Deep Yellow filter Orange filter Kodak Ektachrome Infra-Red film is interesting stuff to play with, its rated at
about 200ASA or ISO as it is now! all three layers are sensitive to blue light. So Kodak
suggest the use of a deep yellow filer to filter out all of the blue light,
but good effects can be had by using say orange, red or green filters, all of
which filter out blue light. The film was developed in the war years for reconisonce
work, real green vegatation usually appears red or magenta, painted green camaflague
stays green!! 
Pictures thro' even a modest microscope can be fascinating, and very useful depending
on your hobby or interest. This is the leg of a common garden spider, not a deadly fist sized
thing from the jungle...it was only photographed at x56 magnifacation.
Or try family portraits, by simple lighting or bounced flash.... this is bounced flash, a reflector
to fill-in, and a diffuser filter to give it a SOFT look.
Photography relies on getting the exposure right and getting the image in sharp focus.
What is correct exposure?? the right amount of light for the right amount of time, lets call it X.
A typical daylight exposure might be 1/125 of a second at F11 with 100 ASA, or ISO speed film. So X=1/125@F11
but as F8 lets in twice as much light then F11, X can also equal 1/250 sec at F8, which is twice
as much light for half the time. or even 1/60 sec at F22 which is 1/4 of the light for 4 times as long
and many other combinations... 
All of these aperture-shutter combinations will produce the same exposure!!
Most cameras have shutter speeds of 1 sec to 1/1000 sec at least, the Aperture is an ajusable opening in the lens
that lets light through and is usually given an F number the smaller the better F/1.7 F/2.8 etc..
Many modern cameras especially compact zooms have very small apertures of F/4.5 or smaller.. For
serious work requiring close-ups (like plants, flowers or insects) or telephoto shots of wildlife,
sports etc an SLR (Single Lens Reflex) camera is needed.
Why?? with the SLR you look though the same lens that takes the picture (not a seperate viewfinder) so you see exactly (well about 95-99%)
what you will get on the film! you will also be able to see if the subject is in sharp focus, if
not you will be able to focus it with the lens control (Many are auto-focus now). Use special lenses and close up equipment.
What's an aperture? The aperture is an adjustable diaphram this controls how much light
comes through the lens. Back to F numbers, a standard lens on a 35mm camera is 50mm, this will show a field of view simular to the human eye. If the aperture is F/2 the
actual mechanical aperture is 25mm wide. The F No is equal to the lens focal length divided by actual aperture. This is true for all types of lenses.
Lenes with a focal length shorter than normal are Wide angle and longer ones Telephoto.
F numbers also perform another important function! they control depth of field (DOF) When you focus
on a subject, some distance in front and behind it will also be in focus. There will be more with Wide
ange lenses and less with Telephotos, the smaller the F number the less DOF, larger F numbers give more DOF.
So by using a wide aperture for a portrait you can take a distracting background out of focus, and for a
flower close-up a small aperture will help keep things in focus. There is very little DOF at these close
distances, more at longer distances....
So what does the shutter do?? This is the part that opens for a preset period of time!
it is sometimes just in front of the aperture or diaphram! (inside the lens) on most compact
and rangefinder type cameras.
In an SLR it is usually in the camera body just in front of your film (so don't go sticking your fingers in it, its an expensive
repair) ealry ones were made of rubberized fabric, working horizontally like curtains, most are now a number of
very thin steel blades, working vertically.In a way the shutter can control how clear the picture is!! if the subject or the camera move during the exposure,
the image could be blurred! Using a standard lens you can not hold the camera still enough at 1/30sec
or less, you need a tripod. If the subject is moving fast or you are using a telephoto lens (that magnifys
the movement even more) you will need to use 1/250-1/500sec or more...
And lenses Camera lenses come in all shapes and sizes, very eary lenses consisted of
just a single piece of glass. This had one side concave the other convex, such a simple lens as
many faults or aberations! (millions were used in box type cameras, even in the 1940-60's) and could only work at a small aperture, Soon lenses with 2 and 3 pieces of glass
or Elements were used. Then in 1912 Zeiss in Germany produced A 4 element lens known as the Tessar, in this the two rear
elements were cemented together!! This produced very good results and had an F/2.8 aperture, today there are
many different kinds of Optical glass (that bend or refract light to varying degrees) even Florite and plastic
are used! Now lenses are designed with the aid of computers, zoom lenses can have 20 or so elements.
