sirbridge
newbie
Reged: 09/08/2007
Posts: 8
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I apologise if this has been asked before but is anyone able to give me the exposure compensation factors to be used with either or both extension tubes for this camera. I have both but have mislaid my handbook !
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huwevans
Old Hand
Reged: 05/08/2000
Posts: 15467
Loc: Dorset, UK
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You don't say which lens you will be using - it makes a difference. But in any case, as a general rule of thumb if you add half a stop for a total extension (tube plus bellows) of 20% of the focal length, one stop for 40%, 1.5 for 70%, and two stops for 100%, you won't go too far wrong - it will be wrong, depending on the lens, but it will keep you within reasonable tolerances for most films. The precise compensation will depend not only on the focal length, but on the particular optical construction, and is not something the user would generally be able to work out for themselves, so ideally you should find the provided tables or find a copy of them from somewhere (internet, probably) at some point. (Though trial and error would get you there eventually, of course.)
The rule of thumb will probably be least inaccurate for the 90mm and 127mm lenses, which IIRC are the only non-specialist RB lenses which are not either retrofocal or telephoto. Maybe the 150mm too, though I'm not sure about that. Of course, if you were using the macro lens the factors are marked on the field-flatness compensation ring - but then presumably you wouldn't be asking the question! :-)
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Huw Evans.
  
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OneTen
'Two Breakfasts'
Reged: 23/06/2003
Posts: 2540
Loc: Devon
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There's a table here. HTH
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Richard .......... My Website - My Blog - My Flickr
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sirbridge
newbie
Reged: 09/08/2007
Posts: 8
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Thank you Huw and Richard. I shall be using the 90mm lens.
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