For those of us who enjoyed the 400 f5.6AI / AIS EDIF, these tantalizing telephotos are indeed long overdue.
But today’s DSLR landscape has changed the markets for telephotos of slower speeds. Not only do the exotic Nikkors perform very well with TCs but so does the 300 f4 PF, and the 70-200 zooms (but a bit of a stretch). I often use my 200 f2G VRII as a hefty but well balanced 400 f4 with TC2 III. I find this combo that much easier to handhold than the equally excellent 300 f2.8G with TCs. And the 200+TC2 gives the better IQ and AF performance on the D500 and D850... but I do so wish for a lighter prime of 2 kg and even lighter. The 400 f5.6AIS is a nifty 1.2kg :-)
Together, the TC factor and high-res sensors on top DSLRs focus the choices open to us, as to where one invests one’s money. The high prices, and gear weight, especially those jobs-worth terrorizing airline checkins constrain us to seek the Singular Telephoto. But it must hold the capacity for top IQ with TCs for still longer focal lengths – when needed to 700mm and 800mm. And I readily confess this need for a lighter tele prime in the guise of the 300 f4 PF has become an enduring quest. Such that I have been in email communication with Sigma, motivating for what I see as obvious gaps in inventories.... I'm reliably informed that these requests reach the Optical Design Division across the desk of their affable CEO - most pleasant feedback :-)
The time for lighter AF tele primes delivering topnotch IQ has never been better, given how a swelling market for affordable telephotos interfaces with the modern state of optical technology and the remarkably superb digital cameras. I see the Teleconverter Factor sitting in the core of this triangle....Especially, how a telephoto ranks in its TC Factor.
Here's my summary of options with these potential PF telephotos for FL extension-potential with Teleconverters:
-----------------OL (mm) ------------- TC14 ------------- TC17 ------------------- TC20
300 f4 PF --------148 ------------ 420 f5.6 ------------ 510 f6.7 -------------- 600 f8
400 f3.3 PF ------220----------- 560 f4.8 ------------ 680 f5.6 ------------- 800 f6.7
400 f4 PF ---------220----------- 560 f5.6 ----------- 680 f6.7 -------------- 800 f8
500 f4 PF ----------280---------- 700 f5.6 ------------ 850 f6.7 ------------- 1000 f8
500 f5.6 PF -------280---------- 700 f6.7 ------------- 850 f8 ---------------- N/O
600 f5.6 PF --------320-------- 840 f8 ---------------- N/O -------------------- N/O
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The “DX Performance Envelope” with tighter FoV is another big factor at play, and so too is the “croppability” of images we enjoy out of a D8*0 and especially the D850. IMO the credible IQ with TC14 and DX Performance Envelope underwrite the success of the 300 f4 PF – again especially with wildlife.
Where TC capacity is a key factor for wildlife / action, the sad fact is – really guts me to say this – but the 400 f5.6 is dead-on-arrival. A 400 f5.6 PF is the Perfect Compact tele prime for landscapes etc - but too restricted in its modes of use as the Singular Telephoto for BIF and similar subjects. IMHO, this factor also weakens the potential of the excellent 200-500 f5.6 (primarily Nikon’s response to Sigma zooms, so strategically priced in response to this competition). So here I have no option but put my hard earned lucre in a 500 f4 - the Sigma f4 Sport to be precise, saving 3500 quid for other glass.
The only one of these f5.6 telephotos that qualifies as the Singular investment for wildlife is a 600mm – especially if its PF design keeps it light in weight, and wow!! what a prime in one's hands with a length of ~320mm
