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#1 Paul Bruening

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Posted 03 September 2008 - 01:25 PM

First: Am I using the right word, halation?

http://dictionary.re...h...amp;x=0&y=0

My concern is the glow of light that can end up in the image around an overexposed area. Let's say I shoot an indoor scene metered for the interior and let the included window burn out. The glow around the window is halation, right?

Second: How can I reduce halation? My goal is to shoot scenes with contrasting light values that exceed the range of the stock and then bracket my exposures at my scanner. If I can shoot through the brighter parts (higher density on the negative) to get the details and then tone map them together, later, in the computer, I could fake getting a lot of light into the interior scene by knocking down the intensity of exterior light..

What I can't figure out is how to get rid of that halation. Can I filter it at taking? Can I get rid of some of it digitally in post?

Hit me with your tricks, baby.
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#2 Chris Keth

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Posted 03 September 2008 - 01:38 PM

I've always thought of halation as either what happens to highlights when you have some sort of lens diffusion on, or as what happens to highlights in old black and white films before anti-halation coatings were invented. The light would pass through the film and reflect back into the film off of the polished pressure plate and expose the film again. This would often make rings around lights.

I think what you're thinking of is as much flare as halation. First of all, it will be worse with lens diffusion on. Then, as far as I know, the only other thing to do is to make the area as hot as necessary to achieve a particular tone but not to overdue it.

If anyone has other tricks for this, I would love to hear them. I love to mix very bright and very dark and sometimes dislike that bleeding of light.
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#3 Mike Simpson

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Posted 03 September 2008 - 01:47 PM

The best is probably to drop a net behind or ND on the window, or bring up the interior light as much as possible. I personally like hanging a big net outside the window because it feels like it reduces the harshness of the light hitting the lens to me.

Another thing it consider are your lenses. Higher quality lenses tend to deal with that sort of thing better, as well as optically perfect lenses. If you lens has alot of scratches in it, when the light hits it it will scatter and you might end up with a foggy or pretty low-con looking image. When a significant portion of the frame is very bright that will obviously come out pretty nasty.

You really need to do some tests with your lenses and your post options. To some extent you can try to add contrast in post to make up for the fogging, but its hard to say how far you can go without having all the details.
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#4 Paul Bruening

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Posted 03 September 2008 - 01:51 PM

American Heritage Dictionary - Cite This Source - Share This
ha·la·tion Audio Help (hā-lā'shən) Pronunciation Key
n.

1. A blurring or spreading of light around bright areas on a photographic image.
2. A glow around a bright object on a television screen.


Does that one apply?

Still, what to do about it?
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#5 Paul Bruening

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Posted 03 September 2008 - 01:54 PM

The best is probably to drop a net behind or ND on the window, or bring up the interior light as much as possible. I personally like hanging a big net outside the window because it feels like it reduces the harshness of the light hitting the lens to me.

Another thing it consider are your lenses. Higher quality lenses tend to deal with that sort of thing better, as well as optically perfect lenses. If you lens has alot of scratches in it, when the light hits it it will scatter and you might end up with a foggy or pretty low-con looking image. When a significant portion of the frame is very bright that will obviously come out pretty nasty.

You really need to do some tests with your lenses and your post options. To some extent you can try to add contrast in post to make up for the fogging, but its hard to say how far you can go without having all the details.


I'm trying to use my scanner and computers to get around hanging window treatments and putting up lights.

With that in mind, what tricks will help? Polarizers? What else in the computer?
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#6 Mike Simpson

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Posted 03 September 2008 - 02:20 PM

I'm trying to use my scanner and computers to get around hanging window treatments and putting up lights.

With that in mind, what tricks will help? Polarizers? What else in the computer?



getting a better on the exposure on the window will be nice if you can somehow get it composited in fine. The trickier part will be the fogging around the actor (I presume there is an actor), so I still think the easiest thing to do would be to bring the window down while shooting. Chromatic aberration is another concern that could be tough to deal with in post.
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#7 David Mullen ASC

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Posted 03 September 2008 - 08:53 PM

You use the best prime lenses that flare the least and you control the brightness of windows and lamps whenever possible. What else can you do? That's basically it.

You can add more contrast in post to an image with halation which will help reduce it slightly, and you can time the image darker. If you have access to Power Windows and whatnot, you can darken the area that is flaring. But you're just trying to make the halation less obvious after-the-fact. Better to avoid it in the first place (though personally, I like halation...)
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#8 Paul Bruening

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Posted 03 September 2008 - 10:02 PM

Hey David,

It means a lot to me that you posted on this. I've thought over a bunch of Photoshop tricks and haven't come up with a comprehensive solution. But, there's something I'm grinding on now involving color and dye sites on the negative. What would you say is the dominant color in the halation on a positive print or positive DI image? Blue-ish? It's not quite a balanced white.

I wonder if I could up-res the images to 8K+ and do something to only certain categories of the film's dye sites (grain sites, dye clusters) that would have a cumulative effect. Then bust it back down to 4 or 2K.
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#9 Paul Bruening

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Posted 07 September 2008 - 11:34 AM

I haven't found any info on Kodak's site or elsewhere on the web about how much halation is the result of light bouncing around inside the film layers. Simple tests through the viewfinder indicate that a polarizer does help at certain angles. But, that didn't tell me how much of this problem will manifest in a strip of processed film.

Given that I can bracket the negative in scan and tone map the extremes out, would you rather underexpose the interior in order to reduce the exterior overexposure and reduce halation (interlayer light type), or would you get the right stop for the interior, blow-out the window and do whatever can be done in post to manage the halation? What about a halfway thing? Split the difference of four stops, atwain? (I just used, "atwain")
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#10 David Mullen ASC

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Posted 07 September 2008 - 12:40 PM

Don't overcomplicate things: Use a prime lens that flares the least and control the brightness of the object that is flaring the lens, either with ND gel or scrim/net material, or raise the light level of the interior to reduce the difference in brightness. Putting a glass filter on the lens will only compound the problem.

Modern color neg filmstocks hardly halate on their own due to the rem-jet anti-halation backing so that's not the problem.

You also have to eliminate your scanner as a possible source of the halation by comparing the transfer to one done somewhere else.
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#11 K Borowski

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Posted 07 September 2008 - 01:57 PM

What about a halfway thing? Split the difference of four stops, atwain? (I just used, "atwain")


So are you trying to confuse native speakers of English here on this board as much as you confuse the non-native speakers, with only former riverboat captains having the advantage? :rolleyes:

I agree in that I don't understand why you are willing to take elaborate workflow steps to solve a very much in-camera fixable problem. You're intent upon shooting expensive film with the same callous attitude of those shooting HD who want to "fix it all in Photoshop".

Are fill light, prime lenses, matte boxes really that cumbersome and old-fashioned for you to consider using them?
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