Quote Originally Posted by RJ- View Post
Steven - Corran's right. Even at f22+, it is difficult achieving full 5x4inch film area with the SA XL 47mm f5.6 lens on a field or technical camera. It is possible on a dedicated plane parallel rigid rear standard dedicated architectural type camera with geared shift for precise zero'ing (and still hard work). The challenge with this super wide angle, lies more in trying to terminate and zero all movements completely.

I've always preferred the square format and work 4x4 inch format, using 1/2 inch either side for handling. Perhaps this is too different a work flow, although it enables the lens to be used with cross-shift movements (image), without the fastidious energy to work within its tight image circle.


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Let's not overstate the difficulty. I don't have the XL, but have routinely used the 47mm Super Angulon f/5.6 with the 6x12 format, which it barely covers, in a 4x5 Sinar F1/F2. That camera certainly does not meet the definition of a rigid-body architectural camera, but getting it to work wasn't really all that difficult.

The key is to set up a camera that does not require any compression at all of the bellows. And that's the problem with field and technical cameras--the bellows are usually general-purpose pleated constructions that have to be squashed flat to allow use of the 47, even on a recessed lens board. The stress applied by the compressed bellows will force the standards apart a bit and they won't be parallel. But on my Sinar, I use the Wide Angle Bellows 2 and the 47 is mounted on a flat lens board. I use the non-metering back from an F1, not the thicker metering back from an F2. There is still room for about six degrees of tilt. Parallel can be checked with calipers--it does need to be precise. If I wanted to use the 47XL, it would be worth it to build a Sinar F kit solely for that purpose--the camera plus the bellows would cost less than half the lens, and the camera could be built on a 6" rail extension with the tripod adapter behind the rear standard. That would be a lot cheaper than a specialty architectural camera, but more fiddly, too. I use that setup with a 47 and a 6x12 back and it works.

Back to the OP: The movements you need for a short lens are less than for a long lens. Example: Let's say we want to render the surface of a floor sharp, with the camera basically horizontal and about three feet above the floor. Scheimpflug tells us that the film plane, the plane that is at right angles to the lens axis at its nodal center, and the subject plane all intersect. With a parallel setup, they intersect at infinity, but with tilt or swing they can intersection more closely. Back to the example: With the typical 6" lens (150mm), we'd need (arctan 6"/36" =) 9.5 degrees of tilt. With a 2" lens (the 47 is a hair less than that), we need (arctan 2"/36" =) 3.2 degrees. 3.2 degrees is a very fiddly setting, and precision is important.

But even three degrees of lens tilt will put two corners in shadow. You can, however, tilt the back, which keeps the film in the illuminated circle. The problem with that is the attitude of the film plane determines the perspective projection, and with a lens like this, it has to be critically aligned or the image goes wacky. So, tilt the back to move the focus plane as needed, and then tilt the whole camera to restore the back to true vertical (or otherwise aligned with the subject to achieve the perspective projection you want). Geared movements certainly do make this easier.

Shifting the lens (horizontally, or rise/fall vertically) allows us to correct the field of view without tilting the back. But here we run out of lens coverage pretty quickly. That's the price one pays for going to the wide extreme. So, for subjects such as architectural interiors, the trick is to find the vantage point that is within the field of view and still shows what you want to show.

You will need a tilting loupe so you can point the loupe into the center of the lens for checking focus. It will need to be tilted quite a lot. And it's a good test of the effectiveness of your dark cloth--the image won't be bright.

Or, you can use a tiny aperture and depend on depth of field.

Rick "BTDT" Denney