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10/04/2005 02:53:26 PM · #26 |
This all relates to something called Exposure Value, or EV. EV essentially tells you how much light is present in a scene that you want to photograph.
EV is an absolute number, in that a specific EV value represents a specific light intensity. For each increase in the EV value by 1.0, the light intensity is doubled. So an EV of 8.0 represents twice the light of an EV of 7.0. Note that a full f-stop halves or doubles the light passing through a lens. Note that halving or doubling the camera speed does the same thing. So...behind the lens, and behind the camera shutter, changing by a full f-stop or by a full speed step changes the amount of light hitting the film or sensor by one EV step (1.0). So there's the relationship. An EV step of 1.0 is equivalent to either a full f-stop change or a full speed change. (A "full" speed change means to halve or double the speed.)
EV is directly measured by a light meter. The light meter can be a separate instrument, or it can be integrated into the camera.
A hand-held light meter usually can do spot or area readings. In a camera, where the field of view is available for the integrated light meter, several metering modes can be utilized, depending on the cleverness of the camera designer. In any case, the meter is designed to figure out how much light is available for the picture, so that the proper speed and aperture settings can be made on the camera (based on the ISO value being utilized).
Light meters do a good job of measuring light, but they are none too smart. A particular scene may have an extremely wide range of light. If you are lucky, an average of all the light values will render a good picture. Or you may want to make sure a specific part of the image will be properly exposed, and a spot meter reading will help to do that. But these are boundary cases, and many other cases lie in between. So other metering modes have arisen that try to account for the more common cases that a photographer may run into.
But a light metering system simply cannot figure out all the cases, and sometimes it needs a hint from the photographer. The exposure bias adjustment on the camera allows just that. Usually, cameras allow an exposure bias of +/- 2 EV. That equates to two full stops or two full speed changes. So the meter will always get us in the ballpark of the required exposure, but the exposure bias allows the photographer to "have the final say," so to speak.
Generally, the photographer is not particularly interested in the absolute EV number. The light meter uses the absolute EV as its prime datum and from that and the current camera settings, it determines what adjustments will be made to get a proper exposure for the EV it has measured. What the photographer deals with is ISO, f-stop and speed in lieu of the EV number. If you think about it, ISO, f-stop and speed "add up" to the EV number.
Interestingly, when it comes to photography, it's all about the EV. The ISO setting, the camera speed, and the camera aperture must all coordinate to deal with the EV of the image being captured. It may be the EV of the whole image area, the EV of a particular spot in the image, or an average of several spots within the image. It may also be based on the offset of an EV derived from the metering of the camera when an exposure bias is used. But it all comes back to some EV associated with the image being captured. |
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10/04/2005 03:37:00 PM · #27 |
I would like to thank everyone for their responses. Being new to photography I am very pleased to get help from such experienced photographers.
So, in summary, is what I am hearing is the exposure compensation is a nice tool when shooting in an automatic mode but shooting in manual will give you that same power and more.
I have played with both modes and must say I do enjoy shooting manual. Is that the recommended approach? |
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10/04/2005 04:08:06 PM · #28 |
Originally posted by qbicle:
So, in summary, is what I am hearing is the exposure compensation is a nice tool when shooting in an automatic mode but shooting in manual will give you that same power and more. |
No, not quite...Exposure Compensation is a nice tool when shooting in Automatic mode but in Manual mode you need to do your own "exposure compensating" by changing one of the three settings talked about below (ISO, SS or aperture).
For example, in Automatic mode you might say to yourself "Hmm, I want half as much light to enter the camera". We've learned that 'half as much light' is 'one stop' so you would adjust the exposure control to "minus 1 stop" (-1). The camera will then automatically change the ISO, shutter speed or aperture in such a way that half as much light enters the camera.
Now, if you are in Manual mode and you say to yourself "Hmm, I want half as much light to enter the camera" then you need to do that yourself. So you could change one of the three settings (ISO, SS, or aperture) so that the camera will let in half as much light. The difference is that you control which of the three settings to adjust.
The reason that I prefer manual is that I like to be in control of which setting is being changed. The reasons for that can be discussed in the next post.
I hope that makes sense!
Message edited by author 2005-10-04 16:09:20. |
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10/04/2005 04:15:27 PM · #29 |
Mmmm what if you have a camera that will not allow you to manually set the shutter speed? I can adjust ISO and aperature and the camera determines the shutter speed. This is in AV mode, which is as manual as it gets on my prosumer. I do have exposure compensation in AV mode as well. Just wondering if there are any other tricks I am missing out on.
