Eat your hearts out digital users, this one is strictly for those of us or still like and use film. Welcome to film types 101. Today there are three main types of film. Colour Negative, Slide (Colour Positive), and Black & White.
Film Sizes
In the photography world today there are three categories of film sizes that are still available for use as new stock, some rarer than others, but still there.
Small Format: This is the film that replaced medium format for the hobbyist, commonly called 35mm or 135, very easy to load into cameras, and available everywhere photographic equipment is sold, even convenience stores and drug stores. You can get it in Black & White, Slide, and Colour Negative forms. Very clear results, does well for enlargements but at higher speeds a very noticeable grain. It was first introduced in 1934 by Kodak, and by the 1960s surpassed Medium format film as the film of choice. Very few companies these days still produce film cameras, but Nikon and Canon both have new SLRs available, not to mention a large selection of used equipment available. 135 film is 35mm in width and produces an exposure of 24mm x 36mm.

My Nikon F3 surrounded by rolls of 35mm film

Webster’s Falls in Dundas, ON captured on Kodak Ektar 100 35mm format
Other film sizes that is classified as Small format are: APS (Advanced Photo System), 110 (Pocket Cameras), 126 (Instamatic), and 828 (Similar to 135, but lacks the sprocket holes)
Medium Format: This was the original film for the camera enthusiast, and came in many different sizes and types over the years since it was first introduced in 1890. Today the two most common medium format film in 120 and 220, the only difference between the two, which both are the same width (120mm), but the 220 film lacks the backing paper like 120 has, and as such you can fit twice as much film on a spool. Also with Medium format you can produce many different sizes of exposures, the most common are 6×4.5, 6×6, and 6×7, but in the past there have been 6×9, 6×24. Of course the larger the exposure the smaller number of exposures per roll you can get. 120 and 220 are both still available from photography specialty stores, online stores, and even Ebay. But good luck finding it at your local Walmart Lab.

A Yashica-12 with a 120 roll of Fuji Velvia (RVP). The Yashica-12 is an example of a Twin Lens Reflex Camera producing a 6×6 exposure.

An example of a 6×6 image taken on a Rolleiflex 2.8F camera

The Pentax 645 is an example of a Medium format SLR, producing an exposure 6×4.5, and can use both 120 and 220 film depending on the insert

An example of a 6×4.5 image taken with the Pentax 645

The Agfa Box (circa 1930s) produces a 6×9 exposure. And yes, this camera still works.

An example of a 6×9 image taken with the Agfa Box.
Other older Medium Format sizes are: 127 (still available actually) and 620 (discontinued but if you have 620 spools you can re spool 120 film onto them).
Large Format: Also known as sheet film, these hark back to the days of wet and dry plate photography and can still be purchased new, the two most common format are 4×5 and 8×10 (and that’s in inches). In fact Kodak just released it’s famous Ektar 100 film in 4×5 format. I can’t really speak much on large format, expect that they have incredible detail and next to no grain, and when using slide film, the colour reproduction and saturation is incredible. However the cameras are huge, and it’s awkward to load up film as you can only have one exposure in the camera at a time. And developing when you don’t do it yourself can be expensive. There are even larger sizes that have been available in the past for large format photography, even up to and beyond 11×14.
Film Types
Colour Negative film is the most common type of film and is readily available from any photographic store to your local convenience and drug store. It is usually processed using the C-41 process, which can be done at a local lab using an automatic machine and is available in all three formats, Small, Medium, and Large. When you get the negatives back they will appear as a brown translucient image with the colours looking rather strange, because they have been reversed, hence the term “negative.” These types of films process very normal colours, similar to what you’d see through your own eyes, often cheaper to buy and develop. Some good films to try of this type are: Kodak Ektar 100, Fuji Reala 100, Portra 160VC, Portra 400NC, Fuji Pro 160S, also Kodak Max 400 and Fuji Superia 200.

Colour Negative Film, in this case Fuji NPH 400, 120 Format
Slide Film, or Colour Positive film, when viewed the colours will be as you normally see them, and often come pre-cut and mounted (in the case of 35mm slides). The most common process to develop slide film in E-6. However the older Kodachrome films used the much more complex process called K-14, currently only Dwayne’s in Kansas can process K-14 and then only until the end of 2010. Even Kodak has stopped producing the film and the chemicals for this process. Slide films have a very rich contrasty colour, and often aren’t available at anything over ISO-400. Most slide films these days are only avalible in colour, however you might still be able to find some Agfa Scala, which is a black & white slide film. Some good films to try of this type are: Fuji Velvia 100F, Fuji Provia 100F, Fuji Provia 400X, Kodak Ektachrome.

Colour Slide Scan, Fuji Velvia 100F, 120 format.
The film and the most classic film is Black & White, as the name suggests this is monochromatic film, no colours at all, but rather colours are represented by different shades of gray. This is also a negative film, so when you look at the film they are reversed. There are two types of Black & White film, there is the traditional style which you can develop yourself if you have the right chemicals and equipment, and there are C-41 process b&w films. The C-41 films will often have a colour tinge to them because C-41 is by its nature a colour process. B&W is the oldest film type still available, with several classic films still available to be purchased new (the chemicals have changed over the years of course as newer safer ones become available.) Some films of this type to try are: Kodak Tri-X 400, Kodak TMax 100, Ilford Delta 100

An example of Black and White, in this case Kodak Tri-X, 120 Format.
And on a final note, Polaroid. Instant film was first introduced in early to mid 20th Century, where all the chemicals needed to expose and develop the image was contained in one simple package. However in 2008, Polaroid announced it would cease production and shut down all it’s plant, Fuji still produces instant film and cameras. But Polaroid had developed (pun intended) a cult following, and the Impossible Project was launched and has now started producing new instant film for the thousands of Polaroid cameras still around. Keep an eye here to see how my results with Impossible Project film goes.