790mm F:5.4 ULF Lens Now Available
It's finally here and ready for your inspection...
This lens was prompted by Craig T's request for a lens fast enough for alternative photography to cover his 20x24 Chamonix as well as for his mobile Ford Transit Van ("Australia's largest mobile camera") shooting 24"x32" ambrotypes and ferrotypes. Another customer wanted to make life-size portraits with his caravane (trailer). And there are those who are resurrecting the old Century Studio cameras. Let's not forget the folks designing and building their own cameras...
This is a custom ground lens using the same optical glass as in premium camera filters.
The diameter and focal length was selected to result in a fast (f:5.4) lens that would project an image circle of at least 1200mm (±48") for negatives/plates of up to 24x30". In reality, the lens covers 32x40" easily and creates a striking 6' diameter camera obscura image. The lens follows the classic Wollaston meniscus design of 1812.
As with my original lenses, I use PVC materials, in this case the exterior is white PVC. A black finish would be vulnerable to white scratches. If you want brass 'cause it looks cool, the cost would be 3x. It is not small, the lensboard hole must be at least 165mm (6.5") diameter to get maximum coverage without vignetting. If you are shooting smaller, say; 16x20 or 14x18, it may be possible to adapt the lens to interface with smaller boards.
If you are used to seeing lots of flare with a shorter meniscus lens, you will be pleasantly surprised at how easy it is to use the lens. As focal length and glass diameters increase, the curvature is flatter and flare is significantly reduced. This means that there is a wider zone of transition from a soft/diffuse image to a sharp/crisp image as the lens is stopped down. To take advantage of this wider zone of image formation, I supply aperture cards in 1/2 stop intervals.
Since a 790mm focal length is quite long, depth of focus is quite short. By utilizing this fact, portraits can be composed so that the subject is in focus and the background falls out of focus quickly, This will emulate the classic sharp center/diffuse background style of historic portraiture.
The stop card slot is a bit wider so a gel filter could be taped to an aperture card for contrast control or for selective filtering according to your emulsion's chromatic response characteristics. If you want to experiment, blank cards are available for cutting into a "sink strainer" for even more diffusion control.
The basic lens package includes the lens, six aperture cards in 1/2 stop increments, one blank card as a front lens cover, mounting screws, a cleaning cloth, and a documents packet. The price is $375 plus shipping.
The accessory package includes a slip-fit front lens cap which doubles as a shutter (please specify knob style), four aperture cards (f:22, f:32, and two blank cards), an expandable folder to keep the cards organized and handy, and a birdcage awl for drilling the screw mounting holes. The price is $49 (plus shipping if ordered separately.
It's been a while getting this lens ready, thanks for your patience,