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06-06-2008, 07:07 AM   #16
JMS
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QuoteOriginally posted by ftpaddict Quote
Technically, it's 1/4 a stop. You decide if that's important to you or not.
Actually, it's 1/6 stop.

06-06-2008, 07:31 AM   #17
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F-numbers Maths!

QuoteOriginally posted by JMS Quote
Actually, it's 1/6 stop.
Yes, you're right. To be more exact, *if* we believe the f/1.7 to be exactly 1.7000000... and the f/1.8 to be 1.8000000...., the difference is actually 0.1649243202 stop.

However, the round up is practically not applicable for most of the time, unfortunately. It is because in real, f/1.4 is f/1.414213562 theoretically and f/1.7 is f/1.68179283 where as f/2 is exactly f/2.000000.... and so on!

Last edited by RiceHigh; 06-06-2008 at 09:40 AM. Reason: To correct a calculation error
06-06-2008, 08:26 AM   #18
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QuoteOriginally posted by JMS Quote
Actually, it's 1/6 stop.
Well dang. That's why I didn't go to math school.
06-07-2008, 12:59 PM   #19
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Joe,
I beleiving that the note applies to matrix metering which requires the appeture position lever to connect to the camera. The DSLRs use the crippled KA mount. No connection, just the electrical contacts and diaphram lever.

Dave

QuoteOriginally posted by joefru Quote
At the bottom of that page, it says there will be no effect for Pentax dSLRs. Maybe they read the aperture differently? And I must have been mis-remembering, because I just took a shot with my K10D/FA50 at f/1.8, and the lens, camera, PEF EXIF, and JPEG EXIF all listed f/1.8.


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