Aperature/Shutter Speed

[vegas]

I am so lost ... I just started the class and I know this stuff doesn't just hit you over night (or atleast me) but I cannot grasp the concept of aperature and shutter speed:meh: . I mean I know that aperature is the amount of light:thumbup: and that shutter speed is how long the shutter is open:thumbup: but I don't understand how to put the two together to create a decent photograph:thumbdown: . We are not allowed to you auto cameras so everything must be done in manual mode. I have read the text over and over but it all looks random numbers to me. Any suggestion or ways to simplify this would help. Thanks guys

Oh and its a Nikon N55

 

[EBphotography]

It's hard for me to explain things, but I'll try. Think of it like a balance. On one side we have aperture, on the other we have shutter speed. We need to get these two things to a point where our balance sits nice and equal. How we modify each depends on what we are shooting. If I am shooting sports, my shutter speed is going to be my priority over aperture. So, first I would adjust my shutter speed to what I need. Then, I would adjust aperture accordingly, so that my balance is equal. You will need to compromise in some situations. Sometimes there is just not enough light to have optimal settings on both. If I was shooting an object such as a flower, where I Depth of Field was very important to me and fast shutters are not crucial, aperture would be set first and then shutter adjusted accordingly.

It's not something you can really put a mold to and say "use this all the time." A general way to think about it is this, as shutter goes up, aperture goes down. If you have a fast shutter speed, you will need a low aperture to allow plenty of light in. The reverse applies. If you have tons of light coming in through the lens, the shutter doesn't need to be open as long, hence a faster shutter speed.

Another more real-life comparison would be a damn. You can control two things when letting the water through. How big the opening is, and how long we leave it open. If we have a certain amount of water we want to get through, we need to adjust these accordingly. The bigger the opening, the less time it needs to be open. The smaller the opening, the more time we will need to get our appropriate amount. Other factors apply but this is a simple shutter/aperture comparison.

Hope these descriptions help.

Eric.

 

[Big Mike]

This is an analogy I've heard before...it's not perfect but it may help.

Lets say that the film is a bucket and light is water. The idea is to fill the bucket to the top with water (create a properly exposed photo). You can open the tap (aperture) and the length of time you have the tap open...is the shutter speed.

So lets say that if you open the tap 1/4 of the way...it takes 10 seconds to fill the bucket. Got that?

Now if we want to fill the bucket in a shorter time (faster shutter speed)...then you can open the tap more. If you double the size of the tap opening (from 1/4 way to half way)...then you will reduce the time to fill the bucket by half...so 5 seconds. Got that?

We still end up with a full bucket. Now if we had opened the tap but still had 10 seconds...we would have had too much water (over exposure).

That's the way that shutter speed and aperture work. If you change one of them...you have to change the other one...to even it out and keep the same exposure. Got that?

Now...you can't be expected to know where to start...right off the bat. That is where a light meter comes in. Most modern cameras have built-in light meters...so that you know where to start. That would be where we got the 1/4 tap @ 10 seconds. So once you get a reading from the camera's meter...then if you want to change one of the settings...you also have to change the other setting to compensate...or else you will get too much or too little water (exposure).

To make it more complicated...the camera's meter always wants to fill the bucket to the same level...which might not always be what you want. So you can put in more or less water (exposure) to get what you want. To do this, you would check what the meter says...and then change only one setting.

Does any of this make sense to you?

 

[vegas]

I am starting to see light at the end of the tunnel I just don't know what situations I would need to adjust these settings. Is the Cameras light meter usually correct or do i need to adust it more often then not?

 

[Big Mike]

I am starting to see light at the end of the tunnel I just don't know what situations I would need to adjust these settings. Is the Cameras light meter usually correct or do i need to adjust it more often then not?

Now you are getting into the subject of metering. It's sort of the next step once you have learned about exposure.

Some people always go with what the camera's meter says...other will make adjustments all the time. The meter is designed to give you an average exposure for an average scene...so it should be pretty close most of the time. Also, if you shoot regular color film (negative or print film) or B&W film...there is a fairly large margin for error...so you don't have to get it just right. Slide film, however, has a very small margin for error...so it's important to get it right.

Knowing when and how much to adjust the settings away from the meter's reading...I'd save that until you have got a good handle on exposure.

