only on the P, P2, X, and only on the rear standard of the C & C2 models) are a sort of modified base tilt system that places the tilt axis into the picture area, but well below the center line of the negative. Arca has an optional similar system (Orbix) but only on the front (lens) standard.
I prefer a yaw free design, which by necessity of design eliminates axis tilts (unless as Bob Salomon of Linhof's USA distributor, you tilt your camera on it's side.) eliminates axis tilt designs. A yaw free design requires the tilt mechanism (regardless of where the axis is) to be located below the swing mechanism. Not all base tilt designs are yaw free.
-- Ellis Vener (email@example.com), January 01, 2001.
Actually Ellis the first yaw free camera ever produced was the original Linhof Kardan which had a unique knuckel type joint that did both the tilts and the swings from the same point.
That joint was called a kardiac (sp) joint in German and was the derivation of the Kardan model name that Linhof uses today.
Currently Linhof makes 3 different yaw free cameras and one that can be nodified to be yaw free.
Both the GT and GTL models have 2 tilt points. One on each camera below the swing point. On the GTL there is also an in the film plane tilt point and on the Gt a center tilt.
The E can be modified to become a GT.
In 69 the M679 has 2 tilt points as well, one below the swing and one above the swing point.
-- Bob Salomon (firstname.lastname@example.org), January 01, 2001.
Bob's history is correct. But more to the point, why should you want a yaw free camera?
If you ever make photos with the base of the camera inclined and both front and rear standards tilted back or forwards and then swing used, being able to keep the two standards vertically parallel to each other makes your life much simpler. This situation occurs often when photographing products in the studio and in some architectural situations.
If you are making landscape photos which make fewer geometrical demands on the camera, this situation is less likely to occur so you may not need a camera that is yaw free if that is your primary goal. Still my feeling is it is better to have than not.
-- Ellis Vener (email@example.com), January 02, 2001.
If you have a center axis camera the image shifts are minimal or (with optical axis cameras) virtually non-existant.
If you have a base tilt camera the image and focus shifts can be severe and with those types of cameras a yaw free design may be preferable. Especially as with a base tilt camera when doing a tilt and a swing it is possible to create enough yaw that the subject may not be able to reposition as the shooter wishes.
Although Linhof rather quickly discontinued the original yaw free Kardan and went instead to designs with a large degree of direct shifts and canter tilts Sinar did not. The original metal Sinar was a base tilt design and for that design a yaw free movement became important. especially as it was a camera commonly used for 3 point perspective.
So do you need yaw free? Probably not. The vast majority of all large format images ever made for all fields have been with yaw prone cameras. But, especially with base tilt designs, yaw free can be worth the additional weight.
-- Bob Salomon (firstname.lastname@example.org), January 02, 2001.
How many of us would use a view camera if its only advantage was the larger size of the negative (or positive)? With the problems of film flatness, the shrinking availability of film types, the extra weight of the equipment etc. combined with the excellence of medium format cameras and films, why bother?
Of course the answer, at least for me, is the amazing control of the image that camera movements can provide.
I enjoy the intellectual exercise of looking at a scene and trying to visualise how the application of various movements will affect the focus, position, and shape of the image on the ground glass (and then seeing if I'm right). To do this successfully requires an understanding of what each movement or combination of movements does to the image. Whether your camera has axis or base or asymmetrical tilts doesn't really matter as long as you appreciate that the effect of tilting the lens does vary between the various types.
I prefer axis tilts because of the relatively minor effects they have on focusing. Base tilts not only alter the distance between the centre of the lens and the film plane (requiring a greater degree of refocusing), they also inevitably produce a slight fall in the position of the centre of the lens - so using base tilts can make it more difficult to accurately predict what effect the sum of all planned movements will produce.
As to yaw, I agree with Bill and Ellis that it is of little or no relevance to most landscape photographers and all else being equal, I would personally go for a camera with axis tilts rather than one with a yaw-free design.
-- Philip Y. Graham (PYG@plastsurg.com), January 02, 2001.
The real answer is that no method is without its advantages and disadvantages. The advantage of on-axis swing or tilt is that the focus isn't disturbed too much (although this depends on the lens design, and whether a sunken lensboard is used). The disadvantage is that the optical axis of the lens no longer intersects the centre of the film plane, and so some shift must also be applied if the lens is to give optimum image quality.
The disadvantage of base tilt is that the focus is invariably shifted, but the advantage is that some compensation for optical axis shift is automatically applied when the lens is tilted forward.
Whatever system your camera has, you quickly get used to it. Like the gear change on a car, no two are the same, and none are perfect, but few people actually let their lives revolve around it.
-- Pete Andrews (email@example.com), January 03, 2001.