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Old February 21st, 2007, 03:43 PM   #16
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Quote:
Originally Posted by David Scattergood
Increasinly getting the impression that there's a wealth of difference between digital camera's, digital camcorders and (may I suggest professional?) camera's such as the HD100. It's been said here a few times that the camera really makes you work for that fantastic footage...which isn't really a bad thing in the end.
Not really. I use my Nikon D70 all the time on location scouts to judge available light levels. When in "auto" mode, Digital still cameras will simply stop down and use a high shutter speed when outside (probably around 1/500th) which is 10 times higher than the 1/50th shutter speed you would ideally use with 25P. You could also increase your shutter speed to control exposure, but every frame will have that very sharp look.
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Old February 21st, 2007, 03:46 PM   #17
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Quote:
Originally Posted by Liam Hall
PRST (preset) can be set to either 3300k (tungsten) or 5500k or auto white balance via the menu. I'd avoid auto white balance, and even then I'd avoid it.
Tungsten (indoors, outdoors night, artificial lighting, theatre, concert, etc.) = 3200K
Daylight (outdoors day, HMI lighting, interior day if large windows allow daylight in, etc.) = 5600K or sometimes 6500K

The lower the temperature (measured in degrees Kelvin - K) the more sensitive to the changes the number is. I.e. you can see the difference between 3200K and 3300K with your naked eyes. However, the higher the number, the less difference would be visible. I.e. you are unlikely to see the difference between 5600K and 6500K. They are almost interchangeable. That's why I mentioned in another post that during the day and typical shoot, one might be just fine to set the WB to a preset (in this case 5600K) and just live with it. As Tim mentioned, if the day is very cloudy with those white bright clouds, the colour temperature is going to climb to 7000-10,000K. Again, even if you shot under those circumstances with the WB in preset 5600K, you'd be fine, the colours might be a tad cool but that's how they look to our eyes anyway (if you really pay attention). You can imagine the difference to follow a logarithmic curve where the steep part are the lower temperatures from 0 to say some 4000K. Further on the curve flattens and the differences become very small.
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Old February 21st, 2007, 04:16 PM   #18
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Quote:
Originally Posted by Tim Dashwood
If you want to maintain the rich "blue" of the sky, invest in a polarizer (NOT a circular polarizer) and a matte box with a rotatable filter stage. Polarizers can cut your exposure as much as 2 stops and the effect is controllable. The versatility of a polarizer for controlling reflections in glass/water as well as the "blueness" of the sky means I never leave home without it.
Tim,

I'm curious about your admonition against circular polarizers. It was always my understanding that circular polarizers were prefered for digital video cameras in order to preserve the ability to meter through the polarizer. My experience has been that both linear and circular polarizers give you the same effect on the light, but I thought that the slightly more expensive circular polarizers were needed to ensure that light made it through the prisims in the optical path. Perhaps I've been laboring under a delusion.
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Old February 21st, 2007, 04:24 PM   #19
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Originally Posted by Ralph Keyser
Tim,

I'm curious about your admonition against circular polarizers. It was always my understanding that circular polarizers were prefered for digital video cameras in order to preserve the ability to meter through the polarizer. My experience has been that both linear and circular polarizers give you the same effect on the light, but I thought that the slightly more expensive circular polarizers were needed to ensure that light made it through the prisims in the optical path. Perhaps I've been laboring under a delusion.
Circular polarizers are designed for SLR still cameras that use TTL metering systems and AF rangefinding systems with "half-mirrors." Using a linear polarizer screws up those auto exposure and auto-focus systems, and that's why most photo stores will recommend circular over linear.

Professional cameras don't even have autofocus, and they don't need separate TTL metering systems because the CCDs are always on.
You can use a circular polarizer on any camera system if you want, but you won't be able to control the intensity of the effect by rotating the filter in a matte box.

