This is a well discussed subject, but I found a new twist that I didn't find any previous post about.
In many previous posts it is suggested that when you use then Kenko 1.4x TC you should also add a 20 mm extension ring. So far so good.
But when I read Aquatica's guidelines (for Canon 1.6 crop, in my case) on how to combine lenses, ports ans extension rings, I get confused. I read that when using Tokina 10-17 FE in the mini-dome I should add the 16.5mm extension ring (18456) and when I add the Kenko 1.4x TC I need to replace the previous extension ring with the 28.5mm extension ring (18453).
Now, the difference between these two rings is only 12 mm, which is significantly less that 20 mm. Is this OK?
Is there anyone out there who has experience in using the Tokina 10-17 FE + 1.4x TC in 100 mm mini-dome with the 28.5 mm extension ring and who can confirm that it works fine?