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ok, so I am new to the wonderful art of Photography and I love it. there isn othing better then going out and taking photo's. It can be very peacfull and relaxing. I have a completly diffent look on the world now after looking through the eye piece of my camera. I am trying to get more familiar with my Canon t90 and all the wonderfull options that it offers but it just seems like there is too much and i ger overwlemed. I keep hearing about apertures and all that good stuff but i just dont know when to or what to adjust the aperture to when i want to change it. Can anyone give me any advice on a good way to learn more about how to use the F-stop and when? thanks
Mitch

There are way to many things to explain about the f/stop here, and lots of things have been written. I would suggest a google search on the term "f/stop" and pick something out that you can understand (I am not infering anything here, but people comprehend things differently).

I found a pretty good explanation at http://www.uscoles.com/fstop.htm if you are intersted. It covers many questions and misconceptions.

If you have more questions, post them here. Usefilm is a pretty helpful bunch of people.

I just looked at the link David posted and it's excellent.
But, here's a more simplistic way of explaining what it DOES rather than what is IS.
F stop numbers are backwards (there's a reason why, but I forget what it is). So f 1.4 to BIGGER than f8 and f8 is bigger than f22.
The smaller the f stop (larger number) the greater the DOF (depth of field...what is in focus)...but, when you use f16, for example, you are using a much smaller opening than f2.8 so you will have a much longer time the shutter is open. (slower shutter speed).
So photography is about making the decision of how much of the scene needs to be sharp and determining your f stop from that point.
Or, lets say you want to blur water. Then you would need the smallest f stop your lens has (usually f22 or f32) so you can use a very slow shutter speed (and a tripod!)
I am not familiar with the t90, but if it has a DOF preview button, use it. Just take the camera, arrange some objects on a table in a line going away from you, focus on one of the objects close to you and use the DOF preview button. Keep doing it till you get the feel of how many of the objects are in focus at different aperatures. You will see a HUGE difference between the smallest and largest aperatures.
Hope this helps. It is confusing to everyone at first.

f-stop is backwards because the are fractions of the focal length!

Eg: focal length divided by 1.4 (f/1.4) is BIGGER than focal length divided by 8 (f/8).

So an f/1.0 lens would have an aperature as WIDE as the focal length. Now you can see (in part) why those pro telephoto lenses are so huge :)

Hi,

you've already got the best way to understand what the hell an F-stop is: your T90. How to do it? Activate the exposure compensation and move its setting to the plus or minus side and observe how it changes speeds and or aperture right on the T90's LCD screen.

The exposure compensation on the T90 goes at 1/3 of a stop a time, if my memory is fine.

On an objective explanation, an F-stop change is when you change the amount of light reaching the film by its half or double.
Example - you're shooting at 250/3.5
Changing speeds, an F-stop plus is 125/3.5 and an f-stop minus is 500/3.5. Remember that the plus and minus is relative to the quantity of light reaching the film, NOT to speed nominal values.
Changing apertures you'd have 250/2 and 250/4.5 respectively.

Hope that helps.

Regards,

Jose Azevedo

F-Stop:

It's one piece of the exposure puzzle. So, we all know that with the right exposure the right amount of light gets into the camera to make the perfect exposure (play with me here and agree).

There are two pieces to getting the right amount of light: F-Stop and exposure time.

Part I: The more time (longer or shorter exposure), the more light will get into the camera. Part II: The smaller or bigger the opening the more or less light will get into the camera.

F-Stop is just a measure of how big an opening your camera is making to let light in.

F-Stop is the ratio of the length from the beginning of the lens to the plate in the camera where the light hits to the width of the lens. So if my lens is an inch wide, and the beginning to the flim or sensor in my camera is 4 inches, the F-Stop is 4.

The longer the lens to the opening, the less light gets into the camera, and the higher the F-Stop. So a higher F-Stop means LESS light.

Make sense so far?

Well, your camera has a little metal iris that can open and close like your eye, letting in more or less light. When you close the iris and make less light get through, the higher the F-Stop.

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There are two major things to consider after all this blah-blah-blah:

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In the end you need the right amount of light. So the higher the F-Stop the less light you let in, so the longer the exposure. For sports, action, or something where you want to freeze something moving fast you want a higher shutter speed (a short exposure), and you may need a low F-Stop to let a lot of light into the camera.

If you want a long exposure, for waterfalls, or you want to make people blurry, you may need a higher F-Stop to make the exposures really long.

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The second thing has to do with physics and light diffraction. Just trust that when you make a smaller opening in the camera the light actually will bend to make more of your surroundings sharper and more in focus. This is depth of field (DOF). So the less f-stop, stuff not directly focused by you will appear more blurry the further away they are from your point of focus. This is shallow DOF.

The higher the f-stop, and the smaller the hole, more of the stuff away from your point of focus will appear in focus. You will have a greater DOF.

So, if you want to have a shallow depth of field, you need a low F-Stop. To have everything crisp and clear, a higher F-Stop.

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So, in summary, think of whether you want to put importance on the shutter speed (stopping action vs. blurring motion), or if you want to put importance on the depth of field (F-stop).

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Make sense?

Ann .	Greg S.	Jill B.	Jesper K.	David R.	Neil M.	Allen ..	Jill B.

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