Originally posted by wehavenowaves! so with an extenstion tube you have no auto focus. does that mean you have no control over the shutter speed as well???
Some (rare) extension tubes allow autofocus (AF). Some people buy teleconverters (TC's) with AF, then remove the glass, so they function as AF tubes. IMHO these are only cost-effective options when using short AF lenses, because more extension (buying more tubes) is needed to get much magnification. And AF tubes and TC's ain't cheap.
And AF isn't really needed in most macro work. Where the system wants to focus may not be where YOU want to focus. With manual-focus lenses, you can use Catch-In-Focus to serve as a cheap AF if desired. I do that a lot.
No, you don't lose control over shutter speed. That's completely in the camera. More significant is aperture automation (AA). Some extension tubes and TC's support AA but not AF; they're cheaper than their AF kin, but costlier than simple tubes. With this automation, using flash is fairly simple, using A or F or FA or DA lenses. Without it, you need to control light manually: ambient light, external lights, etc.
All this with AF and AA involve camera lenses, with focusing mounts. Enlarger and projector and bellows-macro and other non-focusing lenses never had any focus nor aperture automation, so you just handle those as any other totally manual glass.
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Some examples:
* I can put my FA50/1.4 on a couple AA TC's (glass removed) that total 52mm thick. It now does 1:1 magnification with camera control over the aperture, so I can use a ringflash or other flash setup easily. Or I can focus on something with the aperture wide open, which then stops-down to take the shot.
* I can put my M50/1.7 on the same TC's, but I must set the aperture manually, and flash is a pain. Because the TC's contain a mechanical aperture linkage, I can put the camera in M(anual) mode and use the Green button to take exposure readings and set the exposure for a shot.
* I can put the M50/1.7 on simple cheap macro tubes. Then the lens acts as a preset -- wherever I set the aperture, that's where it is. Now I can work in Av mode: just set the aperture, aim, focus, and shoot. I can put any enlarger lens on cheap tubes and/or bellows, or put any totally-manual lens on the camera, and it works the same way.
Yeah, there's lots of stuff to learn here: the differences between electrical and mechanical linkages, the limitations of various setups, how various lenses behave with extension or reversal or whatever. But what it boils down to is this:
* A Raynox macro adapter on a modern lens gives great results, doesn't cost a lot, and is easy.
* A dedicated camera macro lens is most convenient and easy, and gives best results, but costs the most.
* You can do macro real cheap with a reversed prime lens, but you must work REAL close, under two inches.
* You can do quality macro with tubes, bellows, and cheap enlarger lenses, but light can be tricky.
* People have been shooting macro since long before any automation was available.
Keep studying. Keep asking questions. Have fun!