Quote:
Originally Posted by grsphoto
Putting an extender on a lens does alter it's focal length, you are changing changing the physic of the lens ( glass and distance)
By using a different sensor you do not change the distance or the glass, all you are doing is using a smaller sensor that gets blown up to a larger size...cropping the image.
A 1.4x entender changes the physical properties of the lens, while changing the cropping factor ( sensor size) does not change anything about how the lens moves light.
Glenn
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No argument here but the cropping magnifies the images; same effect as the use of an extender (optical v.s. digital). And the issue if not one of coverage; it is one of exposure...as shown in the images presented, when the lens is set at 35 mm and the flash head as 35 mm, the image is underexposed compared as to when the lens is at 35 mm and the flash head is at 50mm (note that illumnation across the image is even at both the 35 and 50 mm flash zoom settings). My point is that the Flash should automatically set the zoom to 50 mm rather than 35 mm since in the Canon 40D the 1.6X sensor makes a 35 mm a virtual 50 mm.