Photometry
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Forbiddenbiker
The Enforcer
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Photometry is not a common photographic term for us.
Do you mean the effect light has on the three main types of camera light meters.
For understanding how those meter types read the light differently.
Do you mean the effect light has on the three main types of camera light meters.
For understanding how those meter types read the light differently.
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I guess you mean exposure metering, and metering patterns/modes?
All in-camera metering systems measure the light refelected back from the subject (as opposed to the light falling on it, which is called incident light metering). Since this varies a lot depending on how bright or dark the subject is, eg bride and groom, whereas the light falling on both - the important bit for exposure purposes - is obviously the same, there are various methods used to try and get it right.
There are basically three modes: centre-weighted which reads the whole image area with an emphasis on the middle; spot which reads just a small section in the centre and has to be used with some knowledge; and evaluative or matrix which is 'smart' and by far the best mode for newcomers.
Evaluative takes multiple readings from all over the image, sometimes dozens of them. In this way, it knows the overall scene brightness, it knows the extremes of light and dark, it knows where they are, and it knows how large an area they occupy. This data is often linked to the AF system so it knows where the main subject is (depending on AF mode) and how far away it is.
This is a lot of great information, but it then interprets it intelligently so that if for example there is a large area of bright tone near the top of the image, and distant focus, it's a fair bet this is a landscape so it will downweight the sky to prevent it influencing the reading too much which would otherwise under exposure the foreground.
All in-camera metering systems measure the light refelected back from the subject (as opposed to the light falling on it, which is called incident light metering). Since this varies a lot depending on how bright or dark the subject is, eg bride and groom, whereas the light falling on both - the important bit for exposure purposes - is obviously the same, there are various methods used to try and get it right.
There are basically three modes: centre-weighted which reads the whole image area with an emphasis on the middle; spot which reads just a small section in the centre and has to be used with some knowledge; and evaluative or matrix which is 'smart' and by far the best mode for newcomers.
Evaluative takes multiple readings from all over the image, sometimes dozens of them. In this way, it knows the overall scene brightness, it knows the extremes of light and dark, it knows where they are, and it knows how large an area they occupy. This data is often linked to the AF system so it knows where the main subject is (depending on AF mode) and how far away it is.
This is a lot of great information, but it then interprets it intelligently so that if for example there is a large area of bright tone near the top of the image, and distant focus, it's a fair bet this is a landscape so it will downweight the sky to prevent it influencing the reading too much which would otherwise under exposure the foreground.
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@ Hoppy. Thanks for such a detailed explanation. Such a great group of people on this forum. Again thanks for taking the time to respond to such a beginners problem
You're welcome bud. Good to see Mark Webber soundly thrashed today
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