Which ND filter ?

I picked up a Sigma 85mm f1.4 art and plan on playing around with it outdoors this summer. What stop ND filter will i need if I want to use 1.4 in bright daylight ? I just saw B&H has Formatt Hitech filters at half price , so now is a good time to buy.

Of course it depends on specifics, but I typically see people using a 3 stop ND.

Sunny 16 rule has something to provide on this topic.

8 stops from from f16. Minus 3. Means you are a 1/3200 for a shutter speed at isolated 100.

Seems kind of limited 1.4 envelope at 3 stops.

My humble opinion.

If you want to shoot long exposures like 30 sec or more in bright daylight you could need up to 8 or even 10 stops.

Maybe look at a Tiffen or Singh-Ray Variable filter.

Ha.... I saw 85 f/1.4 on my phone and automatically assumed outdoor portraits. But....the exact purpose was not specified.

So, Joel is right, it really depends on your use. A quick chart with EV of different light:

Attachment 2633

EV = log2 N2/t, with N = f number (aperture) and t = time in sec. So you can generate a table of EV with aperture and shutter speed:

Attachment 2634

So, in full sun, we have 15 EV. Say you want shoot 1/250 of a shutter speed and f/1.4, which is EV 9, then you would need a 6 stop ND filter (EV 15- EV 9). But even say you aren't in full sun (EV 13), and want a bit of DoF for outdoor portraiture (f/2.8), then you only need 2 stop ND filter.

But, it really does depend upon your purpose.

I typically use a 3-stop ND for outdoor portraits with my 85/1.2L.

There is an app called ND Exposure it's free and easy to use.

I have used it to successfully calculate exposure times using an ND filter

I started with a 3-stop, and although rarely used, it typically seemed to be "right". As I got into strobe photography more, when outdoors I found the 3-stop wasn't always enough, so I've added a 6-stop to my arsenal, and it gets used even less (but does come in handy). I figure in a pinch, I could stack them and have a 9-stop, which puts me in the neighborhood of a 10-stop and would give me a chance to decide if buying a 10-stop was worthwhile. If nothing else, I find a 1-stop or 2-stop ND to be a waste - if you want to ND, you probably _want_ to ND.

Thanks guys . It will mostly be for outdoor portraits , or at least an attempt lol. I will go with a 3 stop .