f. stop V. Aperture value
Posted 05/02/2010 - 19:29
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Anvh wrote:
I was referring to the changes in effective aperture when focusing at less than infinity.
thoughton wrote:
Perhaps one is the 'actual' aperture and one is the aperture as seen by the camera.
Huh? Perhaps one is the 'actual' aperture and one is the aperture as seen by the camera.
Tim
AF - Pentax K5, Sigma 10-20/4-5.6, Tamron 17-50/2.8, Sigma 30/1.4, Sigma 70-200/2.8, Tamron 70-300/4-5.6
MF - Vivitar CF 28/2.8, Tamron AD2 90/2.5, MTO 1000/11
Stuff - Metz 58 AF1, Cactus v4, Nikon SB24, Raynox 150, Sigma 1.4x TC, Sigma 2x TC, Kenko 2x macro TC, Redsnapper 283 tripod, iMac 27, Macbook Pro 17, iPad, iPhone 3G
Flickr Fluidr PPG Street Portfolio site
Feel free to edit any of my posted photos! If I post a photo for critique, I want brutal honesty. If you don't like it, please say so and tell me why!
AF - Pentax K5, Sigma 10-20/4-5.6, Tamron 17-50/2.8, Sigma 30/1.4, Sigma 70-200/2.8, Tamron 70-300/4-5.6
MF - Vivitar CF 28/2.8, Tamron AD2 90/2.5, MTO 1000/11
Stuff - Metz 58 AF1, Cactus v4, Nikon SB24, Raynox 150, Sigma 1.4x TC, Sigma 2x TC, Kenko 2x macro TC, Redsnapper 283 tripod, iMac 27, Macbook Pro 17, iPad, iPhone 3G
Flickr Fluidr PPG Street Portfolio site
Feel free to edit any of my posted photos! If I post a photo for critique, I want brutal honesty. If you don't like it, please say so and tell me why!
Posted 05/02/2010 - 19:31
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thoughton wrote:
Ah okay but that can not differ so much right?
Anvh wrote:
I was referring to the changes in effective aperture when focusing at less than infinity.thoughton wrote:
Perhaps one is the 'actual' aperture and one is the aperture as seen by the camera.
Huh? Perhaps one is the 'actual' aperture and one is the aperture as seen by the camera.
Stefan
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Posted 05/02/2010 - 19:33
Link
Wiki strikes again.
The Av value is the aperture expressed according to the APEX system of calculating exposure.
AV 0 = f/1.0
AV 1 = f/1.4
(...)
AV 5 = f/5.6
AV 6 = f/8
etc.
I cannot say I understand all the maths, but at least we have an answer. Of sorts.
K.
The Av value is the aperture expressed according to the APEX system of calculating exposure.
AV 0 = f/1.0
AV 1 = f/1.4
(...)
AV 5 = f/5.6
AV 6 = f/8
etc.
I cannot say I understand all the maths, but at least we have an answer. Of sorts.
K.
Kris Lockyear
It is an illusion that photos are made with the camera they are made with the eye, heart and head. Henri Cartier-Bresson
Lots of film bodies, a couple of digital ones, too many lenses (mainly older glass) and a Horseman LE 5x4.
It is an illusion that photos are made with the camera they are made with the eye, heart and head. Henri Cartier-Bresson
Lots of film bodies, a couple of digital ones, too many lenses (mainly older glass) and a Horseman LE 5x4.
Posted 05/02/2010 - 19:43
Link
womble wrote:
I cannot say I understand all the maths, but at least we have an answer. Of sorts.
K.
Same here...
I cannot say I understand all the maths, but at least we have an answer. Of sorts.
K.
Stefan
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Posted 05/02/2010 - 22:49
Link
I understood about every third word of that page
Quote:
The example data in Annex C of Exif 2.2 give 1 footlambert for Bv = 0. This is in agreement with the APEX value for B, but would imply K = 1 / N, or 3.125 with B in footlamberts. With B in cd/m2, this becomes 10.7, which is slightly less than the value of 12.5 recommended by ISO 2720:1974 and currently used by many manufacturers
The example data in Annex C of Exif 2.2 give 1 footlambert for Bv = 0. This is in agreement with the APEX value for B, but would imply K = 1 / N, or 3.125 with B in footlamberts. With B in cd/m2, this becomes 10.7, which is slightly less than the value of 12.5 recommended by ISO 2720:1974 and currently used by many manufacturers
Tim
AF - Pentax K5, Sigma 10-20/4-5.6, Tamron 17-50/2.8, Sigma 30/1.4, Sigma 70-200/2.8, Tamron 70-300/4-5.6
MF - Vivitar CF 28/2.8, Tamron AD2 90/2.5, MTO 1000/11
Stuff - Metz 58 AF1, Cactus v4, Nikon SB24, Raynox 150, Sigma 1.4x TC, Sigma 2x TC, Kenko 2x macro TC, Redsnapper 283 tripod, iMac 27, Macbook Pro 17, iPad, iPhone 3G
Flickr Fluidr PPG Street Portfolio site
Feel free to edit any of my posted photos! If I post a photo for critique, I want brutal honesty. If you don't like it, please say so and tell me why!
AF - Pentax K5, Sigma 10-20/4-5.6, Tamron 17-50/2.8, Sigma 30/1.4, Sigma 70-200/2.8, Tamron 70-300/4-5.6
MF - Vivitar CF 28/2.8, Tamron AD2 90/2.5, MTO 1000/11
Stuff - Metz 58 AF1, Cactus v4, Nikon SB24, Raynox 150, Sigma 1.4x TC, Sigma 2x TC, Kenko 2x macro TC, Redsnapper 283 tripod, iMac 27, Macbook Pro 17, iPad, iPhone 3G
Flickr Fluidr PPG Street Portfolio site
Feel free to edit any of my posted photos! If I post a photo for critique, I want brutal honesty. If you don't like it, please say so and tell me why!
Posted 05/02/2010 - 23:07
Link
As you focus closer, the actual aperture does change. usually lenses would be designed to have a magnification of no more than 1:10. Closer than this and there has to be special design to avoid the change in aperture, which becomes significant.
Best regards, John
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10412 posts
18 years
Dordrecht,
the Netherlands
Hmm makes me sorry I asked now
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