Explanation of the F Stop

[Melody]

In talking with a some people just learning and on my continuing quest I thought I would share some of the sites or information I've found in the past. I hope they might help others as well. If you've got a link or want to add your own experience that would be great.


http://www.uscoles.com/fstop.htm


Melody

[cmclaughlan]

Nice one !

Thanks for that Melody.

Colin

[Igor]

Melody, I happen to study some old photo-books since I'm lying in bed with back problem now.
So I even draw a very handy table which displays not only f-stops, but 1/2 and 1/3 f-stops. This can be handy for teleconverters, for example.

In short you only need to remember TWO figures: 1.4 and 2. These are basic f-stops, all subsequent are just multiplied by 2.

Each subsequent f-stop allows TWO times more light into the lens. For example f/2 gets TWICE more light than f/2.8 and so on...

Sorry if this all is just talking down :) :red:

[Melody]

Thanks Colin, glad you found it interesting.

Thanks Igor, I doubt anyone learning thinks of basic/simple instructions as talking down they appreciate it. It's much better then assuming knowledge, folks have to learn I for one LOVE SIMPLE! Thanks :)

Melody

[Gil]

What a great article. It is superb! Now we need to find one that explains inverse square law.
I am printing it out.
Thanks for sharing Melody!



Gil

[Tom V]

Using a bucket to explain exposure is how I taught photography to my friends back in High School. The size of the bucket is determined by the ISO (ASA), the size of the faucet filling the bucket is the lens aperture, and the length of time it takes to fill the bucket is akin to the shutter speed. Fill the bucket, and you have the correct exposure.

F/Stop numbers always remind me of plumbing. A pipe with a 2.8 inch inside diameter carries twice the fluid that a pipe with a 2 inch inside diameter carries. If I ever do any plumbing, it might come in handy.

And of course, 1.4 is the square root of 2, and 2 is the square of 4, and 2.8 is the square root of 8, and 5.6 is the square root of 32, and so on. (The numbers are rounded off.)

[proberts]

I for one LOVE SIMPLE! Thanks :)


That explains why you talk to Brian :rofl:

(running and hiding)

Paul

[Melody]

That explains why you talk to Brian :rofl:

(running and hiding)

Paul

Oh I couldn't miss this although I am in a hurry here ya go:

It takes a VERY BIG MAN that can explain things in a simple manner the others try too hard to impress (uh they aren't :P) That's why I talk to Brian :getdown: hey I have excellent taste I know who can teach me and has the patience to :) (gosh that was such a good response...where is my pat on the back smilie??) darn I'm on a roll and have to get back to work I shall return! :lol:

Melody

edit: please tell me I don't have to individually list the various people on this list who take the time to teach me?? You know who you are! Thank you!

Ok break time, gosh that was a fun break earlier..........

Glad you found it helpful Gil, Tom now I know something about plumbing too! :) btw Igor I'm sorry I forgot to say it earlier, I hope your back feels better soon and you can go out and take pictures ;)

[Linda G]

Okay, I admit to only glancing through the article, no great concentration powers today. Does the article explain why you would want to change the combinations other than to get enough light on the film/sensor?

I used a slide show example for my children and their friends when I taught them my 'dinning room table' class of photography that had my purse on the top of a slide at a play ground. The exposure was right in each yet one had it wide open and the other had it stopped down. The kids, being kids, gave it an analogy of 'good thief, bad thief'. The good thief would be aware of everything and the whole surroundings would be in focus, stopped down. The bad thief would see the purse and be oblivious to everything else and the purse would be the only thing in focus, wide open.

[toners]

Good thief vs. bad thief - that's pretty good.

Ok, my contribution is something I dug up years ago when I was teaching photography at a community college. The something is how the term "stop" made its way into photography. In the early days to control light cameras used metal slides with circular openings of various sizes that slid into a slot in the lens. The idea was borrowed from similar devices called "stops" used to control the flow of air in pipe organs. Small hole, less air, quieter sound, and vice versa. "Pulling out all the stops" became a phrase for putting a lot of energy into something.

And, no, other than it is likely that the word "stop" was used because the device stopped the flow of air to more or less of a degree, I have no idea how the term got to be used in relation to organs.

I think this is likely correct, but before you incorporate the information into that Encyclopaedea Britannica you're writing maybe you'd better check me on it!

[lightwrangler]

I think you are correct Tony. Stops, stop light. I seem to recall that stops got their name from Waterhouse Stops, which were plates with different size openings on them. Some motion picture cameras use lenses that have stop plates in them. When you change the f stop you must physically change the plate. I remember using a large format lens many years ago which had small changeable aperature plates, but even then it was considered really, really old equipment. (from the '20's or '30's) The eventual use of a iris to control aperature, elimated the use of "stops" in most situations but the term remained. I guess that we correctly use aperature openings these days which are marked with stop settings.

Cheers,
Adrian
(currently running at f8 today) :lol: