Hello,
i wanted to share my recent experience. I rediscovered this accessory, the "Panagor auto macro converter"
PANAGOR AUTO MACRO CONVERTER reviews - Pentax Camera Accessory Review Database
that is probably also sold with other names.
Since i acquired my macro lenses i hardly used it, until a couple of days ago i tried to put the DFA 50mm macro on it, and to my surprise i discovered that the combination of the teleconverter fully extended provides roughly a 3:1 reproduction ratio with a very decent working distance of 2-3cm , not much less than the macro lens used alone.
I arranged a quick and dirty tabletop setup with my tripod, a diffused powerful led light, a cable release and tested the combination with some pretty decent results. I also noticed that the depth of field provided was broader than i expected, shooting with the DFA at f5.6 provided the best sharpness, with a very rapid decrease at other fstops.
Came back after lunch and found a common fly dead on my desk...decided to try a focus stack.
It's interesting that if you operate on the focusing ring of the teleconverter, with the macro lens at 1:1, the focus plane shifts without almost any change in magnification (on the contrary, when i tried to do focus stacking with the DFA alone, the magnification varied substantially, i guess it depends on the optical design and the way it achieves focusing).
So i think this system can be a nice alternative to dedicated macro rails if you are on a budget, and can get your conventional 1:1 lens into extreme macro territory with little effort. It is rather short, probably around 50mm, and if i am not mistaken with an hollow extension tube of the same length one should achieve "only" 2:1 magnification with a 50mm lens capable of 1:1 .
The results ?
This is a focus stack of 25 shots taken at f5.6 and stacked with the trial version of Zerene Stacker...tried to use the open source combination enfuse+align_image_stack but the result was orders of magnitude worse. In the past i had obtained very good result from enfuse but i was stacking 3-4 shots max.
Of course i've seen much better shots around, but i dare to say i'm pretty impressed by the output. I encourage you to look at full res for the best view
...and to consider this inexpensive piece of equipment as a possible answer to the ever recurring question : "How do i go beyond 1:1 ? "