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Old Aug 31, 2007, 10:22 AM   #21
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Warning, long winded post. ;-) Some of this is redundant with what I've already posted in this thread:

The meter in your viewfinder is designed to let you know if your settings are going to result in a darker or brighter exposure, compared to the way the camera's metering thinks it should be exposed (and the metering mode and what you meter on will impact what the camera thinks is needed).

When you are shooting in non-manual modes, this meter is used for a feature called Exposure Compensation. If you set the camera so that the pointer is higher than zero, it will take a brighter exposure than the camera would have used by default. If it's set to a -EV value, it will expose it darker than the metering thinks is needed.

If you're shooting in Manual Exposure mode, there is no Exposure Compensation (because your aperture and shutter speed settings take the place of it since you're controlling both of these variables, although most cameras have a meter that shows you how your settings are impacting exposure).

Exposure Compensation lets you alter the way a camera's autoexposure/metering algorithms expose an image (brighten or darken it compared to the way the camera metered the scene). It's one of my most frequently used settings on most cameras.

A +EV value gives you a brighter exposure. The camera uses a slower shutter speed and/or larger aperture (smaller f/stop number) to get a brighter exposure, compared to what the camera's autoexposure/metering algorithms would have selected.

A -EV value gives you a darker exposure. The camera uses a faster shutter speed and/or smaller aperture (higher f/stop number) to get a darker exposure, compared to what the camera's autoexposure/metering algorithms would have selected.

If you're in Av Mode (Aperture Priority) and use Exposure Compensation, the camera will vary the shutter speed (since you're setting the aperture). If you're using Tv (Shutter Priority) mode and use Exposure Compensation, the camera will vary the Aperture (since you're controlling the shutter speed).

If you're in Auto (or other similar modes), the camera may vary aperture or shutter speed when you use Exposure Compensation. In low light, since your aperture is already wide open, it varies shutter speed if you use a -EV setting.

If you're shooting in Manual Exposure mode, there is no Exposure Compensation (because your aperture and shutter speed settings take the place of it since you're controlling both).

This is the concept you need to become familar with, so I'll make it bold:

Correct Exposure comes down to the amount of light, the ISO speed, the shutter speed, and the aperture. A variety of combinations will produce identical exposure.

These exposure calculators and simulators may help you understand it better, too:

http://www.robert-barrett.com/photo/...alculator.html

http://www.photonhead.com/simcam/shutteraperture.php

You use Exposure Compensation if you want a brighter or darker image compared to what the camera's metering would normally give you in the same conditions if you're not using manual exposure.

An example of when you may want to use a +EV setting is for a backlit subject, where the subject would normally be much darker than the rest of the image. Since the camera has a limited dynamic range, it doesn't know that you want the dark subject exposed properly (at the expense of the rest of the image). So, you can make the darker subject brighter for correct exposure (which might cause the rest of the scene to be overexposed some).

If your subject is much brighter than the rest of the image (for example, direct sunlight hitting your subject, even though most of the photo is in shadows), you may want to use a -EV setting for Exposure Compensation so that your subject is not overexposed (making the rest of the image darker, too).

The camera has a limited range of bright to dark that it can capture. So, it makes choices so that most of the iimage is correctly exposed, depending on your metering mode. Sometimes that may not be what you want. That's where exposure compensation comes in.

In manual mode, you're controlling the Exposure with your settings for aperture and shutter speed (and your meter will show you if the camera thinks they will result in under or overexposure, much in the same way it will show you if your Exposure Compensation settings in non-manual modes will expose brighter or darker).

Although we have a lot of automation with newer camera models (both film and digital), the concepts of exposure still work the same way as they do with old manual only cameras.

You still have only 4 main variables to take into consideration for exposure (and I use the term "main" since there are a lot of nuances to how you measure the light (for example, your metering mode), as well as different film characteristics if shooting film, and camera settings if shooting digital for the desired tone/contrast curve within an image and more). Once you have a better idea of how these 4 variables work together to give you a properly exposed image, the other fancy features will make more sense.

