Best way to photograph a half-inch area in large format
I want to get maximum detail and color fidelity in photographing a half-inch area (technically 14x21 mm) such as for example the human iris in vivo, and usin g existing custom fiberoptic to deliver both the focusing light and the strobe i llumination.
The preferred 35mm configuration I've been using is a Nikon N8008 (or N90 or N70) on manual focus and manual exposure mode, two 27mm PK-13 extension tubes (o r Vivitar 36+20mm), and the Nikon Macro 105 set to closest focus. Camera is moun ted on an macro focussing rail on a two-axis fluid video head. Working distance is 108mm (4-1/2) inches which is optimal, although longer distances are okay. Th e speed of the lens seems to be halved by the 55mm extension. Typical exposure ( with the custom flash and ISO 200 film) is with the dial at f/8 (f/4 effective). For brown eyes I go down to dial f/5.6 (f/2.8 effective), but any further loss of depth of field is not acceptable.
First, I am partial to Nikon for backwards compatibility and other reasons, b ut I am open to building these film cameras from a different brand. But I am hav ing a hard time getting the original Nikon bodies and need to know any alternati ve configurations that will give a good 35mm result. What would others recommend for a 35mm solution to imaging a 13 or 14mm diameter area and keeping the 4-inc h or more working distance?
Second I have always wanted to use the large format to allow for capturing mo re detail. The film grain seems to be the limiting factor in the 35mm images. Bu t I have read in the Close-up Photography discussion that going from 35mm to 4x5 cuts the depth o f field by a factor of about four for a given lens speed. The implication is tha t a lot more light is needed to image a given subject onto a bigger film area (t rade-offs and no free lunch), given the same type of film (can this be at least in part offset by using faster film). Okay given twice as much light and double the film speed. What type of 4x5 (or larger) camera components will image a 13 o r 14 mm diameter area with at least a 100 mm working distance and with better co lor and detail than the 35mm setup described above?
p.s. I am not a professional photographer, but am in biomedical imaging.