Phase One digital backs are so versatile, and that is one of the reason why I do like them so much. Some months ago I procured an old Cambo DS Wide technical camera fitted with a 57mm analogue lens and a 4×5 glass plate back.
I decided to create a hybrid system, combining the analogue Cambo/lens with my IQ140 back.
Intended to create a super-duper virtual sensor. The Cambo with the 57mm lens (analogue) projects a circle of light with a diameter of more then 153mm. And since the camera is a technical camera it can shift 20mm left /right and up/down while staying in the projected circle of light. This creates in turn a virtual sensor of 73 mm x 84mm or 14000 x 12172 (170Mpx)Pixels .
Of course I will need to shift L/R-U/D for the ultimate picture (9 shots). Some will say “Not much different then a standard Panorama shot ”, yes indeed. But with that difference that I do not lose any pixels in the stitch processes and everything is tight controlled as the X and Y axis’s are determined by the Technical Camera mechanics.
I had one concern, the resolution factor of the analogue lens (lines per millimeter) and the associated airy disks. But then again I am resolving a view onto a 73mm x 84mm surface versus a 32,9mm x43,9mm sensor. So I can afford to have less effective pixels (defraction). The first test shots are not that bad in terms of resolution.
However shooting takes a bit of time and getting used to, as everything is manual. But then again it makes you feel like a real photographer (whatever “real” means).
Here are the processes of taking a shot, and once again the IQ features are so helpful.
[b][i]Placement: (IQ X and Y axis’s on display)[/i][/b]
It all starts with having a correct vertical and horizontal axes, an easy thing to do as the Cambo has several glass level/air bubble gauges. To be double checked by the IQ’s vertical and horizontal level indicators (backs display).
[b][i]Framing (with the IQ back live view and Horizontal/Vertical level indicators):[/i][/b]
Position the IQ in the central position of the camera (X=0,Y=0), no shifts.
In IQ live view , and the lens set to open (button to open the shutter) move the X and Y shift positions of Cambo to +20mm and -20mm; this provides an impression of the total framing. Adjust the tripod position so that the final aggregated capture is what is wanted. In bright environments the aperture needs to be stopped down (higher F number) so that the back does not get over exposed (if the light is to strong, the live view will look awkward with black patches, magenta streaks and lines).
[b][i]Measuring the light (check with the IQ’s preview histogram and burn-out mask):[/i][/b]
With the ISO set on the DB, measure the light on the subject. I use a seconic 758 lightmeter, this allows me to aim (look through the light meter) at the high and low lights and get the readout of the aperture and shutter speed. Since the IQ has 12.5 stops of dynamic range and the high and low measured values are know the best aperture/shutter speed can be determined. There is nothing to be set on the DB besides the ISO. The lens of the camera is adjusted for aperture and shutter speed as calculated.
First test shot to check the exposure:
The shutter is armed (on the lens) and the “Wake-up” signal is triggered from the little pushbutton on the cord attached to the IQ. Within four seconds, the shutter needs to be triggered by depressing the mechanical shutter release knob on the lens. The lens has a copal shutter and creates the “Capture” signal as long as the shutter is open. Once the shutter is closed, the contact is opened and the IQ recognizes the end of the capture. Checking the light with the IQ is easy, just view the picture and turn on the “high-light” warning mask. The Histogram is the second tool to look at. Adjust, as needed the shutter or aperture.
[b][i]Focus and Sharpness (IQ sharpness mask and live view);[/i][/b]
The Live view is not the best method to start; I tend to use a “laser based” distance meter as used in construction work ( Bosh DLE50) . It measures the distance between the object focus point and the DB sensor plane. The lens is then adjusted accordingly (distance markers are on the lens) by turning the ring to the right distance. This should get the focus fairly close to where it should be.
The sharpness is checked in live view on the back while zooming in (on the back – 100%). The lens is fine adjusted if needed (can be hard to see in live view).
The best verification is an actual test shot and view it with Sharpness mask applied on the IQ (unless you are shooting tethered) .
[b][i]Ready to shoot (LCC and capture one);[/i][/b]
Easy, just shoot nine times (no more camera or back adjustments). One picture per position (moves are with the TC Horizontal and Vertical shift wheels). For each new position, a capture of an opaque plexi glass (Phase One provided) is required. This allows Lens Color Cast correction for each picture taken in post processing.
All shots are taken, and the pictures are LCC corrected in Capture One Pro 7.2. Once complete the stitching can start by selecting the 9 pictures (with LCC correction) , click on the top bar right stitch Icon in CO. That will start the Photoshop “Photo merge” process. Note that it only works for CS 3-6. If you use CC it will not work. For CC you can export the pictures from CO and then open CC manual and start the work.
I really have enjoyed this work, however I still wonder what the effect would be with a Digitar Lens.
Comments / recommendations more then welcome .