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Minimizing Grain


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#1 David Regan

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Posted 17 November 2007 - 12:02 PM

I'm currently trying to understand better how to minimize the appearance of grain in shooting 16mm, as I have a shoot coming up on 500T and know I will be subject to having grain if I don't handle it properly. I understand (I think) that grain is often pronounced when the image is underexposed, and a slight overexposure can help reduce this effect. But how do you keep grain out of the shadow areas of your image? If I was shooting something and wanted lots of shadow, a low key environment for example, aren't shadows just underexposed areas of the frame? However I have seen examples where there are shadows maybe 3 stops under key, or scenes at night with areas of total black, that look quite clean and free of grain.

Any advice to understanding the appearance of grain and tips for reducing it? I am going into shooting tests in a couple weeks, and just thought there might be some things to look for and try.

Thanks for the help
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#2 David Mullen ASC

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Posted 17 November 2007 - 12:07 PM

You don't need every portion of the frame overexposed to reduce grain. The point is that if your negative is a little overexposed overall (i.e. your key subject is exposed a little brighter), then you'll have to darken it a little in post to bring it down to normal brightness and this will keep "tighten" up the grain in the image and make the blacks more solid, thus hiding the grain in the shadows more.

The only way to really reduce grain, i.e. have no large grains, is to shoot on slower film stock. Overexposing faster film stock just exposes more of the smaller (slower) grains inbetween the larger (faster) grains that got exposed immediately, so it fills in the gaps and makes the image seem less grainy.

Also remember that grain is most visible in large areas of flat midtones, so low-contrast images show off the grain structure better than high-contrast images. It's easier to see grain in an 18% grey field than it is in a black or white field (if you see grain in the whites, it's electronic noise from the neg-to-video transfer process, not grain.) Therefore it's a good thing at night to have lots of dark areas. The worst situation for showing the grain would be under flat supermarket lighting.
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#3 John Brawley

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Posted 17 November 2007 - 06:04 PM

I'm currently trying to understand better how to minimize the appearance of grain in shooting 16mm, as I have a shoot coming up on 500T and know I will be subject to having grain if I don't handle it properly.



And to bravely paraphrase what David is saying. It's about contrast. If you have a lot of larger fields of tone that are flat, then you will see the grain. I've found it helps a lot to have something bright in the frame. The eye is naturally drawn there and held. Usually this is also the subject you want the audience to be looking at as well !

I imagine you may be using primes, simply for the stop, but it really helps to have your point of interest razor sharp. As soon as something is off, you will immediately start reading the grain. So even though you haven't changed anything in terms of exposure, the *perception* of grain can change a lot depending on what's in front of your camera. But, yes, a little overexposure also helps.

Seek out a good telecine facility. Soft light sources like the Spirit produce really clean results along with an appropriate amount of noise reduction.

And hey...don't be afraid of a little grain...keeps the image alive....

good luck !

jb
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#4 marc barbé

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Posted 17 November 2007 - 09:52 PM

I'm currently trying to understand better how to minimize the appearance of grain in shooting 16mm, as I have a shoot coming up on 500T and know I will be subject to having grain if I don't handle it properly. I understand (I think) that grain is often pronounced when the image is underexposed, and a slight overexposure can help reduce this effect. But how do you keep grain out of the shadow areas of your image? If I was shooting something and wanted lots of shadow, a low key environment for example, aren't shadows just underexposed areas of the frame? However I have seen examples where there are shadows maybe 3 stops under key, or scenes at night with areas of total black, that look quite clean and free of grain.

Any advice to understanding the appearance of grain and tips for reducing it? I am going into shooting tests in a couple weeks, and just thought there might be some things to look for and try.

Thanks for the help


Hi,
What is your final support, 16mm, 35mm, or digital? What is your final frame ratio, 1:33, 1:66, 1:85, ... ?
I'm not a technician, just a film maker, but I've noticed these are the first questions a DP will ask me before discussing what to shoot with and how..
Regards,
Marc.
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#5 David Regan

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Posted 17 November 2007 - 10:27 PM

Hi,
What is your final support, 16mm, 35mm, or digital? What is your final frame ratio, 1:33, 1:66, 1:85, ... ?
I'm not a technician, just a film maker, but I've noticed these are the first questions a DP will ask me before discussing what to shoot with and how..
Regards,
Marc.


Good point. Final support as of now is undecided, I'm thinking HD transfer, but its still up to the director's budget, and is yet to be finalized. Ratio will be 1:66. The 500T I mentioned is the likely format, as in worst case for grain which is why I used that in my question. Ultimately we may use a Vision2 200T but given our available lighting package is small for student budget, I may go 500T to be safe.

I know its still kind of vague, sorry, we are just still in the very early stages of pre-production so there are tests to be done, and much to be sorted out.

Thanks
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#6 David Regan

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Posted 17 November 2007 - 10:32 PM

Also remember that grain is most visible in large areas of flat midtones, so low-contrast images show off the grain structure better than high-contrast images. It's easier to see grain in an 18% grey field than it is in a black or white field (if you see grain in the whites, it's electronic noise from the neg-to-video transfer process, not grain.) Therefore it's a good thing at night to have lots of dark areas. The worst situation for showing the grain would be under flat supermarket lighting.



And to bravely paraphrase what David is saying. It's about contrast. If you have a lot of larger fields of tone that are flat, then you will see the grain. I've found it helps a lot to have something bright in the frame. The eye is naturally drawn there and held. Usually this is also the subject you want the audience to be looking at as well !


So would I be horribly mistaken in understanding then, that grain will be recorded regardless, in efforts to minimize its appearance its about making the perception of it less recognizable? I have seen several works shot in 16mm that look remarkable grainy, while others, shot on the same stock and transfer, have much less noticable grain and the image appears much smoother, and alwayswondered if there was any approach used in particular. Perhaps I should have been paying more attention to the overal image, and why I noticed so much grain.

Thanks
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#7 Dominic Case

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Posted 17 November 2007 - 11:55 PM

There is always grain - it is what the image is made up of.

As has been pointed out, grains appear larger in the shadow areas of the image. That is because the largest grains in the emulsion are the most sensitive to light, and therefore there is a preponderance of them in the lowest lit areas. If you increase exposure, then you will expose a few more of the smaller grains in those shadow areas, which will fill in the gaps and give a smoother, less grainy image.

However, the measure of graininess includes all the subjective responses to the nature of the image (whereas granularity is the purely objective measure of the size of the grains themselves). When you look at an image, you look for structure - it's the way we perceive things. If the image is lacking in contrast (eg underexposed negative, printed up, giving a murky grey shadow area lacking in information or detail), or if it is soft, then the sharpest thing you can se is the grain structure of the image. With more contrast, or with some bright highlights in the image, or if the image is really crisp and sharp, you will concentrate on those details, and forget about the grain.

Unfortunately, in low light situations, you are liekly to be using faster, therefore grainier stock - and you are likely to be using a wider aperture with less depth of field, so that more of the image is out of focus. A little judicious use of backlighting or rim lighting will often work very well in distracting the eye from those mushy backgrounds.
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