I have been using the Sigma 50-500 for the past few weeks now and today my Canon 100-400L IS came via UPS from B&H. I know many of you are much like me, in trying to work out which of the longer lens to get and or save up for. I have only taken a few hundred shots with it but I have some thoughts regarding this pair of lens to share.
•Sigma costs less, but weighs more, 1.1 pound.
•Viewfinder seems to be brighter with the Canon lens.
•Canon seems to focus much faster & on what I aimed it at.
•The IS feature is very nice with hand helds.
•The Canon pans much easier for me.
•The Canon balance seems much nicer for me.
•In similar light the Canon works much better/quicker.
•IMO the photographs taken w/Canon are MUCH sharper.
•Color is better & brighter for same subjects w/Canon.
•Object detail is better and or more refined ie. feather details w/Canon.
•I miss the extra 100mm of the Sigma 50-500.
•Build of the Canon is just better. (My first L lens)
•The build of the Sigma . . . wiggled near the mount on the copy I used. But is generally robust.
•I don't like the focus ring and tension ring layout on the Canon lens . . . adjusting focus changes tension.
I am thusly very pleased with the Canon all in all . . . even at a shorter mm length. I could use a 1200mm very easy. LOL!
Just my thought from the first days shoot. I have a couple of shots up in the Nature forum if you would like to see. Everything prior to today was taken with the Sigma 50-500 BigMa. I returned the lens this evening to my friend whom lent it to me. Thanks Jim for the loan.
I hope that this can help those of you whom are looking for long lens . . . good luck. Keep shooting!