Sony 200-600: What is the minimal extension tube to prevent focal breathing?

Started 2 months ago | Questions thread
RGBCMYK Senior Member • Posts: 2,394
Re: Sony 200-600: What is the minimal extension tube to prevent focal breathing?

Interesting video and thanks for sharing.  What most don't know or remember is when lenses are focused 8x their focal length or closer there is natural fall off (with the view camera we called it bellows compensation) and older macro lenses literally had it printed on the lens so manual calculations could be made.  With 1:1 magnification with any lens there is a 2 stop fall off so compensation is needed or it will be UE.  With in camera metering this isn't even noticed but with a manual setting from a hand held meter it becomes obvious.  Older medium format cameras where there is a bellows for focusing (Mamya RB67 for example had a scale on the bellows to calculate the required compensation for the extension ).  Interesting note is most older lenses were not allowed to focus closer than 8x their focal length I am sure to prevent customer complaints and their optical formulas were optimized for infinity vs close up.  All lenses work with extension tubes so it isn't like they don't work close up but exposure compensation for the fall of is needed.  So my guess is that if you use an extension tube on the 200-600 it will allow the closer focusing at the true focal length where I bet the lens makers solution to decrease the focal length to enable the close focus isn't needed.  Manual extension tubes are inexpensive and you could get a set of 3 and give it a test before purchasing the more expensive ones that pass the info through.

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