Darkfield and Photomacrography

[augusthouse]

Here is a small quote from Lou Gibson that should help to clarify some aspects of Darkfield for reasonably uninitiated persons - like myself.

The image of 'head of a young millipead, X12) in Gibson's book has always been of interest to me; so too Lester Lefkowitz's 'tadpoles' on page 192 of 'The Manual of Close-up Photography'.

The quote below was taken from 'Close-up Photography and Photomacrography - H. Lou Gibson. * This publication has various names; my copy is the Eastman Kodak combined edition of 1970.

An illustration of Oblique Darkfield Illumination from the book accompanies the text in the publication so I have included it with the quote.

Darkfield Illumination

Some specimens in photomacrography may be transparent but practically colorless, having no natural color and being unstained. Standard transmitted lighting, therefore, will show little or no detail in the recorded image. Specimens of this type can often be photographed to advantage with oblique darkfield illumination. The diagram in Figure II-65 shows how light can be directed through a specimen at an angle of about 45 degrees from below. The light beam misses the camera lens, but light is diffused and scatterted by the specimen.

A brightly illuminated image against a dark background is produced by this technique. For added interest, a color filter may be placed in the illumination beam between the light source and the specimen to provide a color image against a dark background.

Quote and illustration from 'Close-up Photography and Photomacrography - H. Lou Gibson

The link directly below is to one of Charlie's photomicrographs.
http://www.photomacrography.net/forum/v ... 98&start=0


Craig

[Charles Krebs]

Craig,

Darkfield is, of course, a very common technique on a compound microscope. In addition to adding a "stop" centrally in the illumination of a regular condenser, there are all manner of special darkfield condensers made. This page has some nice examples:
http://www.olympusmicro.com/primer/tech ... field.html

Most of the cheap Chinese darkfield condensers for stereo scopes are similar in design to the first illustration (Figure 1)

Rheinberg Illumination is in many ways similar, but instead of an opaque central light stop you use a colored circle.
http://micro.magnet.fsu.edu/primer/tech ... nberg.html

You can really experiment in a variety of ways. The very first microscope image I posted here was done with Rheinberg illumination:
http://www.photomacrography1.net/forum/ ... .php?t=422.
I used it a great deal with my first microscope. It's a little harder do with the "newer" microscopes because of the way most condensers are now mounted.

It would not seem to hard to do something similar with a "tabletop" macro setup.

[rjlittlefield]

It would not seem to hard to do something similar with a "tabletop" macro setup.

In the "extreme macro" range, there's one example HERE, image #3. "Dual-fiber illuminator with ping-pong balls near the tips, one on either side of the subject and slightly behind it." That's a high-mag shot, 20X objective, but done with an objective-on-bellows setup because I couldn't get the lighting I wanted from my microscope condenser.

--Rik

[Planapo]

Charlie wrote:

It would not seem to hard to do something similar with a "tabletop" macro setup.

Yep! Even I with my limited "craftsman skills" was able to build such a condenser, so it really can´t be too hard:

Craig, the lighting of this photo (scroll down to the bottom of the thread where a better post-processed version can be found) was taken with a reversed EL-Nikkor 2.8/50 on bellows, and was accomplished with a "darkfield condenser" that I've tinkered from plastic pots, aluminium foil and matte black paper.

--Betty

[rjlittlefield]

I had forgotten that one. A very nice piece of work!

--Rik

[Graham Stabler]

Hey Craig, check out page 221 of this seminal text:

http://books.google.com/books?id=JV1Pa0 ... ry_r&cad=0

Looks familiar

Also have a look at page 227/228, that is for bright field but gives me some ideas for adjustable illumination.

Graham.

[Harold Gough]

The link directly below is to one of Charlie's photomicrographs.
http://www.photomacrography.net/forum/v ... 98&start=0

Craig

Atypical of the effect but beautiful images anyway.

Harold