1. Light (typically measured as EV for Exposure Value in Photography).

2. Aperture (which works similar to the pupils in your eyes, where you can open up the aperture iris wider to let in more light, or close it down to let in less light). If you let in more light with a wider aperture, you can expose the film or sensor faster. If you let in less light with a smaller opening, it takes longer to expose the film or sensor. Note that aperture is normally expressed as f/stop, which is a ratio between the focal length of the lens and the diameter of the aperture iris. So, smaller values represent a larger iris diameter.

3. ISO speed. This is how sensitive the film or sensor is to light and is the same thing as the older ASA rating for film. The higher the ISO speed, the faster you can expose it.

4. Shutter Speed (this is how long the camera's shutter stays open to expose the film or sensor).

IOW, it all boils down to how senstive the film or sensor is to light (which you control via the film you use with film, or the ISO speed settings you use with digital), and how much light you need to let it see to "expose" the iimage (which you control via the aperture opening size and shutter speed).

So, you've got lots of fancy features on newer cameras to automate what settings it uses, and let you vary it's behavior to expose an image darker or brighter than the camera's metering would normally expose it. But, it really boils down to the camera changing the same things you had to worry about with a strictly manual camera without a fancy metering system, Automatic Exposure modes, etc.

So, Exposure Compensation is just another tool you have to work with, allowing you to expose an image brighter or darker than the camera's metering would normally expose it when using non-manual modes, and it varies shutter speed and/or aperture to accomplish that. With manual exposure, you're controlling those variables (and your viewfinder scale for the metering will let you know if your setttings are exposing brighter or darker than the camera's metering thinks is needed).

P.S.

Don't worry about trying to understand everything at once. Just use your Histogram as a guide, and use Exposure Compensation to make the image darker or brighter if the parts you're interested in are coming out overexposed (too bright) or underexposed (too dark).


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Old Aug 31, 2007, 10:31 AM   #22
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JimC wrote:
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This may help you understand what the camera is doing better:

http://www.photonhead.com/exposure/simcam.php
very nice andhelpfull link. thanks alot for ur help.
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Old Aug 31, 2007, 10:36 AM   #23
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Again, I wouldn't worry about trying to understand everything all at once. Just use your Histogram as a guide, and use Exposure Compensation to make the image darker or brighter if the parts you're interested in are coming out overexposed (too bright) or underexposed (too dark).

I'd also suggest sticking with either Matrix (the default) or Center Weighted Metering, and as time passes, you'll become more familiar with your camera's metering behavior and can better judge when Exposure Compensation may be needed so that your subject is properly exposed.

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Old Aug 31, 2007, 10:48 AM   #24
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JimC wrote:
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Again, I wouldn't worry about trying to understand everything all at once. Just use your Histogram as a guide, and use Exposure Compensation to make the image darker or brighter if the parts you're interested in are coming out overexposed (too bright) or underexposed (too dark).

I'd also suggest sticking with either Matrix (the default) or Center Weighted Metering, and as time passes, you'll become more familiar with your camera's metering behavior and can better judge when Exposure Compensation may be needed so that your subject is properly exposed.
btw, so it would be normal for a shot to have part of it over or underexpose as long as your main subject is in great detail, properly expose, sharp and with good colors.

i asked this awhile ago, and im just wondering in your own opinion, setting the saturation +2 on the alpha system is a good idea? coz i read it somewhere that to boost the colors up u need to set the saturation at +2 on the alpha.

THANKS A LOT...AGAIN!!!:idea:. I LEARNED A LOT TODAY.

im glad i post a question here.
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Old Aug 31, 2007, 10:58 AM   #25
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btw, so it would be normal for a shot to have part of it over or underexpose as long as your main subject is in great detail, properly expose, sharp and with good colors.
I'm not quite sure what you're asking here. The camera has a limited range of bright to dark that it is capable of capturing. The human eye has a much larger range of bright to dark that you can see.

