Technical question on teleconverters

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Matt
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Thought I'd dfferentiate this from the usual 'new lens or teleconverter' threads. Everyone knows how adding TCs, that they affect available light by 1 or 2 stops. My question is, how do they affect the depth of field. For example, if I had a 70-200L f2.8 (I really wish) and added a 1.4x TC, would depth of field behave like a 98-280 f2.8, or like a 98-280 f4? I'm currently in the looooooong process of saving for one, hopefully IS version, but I'd like to know this beforehand.

Thanks for reading and for any answers too.
 
The simple answer is the 98-280 f/4 option.....however, DoF is a function of aperture value and magnification so the focal length doesn't feature in the calculation.

Bob
 
Canon Bob said:
The simple answer is the 98-280 f/4 option.....however, DoF is a function of aperture value and magnification so the focal length doesn't feature in the calculation.

Bob
Click to expand...
It does.
Hyperfocal = FL^2/(A * CC)/1000 in mm
 
Indeed as Bob said, it's tyhe size of the Aperture not the focal lenght that mkes the difference here. So a 100mm f2 = 50m aperture and a 200mm f4 is a 50mm aperture so they in thoery have the same DOF. Or you could say on a M4/3rds camera a 100mm f2 will look exactly how a 200mm f4 on a full frame camera would. Of course this is all in theory...
 
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