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10/30/2006 02:44:46 AM · #1 |
I am trying to understand the exposure compensation meter and want to understand it's uses as I haven't ever used it (on purpose...LOL):
Is f/2.8 at 1/30th, exposure compensation at 0
the same as
f/2.8 at 1/60th, exposure compensation at -1?
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10/30/2006 03:13:27 AM · #2 |
I think it is the other way round -
if you have f/2.8 - 1/30th and set exposure compensation to -1 you will get 1/60th, that is one f/stop underexposure
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10/30/2006 03:53:16 AM · #3 |
Originally posted by eyewave:
I think it is the other way round -
if you have f/2.8 - 1/30th and set exposure compensation to -1 you will get 1/60th, that is one f/stop underexposure |
Oh, ok, so the exposure compensation meter automatically adjusts your settings to give you that underexposure? For some reason, I thought there was more to it than that.
When is the exposure compensation meter useful?
Is it just a quicker way to adjust exposure? |
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10/30/2006 04:42:49 AM · #4 |
Originally posted by JRalston:
When is the exposure compensation meter useful?
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The compensation is useful when you have a scene that you as the photographer either
a) Think (or know because you've already taken one shot) that the camera's metering will be fooled by into over or under exposure (such as a snow scene, or a particularly dark coloured room) or
b) want to capture in a certain way eg lighter than normal.
Originally posted by JRalston:
Is it just a quicker way to adjust exposure? |
Depends how quick and easy your exposure compensation is to change, I suppose ;)
Message edited by author 2006-10-30 04:43:09. |
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10/30/2006 07:23:48 AM · #5 |
And, of course, exposure compensation only matters in one of the "automatic modes" (where the camera gets to pick one of the settings). If you've set the camera to manual exposure and you've dialed in f/2.8 and 1/30th, then the exposure compensation does nothing because you're already in complete control of the exposure.
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10/30/2006 07:18:43 PM · #6 |
Originally posted by dwterry:
And, of course, exposure compensation only matters in one of the "automatic modes" (where the camera gets to pick one of the settings). If you've set the camera to manual exposure and you've dialed in f/2.8 and 1/30th, then the exposure compensation does nothing because you're already in complete control of the exposure. |
Depends on whether or not you use the built-in meter as a guide when setting exposure. Setting exposure compensation will affect what your built-in meter will tell you, even in manual.
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10/30/2006 08:22:55 PM · #7 |
Originally posted by virtuamike:
Originally posted by dwterry:
And, of course, exposure compensation only matters in one of the "automatic modes" (where the camera gets to pick one of the settings). If you've set the camera to manual exposure and you've dialed in f/2.8 and 1/30th, then the exposure compensation does nothing because you're already in complete control of the exposure. |
Depends on whether or not you use the built-in meter as a guide when setting exposure. Setting exposure compensation will affect what your built-in meter will tell you, even in manual. |
That may be true of the Nikon, but not on the OP's camera. I have both the Canon 5D and the 20D. Normally the dial on the front adjusts the settings for whichever mode you are in (i.e. the shutter for Tv mode, the aperture for Av mode). But in manual mode, the dial on the front adjusts the shutter, and the big dial on the back (which would normally be used to adjust exposure compensation) adjusts the aperture.
I like how Canon has set this up because in manual mode I can quickly adjust either one. And besides... with the numbers in the viewfinder, it's easy enough to tell whether I'm plus or minus off the metered exposure. |
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10/30/2006 08:25:54 PM · #8 |
| Thank you all, I think I understand now. :) |
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10/31/2006 05:55:17 AM · #9 |
The first key to understanding exposure value compensation is to know that it is not an exposure adjustment!
There are only three adjustments on the camera that affect how the scene is exposed and those are ISO, shutter speed and aperture. The EV compensation adjustment is a metering adjustment. Or to put it another way, changing the EV compensation tells the meter to read the scene differently, which the camera (or photographer) can then use to expose the scene differently -- but it doesn't affect exposure directly.
What follows is likely more detail than you wanted, but it is so commonly misunderstood it's worth stating.
It starts by defining a standard way to measure light that makes sense in photography -- one that works within the power of 2 increases of light we call 'stops'. The measure that was decided upon is the Exposure Value (EV).
