boriszulj
Senior Member
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Boris
Degustibus non disputandum est!
Boris
Degustibus non disputandum est!
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What exactly does exposure compensation affect?
- Thread starter photoelectric
- Start date
bronxbombers
Forum Pro
but why not learn with the 40D?? i don't get it. nicer user interface. a little better high iso. lots of helpful things about it. better AF. seems to be better ot learn on it if anything.
bronxbombers
Forum Pro
nothing takes place. it blinks the f/22 or whatever. it does what it can until its reaches limits of the hardware and when it can do more it just blinks the values as a warning that it can't do anymore.
Tony Brooks
Leading Member
If you're at f/22 in Tv, you can't under-expose by using EC. You'd have to go to Av (22) and set EC -2 which would decrease the shutter-speed. (Or go to Manual.)
If you're at f/22 and 1/8000 (!!!) you can't under-expose. You'd need ND filter(s). I don't know when there's that much light unless you're spot metering off the mid-day sun.
My point was; the question seems hypothetical. About the only time you'd need to think about f/22 would be for DOF in macro work, when you should also be using ring or multi-flash.
Regards,
Tony Brooks
'The best and most beautiful things in the world cannot be seen or touched...but are felt in the heart.' - Helen Keller
If you're at f/22 and 1/8000 (!!!) you can't under-expose. You'd need ND filter(s). I don't know when there's that much light unless you're spot metering off the mid-day sun.
My point was; the question seems hypothetical. About the only time you'd need to think about f/22 would be for DOF in macro work, when you should also be using ring or multi-flash.
Regards,
Tony Brooks
'The best and most beautiful things in the world cannot be seen or touched...but are felt in the heart.' - Helen Keller
Is this thread back on topic now? Great. I don't think most of you understood what the OP was asking. He/she understands what exposure compensation is, but wants to know HOW the camera accomplishes it. One person answered but I'm not sure they are correct. The answer about "changing the meter result" while accurate still doesn't tell us HOW the camera is affecting a shot when using EC. What parameter is it changing? Let's say we're in P mode and set at ISO 100, f8, 125th sec. We dial in a -2/3 ec. HOW does the camera accomplish this? Does it change the ISO, f-stop or shutter speed? Is there a priority that the camera decides this on based on what mode you're in and what settings you have? i.e. Like the example previously posted, if you were at the smallest or largest aperture and the EC you selected (+ or -) would not have any aperture left to adjust, what would it change next? There is a max/min to each element of exposure, so what order does the camera follow? Does it have a preference to change ISO first, then if that's not possible, change shutter speed and then if that's not possible, change f-stop or what? Even though I KNOW what EC is, I have always wanted to know this too. HOW EXACTLY is the camera accomplishing the shooter's request?
Please refrain from experience/equipment bashing. That is not the point of this thread or this forum. The OP has a legitimate question that is not necessarily a newbie question at all.
Please refrain from experience/equipment bashing. That is not the point of this thread or this forum. The OP has a legitimate question that is not necessarily a newbie question at all.
boriszulj
Senior Member
Why don't learn how to drive on Mercedes or Lexus? You can, if you have money to throw away and fine with not driving it more than 40 mph!
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Boris
Degustibus non disputandum est!
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Boris
Degustibus non disputandum est!
go to many of the great intro to photography sites on the internet:
http://www.google.com/search?q=Photography+Tutorial+%22exposure+compensation%22
http://www.google.com/search?q=Photography+Tutorial+%22exposure+compensation%22
This sure isn't one of those "great photo sites" There have been 20
something "responses" to the answer.
Nobody knows is the result.
KlausW
Active member
no text
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http://www.photoartpro.com
No english native speaker, so please ignore any misspelling generously!
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http://www.photoartpro.com
No english native speaker, so please ignore any misspelling generously!
Yehuda Katz
Forum Pro
My question is camera independent, and applies for other camera too. Those might have a min aperture of f8 and min shutter speed of 1/1000, so my question isn't necessarily theoretical.
Yehuda
Yehuda
If you're at f/22 in Tv, you can't under-expose by using EC. You'd
have to go to Av (22) and set EC -2 which would decrease the
shutter-speed. (Or go to Manual.)
If you're at f/22 and 1/8000 (!!!) you can't under-expose. You'd need
ND filter(s). I don't know when there's that much light unless you're
spot metering off the mid-day sun.
My point was; the question seems hypothetical. About the only time
you'd need to think about f/22 would be for DOF in macro work, when
you should also be using ring or multi-flash.
Regards,
Tony Brooks
'The best and most beautiful things in the world cannot be seen or
touched...but are felt in the heart.' - Helen Keller
I know, without a doubt. But I'm not saying.
