Haya fellas,

Latelly I´ve been thinking a lot about getting rid of my Canons 28mm f1.8 and 85mm f1.8 and getting a Tamron 28-75mm 2.8 instead (it sounds like a very practival all purpose lens with the added benefit of marco, which I love). I know video people LOVE fast lenses but the Canon 6D is a real beast when it comes to high iso (I´ve shot ultra clean 6400 stills with it) and besides you need to have your actors practly still if you want to keep them in focus at f1.8. Plus I will keep my Canon 50mm f1.4 as my low light ace of spades anyway. I know it must sound like I have my mind made up but I would really like to hear the cons of having a fast zoom instead of the 28mm and the 85mm.

I like fast zooms for convenience, but for low light it's tough to beat the really fast primes. 6400 ISO looks a lot worse on video than in stills in my experience, in fact by 3200 in video things start looking pretty rough (except on the 5DmkIII, which seems to have very good in-camera noise reduction). I just had to clean up some 3200 footage from my markII with neat video, and while the results were acceptable they couldn't compete with a few shots done under the same lighting at f/1.4 and 1250 ISO - besides the noise you really start to lose dynamic range at the higher ISOs and your blacks tend to look pretty crushed.

I'm with Evan. There are limits with ISO and video. The 5D3 stretches those limits. The 6D might not. (Like Evan, I'm a 5D2 owner.)

Frankly, there are three reasons to use a zoom:
1) Quick setups,
2) Traveling light, and
3) Precise framing with restricted movement.

Laziness is not a good reason. :) A dirty environment might be considered, but the zoom mechanism can be ruined in a sandstorm. Probably best to choose a single prime and stick with it in a really harsh environment.

So, would a zoom speed up your production significantly? Are you stuffing your gear into carry-on luggage? Are you shooting where you can't zoom with your feet?

Regarding this last point, I think ultrawides are best done with zooms. You can't get an ultrawide faster than f/2.8 anyway. And if you're shooting in a phone booth, elevator, or car, it can be tough to frame without a zoom.

My lens set is now includes...
* 16-35/2.8L II - the wide "problem solver" lens - and my only zoom.
* 35/1.4L - 35mm is my "go to" view and this lets me shoot fast. At 35mm, focusing isn't too difficult.
* 50/1.4 - my least used lens, but it's (relatively) inexpensive and effective.
* 100/2.8L IS Macro - IS is helpful. At 100mm, f/2.8 gives shallow enough DOF for my needs. Any faster and focusing is tough. Also, I can do super closeups when needed, making it my other "problem solver" lens.

So, zoom or primes? That really depends on what and how you shoot. :)

Thanks, guys. All very valid points. I´ve never tested the MarkIII but I´ve seen many comparisons showing that the 6D has a slight advantage when it comes to high iso.
The reason for switching to a fast zoom would be portability (1 lens instead of 2) and practical speed (depending what you are shooting you may just miss that crucial moment while changing lenses).
Like I´ve said on my previous post I would keep the 50mm 1.4 for extreme low light though.

P.S - I would love to have the 35/1.4L. It´s my favorite FOV

I really like primes, I only own one zoom and that is the 70-200/4... But I got primes from 8 to 400 (vintage and new). But at the moment I need a new lens between 24-35 mm with IS. I'm looking at one of the primes from Canon 24/2.8, 28/2.8 or 35/2.0. But I'm really thinking of the Tamron 24-70/2.8 VC. It may be a better choice for the documentary type of films I'm shooting.
My biggest question is, will the bokeh look the same or at least OK with the zoom?
Anyone used any of this lenses?