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Jonathan Burch
18-Sep-2003, 04:29
I'm considering buying the Ebony RSW45 non-folding field camera from Robert White in the UK. This model offers limited movements: rise and fall and a centre tilt of 30 deg + 30 deg - is this sufficeint to be able to exploit the Scheimpflug principle ?

Thanks, Jonathan

Rob Barker
18-Sep-2003, 05:47
Easily - yes. The thread below about LF maths in the field contains a number of useful links to information about the theory behing using tilts and swings.

For a 150mm lens, suspended on a tripod 5 feet above the ground, the most common tilt applied is the get the plane of sharp focus to encompass near and distant objects and amounts to about 6 degrees.

Steve Lewis
18-Sep-2003, 05:52
Hi Jonathan

The short answer would be yes. The front tilt can be used to achieve Scheimpflug, but only in the horizontal plane. The camera has no front (or rear) swing, so Scheimpflug cannot be achieved vertically (unless you turn the camera on it's side).

When considering an Ebony recently, I looked at the RSW45, but found it a little limited. The RSW45 was designed specifically for landscape and architectural work and, for simplicity, has a movements on the front standard only. I ended up with the RW45 which has a full range of movements (excluding rear rise) and a better bellows draw, meaning I can use lenses from 65mm through to 300mm. A new RW45 is more expensive than the RSW45, but a good S/H RW45 is around the same price as a new RSW45.

On a personal note, when the shape of the image is not critical (90% of the time), I prefer to use the rear standard to achieve Scheimpflug. I find it easier to focus on the far point and tilt for the near. HTH

Steve

www.landscapesofwales.co.uk

Brian Ellis
18-Sep-2003, 07:36
Steve - Why can't you focus on the far and tilt for the near using the front standard as well as the rear?

The question of which you focus on and which you tilt for has always puzzled me a little. Fred Picker in his video says to focus on the far, tilt for the near when using the front standard. Tom McCartney, in the materials handed out in his large format workshop some years back, says to focus on the far and tilt for the near if the camera has base tilts and to focus on the near and tilt for the far if the camera has axis tilts. He doesn't explain the rationale for doing it differently depending on the type of tilts the camera has. Both Picker and McCartney were talking about this in the context of tilting with the front standard.

I'd be interested to know people's thoughts as to whether and why it makes any difference which you focus on and which you tilt for when using the front standard, why the method you use might be affected by whether your camera has base or axis tilts as McCartney says, and why Steve seems to think it's necessary to use the back standard if he wants to focus on the far and tilt for the near (as opposed to using the front standard to do the same thing).

FWIW, I've always used the front standard for tilts just because moving the back standard was inconvenient with the Linhof Technika camera I used for years. The only time I used the back standard for tilts was when I wanted to intentionally distort the shape of something in the forground. I haven't really had a fixed way of tilting the front standard. Sometimes I focus on the far and tilt for the near, other times vice versa, whichever way happens to strike my fancy at the moment. It's never seemed to make any difference which way I do it, though Picker and McCartney apparently think it does.

Maybe it's all just a matter of which you find more convenient, but both Picker and McCartney at least seemed to think there was one "right" way to do it.

Steve Lewis
18-Sep-2003, 09:56
Hi Brian

Doesn't using the front tilts (either base or centre) move the image circle off the centre of the GG slightly? Anyway, each to his/her own I suppose, but I find using the rear base tilt easier.

Steve

www.landscapesofwales.co.uk

N Dhananjay
18-Sep-2003, 10:05
Where you focus and tilt does depend to a certain extent on where your tilt axis is. The logic is that the lens to film distance stays unaltered around the tilt axis, but changes progressively away from that point (and therefore progressively changes the distances focussed at). The same principle lies behind the use of asymmetric tilts and why they make focussing easier. Like all such rules, I think it tends to over-simplify matters a bit but I guess the utility of these rules lies only in whether people find them useful or not. The rules were probably derived from specific kinds of subjects - I would say the typical landscape subject with the ground running away to the horizon with clouds in the sky (clouds and horizon at infinity).

