Personally, I chosen the path of prime + TC and have not looked back.
As most wild life in Singapore need a reach of between 500mm to 600mm, I thought I take the opportunity to list the various options to get to that focal range based on FX and sorted by price.
1) 80-400mm f/4.5-5.6G VR II + TC-14E II Price: < S$4,000 (550mm f/8 Usable at F10 to F11)
2) Sigma 120-300mm f/2.8 HSM DG OS Price: S$4,800 < X < S$5,200
3) 300mm f/2.8 VR II + TC-20E III: S$7,000 > X > S$8,400 (600mm f/5.6 usable at F7.1 onwards to F11)
4) 200-400mm f/4 VR II + TC-14E II: S$8,800 > X > S$9,500 (550mm f/5.6 Usable at F8 onwards to F11)
5) 400mm f/2.8 + TC-14E II: S$12,100 > X > S$14,900 (550mm f/4 Usable at F4 with a tad of smoothness but reach equivalent sharpness to a 500 f/4 VR at F5.6)
** Requires investment in a tripod and gimbal head. (Gitzo System 4 series + Jobu HD MK III or Wimberley WH-200 + replacement foot for roughly S$2,550 or Benro Tripod + Gimbal for half the price)
6) 600mm f/4 VR S$12,500 onwards
** Requires investment in a tripod and gimbal head. (Gitzo System 4 series + Jobu HD MK III or Wimberley WH-200 + replacement foot for roughly S$2,550 or Benro Tripod + Gimbal for half the price)
It is not hard to observe that the way to reach between 500mm to 600mm on FX on a tight budget is the 80-400mm f/4.5-5.6G VR II + TC-14E II that can be hand held to retain its optimum sharpness at F11. Under sunny sunlight conditions, it is possible to shoot at F10 | 1/640 |ISO 1250 or in cases of Safari shoots, shooting at F10 | 1/250 | < ISO 1250
For me, IMHO, if one does not yet own or intend to own a 70-200mm f/2.8 VR II, the 80-400mm f/4.5-5.6G VR II is a good option to reach focal lengths between 500mm to 60mm with option to shoot between 80-200mm followed by from 200-400mm and it can also be shot wide open at 400mm f/5.6 and one could be surprised that it is almost if not as sharp as the 200-400mm f/4 VR II at distances less than 80m at 400mm f/6.3 (Yes, it has to be f/6.3 as at f/5.6, the 80-400 f/4.5-5.6G VR II is wide open and will be softer than the 200-400mm f/4 VR II stopped down)
*** It is possible to recover sharpness in PP. That is what make using TC a viable option although there is a limitation to distances as would shooting distance apply to the lens itself.
