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Why ND on ext. 16mm?


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#1 Will von Tagen

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Posted 01 April 2009 - 07:07 PM

Hi all. So I've been shooting super 8 for about a year and a half now, and I've decided to make the jump to 16. I've been reading a lot of the posts in this section on film and there are a couple of things I'm confused about. Principally, I have been reading a lot that when shooting 200t or 250 that you should load up with the ND's. What is this for? Can you not just close up the aperture? I hope I don't sound too ignorant, but 16 is turning out to be a whole different ball park.

Also, a lot of people are suggesting a 2/3 stop over exposure, I understand the need to do this for finer grain, but would I also do that with the ND's on? I don't get why I would cut light ad then try to over expose.

And when I do the 2/3 over, will I have to notify the lab and treat it like a push/pull type situation? Or do I just let it be processed as such and fix it during the telecine and in post within color (mac)?

Thanks a bunch.
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#2 David Rakoczy

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Posted 01 April 2009 - 07:50 PM

FILM LIGHTING

PHOTOGRAPHER'S GUIDE TO USING FILTERS
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#3 David Mullen ASC

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Posted 01 April 2009 - 08:18 PM

Most lenses can't be stopped down past f/16, and most of the time, you don't want to use a lens that stopped down because it becomes a bit softer due to diffraction, plus you get all that depth of field.

On 50 ASA film with no filters, at 24 fps with a 180 degree shutter, in frontal bright sunlight on a clear day... your meter will tell you to shoot at f/16. So at 200 ASA, that would mean shooting at f/32. Of course, it may not get that bright that day or you may be shooting in the shade where you have less light, but as you can see, you are working close to the point where the lens can't be stopped down much more. Or hope for a really dark overcast day...

So yes, you need ND filters.

You want to overexpose by 2/3's of stop but process the film normally. The lab doesn't care how you exposed the film, they can't see an image until after it's been developed anyway... they just want to know whether to develop normally or push or pull the negative, and usually that's by whole stops. The idea is that you develop normally but overexpose a little so that the final negative is a bit denser than normal (the more you overexpose negative, the denser or darker it gets because bright areas in the image correspond to the darkest parts of the negative.)

The way you tell the lab making a print or a person doing the transfer that you want them to correct out the 2/3-stop overexposure and give you an image of normal brightness is to shoot a grey scale or card, or color chart, with a face at the head of the roll in boring flat frontal light, at the ASA rating you are using, so overexposed by 2/3-stop if that's what you decide -- so they will see this chart and adjust the brightness of it so it looks normal in the print or the dailies transfer. The reason you want to do it in flat boring light is so that there is no creative decisions to be made as to how it should look.

Overexposing negative a little helps expose the smaller slower grains in between the larger and faster grains, improving the appearance of graininess (faster film still has larger grains than slower film no matter what you do though but overexposing faster film helps reduce the visibility of the larger grains by tightening up the grain pattern).
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