When is an aperture value not an aperture value?
Aug 4, 2012 19:43:35 #
Jersey guy
Loc: New Joisey
After noting that many high quality zoom lenses boast of 17 or more elements, (in so-and-so many groups) I began to ponder how much light is lost from all those air-glass interfaces despite the best that anti-reflection technology has to offer. Is a 3.5 aperture physically 3.5 or is that the effective speed of the lens after taking into consideration the loss of light from all those reflecting surfaces? Putting it another way, if 3.5 is the physical dimension, just how much light is lost for the above reason?
Aug 4, 2012 20:25:33 #
You are referring to the t-stop; the f-stop is the geometric value of the aperture, whereas the t-stop (transmission stop) refers to the actual amount of light transmitted through the lens. I'm not aware of t-stops being included in EXIF data, so I'd guess you'd need special software or equipment to measure it.
Aug 5, 2012 00:08:03 #
snowbear wrote:
You are referring to the t-stop; the f-stop is the geometric value of the aperture, whereas the t-stop (transmission stop) refers to the actual amount of light transmitted through the lens. I'm not aware of t-stops being included in EXIF data, so I'd guess you'd need special software or equipment to measure it.
EXIF data usually contains all camera and lens data. See:
http://en.wikipedia.org/wiki/Exchangeable_image_file_format
You are correct that f-stops do not accurately measure the transmission of light. For more info than I want to type see:
http://en.wikipedia.org/wiki/F_stop
Light transmission is the same lens to lens for any given t-stop (which is different than f-stop).
Aug 5, 2012 12:56:04 #
Jersey guy
Loc: New Joisey
Snowbear and Robert-Photo....thanks for the tutorial...it fleshes out my supposition it an understandable way.
I guess it's somewhat academic since the autoexposure feature of all modern cameras looks only at the light levels that fall on the sensor and could not care less what the theoretical f-stop is supposed to be. It gets to be a bit of a problem when the photographer starts using the aperture and shutter numbers to try to accomplish something specific.
I guess it's somewhat academic since the autoexposure feature of all modern cameras looks only at the light levels that fall on the sensor and could not care less what the theoretical f-stop is supposed to be. It gets to be a bit of a problem when the photographer starts using the aperture and shutter numbers to try to accomplish something specific.
Aug 8, 2012 18:10:31 #
Aug 8, 2012 18:39:49 #
Aug 8, 2012 21:46:05 #
Jersey guy wrote:
Snowbear and Robert-Photo....thanks for the tutorial...it fleshes out my supposition it an understandable way.
I guess it's somewhat academic since the autoexposure feature of all modern cameras looks only at the light levels that fall on the sensor and could not care less what the theoretical f-stop is supposed to be. It gets to be a bit of a problem when the photographer starts using the aperture and shutter numbers to try to accomplish something specific.
I guess it's somewhat academic since the autoexposure feature of all modern cameras looks only at the light levels that fall on the sensor and could not care less what the theoretical f-stop is supposed to be. It gets to be a bit of a problem when the photographer starts using the aperture and shutter numbers to try to accomplish something specific.
That is the whole point of learning to use your camera and lenses....so you have creative control. It is an art form.
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