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 using existing custom fiberoptic to deliver both the focusing light and the strobe illumination.

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 (or Vivitar 36+20mm), and the Nikon Macro 105 set to closest focus. Camera is mounted 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. The 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, but I am open to building these film cameras from a different brand. But I am having a hard time getting the original Nikon bodies and need to know any alternative 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-inch or more working distance?

Second I have always wanted to use the large format to allow for capturing more detail. The film grain seems to be the limiting factor in the 35mm images. But I have read in the Close-up Photography discussion that going from 35mm to 4x5 cuts the depth of field by a factor of about four for a given lens speed. The implication is that a lot more light is needed to image a given subject onto a bigger film area (trade-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 or 14 mm diameter area with at least a 100 mm working distance and with better color and detail than the 35mm setup described above?

p.s. I am not a professional photographer, but am in biomedical imaging.

-- Jon (jonmiles@pacbell.net), January 07, 1999

Answers

I am no expert in this field, but i have some suggestions that might be helpful.

1.) Is brighter light safe for the patient? If so if you can use a light that is 4x to 8x times brighter you can use a much better film like Fuji Velvia (ISO 50) and stop down an extra stop.

Both Elichrom and Balcar (and maybe Profoto and Broncolor) make fiber optic adapters to fit their high powered studio lights. However that light level may be too intense for the well being of your patient. Finally Plume ltd. makes a very highout/low heat daylight balanced flourescent light called a Scandles this might be bright enough for both focusing and photography. Of course you might not need this much light. Perhaps you can replace the light source you are currently using with a Quantum Q-flash. The Q flash can be controlled via the TTL ina Nikon N90 or N70 for correct and bracketed exposures.

2.) Think about doing this with a medium format camera like a hasselblad instead of a large format 4x5. Contact Hasselblad directly, but I know that given a special macro lens, the bellows unit, and a standard camera you'll be able to go at least 3:1, and there are many more films availible in medium format roll film (image size 6cmx6cm) then there are in sheet film. Hasselblad works closely with the most acclaimed medical photographer ever, Linnert Niellson (sorry if i got the spelling wrong). When you call Hasselblad ask for Ernst Wildi.

3.) If you decide to go with Large format (4x5) probably the best way to go will be to get a rear frame/groundglass and a lens board and then have someone fabricate a rigid tube of the correct focal length for the combination of lens focal length x magnification factor @ "x" working distance. Realize that this will be a big, slow working rig. and if you are just getting the depth of field you want @ f/5.6 on ISO 200, then you will probably want to be minimally at f/16 for the 4x5 macro rig ...and I think where you can see where this is going in terms of film ISO.

-- Ellis Vener (evphoto@insync.net), January 08, 1999.

Thanks for the answer. As for amount of light, the custom illuminator has a 30watt halogen spot directed on the fiberoptic lightguide panel adapter (the input end) for a focussing light, and just ahead of it (collinear) is a small xenon tube from a Rokunar SP147 strobe, so this is a small amount of light but efficiently directed with the branched lightguide output ends about 2" from the subject.

When I was doing ophthalmic photography I used Zeiss, Topcon, and Nikon cameras that had 10 or more times the light output. Those are considered safe, but the flash was not comfortable. Also was using mostly ISO 25 Kodachrome. With my current setup there is a noticeable loss of detail going from 200 to 400 filmspeed, but it's hard to see much improvement going from 200 to 100. I thought a larger film image area would be a better way to get more detail. Portraits shown in magazine ads seem to have much more skin texture detail than 35mm could ever give.

The Hasselblad approach is a good tip, I once spoke with a Hasselblad rep and they did not have a ready solution, the closest they knew about was 1:1 and I think it was with a 200mm lens and 100mm extension, but I will check again. (I have a friend who owns a camera store.) The problem was that in using extension to move the lens away from the film for more mag (any format), most of the collected light never hits the film. The other problem was the working distance requirement (4"). But using 6x6 (or 6x7) makes much more sense and any suggested lens/extension length is appreciated.