The original question is a valid one, and I answered it earlier in terms of aperture, shutter speed, or (in P mode) a combination of the two being varied evenly by the camera to achieve deliberate exposure compensation.
The person then brought up a good point: if you are in a mode (Tv is a good example), where, for instance, you've picked a shutter speed and the lens happens to be near its widest available aperture, what happens if you try to over-expose two more stops? The lens really can't open up any more.
The answer is nothing. EOS cameras do not change ISO sensitivity in any way to achieve exposure compensation, and they CANNOT go to the other value (shutter speed in the example of Tv mode) and alter it unless the user has engaged the Safety Shift feature (not all EOS bodies have this).
So the point is you can dial in +2 when in Tv mode with the lens already wide-open, but your exposures won't change. As another poster mentioned, the aperture readout in the viewfinder would start to blink on and off, to warn you that you're asking for a wider aperture than it can provide. But even though your exposure scale in the finder would read +2 if you set it there, understand that in this case, the camera can't achieve what you're asking it to do.
The only way (in this example) to get exposure to lighten by two stops would be to go to a slower shutter speed, which would force a smaller lens opening; now, the camera has the ability to further open up the lens. But on its own, in the absence of Safety Shift, the camera still only varies the settings I mentioned in my original post.
Cheers!
The person then brought up a good point: if you are in a mode (Tv is a good example), where, for instance, you've picked a shutter speed and the lens happens to be near its widest available aperture, what happens if you try to over-expose two more stops? The lens really can't open up any more.
The answer is nothing. EOS cameras do not change ISO sensitivity in any way to achieve exposure compensation, and they CANNOT go to the other value (shutter speed in the example of Tv mode) and alter it unless the user has engaged the Safety Shift feature (not all EOS bodies have this).
So the point is you can dial in +2 when in Tv mode with the lens already wide-open, but your exposures won't change. As another poster mentioned, the aperture readout in the viewfinder would start to blink on and off, to warn you that you're asking for a wider aperture than it can provide. But even though your exposure scale in the finder would read +2 if you set it there, understand that in this case, the camera can't achieve what you're asking it to do.
The only way (in this example) to get exposure to lighten by two stops would be to go to a slower shutter speed, which would force a smaller lens opening; now, the camera has the ability to further open up the lens. But on its own, in the absence of Safety Shift, the camera still only varies the settings I mentioned in my original post.
Cheers!
As a relative newcomer to this forum, I am shocked by the rudeness and condescension by many posters who are self-styled experts (or pose as such).
In other forums, experts take pride in constructively helping newcomers learn their way around the community. At the least, they encourage rather than disrespect. Why is that so difficult for so many here?
I am considering buying a 40D (after 2 years with a 300D) and I don't know the answer to the OP's question because I use M mode exclusively on my SLRs. Care to offer a witty retort?
You're right, there are a number of great books out there. Consider reading Dale Carnegie's How to Win Friends and Influence People.
In other forums, experts take pride in constructively helping newcomers learn their way around the community. At the least, they encourage rather than disrespect. Why is that so difficult for so many here?
I am considering buying a 40D (after 2 years with a 300D) and I don't know the answer to the OP's question because I use M mode exclusively on my SLRs. Care to offer a witty retort?
You're right, there are a number of great books out there. Consider reading Dale Carnegie's How to Win Friends and Influence People.
Ed Halley
Senior Member
In simple terms, it basically forces the metering system to lie, and that lie is passed on to the program that decides the aperture, time (and sometimes sensitivity).
The camera has a light meter built in. That light meter sees a blurry summary of the scene through the lens, and computes a single number: the "effective eV" number. One eV is basically one "stop" of light.
The camera also has a number of "programs." One is called just that: P mode is short for "program mode." It turns that "effective eV" number into a balance of aperture and time settings, and leaves the sensitivity (ISO value) to whatever you set. Av mode is just like P mode except it locks the Av to your choice so the time value has to be adjusted instead. Tv is the opposite. M mode, or manual mode, does not adjust anything, it's like a dead program.
The EC is just inserting a false bias in the process. It adds or subtracts a constant amount from that "effective eV" value before the program learns of it. If you have +1 eV dialed in, then the false bias SUBTRACTS 1 eV from the effective exposure, causing the program to expose for LONGER or more OPEN. For a -2 eV compensation, the false bias adds 2 eV and the program will think it needs to shoot shorter or more closed (or both) to achieve a good exposure.
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[ e d @ h a l l e y . c c ] http://www.halley.cc/pix/
The camera has a light meter built in. That light meter sees a blurry summary of the scene through the lens, and computes a single number: the "effective eV" number. One eV is basically one "stop" of light.
