Should I cheat and delete the last blog before the entire Internet World (humor, humor) learns I have been WRONG!!
Wiki agrees with me--on their macro page they say flat out that, like regular photography, in macro photography short focal length lens have a greater depth of field than long focal length lens. So I am not alone in my WRONGITUDUALISM!!
So what reduced me to this embarrassing state?
Dr Guru 'Ray, Sidney F.' in his Applied Photographic Optics--500+ pages of everything you want to know about lens plus a hell of a lot more--told me that when you get into the macro world where your magnification is close to 1 to 1 you can whack off parts of the DOF equations because they don't amount to much.
After the whacking is complete all you got left is the f#, the circle of confusion. and the magnification. So that means--I hang my head in shame--my S3IS doesn't have a better DOF than the $550 Tamron 90 mm macro lens. Focal lengths don't count in the macro world
But then, since focal length don't count, the S3IS's DOF ain't worse either. It will still hang around my neck. I already own it, so it's a hell of lot cheaper than that new $550 Tamron lens. Besides, with only a small fraction of the fancy lens price, I bought a set of extension tubes and an extension bellows. Shipped yesterday according to this morning's e-mail.
Add in what I already own--suitable garage sale and closeup lens plus an x,y focusing stage left over from an ancient optics project--I can now take macros until the cows come home. Mixed metaphor--until the memory cards melt.
You have been warned! Twice!