What level ND filter to shoot at f2.8 1/50th shutter and 320 ISO on a sunny day?

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Pickles

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I would like to shoot at f2.8 to f3.5 at 1/50th shutter and 320 ISO outside on a clear sunny day and am wondering what strength ND filter I would need? I would be shooting with the 20mm f1.7 pancake lens. Any suggestions?
 
Well, if we use the sunny sixteen rule, we know we should shoot at an equivalent of F16 @ 1/ISO, a.k.a. 1/320. Let's add enough stops to our aperture to reach 2.8, and subtract an equivalent number from our shutter speed. F16 is 5 stops darker than F2.8, so we'll subtract five stops from our shutter speed. That gives us 1/10240, but let's pretend it's 1/10,000 cause that's easier. We now need to bring it down to 1/50, which is about 7 and a half stops difference. Which is like an ND 192?

Judges? That was probably more complicated than necessary.
 
Huh? ND 192? Sorry, but now you really have me confused...:huh: So, is that ND 2.0, ND 3.0, ND 4.0?
 
yes just curious why you want to shoot at 320 ISO in open sunlight? Isn't raising the ISO just adding unwanted noise? Why not keep ISO at its lowest i.e. 100 and then just get the aperture you want via the filters
 
If i remember correctly that's the same ISO Kholi likes to shoot at in the day time. So the question about ND filters might be better directed towards him.

Why shoot at ISO 320??? I think maybe because ISO 320 "could" be cleaner than ISO 100 (not that 100 is noisy at all). It sure seemed that way in my old Canon 7D. I have not looked into it with my new GH-1.
 
Well, you want to block out 7.5 stops of light, so whatever does that (presumably two filters together, I guess). I'm used to just flipping the switch on the video camera, so I suppose I'm slightly stupid about nd filters.
 
I think it's because the 320 is slightly noisier than 100, and the noise masks the banding issues in gradients.
 
Yes, Ian is correct. Kholi likes to shoot at 320 ISO in broad daylight and I heard from other GH1 users that around 320 or 400 ISO is the cameras "sweet spot". I have been shooting at 100 ISO with the Vari ND filter at about 7.5 stops of ND but, I want to do some experimenting and see how 320 or 400 ISO looks in bright sunlight so, I need to know what strength ND filter I'll need. So far, I'm guessing I'll just need to add a ND filter (on top of my Vari ND) that will give me 3 stops of ND. So, I guess maybe a ND of 1.8? That would give me a maximum of 10 stops of ND (I know the Vari ND says it goes all the way down to 8 stops of ND but, from my experience using it, at 8 stops I start to see some polarization artifacts) and a minimum of 5 2/3 stops of ND. Ten stops should be enough to shoot at 320 ISO at 1/50th shutter at f2.8, right? Learning all this as I go along... :huh:
 
In my experience iso 100 is the cleanest. Anything over and I start to see banding in flat shadow areas. Anyone seen any good evidence that 320 is better?
 
320 is one of the few "intermediate" ISOs which are generally "cleaner' than the ISOs just before them. For example....on my 7D ISO 320 (if I remember correctly) looked just as clean as ISO 100 (or it might have been 200) but the obvious advantage is that you get a brighter image. From what I understand it's the same way on the GH-1. you have to set your camera up for 1/3 stop increments to take advantage of this.
 
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