This is probably easiest to visualize with rear tilts (the picture is the same with front tilts in terms of shifting the plane of focus i.e., ignoring the other issues of perspective etc which might lead you to choose tilt on either the front or rear standard). Imagine a landscape with the ground running away to the horizon. The distance appears at the bottom of the GG and the near ground at the top. Therefore for good focus through the entire area, the lens-film distance should be greater at the top and smaller at the bottom. If your camera has base tilts, focus on the far (i.e., with standards zeroed, focus till the bottom of the GG is sharp). Now as you tilt the rear standard, since the axis of the tilt is at the base, the lens-film distance at the base will not change but the lens-to film distance will progressively increase as you move towards the top of the GG (in other words, you are focussing at progressively shorter distance towards the top of your GG). If you had axis tilts and the horizon line ran through the tilt axis, it complicates matters a bit. Now as you tilt back, lens-film distance increases towards the top of the GG but decreases towards the bottom of the GG. So strictly speaking, you should focus on the middle distance and as you tilt, the top of the GG will progressively focus on closer and closer distances while the bottom of the GG will focus on progressively further and further distances. If the horizon line runs approx through the middle of the plane i.e., coincides with the tilt axis, as you tilt, the horizon line will stay in focus while the closer distances will come into focus at the top of the GG.

I think one is better off understanding the optical principles invlved rather than relying on rules like these and then running into a situation where they do not work. The basic principle to keep in mind is subject matter around the tilt axis will stay in focus as you tilt (because the lens to film distance is not changing).

As long as shape of the object and perspective issues do not impact the decision, I prefer using rear tilts because it is less demanding on the image circle and allows you to use the better performing center of the projected image circle but clearly there are times when front tilts are the way to go.

Cheers, DJ

Jorge Gasteazoro
18-Sep-2003, 10:26
Steve, if you are planning to do Landscape photography the movement specs you mention are more than enough, rarely have I used more than 10 in either direction for any of the movements.

The way I focus, since my camera has depth of field markings it is to focus on the far, mark the position, focus on the near, mark the position. Place the "focus" in the middle of these two distances and then tilt until I can get the best near focus. Usually it takes me 2 or 3 tries before I get the best focusing (smallest distance beteween near and far on the scale).

Good luck and enjoy the camera....

Doug Dolde
18-Sep-2003, 12:08
See Richard Sexton's explaination of asymetric tilts on Ebony's website.

http://www.ebonycamera.com/cam/assym.exp.html

Ralph Barker
18-Sep-2003, 12:51
Jonathan - I'm not familiar with the RSW45, and couldn't immediately find a listing of its specs on the Ebony site. But, if Steve's description is correct (i.e. no back movements), you may find it too limited to "exploit" the Scheimpflug principle to its fullest. Without back movements, the assumption would be that the camera is set up with the back "plumb" (at 90 to the ground), and then the front movements are used to control the plane of sharp focus. Or, that the whole camera is tilted, and the geometry of the subject doesn't matter.

Although this arrangement may be sufficient for most landscape situations, it would be very limiting for architectural or product photography, where back tilt and swing (and somewhat less so, rise/fall) are essential to both composition and focus control. Thus, if you are looking to "exploit" the Scheimpflug principle, you'd probably be better-served by a camera that has full movements - front and back.

Julio Fernandez
18-Sep-2003, 16:29
Jonathan et all: I am on the understanding that tilting the back changes perspective while tilting the lens does not. I frequently see this advice to tilt the back for focusing purposes, and if the above is true, totally ignoring the issue of perspective. Aside from architectural photography, should the landscape photographer not try rataining some of the visual features of the landscape or rather do a caricature? It is easy enough!

Steve Lewis
19-Sep-2003, 02:23
Hi Julio

The amount of tilt applied to the back is usually so small, and the landscape objects so irregularly shaped, that the image looks entirely natural.

I don't tilt the back where the shape of the image is important, say architectural work where I want to retain true verticals.

Steve

www.landscapesofwales.co.uk

Jonathan Burch
19-Sep-2003, 05:26
Many thanks to all of you who provided replies to my question. All of them were very useful and have convinced me that I should bear the expense and buy one of the Ebony's that has a greater range of movements than the RSW45.

Best regards, Jonathan.