I'd also like to take an even higher power color photo of say a 10x10 mm area (with a similar w.d.) but this also seems theoretically difficult. Why is it so hard to get a nice clear sharp photo of something so small? Is it because so much glass and refraction is required.

p.s. using the extension tube (in the 35mm setup) instead of doublers etc gives a noticeably sharper image due to the lack of added glass.

-- Jon (jonmiles@pacbell.net), January 08, 1999.

I hate to disagree with Ellis, but although the DoF from large format is worse at 'normal' distances, this is reversed for macro. Filling a 5x4 inch negative with a 17x21mm subject gives you more DoF than a 14x21mm subject on 35mm format, for the same marked apertures. In fact, about four times as much.

However, there are certainly many other problems that would be faced, one being that LF lenses are more sensitive than 35mm ones to aberrations at large apertures, so you would probably want to stop down to avoid these.

Another problem is composing and focusing on the ground glass screen. If you use a 105/2.8 lens on the LF, the maximum effective aperture is f/16, before you have stopped down, so the GGS image is pretty dim.

For better results than you currently get, I would think that more light and slower film would be the first direction to try.

Jon, you might talk to the camera manufacturers directly, they have plenty of goodies that we 'consumers' know little about.

-- Alan Gibson (Alan.Gibson@technologist.com), January 08, 1999.

Concerning abberrations, I've noticed another unusual behavior of the 35mm system with imaging the iris. Setting the dial on the 105 to f/8 (which reads out as f/16 in the viewfinder due to the 55mm extension) will give pictures with more detail and better color than the f/11 or f/16 settings. It seems counter intuitive, but one reason may be that the smaller apertures bring more into focus the ocular media anterior to the iris (the aqueous fluid and cornea), thereby diminishing the iris detail and color saturation. So depth of field is best at less than a millimeter, about .3 to .6 mm. I think at the 5.6 setting it's about .1 to .2 mm.

But there is still the theoretical question about color: it only exists at the larger scales. For something to have 'color' as an intrinsic property, doesn't it have to be at least the size of a wavelength (half a micron or so)? I have seen live blood cells (7 microns in diameter)look red through a viewing scope, but they are not highly saturated in color. Electron micrographs (sub-micron subjects) do not include chromatic information.

I tested out some industrial zoom inspection lenses and was imaging down to 1x1 mm but the color was no good at that mag.

I very much want to get a good color photo of a 10x10 mm live subject and I'll settle for any format, I just need the 4" wd.

As for the clear sharp color photo of a 1x1 mm live subject, there is a greater challenge.

-- Jon (jonmiles@pacbell.net), January 08, 1999.

Regardless of the format, the depth of field is the same at the same size reproduction. 1/2" reproduced at 1:1 on 35mm or 4x5 will have the depth of field at the same f-stop. If you want large scale of reproduction on the film, the depth of field will be less. Good luck with your efforts.

-- Eric Lohse (elohse@suffolk.lib.ny.us), January 08, 1999.

I could well be wrong, but I thought electron microscopes didn't work with light at all, so they cannot record colour.

Even if colour ceases to have meaning at extremely high magnifications, this shouldn't be a problem for subjects around 10mm.

Random thoughts:

1. A live subject means you have to use flash.

2. If you can extinguish the other lights, you don't need a shutter, so you could use, say, a reversed 105 macro lens on a 5x4 camera.

3. With the greater magnification of 5x4, you lose more stops with the bellows extension: 5 stops, rather than the 2 stops of 35mm. Unless you can increase your light source, this might exclude using 5x4. Similarly (but not as bad) for 120 format.

3a. The difficulty of focusing this rig might be relieved by having it fixed focus, with a wire frame or similar mounted on the camera. When this frame is rested against the subject, the subject is in focus.

