Expert: David Silver - 3/7/2004

Question
I am helping someone with a school project about cameras and was wondering if you could help me with a few questions.
The type of information they need deal with cameras.

Do you know what chemical is in camera/film that makes it work?

Do you who invented the first color camera?

Are the lens a special kind of glass?

What is your favorite brand of camera?
Why?

How does a zoom work on a camera?

Any help on any or all of the questions will be very helpful.

Thank you!

Answer

Hello Allen,

Let's see if I can help you with these questions from your school project:


1) Do you know what chemical is in camera/film that makes it work?

The chemical isn't in the camera, but definitely in the film.  The "emulsion" of film (the extremely thin layer that actually produces the photographic image) has many different chemicals in it, but there is a certain category of chemicals upon which ALL films depend.  These are called silver halides (or sometimes called silver salts) and they include silver iodide, silver bromide, and silver chloride.  These are the chemicals that are sensitive to light and do all the work!


2) Do you know who invented the first color camera?

Okay, it's not the camera, but the film!  ANY camera can shoot color pictures, but you need to have some sort of color film.  The first truly effective color film process was probably the autochrome process, which was introduced in the photography market by the Lumierre brothers of France around 1909 and was popular through the 1920's.

There were some unusual cameras, dating back into the 1890's and manufactured as late as the 1940's, that were specifically called "color cameras", but they actually produced black & white negatives that were later rendered as color during a printing process.  They were used primarily in the lithography business for making color prints for magazines and such, but occasionally professional photographers used these special cameras for creating quite striking individual color photographs.

However, the true beginning of practical color photography is with the autochrome process.


3) Are the lens a special kind of glass?

For a very simple lens, like those that were used on the very first cameras in the 1840's, plain glass can work.  But to make the more advanced sort of lens that will gather a greater amount of light and will focus much better, something called "flint" glass was used.  When light passes through glass, and the glass has a rounded surface (like a magnifying glass), the light is bent so that the image is focused differently.  A magnifying glass is simple glass, with just a little bit of roundness to the surface.  Something like that would have worked as a simple lens on an old camera.  But if you want to make a better lens, one that focuses the light better by bending it more, simple glass won't work.  The rounder it gets, the more the light starts to break apart, spread out, and make rainbows!  Flint glass, however, has some extra chemicals melted into it that allows the light to bend MUCH more without spreading apart.  There are other more complicated types of glass that are used today, but flint glass remains the most successful and popular in photographic lenses.


4) What is your favorite brand of camera?  Why?

My favorite brand has always been a company called Leitz, they are in Germany, and for many years they made a series of 35mm cameras called Leica.  I have owned and used many Leicas, and I love them because they are made to very high standards, they are very rugged, and the lenses made by Leitz are some of the best in the history of photography.  There are people who enjoy using "antique" cameras who still shoot with Leicas made in the 1920's and 1930's, and the pictures are super!  My favorite Leica camera is the M3, which was made during the 1950's and early 1960's.  I have two of them right now, they have always worked perfectly, and I particularly love the Elmar 50mm f2.8 lenses that I have mounted on each of them.  I have many other Leitz lenses, and they are all excellent, but I shoot more with those Elmars than any other.  By the way, from the 1950's through the 1970's, the Leica cameras were the absolute favorite of many famous photojournalists in the world.


5) How does a zoom work on a camera?

Allen, that is actually a VERY technical question that I'm not quite sure how to explain.  Seriously, you sort of need to have a scientific degree in the physics of optics to understand how a zoom works!  However, in theory what happens is you have a complex lens with MANY individual pieces of glass in there, what we call "elements", and these elements are designed to move back and forth inside the lens barrel.  As the distance between the different groups of elements changes, the "focal length" of the lens changes as well.  The focal length tells you how much magnification the lens creates.  A fixed 50mm lens, not designed to zoom, is considered the normal focal length for most 35mm cameras.  Something like a 35mm lens or 28mm lens would be wide angle because it's a smaller focal length, while something like a 75mm lens or bigger would be a telephoto because it magnifies the image more.  So, just as an example in a zoom lens, perhaps if the elements are close together a lens will have a focal length of about 75mm, but when you "zoom" the lens and make the elements move apart inside, the lens can stretch its focal length to maybe 200mm.  In summary, most lenses have elements that stay in one place and provide a single focal length, but zoom lenses have groups of elements inside them that can be moved back and forth to provide different focal lengths.


That's it!  I hoped I've been able to help!

Good luck with your project, and please let me know if I can answer any other questions.

David Silver