The camera also has a number of "programs." One is called just that: P mode is short for "program mode." It turns that "effective eV" number into a balance of aperture and time settings, and leaves the sensitivity (ISO value) to whatever you set. Av mode is just like P mode except it locks the Av to your choice so the time value has to be adjusted instead. Tv is the opposite. M mode, or manual mode, does not adjust anything, it's like a dead program.
The EC is just inserting a false bias in the process. It adds or subtracts a constant amount from that "effective eV" value before the program learns of it. If you have +1 eV dialed in, then the false bias SUBTRACTS 1 eV from the effective exposure, causing the program to expose for LONGER or more OPEN. For a -2 eV compensation, the false bias adds 2 eV and the program will think it needs to shoot shorter or more closed (or both) to achieve a good exposure.
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[ e d @ h a l l e y . c c ] http://www.halley.cc/pix/
Tony Brooks
Leading Member
Ok, so on 'your' camera you're at f/8 and 1/1000 (and your lowest ISO). You can't use EC to under-expose any more, you're 'up against the stops'. You've reached the limitations of your camera. So you have to change the light, or change the light entering the lens (filter), or forget the shot. Or buy a new camera!
Regards,
Tony Brooks
'The best and most beautiful things in the world cannot be seen or touched...but are felt in the heart.' - Helen Keller
Regards,
Tony Brooks
'The best and most beautiful things in the world cannot be seen or touched...but are felt in the heart.' - Helen Keller
KHemmelman
Member
Boris, it sounds as if you feel the OP shouldn't be asking questions here, and instead go somewhere else on the internet or a local library and attempt to find the answer. I guess for experienced photographers, it can be tiresome to see what you feel is a newbie question or that less experienced photographers such as myself or others come here to read and learn.
The entire basis for dpreview having this forum is to ask questions and learn. Right? At least that is what it states on the dpreview website when you goto the top of the discussion forums. It says:
"Here you can discuss, ask questions or generally debate anything related to digital photography, digital cameras or digital imaging technology."
So I'm not sure why you would take issue with a question about digital photography, when it clearly states this is the place to do that. I've learned a great deal here reading replies to questions like this and appreciate them being asked. But then I'm not a pro photographer, so perhaps my interpretation of why this forum exists is different than others.
The entire basis for dpreview having this forum is to ask questions and learn. Right? At least that is what it states on the dpreview website when you goto the top of the discussion forums. It says:
"Here you can discuss, ask questions or generally debate anything related to digital photography, digital cameras or digital imaging technology."
So I'm not sure why you would take issue with a question about digital photography, when it clearly states this is the place to do that. I've learned a great deal here reading replies to questions like this and appreciate them being asked. But then I'm not a pro photographer, so perhaps my interpretation of why this forum exists is different than others.
chevysales
Senior Member
so he bought a 40d as first dslr? big deal if he has the coin so what.
and all the books in the world for some won't do what one specific answer in a forum will do.
while i see many tout the excellent "understanding exposure" (digital revision of book many don't mention) for someone with no slr experience it isn't all that much of a help.
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Forty Dee and a Seventy-Two hundred IS f4L along with Seventeen-FiftyFive IS 2.8... and growing
and all the books in the world for some won't do what one specific answer in a forum will do.
while i see many tout the excellent "understanding exposure" (digital revision of book many don't mention) for someone with no slr experience it isn't all that much of a help.
--
Forty Dee and a Seventy-Two hundred IS f4L along with Seventeen-FiftyFive IS 2.8... and growing
rdspear
Senior Member
On both my 10D and my 40D it reduces the shutter speed. What camera do you have that it blinks and does nothing?
bronxbombers
Forum Pro
i saw 17 years old all over SoCal in BMWs and porsches and they seemed to be doing just fine in them. anyway, ok, learning a car, perhaps you'd be afraid to scratch it up at first or worse. but you don't crash or poorly parallel park cameras.Why don't learn how to drive on Mercedes or Lexus? You can, if you
have money to throw away and fine with not driving it more than 40
mph!
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Boris
Degustibus non disputandum est!
i just don't see how a 400D is easier to use or learn with than a 40D. why pay for it when you might 40D stuff in a few weeks or 12months. heck, if you were trying to do sports, a 1D with the AF assist cluster would probably make it easier for the beginner to get on track than a 400D. seems like this would be mess cost effective for most. and again, I think a 40D is actually a little bit easier to learn with than a 400D because of the control layout and the fact that some stuff on it works better.
anyway, we obviously disagree. nice photo in your profile btw.
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