Control is the key with digital cinematography, and the ability to control the "darkness" of the sky or opacity of reflections by simply rotating the filter is essential. Therefore, the standard (and cheaper) "linear" polarizers are my preference.
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Old February 21st, 2007, 04:41 PM   #20
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So the prism blocks that split the incoming light to the 3 ccds is not effected by full linear polarization? Makes sense. Thanks for the info.

You can, btw, see the effect through a circular polarizer. I have a 4x4 Tiffen circular polarizer that I adjust in the mattebox just as you describe.
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Old February 21st, 2007, 04:49 PM   #21
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Quote:
Originally Posted by Ralph Keyser
So the prism blocks that split the incoming light to the 3 ccds is not effected by full linear polarization? Makes sense. Thanks for the info.
I've never heard of it being a problem. I use a linear 4x4 polarizer on a regular basis without issue.

Quote:
Originally Posted by Ralph Keyser
You can, btw, see the effect through a circular polarizer. I have a 4x4 Tiffen circular polarizer that I adjust in the mattebox just as you describe.
You're right, it is slightly controllable in a matte box, but linear polarizers are much more effective.
I should have also mentioned that I'm trying to sway people from purchasing "screw on" type filters that you typically see on SLR cameras, unless it has a "double-ring" that allows for independent rotation.
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Old February 21st, 2007, 05:07 PM   #22
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Quote:
Originally Posted by Tim Dashwood
I should have also mentioned that I'm trying to sway people from purchasing "screw on" type filters that you typically see on SLR cameras, unless it has a "double-ring" that allows for independent rotation.
As long as the screw-on polarizer has the double ring allowing for rotation, is there any disadvantage to the screw-on type?

Also, it has always been my understanding that the circular polarizer is only needed for certain automatic focusing systems. Since the JVC camera does not have autofocus, the circular polarizer is not necessary. This link explains this:
http://www.geocities.com/cokinfilter.../polarizer.htm
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Old February 21st, 2007, 05:31 PM   #23
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Re chepaer Polarisers - wouldn't you have to factor costs of the mattebox (with french flag?)?
I can see that a mattebox and linear polarizer is certainly something I'll require have to add to my kit...but cost at the moment is putting me off.
The odd bit of low budget corporate work (at the moment) make these seem a little surplus at the moment, but it's probably the right time to be thinking about adding these in the very near future. Are there any budget ranges - and ones that don't fall apart within a few weeks?

I get some nice sky shots from my old 35mm SLR with a circular polariser - it would be great to start capturing these skys with the JVC.


Meanwhile, the screw on ND filters are of top priority...morning telephone call - reading the previous posts 1 x N3 and 1 x N6 should help.

Cheers.
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Old February 21st, 2007, 05:33 PM   #24
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And thanks for that linkie Jack - interesting read.
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Old February 21st, 2007, 05:33 PM   #25
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Quote:
Originally Posted by Jiri Bakala
Tungsten (indoors, outdoors night, artificial lighting, theatre, concert, etc.) = 3200K
Daylight (outdoors day, HMI lighting, interior day if large windows allow daylight in, etc.) = 5600K or sometimes 6500K
Correct me if I'm wrong and I apologize if I am, but this is completely wrong and a touch misleading.

If what you say were true explain to me a sunset shot, where you have 2300k coming from the sun and 10,000k or more coming from the sky or how a kino flow can be either daylight or tungsten when it's actually a fluorescent or how some artificial lighting has no measurable colour temperature at all.

The point is simple; everything you point your camera at will be made up from a mix of colour temperature and that colour temperature varies massively, be it natural or artificial. It's up to the DP to determine what colour temperature is important to capture -usually the key.

What I was trying to do was give David some basic advice so he can get some usable material on tape.

Please, shoot me down if I'm wrong, unlike Lord Kelvin I didn't attend university at age ten.
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Old February 21st, 2007, 06:37 PM   #26
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Originally Posted by Liam Hall
It's up to the DP to determine what colour temperature is important to capture -usually the key.
Absolutely right... and it is important for the DP to first understand the different colour temperatures of different sources. That's all Jiri and others (including myself) were trying to educate David on.

