I've been experimenting with different lens/extender combinations and just wondered if anyone could shed light on the question of using a Proxar F=1m on my 150mm Sonnar vs. using a Model 21 Extension Tube on the 150mm. I have not done extensive side-by-side testing yet, but the two approaches seem to yield similar results.
I'm tending to lean toward the extension tube approach because it allows me to work slightly further from the subject. I don't think depth-of-field is an issue because I'm working under very powerful studio lighting. All things being equal, will one of these approaches result in a sharper image?