Originally posted by Wheatfield Consider that even if there is no "100% rule", there is pretty overwhelming evidence that all else being equal, using a quality tripod under the camera will give a sharper picture than a hand held exposure, and this just gets more true at higher magnifications.
A 1:1 macro lens with any extension tubes to increase magnification beyond it's native limit is going to be giving magnifications that are well nigh impossible to handhold.
I don't see how you are spinning this into that I was saying shots taken w/o a tripod are less sharp than hand held...if something I wrote gave you that mistaken impression sorry for that...
Taking a lens beyond it's native mag using tubes, which btw are 100% air inside, has no effect on IQ and that also is proven out by millions of example shots anywhere you care to look. It may make flaws in a given lens more apparent just as cropping will, but it does not reduce the actual IQ only the apparent IQ depending on the lens.
Sounds like ya don't have much practice with true macro. I would offer as an example these shots by one of my favorite macro shooters:
Insect/bug Macros 2009 - a set on Flickr
These days he shoots almost exclusively with an MP-E 65mm anywhere from 1x-5x...hand held...but he is an amazing shooter and is by no means the rule. Not a lot of us can shoot hand held at more then 3x and get the keeper rate Brian does. I have yet to see a shot where he uses more than his quite, ummmmm, unusual and unique "bean pole" technique...funniest and simplest trick you can imagine to provide fast adjustment as well as a fair bit of support when needed. Just a cheap plastic garden "stake/pole" held between your hand and the camera body. If I can find the example shots he posted I'll add the link.
Many things to consider when shooting macro including to remember the standard methods of shutter speed=1/focal-length but remember to include the crop factor as well as take into consideration the mag ratio, flash, etc...but it is very possible WITH PRACTICE patience and proper planing, to shoot high mag shots hand held. A solid grasp of DOF is also a must and still struggle with it at times myself. By right now since there is nothing like an MPE-65mm for Pentax, my macro shooting is on hold even though I have and love the 35ltd macro. The closest I could come would be to use an auto-bellows and I find them awkward to manage.
I had fun with a Sigma 180mm Macro and a reversed 24-60mm f2.8 that gave me 3x - 7.5x and shot every one hand held. You won't have a high keeper rate but it can be done with success. It was insane but it sure was fun!!
Tripods and macro in the field are pretty difficult to coordinate and you will miss more shots, by a wide margin, than you lose by hand holding at any mag ratio.
And SR on a tripod is always going to depend on the tripod too...but certainly on a solid base SR could induce some vibrations and blur. But as I mentioned it is not a hard fast rule. And that is my point...only practice and experimentation.
And as to the OP's question, I have looked around and given the way the Pentax SR works, it needs to know the focal length of the lens, so I would have to guess the best thing to do is try setting the focal length manually at the lense's actual focal length then what it would be taking the mag ratio into account...mag ratio = 1 + (focal length of lens/length of tubes) so a 50mm macro with 50mm of tubes vice a 2x (2:1) ratio so try manually entering first 50mm, take a few shots, then enter 100mm and take the same shots and go from there...the important factor for the using the Pentax system is to register the right focal length in the body. On the K20D it's the last item on the 2nd screen of the
Rec. Mode Menu and I assume it is enabled when the lens is not reporting a focal length, but that can be looked up in the manual.