David's "mistake" of using 3200K in daylight is exactly the technique I use to intentionally shoot "day-for-night." (along with a 1 or 2 stop underexposure.)
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Old February 21st, 2007, 07:30 PM   #27
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Originally Posted by Liam Hall
The point is simple; everything you point your camera at will be made up from a mix of colour temperature and that colour temperature varies massively, be it natural or artificial.
Well, everything is a mixture of colours, that's true. You used the example of a sunset. Well, sunset typically looks very warm, deep orange and red hues, right? Well, if you white balanced to that (and it may well be colour temperature of around 2300K), you would loose those beautiful hues that make the sunset what it is. Your sun would be more yellow/white and the clouds too and all that. Go ahead, try it.

Now if you add a person to the mix and stick to a daylight preset (5600K), their face, of course, would also look very warm. But that is EXACTLY what the skin tone looks like in that light. And here comes the DP and his/hers expertise and artistic vision for the shot, as well as the need within the context of the scene. If the scene is supposed to take place in the evening and we, the audience, know that (from, say, an extablishing wide shot) we expect the actors' faces to be warm. On the other hand, if this shot is a pick up at the end of the day and it really belongs to a scene that happens during the day (and which was shot earlier), clever white balancing might be necessary to try to match the rest of the scene. The DP would also make sure that they would not shoot in the direction of the sun and avoid direct sunlight on the actor's face. Check some major Hollywood pictures and see how actors sitting around a campfire at night have completely warm (red and orange) faces. If you white balanced to the fire light, that would be lost.

White balancing in video (and the same colour temperature principles in film) is a tool that allows the DP to create a feeling, atmosphere, a tone for the scene and in extension for the whole film.
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Old February 21st, 2007, 07:49 PM   #28
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Quote:
Originally Posted by Liam Hall
... or more coming from the sky or how a kino flow can be either daylight or tungsten when it's actually a fluorescent or how some artificial lighting has no measurable colour temperature at all.
Kino flows use specially designed precision colour balanced tubes giving you the daylight and tungsten options. Regular household/office fluorescent tubes are around 4000-4300K with a nasty green hue. To balance that out, there are some special white balance cards available (Warm Cards), which include a lightly green card that allows the DP to remove most of the green hue and bring back some natural skin tones.

In short, white balancing tells the camera that whatever it's pointed at IS WHITE (even if it's not). The camera circuts attempt to remove all other colours to create 'white'. Hence, back to your previous example with the sunset, if you white balance to the light coming from the sun at sunset, the camera will attempt to remove all the orange and red to artificially create 'white'.

The same principle is used in the opposite direction when the DP wants to 'warm up' the picture. Then a card of light blue shade is used. The camera removes portion of the blue spectrum from the image, making the picture warmer. I have seen (and used myself in a crunch) white balancing on stone-washed blue jeans with very good results. Well, now I use a set of Warm Cards...:-)
http://www.vortexmedia.com/

The creative uses of WB are quite limitless. One needs to understand the principles and then it could be a lot of fun. A great example is what Tim mentioned - doing Day for Night with 3200K.
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Old February 22nd, 2007, 01:55 AM   #29
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For a rather extreme example of what white balancing can do, I did some still photography a while back in a musical venue that only had red and blue stage lights, creating a purple look on stage. I white balanced on the purple and snapped away. Anything off stage had a bit of a greenish tinge, but the band looked fine.
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Old February 22nd, 2007, 03:53 AM   #30
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Originally Posted by Jiri Bakala
Now if you add a person to the mix and stick to a daylight preset (5600K), their face, of course, would also look very warm. But that is EXACTLY what the skin tone looks like in that light.
Again, forgive me if I'm wrong, but shooting an actor/model at sunset with your technique would render orange/red highlights, violet/purple mids and dark blue shadows. Not very flattering I'd have thought. Has anyone got a special technique for shooting people at sunset? We don't get many sunsets in the UK, what with all the fog, but it would be nice to know.
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