I performed a quick test yesterday: Tamron 90mm F/2.8 macro (272E) + DCR-250 versus Tamron 90mm F/2.8 macro (272E) + extension tube, in the same conditions (same magnification, same light, same aperture, same ISO setting).
The shutter speed, in the first configuration, is about 2x the second one. So the extension tubes really eat half of the light.
This result questions my previous tests, I'll have to perform a new batch of test to compare close-up to extension rings with different lenses.
By the way, at the maximum magnification with the DCR-250, the working distance is shallow. With a 50mm I wonder whether a DCR-250 will be useable or not.
As I do not own a 50mm macro, the question remains open.
In general, it is preferable to use extension tubes with short focal length lenses and close-up with long focal lenth lenses, for 2 good reasons:
- a close-up, like a reversed lens, decreases the focal length of resulting setup.
- the mecanic register (provided by extension tubes, bellows etc.) increases the magnification, but this increase is inversely proportional to the focal length.
Last edited by tryphon4; 02-20-2019 at 10:44 AM.