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10/04/2005 04:26:57 PM · #30 |
Originally posted by res0m50r:
Mmmm what if you have a camera that will not allow you to manually set the shutter speed? I can adjust ISO and aperature and the camera determines the shutter speed. This is in AV mode, which is as manual as it gets on my prosumer. I do have exposure compensation in AV mode as well. Just wondering if there are any other tricks I am missing out on. |
Hmmm...that's a toughy. I guess you are limited in the amount of control you can have over the final image but you are able to control the aperture (and therefore the depth of field on your images). Also, by adjusting the ISO it will then change the shutter speed to compensate (although with other possibly adverse effects such as noise).
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10/04/2005 04:31:29 PM · #31 |
For the Canon PowerShot S2 IS, there is a manual mode -- M on the dial. Look at page 84 in your manual. I am not aware of any method of using the built-in metering in manual mode. In other words, you need to decide which shutter speed and f-stop to use prior to your shot, and I do not believe there's a way to get exposure feedback as you are adjusting your settings.
In older cameras, there was an exposure needle that you could look at, and its position would change in response to your adjustments to ISO, SS, and aperture. I'd like to see an implementation of that on the viewscreen of modern digital cameras. Then you could shoot as if it were an old-style camera. |
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10/04/2005 04:37:50 PM · #32 |
Originally posted by hblake:
For the Canon PowerShot S2 IS, there is a manual mode -- M on the dial. Look at page 84 in your manual. I am not aware of any method of using the built-in metering in manual mode. In other words, you need to decide which shutter speed and f-stop to use prior to your shot, and I do not believe there's a way to get exposure feedback as you are adjusting your settings.
In older cameras, there was an exposure needle that you could look at, and its position would change in response to your adjustments to ISO, SS, and aperture. I'd like to see an implementation of that on the viewscreen of modern digital cameras. Then you could shoot as if it were an old-style camera. |
I could just swear that M was for macro's... since it requires you give it the distance to your subject... I I will check when I get home... all pics that are beyond a certain distance are blown full white in M mode... so not sure
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10/04/2005 04:52:17 PM · #33 |
Originally posted by res0m50r:
Originally posted by hblake:
For the Canon PowerShot S2 IS, there is a manual mode -- M on the dial. Look at page 84 in your manual. I am not aware of any method of using the built-in metering in manual mode. In other words, you need to decide which shutter speed and f-stop to use prior to your shot, and I do not believe there's a way to get exposure feedback as you are adjusting your settings.
In older cameras, there was an exposure needle that you could look at, and its position would change in response to your adjustments to ISO, SS, and aperture. I'd like to see an implementation of that on the viewscreen of modern digital cameras. Then you could shoot as if it were an old-style camera. |
I could just swear that M was for macro's... since it requires you give it the distance to your subject... I I will check when I get home... all pics that are beyond a certain distance are blown full white in M mode... so not sure |
The "distance to your subject" you are referring to is the focus.
And if you're getting blown highlights, either close down the aperture, make the shutter speed faster, or reduce the ISO. Remember, the camera won't determine the correct exposure for you...you have to do it yourself in manual mode.
Message edited by author 2005-10-04 16:54:52.
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10/04/2005 04:59:23 PM · #34 |
Originally posted by hblake:
In older cameras, there was an exposure needle that you could look at, and its position would change in response to your adjustments to ISO, SS, and aperture. I'd like to see an implementation of that on the viewscreen of modern digital cameras. Then you could shoot as if it were an old-style camera. |
Hmm, in all 3 canons I owned, there is a 'needle' in the viewfinder that moves left/right showing me the results of the integrated lightmeter and its relation to the manual settings I picked.
Are we talking about the same thing here?
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10/04/2005 05:11:29 PM · #35 |
Originally posted by justin_hewlett:
Originally posted by res0m50r:
Originally posted by hblake:
For the Canon PowerShot S2 IS, there is a manual mode -- M on the dial. Look at page 84 in your manual. I am not aware of any method of using the built-in metering in manual mode. In other words, you need to decide which shutter speed and f-stop to use prior to your shot, and I do not believe there's a way to get exposure feedback as you are adjusting your settings.
