Wild idea on hacking the 200-400 teleconverter

[ghanbal1]

I’ve been looking at reviews of the 200-400 and most of the complaints are about the internal teleconverter not being very sharp.

Well I don’t believe it’s the same elements as the 1.4x III, it’s probably either the OG or II version.

So what if you opened it up and replaced the internal with the elements from a III version? Wouldn’t that make it a lot sharper? (Considering the significant improvements they made on the version III). Any techies know if this would work?

[wq9nsc]

The EF 200-400 f4 teleconverter is matched to the lens and its parts are not directly interchangeable with a free standing converter. Although the basic design philosophy is the same, the specific structure is intended for this lens with a switch selectable use of the extender.

I have the EF 200-400 f4 extender lens and although it is excellent, it is NOT as sharp as my 200 f2, 300 f2.8, or 400 f2.8 primes and that is no surprise because a prime is a much simpler lens.  The 200-400 f4 is sharper without its extender in operation than when using the extender, again no surprise because EVERY extender is going to reduce image quality.  I have both series II and III of the 1.4X extender and image quality differences between them are minimal; the difference is more noticeable between versions II and III of the 2X but adding a 2X to any lens reduces the image quality far more than I will accept.

I use the 200-400 lens when the need for versatility exceeds the need for absolute quality and wide aperture requirements, it is a great lens.  I wouldn't consider "hacking" a lens of this caliber because all you are going to end up with is something that doesn't perform as well as the original which is a very good lens.  The average viewer wouldn't notice a difference between images taken with this lens and images taken with my 400 f2.8 and the built in 1.4X reduces quality about the same as any extender would.

Be careful with reviews because there is sample to sample variance in this lens like any other AND for maximum performance the lens must have the micro focus adjustment profile done in camera for all four iterations (200 and 400 without extender, 200 and 400 with extender).  If this isn't done, poor AF calibration will result in reduced image quality.

Rodger