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#76 | |
Inner Circle
Join Date: Jan 2004
Location: Boca Raton, FL
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Re: Cine gamma settings in the EX1
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#77 |
Inner Circle
Join Date: Aug 2006
Location: Poland
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Re: Cine gamma settings in the EX1
I'm exposing faces up to 65, and I'm good with it.
But that's just me,,, Alister?
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#78 |
Major Player
Join Date: Nov 2004
Location: Detroit, MI
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Re: Cine gamma settings in the EX1
Here is a good article by Adam Wilt on the effect of Cinegamma on images.
ProVideo Coalition.com: Camera Log by Adam Wilt | Founder | Pro Cameras, HDV Camera, HD Camera, Sony, Panasonic, JVC, RED, Video Camera Reviews |
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#79 |
Regular Crew
Join Date: Oct 2010
Location: Copenhagen Denmark
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Re: Cine gamma settings in the EX1
Yes I realize that, but it does not change the fact that you OVEREXPOSE your bright background quicker (If exposing for Caucasian skin tones at 75%) when using cinegamma 1.. Even beyond 109%, then you cant grade yourself out of that.
Last edited by Dominik Krol; May 6th, 2011 at 12:43 PM. |
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#80 |
Vortex Media
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Re: Cine gamma settings in the EX1
Wow, I didn't realize everyone in Poland had the same shade of skin. In my country, we have whites, blacks, latinos, asians, and all different kinds of skintones to deal with. 65% on one guy might be fine, but totally wrong for the next guy. No matter how you slice it, using zebra on skintones just comes down to guessing because every face is different. Sure, an experienced shooter can still guess right most of the time, but it's still just guessing. I can do that without zebra. Zebra is one of the most important functions on a pro video camera, but it is only correct if you know the value of WHAT you are measuring -- and usually that should be white card, gray card, or chip chart. Anything else is just guessing.
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#81 | |
Inner Circle
Join Date: Aug 2006
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Re: Cine gamma settings in the EX1
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I just wanted to stress that - in spite of the common "recipe" for the Caucasian skin tone to be exposed with zebra at 70-75% - after some experimenting, I settled with 65% as being safer from decolorization due to highlight compression.
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#82 |
Vortex Media
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Re: Cine gamma settings in the EX1
Piotr,
Well, one of these days I'm going to get over there to Poland and see the faces for myself! I've traveled all over the rest of Europe better never made it to Poland. It's on my list.
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#83 |
Inner Circle
Join Date: Dec 2005
Location: Bracknell, Berkshire, UK
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Re: Cine gamma settings in the EX1
Either I don't understand you Dominik or I believe you are wrong.
The standard gammas (without knee) will give you about 2.5 stops of head room above 70IRE while the cinegammas give you around 5.5, stops of headroom. Total DR for standard gamma with no knee is about 7.5 stops and cinegammas is 12. A well set knee will extend the standard gammas out to around 10-10.5 stops giving you about 5 above 75IRE. If you take a look at the plots prepared by Serena earlier in this thread, or the published curves you can clearly see the extra headroom the cinegammas give you. But the key principle when using the cinegammas is that you should lower your midtone levels to keep them in the more linear part of the curve so that you can make use of the gradually compressed highlights. Taking something that with a standard gamma you would have exposed at say 75ire and now exposing that at 60ire gives you around an extra 1.5 stops of useable headroom. Then in the grade you sort out you contrast range to give the tonal range that you want. You don't want to do this with a standard gamma plus knee because the knee area is either compressed or not, there is nothing in between and due to the sharp onset of the knee you don't want the knee point set too too low, so to get good dynamic range you end up using just the range from 85ire to 100 (109)ire for the knee (15-19% of recorded data) for 4 to 4.5 stops which is a lot of compression. As a result if you try to grade this it will look bad as you have not really used sufficient data to enable you to extract useable picture information. Cinegammas on the other hand start the compression at around 30ire with it steadily increasing especially above 65ire. As a result the same highlight range that with the knee is squashed into just 15 to 19% of the available data is now spread over 35%-39% of the recorded data so you have much more data to work with so the information recorded can be manipulated in post without so much degradation, thus making this useful information that you can do something with. In addition the gentle increase in compression means that more data is allocated to the areas that are most important, gradually decreasing as you approach overexposure and clipping.
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#84 |
Regular Crew
Join Date: Oct 2010
Location: Copenhagen Denmark
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Re: Cine gamma settings in the EX1
Alister
Apparently you don't want to understand me because I never mentioned Standard gammas.. I'm sure you are a experienced guy, but try to read my post for once before you begin taking it apart. I will repeat for you once more. CINE gamma 3 and 4, will give you more headroom to the bright sky, if you are exposing for a caucasian skin tone. Even when grading, you would appreciate that the second most important subject in your shot (the sky in this example) laying closely exposed to your first (the person in front of it). Otherwise you are just "fixing" in post what you did wrong in the field. If thats what you like to do. ok. It still doesn't make it optimal. And I repeat. No mention of Standard gammas in this post. ---- Im sorry for sounding arrogant, but it annoys me endlessly when people pick apart my arguments, and making me sound stupid, with fancy "I know it all" answers that don't even relate to what I wrote in the first place. Last edited by Dominik Krol; May 6th, 2011 at 09:02 PM. |
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#85 | ||
Inner Circle
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Re: Cine gamma settings in the EX1
Ok Dominik, I've re-read your post and I apologise for bringing standard gammas into my reply, but I still don't believe you understand the way the Cinegammas are supposed to work.
