Exposure vs Shuttle Speed?


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sapphy

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Jun 17, 2007
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#1
Hi, I was just wondering what's the different between these 2?

Increasing exposure = lowing shutter speed no?

Since I can manually change the shutter speed why would I need the exposure option? Please clarify my doubts =/

Thanks! Just using a F31FD.
 

Rashkae

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Nov 28, 2005
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#2
Remember, it's "Shutter", not "Shuttle".

I'm assuming you're referring to "Exposure compensation". It basically allows you to modify the exposure sensitivity without changing the shutter speed.

Let's say you want to take a 4 second picture of a watefall to get the nice smooth smoky effect. So your shutter speed is set to 4 seconds. But if even at the smallest aperture and lowest ISO you're still getting an over-exposed shot, you'll need to reduce the exposure value. Makes sense?
 

Rashkae

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#4
BUT, it's also good to note that some cameras, especially newer ones, modify exposure in a more literal way, by allowing you to over/underexpose based on the metered light.

Let's say your camera's metering say that the shot will require 1/500th sec exposure at f4.0. So you set the exposure higher, and the camera will then open the aperture to f3.2 to let more light in. You're essentially deliberately overriding the camera and telling it to over-expose a pic.
 

Rashkae

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#5
It mainly has a lot to do with camera meters treating incoming white light as 18% grey. So you can manually compensate for it. a good example is a snow-covered landscape... The camera can get "fooled" by all the snow and not get the exposure right, making the snow look grey. By adjusting the compensation, you can make sure the "white" comes out correctly.

Mostly black images can fool the metering and over-expose the shot. So you can apply negative exposure compensation to correct it.
 

Scaglietti

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Jan 14, 2005
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#6
Hi, I was just wondering what's the different between these 2?

Increasing exposure = lowing shutter speed no?

Since I can manually change the shutter speed why would I need the exposure option? Please clarify my doubts =/

Thanks! Just using a F31FD.
I assume you mean exposure compensation when you said "exposure option".

Assuming ISO is fixed, there are 2 component in the exposure: shutter speed and aperture.

Yes, if you are in full manual exposure mode (M mode), you decrease the shutter speed, you will increase the exposure value (aperture is unchanged).

If you are in Shutter priority (S mode), you set the shutter speed and the camera determines the aperture. If you lower the shutter speed, the camera will reduce the aperture to maintain the same exposure value. You will need to use the exposure compensation to "over" or "under" expose.

BC
 

megaweb

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#7
Adjusting exposure is like compensate the exposure. The changes will determine the overall exposure. For instance, if your shots turn out overexposed, so you set your exposure -ve to compensate the overall exposure to become more accurate.


Adjust shutter speed or aperture will not affect the exposure. The exposure is constant and depend on the exposure settings like -1, 0 or +1.Adjust the aperture will depend on DOF and shutter speed affect the effect.
 

sapphy

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Jun 17, 2007
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#8
Thanks for clarifying. So does that mean that "exposure compensation" is purely 100% from image processing and nothing to do with aperture? Or does it depend on the mode like what Scaglietti mentioned? Sorry I'm still quite new to photography and only recently picked up interest in this. And that is the reason why I picked F31FD to play around before I go for a DSLR.
 

sapphy

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Jun 17, 2007
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#9
I just read on the short tutorial. Exposure compensation basically means adjusting the shutter/aperture accordingly? But what if my camera reached the lowest limit? And for normal indoor pictures to reduce camera shake, lowering exposure = lowering shutter speed right? As in its the same settings that the camera will apply if I were to do it myself?
 

Scaglietti

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Jan 14, 2005
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#10
Thanks for clarifying. So does that mean that "exposure compensation" is purely 100% from image processing and nothing to do with aperture? Or does it depend on the mode like what Scaglietti mentioned? Sorry I'm still quite new to photography and only recently picked up interest in this. And that is the reason why I picked F31FD to play around before I go for a DSLR.
Exposure compensation will change the aperture or shutter speed (depending on S or A mode).

Say e.g, your exposure value is 1/125s f/5.6 in S mode. If you dial in a +1 exposure compensation, you will get 1/125s f/4.

BC
 

cantaresg

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Feb 23, 2007
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#11
Well if you were to do it yourself you have more controls over the camera, instead of letting the camera decide which may or may not give you the desired effect.
If the camera reached the lowest limit, usually it will have an indication eg the shutter speed highlighted in red or blinking, to indicate that the exposure limit is reached. So at this point you willl need to change the ISO setting.
 

zoossh

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Nov 29, 2005
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#12
I just read on the short tutorial. Exposure compensation basically means adjusting the shutter/aperture accordingly? But what if my camera reached the lowest limit? And for normal indoor pictures to reduce camera shake, lowering exposure = lowering shutter speed right? As in its the same settings that the camera will apply if I were to do it myself?
it is a little long to explain. you may need to read up more and shouldn't be too difficult.

light input & data conversion = data collection and storage
A x B x C x D = E

A=frame intensity
B=aperture size
C=shutter duration
D=ISO
E=exposure.

you can alter the eventual exposure you want for the picture, say maybe 9 exposure values for night scene and 14 exposure values for day scene. the camera will intelligently help to suggest an exposure E for you, but you might want to adjust to your taste, by exposure compensation to E. note exposure compensation is a separate function that alters E. metering mode and external grey card calibrations are other function that alters E.

Once the E is set, A to D will be set by you depending on which items you chose to manually control, the rest of A to D will be set by the camera - hence it is semi-automatic. if you set E but let the camera decides B to D, it is considered full-automatic where you only control the scene modes and the framing A.

Note the workflow here is reverse. we start with E and then the camera works backwards.
E with any adjustment = A x B x C x D with variable semi-automation or full automation.

manual mode basically means the camera will not set the E for you. whatever you enter for A to D, will give you E to whichever values the equation gives. however, the system will still tell you how far your E is away from the calculated value, and you can tune A to D till it reaches the satisfactory E you want.

in manual mode, it works the normal way we understand the equation. it is done by trial and error or some old rules depending on lighting.
A x B x C x D = E
 

#14
actually aperture and shutter speed are INDEPENDENT OF EACH OTHER. What you change to aperture will NOT affect shutter speed DIRECTLY.

But since eV (expo compensation) = aperture x shutter speed... it will affect the resulting exposure of the whole photo.


"loss of aperture" (due to choosing wrong aperture) results in focus lost (f1.8 will cause the object in focus and minor area around it to be blur, it affect static and moving objects. THIS greatly affect all pictures no matter what situations. )

"loss of shutter speed" (due to choosing wrong shutter speed) results in focus lost also. (choosing of 1/250 instead of a 1/500 when shooting birds flying for example, the wings will be out of focus heavily or slightly on how much difference.)
 

sulhan

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#15
All the fuss about Exposure compensation has its realations based on APEX equation. You can have a read here: http://doug.kerr.home.att.net/pumpkin/APEX.pdf in fact all camera would have their exposure tables derived related to this equation in away or another.

Or Just read the "user" point of view in my notes here under Metering : Exposure compensation.http://www.md-sulhan.com/learning11.html
I woundn't say that a camera is fooled in a snow or black scene. Its basicaly how the camera metering "see" the field of view (18% grey). It does not know what its looking at.
 

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