From: Godfrey DiGiorgi [mailto:[EMAIL PROTECTED] Using an extension tube is virtually the same as using a macro lens,
Ooooooo, if JCO were here he'd tell you buddy! ;-)
Who is "JCO" and why would I care what he'd have to tell me? I've only been using extension tubes, bellows and macro lenses for 40 years or so.
Seriously, I used tubes for a long time. It was inexpensive, with some very good results. Now that I have some true macro lenses I get some outstanding results, rather than just very good.
Presuming that you have equal quality lenses, there should be no difference in the quality of your results. Of course, as you point out below, true macro lenses are optimized for near-field focusing requirements and usually perform better. I often use an extension tube in conjunction with a macro or enlarging lens if my macro lens doesn't suit a particular purpose by itself.
1. True macro lenses are designed for the purpose and will generally yield superior results, hence their higher cost. 2. You will lose some light when "going macro", this is true of even dedicated macro lenses. In other words an already slow f/4-5.6 lens can get pretty dark when extended. Focus is critical at high magnification, dark = difficult.
This is true of all lenses that focus by extending the objectives away from the imaging plane. Light falloff simply isn't significant until you reach a substantial extension.
You usually need to stop down a lens quite a bit to gain enough DoF in macro work too. Settings of f/16-f/32 are common place, exacerbating the need for a steady camera support.
My favorite lens to use with tubes was the M50/1.4, it did a great job.
I've used both A50/1.4 and A50/1.7. They both do a good job, but the f/1.7 model has better flatness of field at close distances and is a superior macro performer.
Godfrey
