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Focus in all Red Gelled Light


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#1 Scott Weatherford

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Posted 06 November 2006 - 09:32 PM

So we were shooting studio mode with about 3 babies and a few 650s, which were all gelled with a Red Lee party gel (cant remember which one exactly, but thats superfluous). A friend of mine came in and told the 1st and me (i was 2nding) that's he's read about how scenes with all red light, or at least the majority of light being red (approx 400 nm., right?) will throw off your focus, because, im assuming, of just something to do with the characteristics of that wavelength being solo... how it travels or reflects. Anyone heard about this? Is this just for red or for any other colours (keep in mind we're talking ALL of the light being ONE colour ONLY)? how do prop and wardrobe colours effect this, especially black and white? i though this was pretty interesting schtuff... lemme know what you think.
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#2 Jon Kukla

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Posted 07 November 2006 - 08:22 PM

I don't suppose this has anything to do with the red layer being the deepest one and flange focal distance? I seem to recall that the FFD in cameras was reconsidered in the past decade or two and they chose to set it to within the emulsion instead of the top of it in order to optimize depth of focus (note - focus, not field). Might have been more of an issue in the past.
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#3 Kevin Zanit

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Posted 07 November 2006 - 08:31 PM

I forget the exact details, but it does have to do with the red layer's placement.
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#4 Wendell_Greene

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Posted 07 November 2006 - 09:39 PM

The red layer of the film is third in the chain and therefore last in sharpness. If you put very saturated red gels on all your lights the image will look soft and out of focus.
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#5 Kevin Zanit

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Posted 07 November 2006 - 09:50 PM

If I recall correctly, in one of the Charlie's Angeles movies, Panavision remarked the focus marks on their lenses for a scene taking place in entirely red light to correct for the focus issue.


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#6 timHealy

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Posted 07 November 2006 - 10:17 PM

here's an article about warmer colored lights and density. It doesn't completely address this issue but dances around the subject.

http://www.cameragui...candlelight.htm

best

Tim
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#7 Stuart Brereton

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Posted 08 November 2006 - 06:05 PM

I've found that highly saturated red light looks soft no matter what. The placement of the red layer on film may have something to do with it, but it happens on video too.

I believe that the eye is least sensitive to the red end of the spectrum. Perhaps this leads to the perception that red lit shots are soft....
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#8 Craig Knowles

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Posted 08 November 2006 - 11:08 PM

I've found that highly saturated red light looks soft no matter what. The placement of the red layer on film may have something to do with it, but it happens on video too.

I believe that the eye is least sensitive to the red end of the spectrum. Perhaps this leads to the perception that red lit shots are soft....


Focus issues aside, the eye/brain is apparently least sensitive to the colour red, and as such, all-red scenes throw off your ability to judge depth cues properly. It can be a very off-putting effect.
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#9 Frank Barrera

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Posted 09 November 2006 - 12:17 AM

i was burnt by this effect once about ten years ago. it was a bar scene with mostly white light and some various party gels. but the girl was sitting in this red gelled light on her face. ouch. shot on 16mm film and she looked absolutely out of focus and it just ruined the shot.

so i learned that if i really need there to be red on somebody's face i must be very careful. i will use a kicker or two from behind with full red gel and then for the key i will slice the red gell with a knife so that just enough white light spills through and allows the face to fall into focus. this doesn't work for all applications but for most yes.

f

Edited by Frank Barrera, 09 November 2006 - 12:19 AM.

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#10 James Steven Beverly

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Posted 09 November 2006 - 04:26 AM

I'm working on a film that is going to use a LOT of red light, however, I'm working with a friend of mine Mel Kakuewa, that has a lot of expirence and will be the DP on this shoot so I'm sure we can overcome the problems associated with red light, but just for my own knowledge, can't you set focus then throw the gel on, or it doesn't work that way? Are we talking a slightly soft image or completely out of focus and how does red light effect your F-stop if at all?

