I do not disagree, there is indeed value in both experience and theory. I'm not trying to dismiss experience, honestly. However I do believe that if tilt is of no value at macro scale, it should be easy to prove, especially for someone who has ready access to a wide variety of tilt/shift lenses with a range of capabilities and designs. I'm also not above admitting I could be 100% wrong here, but I honestly do not believe I am.
PrivateByDesign and I have a long history. He has his way, and he thinks it is 100% purely objective, and in many cases he very much is, however there have been cases where I believe he is blind to his bias, and his bias is very persistent. Hence my reason to doubt him until I get some kind of concrete proof. You came on pretty strong, immediately claiming a superior position then also immediately and subsequently trouncing any possibility that you would provide any evidence to back up your position. I'm happy that your happy and confident in your position...but that doesn't change anything.
You have still made claims I have no reason to believe just on your word alone, or even the combined word of you and private, and given that there is apparently quite a number of T/S bellows systems explicitly designed for
macro photography, some with magnifications up to 2:1 and tilts from 10° to 25°, that only gives me further cause to doubt your strong assertions, based on
your own personal experience, that tilt is of no practical value for macro photography. Experience is well and good, but how different, really, is photographing a carpet of moss with a tiny mushroom in the middle different from photographing a ring on a slate in a whitebox? I don't see any fundamental difference in the subject distances, angles, or viability of T/S between these two things. In the case of the fly, it's head as a whole is indeed a largely round object like a ball...but from the standpoint of what's visible within the field of view and what really needs to be in focus, the top of the eye and front part of the fly's head that is within view ALSO make for a relatively
flat subject at a slight incline, which is again not all that different from a carpet of moss with a mushroom in the middle or a ring on a slate in a product photography box.
If T/S can be useful for product photography at macro distances, it can be useful for nature photography at the same distances. Insects, being ever-mobile subjects, are certainly rather arbitrary subjects...your not always going to have them cooperating and giving you the opportunity to get a good composition with a good angle on the interesting parts to fully maximize the potential of a flexible T/S macro system. But the same core argument could be made about insect macro in general...that you can't really get the most out of macro photography with insects, for the very same reasons. And yet...thousands of photographers have found a way, not only to make their subjects cooperate, but even photograph them, sometimes hand-held, at magnifications up to 5:1, even in natural lighting.
So, epistêmê or technê, theory and/or experience... I'm not speaking from a purely theoretical standpoint myself. While I have not actually used a macro t/s bellows before (hopefully something that I'll rectify before too long, I actually really want to get some actual evidence that demonstrates what, if any, and how much of a difference tilt could actually affect focus at macro scale now...I'm about ready to DIY myself a little bellows system and use my 50mm and 100mm lenses to test the theory out in the short term), I am not without experience with macro or T/S photography. The assertion that I am simply an ignorant, hopeful idiot doomed to be disappointed, well, it's certainly your right to have an opinion, but it also certainly doesn't give me any reason to trust what you say at face value any more than I had reason to before.
Well, good night.