4. In 35mm format, you won't find anything much better than the Nikon 105mm Macro. The 200mm Macro would give you a greater working distance, but that isn't a real problem for you.

5. What you want is higher resolution and better colour. You haven't told us what film you are using. I know little about colour films, but I suspect Kodachrome 25 is higher resolution than your ISO 200.

6. I keep thinking: you need more light!

-- Alan Gibson (Alan.Gibson@technologist.com), January 08, 1999.

Alan,

Electron microsopes do not use light, but a different form of electromagnetic radiation that also creates shadows and highlights, but definitely non-chromatic. Screen image is usually grey or green, prints are b/w.

I use a flash but also require the focussing light since the camera is focussed using a macro slider focussing rail. Focus has to be within a fraction of a millimeter and the subject has head and chin in a forehead/chin rest for stibility. Position (depth) of the iris will have variability, so the camera has to be focussable.

I like the idea of reversing the 105, but I think that will lose the stop-down feature (which allows for focussing at full aperture). This could be a draw back to the medium/large format, the preview image too dim for focusing.

The working distance cannot be over 7 or 8 inches or so, otherwise jitter and focussing is a problem. 4-1/4 is ideal.

Normal film is Ektachrome 200, Kodak seems too warm.

More light is helpful: yes, or to make more efficient use of the existing source by directing it as a focussed spot of light. If this spot can go down to a few mm then imaging a 5x5 mm area is possible.

-- Jon (jonmiles@pacbell.net), January 08, 1999.

Hmm, I'm running out of ideas. Yes, my idea of a fixed-focus camera with 'distance-frame' won't work.

You could put a gadget on the back (now the front) of the reversed Nikkor to give you stop-down. But unless you increase the subject illumination, LF is a non-starter.

If Kodachrome is too warm, just use a mild cooling filter, CC10B or whatever. But you need more illumination for this slower film.

-- Alan Gibson (Alan.Gibson@technologist.com), January 08, 1999.

Another issue is the quality of the image your Nikon 105mm lens can provide at greater than 1:1. I checked the Nikon web site but did not find the optimal working range of this lens. There is a big difference between 1:2 and 2:1 and you are likely pushing the limits, particularly if finer grained films do not improve your images. It is not uncommon for lenses labelled Macro to be optimized for about 1:2 to 1:10.

Nikon may not offer lenses suited to greater than 1:1 applications, I do not know. Olympus, however, certainly does---perhaps because they specialize in microscopes and medical imaging. For example they offer

• a 80mm lens optimized for 0.5x to 1.2x

• a 38mm lens optimized for 1.7x to 6.7x

• a 20mm lens optimized for 4.2x to 13.6x

While the 80mm lens would give about your desired working distance, you should probably see if you can get closer. The 38mm would give you only about half the working distance, but would no doubt produce much better quality at the magnifications you want. I would definately try this route before resorting to the much more expensive (medium format) or awkward (large format) solutions.

More info at www.olympusamerica.com. In particular, see the PDF format OM lens brochure.

I have no affiliation with Olympus, apart from owning one of their cameras.

-- Michael Heal (kmheal@audiolab.uwaterloo.ca), January 08, 1999.

Alan, thank you for correcting me, as i said I'm no expert in LF macro work. I know there are lenses out there specifically made for LF macrpo work beyond 1:1. Speak with E. Wildi again at hasselblad. they might not make them but i guarrentee he will know who does. perhaps these are microscope optics? Also speak with Sinar, Rodenstock & Schneider. Sinar specifically has illustrations of such a lens on page 42 and on page 71 of the 1990 editon "The Large Format, handbook of the Sinar System" by Carl Koch (ISBN 3-7231-2600-6) but there is no discussion of which lens it is. But if it can be fitted to a sinar board it can alsobe fitted to a hasselblad lens mount and from there to a bellows. My feeling is that the lens is probably much shorter than the 100mm lens you mention.

-- Ellis Vener (evphoto@insync.net), January 08, 1999.