I've never worked excessively with red light and never heard of these problems before, but looking back on some movies I remember from the past, I do remember that many of them had a soft look to them in scenes where red loght was abundent. Because the look and feel of my vision for the picture as well as certain plot elements within the script depend on the use of red light, I am very interested in the problems we'll face in largely lighting the film using it. I don't plan on shooting faces so much in red, although there will be moments when the scene demands it, but for background and fill lighting it will be essental so I'd like to know as much as I can before shooting. Are there stocks that I should avoid? I was planning on going with 5218 because most everything will be shot at night, does it handle reds well? Are there certain red gels that are more camera friendly than others or perhaps better suited towards certain stock than tp others?

My plan was that as the film moves along, the scenes get progressively redder and the colors more vivid to eventually approach a blood red. I've seen this done to a somewhat lesser extent in a couple of Dario Argenta's flims, not so much the progression but the use of vivid reds and it was very effective. I am committed to this idea so anything you can give me would be appreciated. B)

Edited by James Steven Beverly, 09 November 2006 - 04:30 AM.

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#11 Hal Smith

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Posted 09 November 2006 - 09:45 AM

I'm working on a film that is going to use a LOT of red light, however, I'm working with a friend of mine Mel Kakuewa, that has a lot of expirence and will be the DP on this shoot so I'm sure we can overcome the problems associated with red light.


Hi Capt,

Some of the "red light effect" is probably that the eye itself has reduced resolution in red light. Interestingly enough color film itself has greater resolution in red, for instance Koday 5218 has about 50% better red resolution than green. That may be done to give red (like peace) a chance.

Try emailing John Pytlak ( john.pytlak@kodak.com ) to see if there any public information on how thick the color film pack is and any recommendations on how much to change focus. Whatever the change is the effect will be worse with wide angle lenses. WA's have less back focus depth of field and their sharp focus depth willl "miss" the red layer more.
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#12 James Steven Beverly

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Posted 10 November 2006 - 02:59 AM

Great to know, Hal! I'll drop John a line and see what he has to say or if he reads this maybe he can just answer here so everyone can read his reply rather than just me. I was planning on cutting between long lenses and fairly wide ones which I may have to now rethink.

Another problem will be the camera packages we plan to use. I plan on using older ones due to cost factors and these older packages probably will not have the fastest OR best of lenses come with them, availible for them or availible for them in a place where I can find them or at a price I can afford to pay for them. I will be using my Konvas 1m (which which is very cost effective because I already own it) for second unit and steadicam work, IF my steadicam will hold up the damn thing up and I can figure out a way to set up a video tap on it. I have several lenses in the package, all Lomos (which are equivilant to Zziess)- 28mm, 35mm, 50mm, 75mm and 135mm, none of which are fast lenses. For sound sync, I am looking at getting eather a Kinor 35H or C (which ever I can get the best deal on. These are SUPPOSE to come with fast lenses IF the package is complete, a BIG if), an Arri 2B or C with a blimp and flat base, crystal motor or an Arri BL 1 (with a Barney, the original lenses and a lens blimp in good condition) or 2 . Sence there aren't really any rental places or labs in El Paso, we're gonna have to be fairly self-seficent so I'm going to end up using whatever I can afford to buy. From what I'm reading though, fast lenses might actually be a detriment when using a lot of red light anyway but then there's that old "most of this takes place at night" thing that keeps me up at night, worrying, so I'm not sure.

I'm also wondering if, in some instances throughout the course of shooting, a red filter on the camera might be called for. If so would the same type of problems arrise and are they be handled in the same way, also are there processing issues that have to be addressed? If so, sense I'll be using my machine to process the exposed film, I would also like to know about those in advance as well.

Mel (my DP) seamed to feel quite confident we'll be able to get a good focus despite the excessive use of red lght when I brought my concerns up today, (as expressed with the words "Don't tell me how to light"...to which I had no argument for, sense he know a Hell of a lot more about this poop than I do) so prehaps I shouldn't be overly concerned about the potential problems we might face, but there's still this knawing feeling in the back of my brain that keeps whispering to me "We're going to run head on into those problems if we're not careful" and this is a picture that can't afford a lot of problems, so I'd rather be safe than overbudget and out of money (IE sorry). B)
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