Photography 101

[BigV]

"F8 and show up"

There *is* more to it than that, right? Of course. I know that.

I take a lot of pictures. Goodness knows I've subjected many of you to many of them, and your patience and forbearance is sincerely appreciated. But I do yearn to learn. I want to be better. I read a lot, I take a *ahem* lot of pictures. And I continue to struggle.

I have seen some of footfootfoot's artistry, and we have all enjoyed his wisdom. I found this remark especially instructive.

There is no such thing as a "real" photo no matter where you look.

I could have posted it in the HoF, but I chose to use it as a springboard here.

Many times I have read something and failed to comprehend it completely. I wished I could have had a place to ask my question. This thread is that place for me now, and for others.

I hope to learn from dwellars here. I'll post some questions, and some pictures as examples. I'm not going to be shy--my mistakes will be standard fare. If I have something neat to post, there's a place for that already, and other cool threads. They're not likely to be pretty, but I do expect them to be instructive.

Class is in session.

[BigV]

First question:

I don't really understand "exposure".

Increasing exposure, stops, etc. I (think) I know some ways to do it. That is, I'm sure there's more than one way to do it. And each different way has different "side effects". Increasing the aperture, the size of the opening behind the lens. Naturally, this will increase the amount of light entering the camera.

Or, increasing the length of time the shutter is open. That also lets more light in.

And making more light reflect from the subject, like with a flash, that also increases the exposure, right?

Stops? I'm confused. And to what extent is six of one indistinguishable from half a dozen of the other when it comes to trying to reach a certain point?

I'm trying to clear a backlog of unarticulated confusion, and I'm certain that shows. I'll organize my questions better in the future, now that I have a place to put them.

Thanks.

[SteveDallas]

There is actually a book called "Understanding Exposure"! It comes highly recommended. (I admit I've never gotten around to reading it in depth.)

You're simply dealing with the amount of light entering the camera. One "stop" represents either double or halving (depending on which was you go) the amount of light coming in. So f/16 lets in twice as much light as f/22. (Why 16 and 22? I dunno. It's probably some math thing about inverse square laws but I don't really know.)

As you say, you can manipulate the camera (aperture and shutter speed) to control the amount of light, or you can add artificial lights such as a flash. strobist.com is a great site for info about combining off-camera flashes with existing light.

[jinx]

I don't know anything, I just wing it.

[Bullitt]

Check this thread out Bigv: http://cellar.org/showthread.php?t=1...hlight=shutter
Might help ya a bit. Keep asking questions though, one of us is bound to have a halfway decent answer for ya.

[Undertoad]

I'm a total amateur, but I think I get the notion of either you let a lot of light in for a little time, or a little light in for a lot of time. But I don't understand how, exactly, you vary the amount of light you let in.

I could see how different lenses would let more or less light in, depending on their quality, but I don't understand how a camera can decide to let less light in.

[SteveDallas]

There are two basic ways. Change the size of the hole the light's going through. (Many camera lenses have a variable aperture.) Or, change the amount of time the shutter is open.

[Ibby]

To expand on what steve is saying...
inside the lens is an aperture ring. It consists of a bunch of 'wings' that roughly simulate a circular opening, measured in f-stops and usually able to move between 3 (or 4.6) and 22 (or even 30 in high-end lenses); in OLD, old cameras, pre-automatic, one had to physically turn a ring on the lens which would open or close this hole. Now, the cameras do it automatically with motors. Then, secondly, inside the camera itself is the shutter. on most DSLRs and film SLRs the shutter can stay open for up to a minute (or 30 seconds, depending on the camera; my old Minolta only goes up to 20 seconds, while my Olympus digital can go up to 90 seconds I think) down all the way to 1/2000th of a second.

'But', you say, 'why would I need TWO variables there?' The answer is twofold. A smaller aperture, confusingly referring to LARGER f-stop numbers, results in a bigger depth of field. For example, at a wide aperture, like 4.6, the depth of field might only be 2 or 3 inches deep, meaning less of the picture will be in focus, while a small aperture, for example 22, would result in a much greater depth of field, meaning that background and foreground elements would be much clearer. Thus, if the intended effect is to have a very small amount of the shot in focus, like a macro shot, a wide aperture is used. And so, the shutter speed would change to reflect this; f.22 would require a longer shutter speed. This ends up taking us to the second point; the shutter speed. A longer shutter speed would be used to create affects of, say, motion blur, or used with strobe lights or repeated flashes to create the affect of multiple exposure; a short shutter speed, to 'freeze' action like at sports events. However, dark situations, like indoors or at night, would obviously require a long shutter speed AND a large aperture; this makes night/dark condition photography very problematic without a tripod or a powerful flash.

[Undertoad]

Yeah, the thing I don't get is why opening the hole larger works. When I hold up my hand to my eye and make a ring of it, opening the hole larger just makes me see more stuff. I can see how it lets in more light too, but why doesn't it just enlargen the size of the picture?

[SteveDallas]

Your eye and brain adjust for the different light levels.

But note that your "field of vision" is exactly the same. It's just that part of what you're seeing is your hand blocking stuff. When you change the aperture of the camera, the field of view doesn't change any more than the field of view of your eye changes when your pupils contract and dilate to account for different light levels.

Oh, umm, you asked WHY doesn't it change? I don't know.

[footfootfoot]

When I get back home I'll post a text file of some of my lesson plans from my teaching days. Ibby's got a pretty good explanation but has crossed a couple of minor wires.

The simplest explanation for anyone with simple math skills is

Exposure equals intensity * time.
E=I x T Just like any equation you can shift the parts around.

f stops are a fraction. The diameter of the opening in the lens over the focal length (the distance from focal point of the lens to the film plane when the lens is focused at infinity) of the lens.

eg If the diameter of the aperture or opening is 25mm and the focal length of the lens is 50mm then you are at f:2.

Another way of saying it is f: (in this case focal length 50mm)
50mm:2 = 25 mm

That is why when the f: number gets numerically larger, the opening gets smaller, because the f: number is just part of a fraction.
50:25 = 2mm.

It doesn't surprise me that you don't understand exposure since you live in a city which has no light to speak of. (nyuck nyuck)

But An example of E= I x T is getting sunburned.

Anyway, more later

[Ibby]

UT, think of it like this

not 'holding your fingers in a circle around your eye
but rather
your actual pupil dilating/contracting.
THAT is our equivalent to an aperture.

[Clodfobble]

Sure, but why doesn't your field of vision get bigger or smaller when your pupil gets bigger or smaller? Or maybe it technically does, but imperceptably so? I did some googling but couldn't find the answer.

[footfootfoot]

Originally Posted by Clodfobble

Sure, but why doesn't your field of vision get bigger or smaller when your pupil gets bigger or smaller? Or maybe it technically does, but imperceptably so? I did some googling but couldn't find the answer.

Field of vision is the angle of view, ie. how wide you see which has to do with focal length or in this case the shape, size and spacing of your eyes.

Depth of field is the distance between the nearest and farthest object with an acceptable degree of sharpness. There is only one point of focus, but as aperture gets smaller the degree of sharpness increses.

This happens with the human eye as well. You have greater visual acuity on a bright sunny day than you do in the dark. (leaving aside the issues of color vs b&w vision) That is why when you get your eyes checked it is done in a dark room. Your pupils are dilated and therefore at their worst, sharpness wise.

Is spexxvet still around?

[Clodfobble]

I understand those to be true facts. I just don't understand why the size of the opening doesn't affect the angle of view.