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The reason why CG's 3 and 4 work better for darker scenes is not to do with the top end of the curve but the middle and bottom end. CG3 and CG4 lift dark and mid range parts of the image, improving shadow areas and dark areas and giving you more to work with in post in these darker scenes. Exposure is not just about highlights and skin tones. As an option when shooting a dark scene this would allow you to have skin tones and mid tones at a lower ire level and still get a good looking image after grading as by reducing the exposure a little you will not be compromising you shadow and dark areas as much as with CG1. Trying to fix skin tone exposure at 70-75ire (which is too high even for standard gammas IMHO) is not the way to use Cinegammas or Hypergammas. Not only do faces vary from person to person, but the brightness of faces will change from scene to scene. On a bright sunny day a face would typically be bright and well illuminated and should be exposed as such, in a dark scene the face might well be much darker and should be exposed darker to keep the mood of the scene. Quote:
On the majority of cameras using -3db gain reduces the dynamic range of the camera by -3db (half a stop), EX1/EX3 included. It can however bring a -3db noise improvement. Using -3db gain and then adding that gain back in again buy adjusting the curve level is pretty pointless as you will also increase the noise again, you may as well just stick to 0db. Adjusting the curve level adjusts the gain level of the curve and thus noise levels as well.
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Alister Chapman, Film-Maker/Stormchaser http://www.xdcam-user.com/alisters-blog/ My XDCAM site and blog. http://www.hurricane-rig.com Last edited by Alister Chapman; May 7th, 2011 at 05:25 AM. |
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#86 | |
Inner Circle
Join Date: Dec 2005
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Re: Cine gamma settings in the EX1
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If you are shooting for a higher dynamic range output, or plan to grade then I would switch to Cinegamma 1 unless it's a low key scene in which case I would most likely use CG4. I would want to keep any skin tones below the more highly compressed part of the curve, so below 65ire, typically around 60ire depending on the shoot. This will look a touch under exposed when shooting. That way you keep any highlights in the more linear part of the curve so they will look more natural once you've done your grade, overexposed cinegamma faces don't look good.
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#87 | |
Vortex Media
Join Date: Jan 2009
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Re: Cine gamma settings in the EX1
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The term "caucasian" skin has no meaning. Show me two white people, and I'll show you two different skin tones. 65% might be great for one, and over-exposed on the next. By using zebras, I would set my exposure based on either a white card or gray card of known reflectance value. And in this example, the background is irrelevant. The face should be exposed the same whether the background is white, black, pink, yellow, or a green screen. The face is the subject, and that is what matters.
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#88 |
Inner Circle
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Re: Cine gamma settings in the EX1
Thanks Doug. I mentioned the black background because I want the blacks to crush. I mentioned Caucasian because I expected the technique for judging exposure based on highlights to be different in the Caucasian range than dark skinned. And so I was wanting to draw out that technique as I was shooting that today and would adjust the technique I use.
What I've been doing is lightIng the scene using a mannequin so as to get the relative intensity between fixtures as I want them. I then adjust the iris using false colors so that the highlights on the face have no yellows indicating under 70 (I use the Marshall 7" monitor). If my iris is in the desired range, i'm done. Otherwise I adjust the lighting or nd so I can get the iris where I want it. When the talent shows up, I adjust the iris to achieve he same false color reading on their actual skin (no yellow). So with this technique I think I'm dialing the same level on the highlight Thus compensating for skin to es (wihin a range at least) and letting the relative intensity of the fixtures handle the rest. |
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#89 |
Vortex Media
Join Date: Jan 2009
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Re: Cine gamma settings in the EX1
Unless I misunderstand how you are describing your technique, it sounds like you are saying everyone's skin tone should result in the same false color display. Is that what you are saying? Because, if so, you are wrong. If false color works on a fair-skinned white guy, it can't also be correct for a darker skinned latino, someone with a good tan, or a black person. Your technique does not take into account different shades of skin. False color and/or zebra on skin tone tells you nothing about the proper exposure because you don't know the reflectance of the subject's skin. Ultimately, you're just guessing at the exposure.
Proper exposure is more complicated than just not blowing out the highlights. If you applied that same logic to sound, then recording a whisper and someone shouting should both be just under the redline on a VU meter. Obviously that would not sound right. And exposing everyone's skin tones at the same zebra or false-color level (no matter what the level is) is wrong too. A darker person should look darker than a lighter person, and if you exposue them both to the same IRE, at least one is going to be wrong.
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#90 |
Major Player
Join Date: Nov 2008
Location: Santa Monica, CA
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Re: Cine gamma settings in the EX1
And what about adjusting the Gamma Level? I remember once reading that (+) darkens mid-tones and (-) lightens mid-tones, yet the opposite appears to be true when looking at my camera's LCD.
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