well, ako i used to have an all-sigma lineup. masasabi ko lang, it's not too bad compared to nikkors and considering the price difference, i'd say kung nagmamadali ka na bumili ng lente, sige kaya mo pa siguro pagtiyagaan ang sigma. pero as the others suggested, sulit din ang nikkors kahit mahal.
ang mga napansin ko sa sigma lenses, in terms of IQ, medyo warm ang kuha ng sigma. meaning may pagka-yellowish as compared to nikkors. mas neutral yung mga kulay ng nikkor. same goes for tamron, medyo warm din yung mga tammy, pero mas orangey kind of warm sha. medyo mas malala nga lang ang CA (chromatic aberration) ng sigmas kaysa sa nikkors.
sharpness naman. nikkors are sharp. the 18-55mm kit lens is one of the sharpest "cheap" lenses out there. shempre lalo pa yung mga nikkor primes. the sigmas are quite sharp din. although may sweet spot naman lahat ng lente, including nikkors. usually 2 stops under wide open. yung experience ko naman sa tamron ko dati, wide open, soft sha. it's as if you have a soft filter on. pero sharp sha at f4.
magkakatalo naman ang sharpness sa dami ng glass elements sa loob ng lente eh. kaya ako i opted to go all nikkor primes, kasi konti lang glass elements ng mga prime lens. shempre, the more glass elements the light passes thru, medyo nababawasan ang sharpness ng image.
durability, basically matibay naman ang mga lente eh. as long as you use it for what it's made for. to take pictures. hindi naman pambato ang lente or weapon. pag nababagsak talaga, kahit plastic or bakal man yung body nun, masisira at masisira pa rin. although sabi ng isang lens/camera technician. mas makapal yung coating ng mga nikkor lenses kaysa sa mga 3rd party lenses. meaning mas resistant sha sa fungus.
so bottom line, try out some lenses, then see what results each one brings you. kung happy ka naman sa pictures na nakukuha mo using a 3rd party lens, then by all means, go for it. pero kung sobrang obvious talaga na mas ok ang nikkors for you, eh di ipon ipon ka pa konti.
