I've recently brought the Canon 350D with 18-55mm & 70-300mm lens as a starter kit. I am very eager to use the camera to its full potential and get in to it more professionally. I continue to come up against the term: 'f/11..'. or 'f/8...' Probably a really obvious question but what does the 'f' stand for in these terms? and what function does it perform? ( Im one of these people who really likes to understand everything properly before feeling confident to progress!!) I would be very grateful for any 'idiot guide answers' for complete beginners or any relevant books/sites i could visit which can explain all the main basics to someone like me. Many Thanks.

Hey man, welcome to the site. First of all, as far as I know, the "f" doesnt actaully stand for anything...maybe "full" as in full stop, but I don;t really know. It doesnt matter though, just know that f stops refer to the aperature your lens is using. f/8 is a larger hole (and therefore more light gets in) then f/11. I don't think I explained that very well, sorry. There used to be a beginners FAQ section somewhere on the site which was a really good guide for begginers, but I don't know where its gone now that the site has been revamped. A moderator or someone may come along shortly and know where it went.

I was trying to find the beginners FAQ, but I couldn't. Maybe the Mods could find it and re-sticky it to the top of this forum. Welcome to the forum. I don't know if F actually stands for something...but "F-stops" are the measurements on the aperture scale. The "F number" is a ratio of the diameter of the aperture (hole in the lens) over the focal length of the lens. The smaller the F number, the bigger the aperture (which means more light) Each "stop" is twice as much light (or half as much if you are going down)...although the numbers are not linear. For example, F4 is not twice as much light as F8. You should be able to search out a scale of F numbers to give you an idea. If we can't find the beginners "start here" thread...look up basic exposure, aperture & shutter speed. Once you are familiar with these terms, you can start to understand how they interact with one another to give us the ability to take a photograph. These things have not changed in the digital age...so even old film camera sources will be helpful to you.

Many thanks to you both for your replies, it begins to make sense...slowly! So just to make the connection to the actual shot you take; You would use, for example, f/1 to capture maximum light for say an outside, sunshine shot and f/20 (or whatever the number goes up to) to capture less light for a nighttime shot? Or is it vice-versa? Just trying to make the connection so i understand what setting creates what photograph, and how to make good use of it etc. Many thanks again.

Vice-versa. You would probably use a low F-number for inside/night and a high F-number for bright sun. (but that depends on shutter speed as well) When it's dark, there is not much light...so you want to get more light (bigger aperture/small number). When it's bright there is lots of light, so you might have to limit it with a smaller aperture/higher number. Think of it this way. Your image is a bucket and light is water...you need to fill the bucket with water. You can open the tap wide (large aperture, low number) and fill the bucket quickly (fast shutter speed). OR You can open the tap a little (small aperture, high number) and fill the bucket slowly (longer shutter speed). Aperture also controls DOF (depth of field) but you can learn about that later.

Great explanation, thank you. Do you know of any sites/books which displays what camera setting takes what type of photograph? Sort of a visual scale to see the end result with what setting helped to achieve it. I apologise for the continuous questioning!

Maybe check your local library or Amazon.com etc. for photography books. There are some good ones but I don't know their names.

This one is a bit of a gimme, but not to all people. The ‘f’ in f-stop actually stands for Function as it is used in algebra. It is an unknown that needs to be solved. For those not familiar with this, it basically means that a function is a mathematical action where whatever numbers you put into the function, there can be one and only one answer based on the number put into it. This sounds a little weird, but let me give it to you this way. To achieve the number 4 by adding number together is a function. Thus: 1+3=4. 2+2=4, etc. The numbers do not matter, and the answer will change. But the mechanics behind this do not change and regardless of the number inputted there can be only one! (My apologize to William N. Panzer.) In photography, the consistency of the f-stop to the speed is consistent. You will notice that the slower the speed, the smaller the aperture. The faster the speed, the larger the aperture. F-stop formula: f/stop = focal length ÷ diameter Example: 10 ÷ 0.024 = 416.66666 (f/417) A more detailed answer is here: http://www.google.com/search?hl=en&lr=&q=define%3A+function A detailed answer to the f-stop itself is here: http://www.uscoles.com/fstop.htm

An additional note: Basically the f stands for f= to something. Like x= something. Its the end result of an equation. This from the web site http://tangentsoft.net/fcalc/help/FNumber.htm : Formulæ Used f stops are powers of the square root of two. The first f stop is to the zeroth power, or f/1.0. Next is to the first power, or f/1.4, and then squared for f/2, etc. As you can see, common values like f/2.8 are actually approximations of the unwieldy "true" values. Some versions of f/Calc show you these ugly values when you pick f numbers from its pull-downs, simply because it does its calculations based on the numbers in the fields. (Other versions are smart enough to show you the approximation but use the true value internally.) To calculate a new aperture value f2 from an initial aperture f1 and a given number of stops, we first convert f1 to a number of f stops from f/1.0, with this formula: Then, we add the result of that to stops, and convert back to an aperture value with: To calculate the number of f stops between f1 and f2, first convert both values to a count of f stops from f/1.0 as above, subtract the results, and convert back to an aperture value.