So, the camera's metering has to make decisions on what exposure to use. Sometimes that may make parts of the image too bright or too dark. You can't brighten or darken just one part of an image by changing your exposure settings (i.e., the aperture/shutter speed combination being used). The entire image is going to be affected.

Matrix metering is usually going to get your desired subject very close to where you want it, unless it's backlit or much brighter than the rest of the scene), since this metering mode places more emphasis on your focus point with most cameras, while still taking the entire frame into consideration. Camera manufacturers put a lot of time and effort into metering so that you don't have to do as much work. That's one reason it's the default metering mode with virtually any modern digital camera now.

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i asked this awhile ago, and im just wondering in your own opinion, setting the saturation +2 on the alpha system is a good idea? coz i read it somewhere that to boost the colors up u need to set the saturation at +2 on the alpha.
That's a matter of personal preference. I tend to leave mine set at the defaults. It's easier to boost settings for things like contrast, saturation, sharpness, etc., using software than it is to correct problems later if you apply too much. But, for more saturated "straight from the camera" images, some people may like to use settings that are higher than the camera's defaults.

P.S.

Sometimes reducing those types of settings (for example, contrast) can help a bit with dynamic range (the range of bright to dark a camera is able to capture). That's because in order to give you "punchier" images with more contrast, the processing may be trying to make darker areas darker and brighter areas brighter. Many users dial back all of the settings like that (for example, contrast, saturation, sharpening) in order to allow the camera to capture more real detail. Then, use an image editor to boost what they want to later with more control over it.


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Old Aug 31, 2007, 11:16 AM   #26
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P.S.

You may also want to experiment with your Sony's Dynamic Range Optimization (D-Range) feature (and advanced seems to work best from what I've seen). It tries to boost or reduce brightness in parts of the image so that you are able to capture more of it without under or overexposure.

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Old Aug 31, 2007, 11:29 AM   #27
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JimC wrote:
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P.S.

You may also want to experiment with your Sony's Dynamic Range Optimization (D-Range) feature (and advanced seems to work best from what I've seen). It tries to boost or reduce brightness in parts of the image so that you are able to capture more of it without under or overexposure.
ill try some experimenting with the dro.

thanks again

btw, i took this photo b4 started messing with the grey card. i shoot this on manual, iso 100, sunny and a +1 exposure compensation. i cant rememvber whats the shut and aper. i think this is what i like with my photos. not too bright or dark. i think its the color just need boosting up a bit.
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Old Aug 31, 2007, 11:41 AM   #28
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this photo i took is one of the shots i like. for me, the 3 of us in the photo is just perfect. got the colors right and the exposure is fine but part of the sky is well overexpose. n the histogram the flashing indicator flashes at the sky. if i would set the exposure comp towards the left it will make us darker. i think this is where u have to sacrifice. ur subject are welexposed but part of the background is not.
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Old Aug 31, 2007, 12:42 PM   #29
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There are many variables. Things like time of day can make a big difference, where the sun is in the sky makes a difference (if it's behind your subject and/or if there is a lot of bright sky backlighting your subject, it will be difficult to get more of the image properly exposed).

For backlit conditions, if you're close enough, you can use a fill flash to help out (but, the camera will be limited as to when you can use the camera's flash, because of x-sync speed limitations with the built in flash). You'll be limited to a fastest shutter speed of 1/125 second with stablization turned on, or 1/160 second with stablization turned off with your Sony.

Use of a flash for fill lets you expose for the sky, letting the flash brighten the closer subjects.

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Old Aug 31, 2007, 1:27 PM   #30
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ur right the most diff is during the day when the good sun is on its brightest. everything is lit. even if the sun is infront of the subject, the rest of the sorrounding is also lit so you get like a backlit subject.

i dont find it diff to shoot in a cloudy situation. most of the times io got it right.

i like shooting macro. but i cant do it just now because i dont have the proper lens. i used to use the sony h1 with raynox dcr-250 attached. but at the moment landscape photography just caught my attention. i only shoot portrait with family.
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