Recessed Lens Boards & Front Tilt\Swing

[rupal]

Will using a recessed lens board mess up front tilt & swing by making the lens axis off centre ?

And will i still effectively be able to use front tilt's & swing's ?

thanks.

[Emmanuel BIGLER]

Hello from the other side of the planet !

Will using a recessed lens board mess up front tilt & swing by making the lens axis off centre ?

As far as Scheimpflug's rule is concerned, only the total angle between the front and the rear standard matters. Hence the actual position of the rotation axis is not totaly crucial.
The interest of using front tilts or swings is that you can maintain your film plane parallel to, say, a vertical building and keep your verticals parallel in the image. This is not very important for landscapes where you do not have verticals or regular objects like square buidlings to be kept "vertical and parallel" on the image.
In principel when a lens is rotated around its exit nodal point H'=N' (this point is located exactly one focal length ahead of the focal plane), you do not have to refocus after applying a tilt or swing, and moreover for distant objects the image will not move very much on the ground glass.
Using a recessed board, if your camera is equiped with axis tilts crossing the optical axis somewhere, your rotation point will be located somewhere in the front part of the lens, at a certain distance, a few centimetres, ahead of H'=N'.
The consequence is that you'll have to slightly re-focus and that your image with slightly move when applying a tilt or swing.
But this is not a big deal.

It is not possible to build a view camera where the rotation axes for tilts & swings crosses the rear nodal point all the times for all lenses ! So in fact nobody ever rotates any lens exactly around the exit nodal point !! ! So you can take pictures safely, hundreds of view camera photographers have succeeded in taking good nice 'n sharp picture, most of them have never herad about H'=N' ;-)

And will i still effectively be able to use front tilt's & swing's ?

By using a recessed lens board, your bellows will be less compressed. Therefore you'll be able to tilt & swing with more mechanical freedom. This is a definite bonus.
For example : I have a 45 mm Apo Grandagon Rodenstock lens. I can use it on a flat lens board with my Arca Swiss 6x9 monorail camera. But when I use the 4x5" camera back with the universal tapered bellows which is bigger than the small 6x9 bellows, I can focus this 45 mm lens, but I cannot easily apply tilts and swings. Hence I eventually have mounted it on a recessed board in order to be able to use it on both configureations, 6x9 and 4x5" (actually, the 45 apo grandagon does not cover the 4x5" format but does cover the 6x12cm for panoramic shots).

However, do not forget that you'll need a recessed lens board mostly for short focal lengths. For the usual application in landscape photography, the tilt angle required to bring the ground = foreground plane totally in focus according to Scheimpflug's rule decreases in exact proportion of the focal length, for a given height of the camera above ground.

For example, take a 90 mm lens mounted on any camera and assume that the lens is located at 1,35 metre (about 4 feet 1/2) above ground.
This is 15 times the focal lengths, in this condition the required tilt angle for the classical "Scheimpflug's foreground' is about 60/15 degrees = 4°
This is quite small and if you use a recessed board you'll have only minimal refocusing and re-framing after applying this amount of tilt.
In conclusion : sure, go for the recessed lens bosrd, but beware that some recessed boards make difficult to reach the .. recessed lens controls ; sometimes you need a L-shaped adaptor for the cable release.

[rdenney]

If you have a camera like a Sinar that has gimmicks on it to help you determine the correct tilt, a recessed lens board will mess that up a bit, because the lens is no longer rotating about the same axis. Or, if you use a camera with axis tilts and you like using axis tilts, the recessed board will move the lens away from the axis.

In practice, all it means is that you may have to fiddle with the movements a bit more, with a bit more iteration, to get things adjusted as you need them. If the alternative is a bellows so compressed that you lose movements anyway, it is a worthwhile tradeoff--you end up with more movements using the recessed board.

My ONLY beef with using recessed boards is that I have fat fingers that don't reach into the recess easily to manipulate the shutter and aperture settings. And, depending on the camera, the recessed lens board may complicate the installation of a cable release somewhat. Thus, I generally prefer to use a bag bellows instead of a recessed lens board, if that is an option.

Rick "who likes short lenses and therefore has lots of experience with recessed boards" Denney

[rupal]

Thank you both for the great detailed explanations.

[Thom Bennett]

Emmanuel,

This is very interesting! One question about the following:

For example, take a 90 mm lens mounted on any camera and assume that the lens is located at 1,35 metre (about 4 feet 1/2) above ground.
This is 15 times the focal lengths, in this condition the required tilt angle for the classical "Scheimpflug's foreground' is about 60/15 degrees = 4°

Where do you get 60? What does that represent?

Very elegant explanation for degree of tilt.

[aduncanson]

Where do you get 60? What does that represent?


Looks like Emmanuel is using tangent(theta) = theta (true for small angles measured in radians) and approximating 1 radian = 60 degrees.