Larry Legg's Learner Projects
Project 2- Let there be Light.

Watch out for these symbols in my projects!
A good idea
Use household stuff
The right way!
You can skip this if yer don't want details! 
A secret unlocked!

 About this page | Project Index | Larry's Learner Purchases on-line | This Project Page: 1 - 2 - 3 - 4 | Micscape  | Mic-UK |
Other ways of manipulating the light cone 
For completeness, I have summarized all the other techniques I know of for interfering with the light cone in order to use it to transmit information to the lens and eye in various ways. This is not a detailed account but maybe it will help yer understand that you ain't just stuck with the methods I've described so far. 

Phase Contrast 
A bit like dark field (dark ground) but expensive. An annular stop is normally built into the substage condenser - much like our black disk. The expensive bit its that while this produces a hollow cone of light - a special objective lens is used which contains a phase ring. Rays of light, deviated by difference in refractive qualities of processes in the specimen, miss the ring. The phase ring is made in such a way that undeviated light passing through the phase plate (containing the ring) is advanced by 1/4 wavelength. This results with deviated light and undeviated light being 1/2 a wavelength out of phase and will cancel each other out when they come together to form an image. 

The result produces very contrasty specimens against more brightly lit backgrounds. 

Rheinberg's Differential Color Illumination 
A big title this one but the technique is one you can exploit quite easily yerself. Yer remember our dark ground method? Well this one is very similar. Here, yer simply replace yer black disk for one which is deeply colored. Yer could use cellophane, or optically sound transparent plastic or even stained glass. The outside space around the central disk must be in another color. Commonly - dark red is used for the stop and green for the surrounding area. Here you will be producing a cone of light essentially two color: the central cone being red and the external cone - green! 

Oblique Illumination 
A good playful one this. Here you simple obstruct most of the light in the cone, leaving just the edge of light cone still illuminating the specimen. You can put a piece of card in yer filter holder ( a complete disc) and then slide the filter holder back into place  such that it leaves some light passing the obstruction. 

You will get a false 3d shadow from your specimen which gives the impression the subject is thicker than it normally appears. Bear in mind that this is an illusion but it is an interesting effect which can help reinforce that in the Microscopical world - things are not really flat at all. 

Closed Aperture Illumination 
If yer microscope has an iris below the condenser, you can close it right down to form the tiniest hole possible. This produces the effect of widening fine lines and contours in the specimen (a contrast control?).  Remember though, that in doing this, yer not seeing how the thing really looks - merely increasing the opportunity to spot the existence of detail where, previously - none was visible. 

If yer (you are) interested in taking photos or video of stuff under a microscope - it pays to experiment with colored filters. Collect yer sweet wrappers if they are colored cellophane, try different colors in the light cone path and you will get more rewarding pictures. Remember to use color filters too to correct the light for the type of film yer using and adjust the manual white balance on video cameras. 

That's it from me for now. Our next project will be all about cutting sections manually for mounting. Yer will need a microtome for this - either one yer already own, or possibly made yerself. I'll be using the one I just bought from the onview shop - The Brunel Bench Microtome. 

See yer... 

About this page | Project Index | Larry's Learner Purchases on-line | This Project Page: 1 - 2 - 3 - 4 | Micscape  | Mic-UK | 


All material is copyright of Larry Legg, Microscopy-UK and Ltd 1998/99/2000. All rights reserved.
The Larry Legg Project pages may be used on your own PC for personal use but must not be 
distributed without permission from Larry Legg or Ltd.
Larry Legg may be contacted at:  Larry
Onview may be contacted at:
Mic-UK co-ord:  email 

All non-email communication to Larry may be made by fax or written (postal mail) to:- Ltd  
69 Commonside West  
CR4 4HB  
Fax: +44 - 181 685 0528  
(We will pass it on!)


© Ltd, Microscopy-UK, and all contributors 1995 onwards. All rights reserved. Main site is at with full mirror at