 

[vegas]

I am shooting B&W film only.. It is so much easier just to leave it on Auto

 

[Torus34]

http://www.thephotoforum.com/node/36

 

[shingfan]

Mathematically speaking.....you are looking at a math equation which with different combinations of aperature, shutter speed, and film speed (ISO)...you achieve different exposure value.......and of course....for proper exposure (not creative exposure)......there is always a fixed value that you would like to achieve......i've never used film camera......so i'm not sure by using auto....can you determine the aperature, shutter, ISO that was used.......even if you cant........what you can do is

1) fixed the film speed
2) fixed either the aperature or shutter speed
3) find out what aperature or shutter speed would yeild the best result in terms of exposure

then from now on....if you want to obtain proper exposure...you would use these 3 numbers as the basis for your calculation......

the formula works like this

exposure = ISO * shutter / aperature ^ 2

you notice ISO and shutter speed work linearly and aperature works a little differently with the "squaure".....because aperature works by factors of 1.4 (square root of 2).....thus on lense...you often see the f number goes up in this sequence...1.0, 1.4, 2, 2.8, 4, 5.6....

for example...for a proper exposure...you have the following setting

ISO = 100
S = 1/100
A = 2.0
exposure = 100 * 1/100 / 2.0 ^2 = 0.25

then in the same lighting situation...to get proper exposure...you would like to obtain the same exposure number 0.25.....say now you have ISO 400 instead of 100.....then you would need anohter combination that would yield the same result.....an easy way of doing it is by know what is the multiplication factor...in this case...it is four....so you have the following options

1) increase the shutter by a factor of 4 (1/100 -> 1/400)
2) reduce the aperature by a factor of 4 (2.0 -> 4.0)
3) increase the shutter by a factor of 2 (1/200) and at the same time decrease the aperature by a factor of 2 (2 -> 2. 8)

and any method above would give you the same exposure value and thus same exposure result....however......with different lighting condition...you would need different exposure value.........to determine what exposure you need to use.....you'll need a light meter......i use digital camera.....it has a build in light meter.....i've never used a real light meter before....so i cant help you on that.....i'm also a beginner on photography.....

and the reason for changing the "3" settings

1) ISO - insufficent, you want to fix the aperature and shutter speed on purpose and you have no choice but to increase the ISO

2) Aperature - you want to change the DOF....to obtain the same exposure...you woudl need to change either the ISO or shutter whichever works the best

3) Shutter Speed - you want to blur (slower shutter speed) or freeze (faster shutter speed) action....again...you would need to adjust either aperature or ISO to acheive the same exposure

i hope this informative ... cheers

 

[Jeff Canes]

-- Is the Cameras light meter usually correct or do i need to adust it more often then not?

Vegas, following up on what Mike said about metering
A lot of cameras have more that one metering mode. Check the manual to see if your camera has more that one. If you do take some test shot in each mode of the same object and light. Also don’t for get to take notes of setting. It’s not that hard you will get a hag of it soon hopefully

 

[bikeuphill9]

I am in the same boat as you vegas. I just finished enlarging my first two photos. The light at the end of the tunnel is beautiful. It took me a few days to figure out the whole aperture/shutter speed thing as well. I sure hope the more photo I take the better I will get at it, as right now I am inconsistent at best. Good luck.

 

[Ab$olut]

if your camera has a histogram use it helps alot :thumbup:

 

[fightheheathens]

most film cameras dont have a histogram.....
the ones that have it though...man....

 

[markc]

This page I came up with might help a little.
http://www.photogs.net/tpf/exposurechart.pdf
The chart itself isn't anything new, but I tried to make it a bit like a game.

Put three pennies down for a certain exposure, like ISO 400, f/5.6, and 1/60 sec. If you move one penny in any direction, one or both of the other pennies must move in the opposite direction for the same total number of spaces. For instance, if you move to f/16, you could move to 1/8 sec, or 3200 ISO, or 1/30 sec AND 1600 ISO. They all will give you the same exposure. The sunny 16 rules will give you a good starting point if you don't have a light meter.

 

[Weaving Wax]

Ok...I'm going to jump in because I'm having a bit of a hard time understanding exposure. (But I LOVE the game!) Let me see if I understand..

Ok..

I'm at f/16. ISO 100 and shutter speed at 1/250.

If I move up to f/11, I'd move to 50 ISO and 1/500 of a second? Because I only moved one f stop up (or down...whatever you want to say)...

 

[markc]

If I move up to f/11, I'd move to 50 ISO and 1/500 of a second? Because I only moved one f stop up (or down...whatever you want to say)...

50 ISO OR 1/500 of a second. You only moved one total space to the right, so you only move one total space to the left. So...

ISO 100; f/16; 1/250 sec
ISO 50; f/11; 1/250 sec
ISO 100; f/11; 1/500 sec

are all the same exposure.