Originally posted by RICHARD L. Nothing limiting the extension, really. Of course you have to compensate your exposure according to the magnification ratio and get enough DOF the be able to recognize a subject. Inanimate subjects can be magnified easily to 5X or more. You can add extension tubes to a set of bellows (here the 645 Auto Bellows with 645 #2 Extension Tube and '645 to K' adapter with a 645 A 75 mm f/2.8 normal lens). The K3 compensated for the light loss and exposed automatically in Av mode. The shorter the lens, the greater a magnification you can achieve.
Outstanding photo - is that blueberries?
Interesting. I have the m100mm macro lens and ordered the m50mm macro lens. So, I can actually get more magnification if using the shorter 50mm macro lens (with extension tubes) ?
---------- Post added 03-30-21 at 06:15 PM ----------
Originally posted by Derek If you are using automatic tubes that close down the aperture when you make the shot, you'll hit a mechanical limit where the linkages cannot perform their function. You are using three tubes? You might get another one or two.
When you use too much extension you can also reach a point where the plane of focus is so close that it is now inside the lens.
I'm pretty sure I'm using the old non-automatic Asahi Pentax extension tubes. I use the green button for Tv shift.
Thanks for your reply - I understand.
Addendum: I think I might have the auto extension tubes - they're the ones like here:
https://www.pentaxforums.com/articles/influential-gear/asahi-pentax-auto-extension-tubes.html But regardless, I'm using the M macro lens where I select the aperture on the lens. I really don't know if the tubes are doing something to the lens (aperture?) when I use the green button (for Tv shift) - ???
Last edited by Michael Piziak; 03-30-2021 at 06:21 PM.