[luka]

Hi

What performance should I expect from a field flattener? Perfectly round stars?

I recently got a Hotech SCA field flattener for my ED80 + Canon 1200D. I thought I would get perfectly round stars in corners but this does not seem to be the case (see the croped corner image below). It is MUCH better than just ED80 but not perfect.

Now, I have noticed that my T-ring is 10mm "thick" and with Canon's 44mm flange-to-sensor distance I have 54mm total distance to the flattener. This is 1mm shorter than the recommended 55mm. Could this 1mm be the reason for non-perfect stars? Hotech does not give a range for the filter but only specifies it as 55mm.

Thanks
Luka