[davidmanze]

Nice lens indeed.

PF and fluorite are not mutually exclusive ;-)
I am under the impression that resolution loss from the use of TCs primarily is due to the cropping the TCs do. So I am a bit sceptical of reports that claim that new TCs cause very little loss of quality compared to the older DSLR TC range...

  I think that up until recently long primes were designed as stand alone configurations and TCs were more like an afterthought ......... with today's CAD abilities the two optics can be design to work more harmoniously together ........ certainly tests using the new S series of TCs have shown now that TCs of 1.7X and even 2X have minimum/acceptable IQ loss.
 For most AF-S long primes the 1.4E III does the best, the 1.7X TC does not do well and frankly the 2.0X TC is next to useless.

See here:
 

https://photographylife.com/reviews/niko...e-fl-ed-vr

......... go to the optical qualities section to see the drop in IQ with the TCs ........ (although I really don't see that amount of loss with the TC14E III/ 600 F4E, making me think that maybe the air quality in those tests slightly compromised their results)


 Resolution results from this site shows the rather severe IQ loss from higher magnification TCs ..........

 "PF and fluorite are not mutually exclusive" ....... I didn't understand that ....... PF is considered lighter though.

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