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02-29-2016, 11:52 AM   #16
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QuoteOriginally posted by Not a Number Quote
So either you have to apply 2 stops of exposure compensation or use manual stop-down metering.
It should not make any difference since the TC attenuates the light. All the contact do is tell the body the range of f/stops max-min. The absolute value is not critical except for exif.


Steve

02-29-2016, 03:30 PM   #17
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QuoteOriginally posted by stevebrot Quote
If you can see "F..." in the viewfinder, the contacts are not working.


Steve
Sorry - I meant to say "I can see the FXXX in the viewfinder" where the XXX is the aperture!!
02-29-2016, 04:50 PM   #18
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QuoteOriginally posted by stevebrot Quote
It should not make any difference since the TC attenuates the light. All the contact do is tell the body the range of f/stops max-min. The absolute value is not critical except for exif.


Steve
Steve, in principle you are correct, but unfortunately, the realmworld has no principles.

There is a well documented exposure error issue with TCs due to the fact(also documented) that the Pentax metering system absolutely needs to know the native aperture of the lens. When you put a TC on, except for a rare few,M they do not alter the reported aperture, therefore what the camera things is attached is 2 stops faster than what is attached. Now look at the curve I attached, on a K10D an F2.8 lens meters about 1 stop under , and anF5.6 about 1 stop over.

Put and F2.8 lens on an A series TC and the camera thinks it is an F2.8 lens, and applies a boost of 1stop above the light the meter thinks is needed because of the inaccuracy, but the lens is an F5.6 which causes the meter to over expose any way by 1 stop, and it adds another, so you end up with a histogram that is 2stops shifted to the right .

Other bodies are better, the K10 was the worst at metering with either manual lenses or a TC but all the bodies have some adjustment.
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