Thank you, I think you're right. I just checked magnification with a ruler and it seems that with the 80mm of extensions, it is about x2.1 and around 72mm FL. This means with 52.5mm extensions it is about x1.75. This makes sense and puts the x1.9 of the coupled lenses between them, which is what I get.
I'm also wondering if the extra "crispness" from the coupled lenses might be from the non-painted metal part of the lens mount reflecting light to whatever I use for testing.
Update - looking for more suggestions
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clarnibass
- Posts: 130
- Joined: Fri Jun 10, 2016 11:33 pm
If anyone is still reading this... 
I did another test with a wasp eye. I can't believe how much better the coupled lenses are. The extended lens is much more hazy, with less contrast for some reason. I doubt the different working distance causes the light to change enough to cause this... but I guess there's a small possibility of that. I don't think it's an issue with the lens because it's good at x1. I tried the lens and extensions at x1 (no extensions), x1.75 (extended 52.5mm) and x2.1 (extended 80mm) with a contrasty flat subject. It seems like it's getting hazier, but it's really hard to say, I almost don't trust my eyes anymore...
I did another test with a wasp eye. I can't believe how much better the coupled lenses are. The extended lens is much more hazy, with less contrast for some reason. I doubt the different working distance causes the light to change enough to cause this... but I guess there's a small possibility of that. I don't think it's an issue with the lens because it's good at x1. I tried the lens and extensions at x1 (no extensions), x1.75 (extended 52.5mm) and x2.1 (extended 80mm) with a contrasty flat subject. It seems like it's getting hazier, but it's really hard to say, I almost don't trust my eyes anymore...