In older cameras, there was an exposure needle that you could look at, and its position would change in response to your adjustments to ISO, SS, and aperture. I'd like to see an implementation of that on the viewscreen of modern digital cameras. Then you could shoot as if it were an old-style camera. |
I could just swear that M was for macro's... since it requires you give it the distance to your subject... I I will check when I get home... all pics that are beyond a certain distance are blown full white in M mode... so not sure |
The "distance to your subject" you are referring to is the focus.
And if you're getting blown highlights, either close down the aperture, make the shutter speed faster, or reduce the ISO. Remember, the camera won't determine the correct exposure for you...you have to do it yourself in manual mode. |
If the focus is represented by.... 1'' to 16'' in the center bottom of the viewfinder than yeah thats focus... but I thought it to be inch's from the subject which is required in macro/super macro mode.
When I am in M mode and I am further away than 16'' which is what I remember being the furthest distance it will adjust to it is not just blown highlights but a blown image... completely white.
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10/04/2005 05:23:45 PM · #36 |
Originally posted by srdanz:
Originally posted by hblake:
In older cameras, there was an exposure needle that you could look at, and its position would change in response to your adjustments to ISO, SS, and aperture. I'd like to see an implementation of that on the viewscreen of modern digital cameras. Then you could shoot as if it were an old-style camera. |
Hmm, in all 3 canons I owned, there is a 'needle' in the viewfinder that moves left/right showing me the results of the integrated lightmeter and its relation to the manual settings I picked.
Are we talking about the same thing here? |
Well...I took a close look at what the camera does in manual mode, and there's no meter or needle. The image gets lighter or darker when you change any of the three settings (ISO, SS, or aperture). That isn't very helpful.
However...I did find that when the shutter button is depressed half way, 1) the autofocus does its thing, 2) an EV offset number is posted in the upper left corner of the screen. If it is red, your image will be dark; if it is white and non-zero, you image will be too light; if it is zero, then your settings agree with what the camera thinks is the correct exposure.
Only having that number appear when the shutter button is partially depressed is, um, depressing. I'd much rather have that number or a needle on a continuous basis. Oh well...not a big deal because I don't plan to do a lot with the Canon in manual mode. |
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10/04/2005 05:52:06 PM · #37 |
Originally posted by res0m50r:
Originally posted by justin_hewlett:
Originally posted by res0m50r:
Originally posted by hblake:
For the Canon PowerShot S2 IS, there is a manual mode -- M on the dial. Look at page 84 in your manual. I am not aware of any method of using the built-in metering in manual mode. In other words, you need to decide which shutter speed and f-stop to use prior to your shot, and I do not believe there's a way to get exposure feedback as you are adjusting your settings.
In older cameras, there was an exposure needle that you could look at, and its position would change in response to your adjustments to ISO, SS, and aperture. I'd like to see an implementation of that on the viewscreen of modern digital cameras. Then you could shoot as if it were an old-style camera. |
I could just swear that M was for macro's... since it requires you give it the distance to your subject... I I will check when I get home... all pics that are beyond a certain distance are blown full white in M mode... so not sure |
The "distance to your subject" you are referring to is the focus.
And if you're getting blown highlights, either close down the aperture, make the shutter speed faster, or reduce the ISO. Remember, the camera won't determine the correct exposure for you...you have to do it yourself in manual mode. |
If the focus is represented by.... 1'' to 16'' in the center bottom of the viewfinder than yeah thats focus... but I thought it to be inch's from the subject which is required in macro/super macro mode.
When I am in M mode and I am further away than 16'' which is what I remember being the furthest distance it will adjust to it is not just blown highlights but a blown image... completely white. |
I would read you camera manual like hblake suggested. I own a Canon but my manual mode is set to autofocus by default. If I set the camera to manual focus it ranges from the minimum focusing distance of my camera to infinity.
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10/04/2005 06:13:26 PM · #38 |
About the Canon PowerShot S2 IS...on the side of the camera on the lens barrel is two buttons...the lower button is the macro mode button. It looks like a little flower. When depressed, it initiated macro mode for the camera. The flower icon shows up on the screen. If the icon is gray, the zoom is set incorrectly. Adjust the zoom out of the yellow (no macro) zone. The yellow zone is only present on the zoom bar when the macro mode is set. If the macro icon (flower) is white, you're good to go.
I've fiddled a bit with macro mode with the Canon, but I've not had much success getting the focus to cooperate. Instead of figuring out why, I grab my Nikon 5700 and use it. Path of least resistance and all that. Well...someday I'll get around to figuring it out. |
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