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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Using a blue filter?

I believe I said, the "cleanest" image you can get is feeding the sensor blue light. Blue at the head or at the glass.

We had simply said that when dealing with full tilt tungsten situations, with out filtration, shifting your latitude up 1/2 a stop helps crush the noise in the blue channel down.
 
J. Eric Camp said:
I believe I said, the "cleanest" image you can get is feeding the sensor blue light. Blue at the head or at the glass.

We had simply said that when dealing with full tilt tungsten situations, with out filtration, shifting your latitude up 1/2 a stop helps crush the noise in the blue channel down.
Click to expand...

I was directing my comment at this sentence:
Zakaree Sandberg said:
Another trick is setting asa to 200-250.. this is basically the same thing as adding the filter (except its free and works like a charm)
Click to expand...
 
And what about the InfreRed Filter does it make sense? I heard problems with the black color in some cloths?? Any advice?

tks
 
Ops...Infra Red
And With Tungsten set...
 
So guys let me get this straight. I was under the impression that for the best image quality you should keep the camera set at it's native 5000K. After reading your posts here it seems this isn't the case because when using 80 filters I cannot let the camera at 5000K because this would make all things blue under tungsten light right ?

so when using an 80 series filter I just have to set the camera to match the 5000K temp including the filter's colour corection ?

What is actually changing the you change the white balance in camera ?
When you are shooting out in the open you set the camera to 5600k or just letting the default 5000K.

Wouldn't it be a better idea to use 85 series filters when using tungsten lights or is this just about how much red vs blue light you are feeding to the sensor ?

Thanks!
 
85 is the wrong way - they bring CT down from 5600 to various lower CTs, ultimately 3200K with an 85B.

If you use an 80B you will get almost exactly 5000K under 3200K tungsten lighting. The trick is to set your camera's CT setting to whatever matches the lighting and filter combination you have selected. With a correctly dialed in CT and an 80 series filter white will look white under tungsten lighting, but with a stronger blue channel...

Hope that helps,
Dom.
 
Shouldn't this be pretty simple?
Just watch your highlights and check which channel clips first (well, without having a very strong coloured light source in the frame). If red clips first, bring it down with a filter, since protecting it by exposure would get blue closer to noise.
If blue clips first, bring it down too, or your red gets weak.
 
So, ideally the light shoud be filtered to 5000K but often when shooting in tungsten there won't be suficcient light for the 2 stops that the 80A steals.

I did some tungsten/bluefilter test a while back (build17), and it seems that altough the bluer the better, just adding a 1/2 stop 80D really helped clean up blue noise in the shadows. a 80C was even a bit cleaner, but the big difference was going from unfiltered tungsten to a 80D.
 
Magnus Flaato said:
So, ideally the light shoud be filtered to 5000K but often when shooting in tungsten there won't be suficcient light for the 2 stops that the 80A steals.

I did some tungsten/bluefilter test a while back (build17), and it seems that altough the bluer the better, just adding a 1/2 stop 80D really helped clean up blue noise in the shadows. a 80C was even a bit cleaner, but the big difference was going from unfiltered tungsten to a 80D.
Click to expand...

This is the unfortunate reality of CMOS technology. It naturally wants to be about 5000K.

If I were God and could change the law of physics I would prefer to filter CTO and bring all daylight sources down to a native tungsten CT since I often have extra light when shooting daylight and not enough with tungsten.

Such is life. :D
 
Not CMOS, but silicon based sensors in general are all relatively in-sensitive to blue light. All of them.

Graeme
 
Schneider CTB shift not equivalent to 80 series shift?

Schneider CTB shift not equivalent to 80 series shift?

Catherine Russell said:
Schneider Optics has recently come out with a set of filters they call CTB, available in 1/2 (equivalent to an 80D), 1/4 and 1/8th strengths, specifically to combat these issues.
Click to expand...


Art Adams has posted his calculations that give the Schneider CTBs a different temperature shift than the Wratten designations above. Does anyone know how this behaves in camera?

Link
 
It looks like Schneider tried to come closer to the MIRED shift caused by using CTB gels on lights -- for example, an 1/4 CTB Rosco gel has a shift of -30; the 1/4 CTB filter has a shift of -35, which is close.

Seems more logical than the 80A-D series of levels.

How it behaves in camera -- well, the closer you get to 5000K, the better the noise in the blue channel, so it's mainly a matter of how much correction can you get away with. Using the 1/2 CTB would be better than the 1/4 CTB, and both would be better than the 1/8 CTB, but any degree of correction would be better than none, etc. So it just depends on how much light you can spare for the filter.
 
Good point. As I understand it, not all wratten-rated filters are the same anyway.

I think I'll spring for the Schneiders, as the Tiffen aren't available in stock for my size tray.
 
the ctb 1/2 came out about 10 days ago. they dropped the first one off at camtec right when i was prepping, so we tested it there and then took it on our job. we used it for a CVS ad in a real store in encino with all practical fluorescence lights, it worked great. then we have used it 5 more times since then and currently have the ctb 1/2 on a two camera shoot in hollywood for espn...we roll with the ctb 1/2 and an ir filter. they work well. ctb 1/2 is .33 of a stop, i used to use the 80 c which was between 2/3 and 1 stop depending on whom you talk with.

good luck.

dino
 
Sorry for all who can't see the images. They are tiff's. Should be fine.

You can get them here:
1st
www.shogunfilm.com/randomimages/histo_nono.tiff
2nd
www.shogunfilm.com/randomimages/histo_bing.tiff

I like the 80c. Gets me close, only cost me around 1 stop.

Who ever asked about IR filters:

The biggest reason people use the IR filters is in combination with ND's. Most ND's are manufactured to cut only the visible light spectrum. Once you cut so much, the visible to infrared balance is tipped and the IR pollutes the visible, first noticeable in your blacks. The IR cuts are designed to bring the level back into balance.
 
Tungsten territory

Tungsten territory

I love the idea of a filter purpose built to raise the color temperature/white point with as little light loss as possible. Several people have contended, some with a fair amount of test results to back up their assertions, that raising the CT makes for cleaner keys and better noise characteristics. Other have argued that when light levels are low it is better to keep every photon you can so that the red and green channels can provide grist to extrapolate the blue information.

From what I've seen there is an issue in terms of the "subjective noise awareness" factor of the viewer when the blue channel is starved and base level sensor patterning reveals. For this reason I advocate the "careful" use of blue filtering, especially in available light situations where the native CT may be less than 3000 Kelvin.

I would not give away a stop or more just to nail 5000K but I would, for example, give away 1/3 stop to get to 4000K. In a perfect world I would carry 3 filters of differing strengths designed specifically to compensate for the lack of blue sensitivity inherent in the current crop of CMOS sensors.

It is my belief that Graeme's algorithms perform best when the inequality of the color channels is more moderate. This advice is based on tweaking a lot of underexposed footy in Scratch in full res, full debayer with an eCinema reference monitor. YMMV.
 
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