An EV of 0 is defined as the exposure settings of f1.0 (aperture), 1.0sec (shutter speed) and 100 (ISO). This relates to a specific amount of light, and not very bright light at that. The exposure values are then adjusted up or down in stops of light. That is EV1 has twice the light of EV0 while EV-2 has 1/4 the light. It doesn't matter which of the three exposure adjustments altered to produce the change, just the total stop difference.
The meter in a camera is designed to always expose the scene it is viewing as if it averaged a neutral grey tone. A grey card is used to meter the scene because with it, the meter is exposing something as middle grey that is actually middle grey. This works well as a substitute for an incident light meter, but that also limits its usefulness to reading available light.
EV compensation (EVc) is provided to allow more creative control over the metering process. What it does is adjusts how bright the meter reads the scene to be. Remember the standard meter always reads the scene to be lit exactly in the middle, not bright and not dark. With EVc it becomes possible to tell the meter the scene should be read as if it was a stop brighter than middle grey (EVc +1) or a couple of stops darker than middle greay (EVc-2).
Note that EV is an exact measurement of how bright the light is, while EVc is a relative adjustment (+/-) to the actual EV of the scene.
EVc has its uses, but really doesn't come into it's own unless using spot/center-weighted metering mode and the zone system of using the metered results. As an example, consider a white swan on a lake at dusk. By metering the areas of the image that have important detail, such as the swan and perhaps the dark leaves of an overhanging branch, the photographer can decide what exposure is needed to ensure detail in both (if even possible). The photographer can just 'split the difference' or by adjusting the EVc to +1.5 and metering just the swan place it halfway between zones 6 and 7 (very light, but plenty of texture detail).
The above may seem like a lot, especially the very brief last paragraph, but it all comes down to one thing -- EVc allows the photographer (or the camera if in an auto mode) to place the scene, or just a portion of it, as bright or as dark as they like.
David
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10/31/2006 07:39:49 AM · #10 |
As with the above post it is most handy with spot metering.
A relatively new and interesting technique that makes use of this is HDR(High Dynamic Range) Images. These use multiple images of the same scene at different exposures. This way you have an image with well exposed shadow areas,highlights and midrange. You can then use a tool like Photoshop to merge the images capturing the whole range of information from the different exposures. Typically these are stored at 32bit per channel vs 8bit for your standard JPG(Just image the dodge and burn possibilities). This is a 16777216 times increase in range per channel. The more exposures the better use of this HDR process.
So when I get an SLR and Wide-angle lens. Ill play with HDR in Wellington.
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10/31/2006 03:09:29 PM · #11 |
Originally posted by JRalston:
I am trying to understand the exposure compensation meter and want to understand it's uses as I haven't ever used it (on purpose...LOL):
Is f/2.8 at 1/30th, exposure compensation at 0
the same as
f/2.8 at 1/60th, exposure compensation at -1? |
This is right isnt it?
If you set the camera to -1 your telling the camera you want the shot a little darker, F2.8 1/60 will be a little darker then F2.8 1/30 i dont know if that is an even represent -1 but the faster shutter will darken the shot so that is a correct way to look at it right? |
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10/31/2006 03:20:00 PM · #12 |
So you are saying with a Canon camera that changing exposure compensation on full manual does not affect the meter in any way? That is is basically useless in Manual mode? I find this strange to believe, but I don't use Canon equipment so I can't comment.
Originally posted by dwterry:
Originally posted by virtuamike:
Originally posted by dwterry:
And, of course, exposure compensation only matters in one of the "automatic modes" (where the camera gets to pick one of the settings). If you've set the camera to manual exposure and you've dialed in f/2.8 and 1/30th, then the exposure compensation does nothing because you're already in complete control of the exposure. |
Depends on whether or not you use the built-in meter as a guide when setting exposure. Setting exposure compensation will affect what your built-in meter will tell you, even in manual. |
That may be true of the Nikon, but not on the OP's camera. I have both the Canon 5D and the 20D. Normally the dial on the front adjusts the settings for whichever mode you are in (i.e. the shutter for Tv mode, the aperture for Av mode). But in manual mode, the dial on the front adjusts the shutter, and the big dial on the back (which would normally be used to adjust exposure compensation) adjusts the aperture.
I like how Canon has set this up because in manual mode I can quickly adjust either one. And besides... with the numbers in the viewfinder, it's easy enough to tell whether I'm plus or minus off the metered exposure. |
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