I’ve never been a fan of 2x converters. While 1.4x works great with many lenses, 2x just seems to loose a lot of acuity. But we photograph in a new world now; the sharpness of new mirrorless lenses way surpasses older versions. I have been very happy using the new Z 1.4x on my 100-400mm and 70-200mm. And the new 400mm F2.8 with built-in 1.4x is just astounding, sharpest long telephoto I have ever used, and still super sharp when using the built-in converter. Since the 400mm F2.8 Z is so sharp, how would it perform with a 2x converter (not engaging the built-in teleconverter)? I decided to try it out on some local birds.
I was shocked. Performance was remarkable in the middle of the frame…very sharp! And things still looked good mid frame, losing a little acuity on the edges…as happens with all lenses. I tested this combo both wide open…so 800mm at F5.6 and also at F8. Sharpness increased a little by stopping down to F8. Take a look at the head feathers on the mallard…shot at 800mm F5.6. Using the 2x on the new 400mm F2.8 works amazingly well. So much so that while Cree will be shooting the new 800mm F6.3, I’ll be using the 400mm F2.8 with 2x. So we both will have 800mm lenses for those distant bird shots!
I’d say this is the sharpest result I’ve ever gotten using a 2x on any lens. Other reviewers have also confirmed these findings. This is a very sharp combination, and makes the new 400mm F2.8 even more versatile of a lens.