Fitting a lens assembly

 

A large format lens assembly consists of Front and Rear elements and a shutter aperture mechanism into which the lens elements screw the shutter is fixed into the Lens Plate through an appropriate sized hole and fixed with a locking screw. in the example shown below the front element has been unscrewed and the rear element is still attached the silver portion is the neck which goes through the lens board.

150mm Rodenstock © Phil Gee

 

Examples of lens plates bottom left Sinar with Size '1' hole and right Cambo with Size '0' hole the circular lens plate for the X2-PRO is shown at top with lens fitted

Lens Plates © Phil Gee

 

 

 

The X2 lens plate had a '0'size hole approx 35mm Dia the Compur shutter on the ƒ5.6 90mm lens requires a 41.7mm Dia hole so rather than wait 3 weeks for a X2 plate with a size '1' hole it was out with the file

The notch in the edge of the plate fits over a location pin at the bottom of the front standard to fix its orientation.

enlarging lens plate hole © Phil Gee

 

The front element is placed thorough the hole and locking ring screwed home using a lens key as can be seen below; before screwing up tight make sure that aperture selector on the lens is at the top of the plate!

shutter locking ring and key © Phil Gee

 

As you can see this leans is rather a beast and the aperture and shutter selectors are at the top of the plate.

Whilst only the aperture selector is required as the shutter in the camera body will be used for exposure, the body could be set to a mirror up and long exposure and a shorter duration used on BtL shutter using a cable release (to minimise vibration) just like the old days!

Completed assembly © Phil Gee

 

Lens assembly on Lens Plate is fitted into front standard and Camera onto rear standard then a bag bellows connects the front Standard and the Camera lens mount fitting. In this image the lens standard is shown below ctr line of sensor at extreme limit of fall -18mm

Position of elements when focused on infinity 'film' plane marker can be seen under 18.5cm position note how close the rear element is to the lens bayonet fitting on camera body; place rear lens cap on and check swings to ensure there is adequate clearance for full movement if not make a note of safe limits and tape to lens standard.

X2 Infinity position © Phil Gee

 

Bag bellows fitted and we are ready to go

Lens fitted to X2 © Phil Gee

Whilst the 36x24mm sensor of the 5D is small compared to the image circle produced by lenses designed for large format cameras, up to 260mm for a 90mm @ƒ22, the range of movements are limited due to the depth the sensor is within the camera body the throat cuts off the image beyond certain limits, ref examples.
I would normally use this lens with a Center Filter to counteract the exposure fall off at the edges (Vignetting) when used in 5x4 and 7x5 formats but should be ok with the 36x24mm format of the 5D.

The new 'Digital' large format lenses have smaller rear elements and only project an image circle of approx' 100mm there is also a range of Macro Digital optimised for magnifications in the 1:4 to 4:1 range

Before use always check the position of the rear element at the infinity focus position i.e. its closest to the camera body, to make sure that the rear element will not be damaged by hitting the body bayonet connector when it swings/shifts. Fitting a stop in the form of a length of wood taped to the top edge of the rack between front and rear standards is an old trick I have employed with students who are not familiar with equipment.

When focusing on objects closer than infinity the distance between standards will be increasing so less chance of in bellows collisions.

 

You then need to familiarise yourself with the workings of the aperture selector, how to determine and set exposure, focusing and composition in particular how the image in the viewfinder corresponds with the final image

© Phil Gee

 

To Be Continued ... next

Shift and Rise & Fall

 

Tilt and Swing