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02-26-2007, 12:50 PM   #1
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SR and teleconverters

I was using my 1.4x TC on my Bigma yesterday for a total apparent focal length of 700mm. However, I notice that my camera still reports focal length as 500mm, meaning the shake reduction is set for that focal length. Is that going to be a problem? Should/can I set it manually to 700mm? How do the rest of you handle this?

02-26-2007, 12:57 PM   #2
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QuoteOriginally posted by rfortson Quote
I was using my 1.4x TC on my Bigma yesterday for a total apparent focal length of 700mm. However, I notice that my camera still reports focal length as 500mm, meaning the shake reduction is set for that focal length. Is that going to be a problem? Should/can I set it manually to 700mm? How do the rest of you handle this?
I reported this shortly after I bought my K10D to pentax who claimed they would report it to their R&D.

Note this also impacts the flash zoom focal length.

I am not sure, but I have been told that Nikon have the TC corrected for automatically. I do not know if this is possible within the Pentax KA and newer mount specification or not. I proposed a start up menu, like what you get with non A lenses, where you can pick the TC from a menu. I suggested 1.4x, 1.7x, 2x, and 3x as reasonable ones.
02-26-2007, 01:35 PM   #3
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QuoteOriginally posted by rfortson Quote
I was using my 1.4x TC on my Bigma yesterday for a total apparent focal length of 700mm. However, I notice that my camera still reports focal length as 500mm, meaning the shake reduction is set for that focal length. Is that going to be a problem? Should/can I set it manually to 700mm? How do the rest of you handle this?
I have long been aware that the EXIF data for shots using a teleconverter reports the lens focal length without taking the teleconverter into consideration. I have spent some time wondering whether this is a mistake or not. After all, at least as I understand it, a teleconverter does NOT actually lengthen the lens's focal length - it simply magnifies the image that's presented to the sensor.

I have shot a lot of photos with my 300mm lens + 1.4x converter with SR enabled, and I have not noticed any problems.

Will
02-26-2007, 04:01 PM   #4
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QuoteOriginally posted by WMBP Quote
I have long been aware that the EXIF data for shots using a teleconverter reports the lens focal length without taking the teleconverter into consideration. I have spent some time wondering whether this is a mistake or not. After all, at least as I understand it, a teleconverter does NOT actually lengthen the lens's focal length - it simply magnifies the image that's presented to the sensor.

I have shot a lot of photos with my 300mm lens + 1.4x converter with SR enabled, and I have not noticed any problems.

Will

Please note that magnification of the image is the same thing as changing the focal length. You also need to consider that focal length and actual lens length are different. The true definition of telephoto lens is a lens that produce the same image magnification as a simple lens while physically being shorter, due to the use of compound optics.

The impact is no different than the guidelines for hand held photography, they suggest a shutter speed of 1 / (f x 1.5) where as with film it is 1 / f. The difference is the change in apparent image magnification due to the sensor size (when compared to film)

02-26-2007, 06:35 PM   #5
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i set mine allowing for the converter with a manual lens.. with a none manual it does its own thing.. i cant say as i have noticed any problems either way.. SR still seems to do its business..

trog
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