Blackmagic Forum

I have a Sony A7sII camera along with a Tamron 28-75, f/2.8 lens and I'm thinking about buying a ND filter strictly for shooting video. Maybe it goes without saying, but my goal here is to be able to shoot using low apertures while not having to raise my shutter speed.

I have a couple of variable ND's on my other lenses, but I've started to question whether I really need a variable variant for this lens. The way I see it, I need a filter that blocks out enough light on a really sunny day to allow me to shot at the native ISO of 1600 for S-log3. However, this would of course mean that I would have to rise the ISO for conditions where it's darker but not dark enough for me to not use the ND at all, and I feel alright with this.

However, I don't know how strong of a ND filter I would need. I guess some of them are made for shooting photos at really long exposures, so I would like to stay clear of those. Is it possible to somehow calculate what type of ND I would need?

You could just reuse your other VNDs on your Tamron. But if you do want to get away from VND then the strength you need depends on a lot of factors, not least of which is how sunny it is. I can't just say that a 10 stop filter will do what you need because shooting straight into the sun would require more and a partially cloudy day would likely require less. So many variables in non-variable filters.