Cooling Filters

[Rob Vogt]

I was looking at Schneider Optics for an alternative to an 80A which will have less of a filter factor and I saw a CTB filter, has anybody used these and are they pretty much the same as the 80 series? I have a shoot coming up in a couple of months and I have one scene which I'm concerned about. We are shooting on 7285 cross processed and we only have a Tungsten package, our largest source being a 2k (I will have 5 of these). My options at this point are use an 80A, unless I can find a different filter (maybe a 80B or C), or CTB all the lights, or some combination. I'm looking for a slightly cool look to the scene which isn't helping my situation any. Also I was looking at maybe using 160T for that scene since it's the only Night Ext. I might be able to get away with a non-cross processed look and maybe fake it a little in post.. In a couple of weeks I will be doing my first test so I might be able to try some of your suggestions to see what I like.

 

Thanks in advance guys,

-Rob

[Satsuki Murashige]

I was looking at Schneider Optics for an alternative to an 80A which will have less of a filter factor and I saw a CTB filter, has anybody used these and are they pretty much the same as the 80 series?

Hi Rob,

 

I'm told the Schneider CTB filters have the same filter factor as the 80 series, so you won't gain any stop by using them. Sounds like if you can't afford a daylight lighting package then creating the look in post is a better option. You could shoot Fuji 500T Vivid, which will get you part of the way there.

[David Mullen ASC]

The amount of light loss due to the density of the blue is the same, though the breakdown of strengths of the CTB line of filters is a bit easier to understand since they match the CTB gel series.

 

Some info I gleaned online:

 

82 converts 3100K to 3200K; + 1/3 stop / MIRED SHIFT -10

82A converts 3000K to 3200K; +1/3 stop / MIRED SHIFT -21

82B converts 2900K to 3200K / MIRED SHIFT -32

82C converts 2800K to 3200K / MIRED SHIFT -45

 

80B converts light from 2900K to 3200K; +2/3 stop.

80C converts light from 2800K to 3200K: +2/3 stop.

 

I think the MIRED shift from 3200K to 5600K is around -67. What's interesting is that the MIRED system seems to suggest that the color temp that is halfway between 3200K and 5600K is around 3700K instead of 4400K like you'd think...

 

Anyway, at least I can quickly guess what a 1/4 or 1/2 CTB filter would do, versus an 82C, let's say. However, I'm not sure if that ease is worth paying extra for, if I can get the 82 series for less.

[David Auner aac]

I think the MIRED shift from 3200K to 5600K is around -67. What's interesting is that the MIRED system seems to suggest that the color temp that is halfway between 3200K and 5600K is around 3700K instead of 4400K like you'd think...

 

Isn't that because of the reciprocal nature of the MIRED scaled having smaller steps compared to K the higher on the Kelvin scale you go? And isn't the human eye less perceptive to changes in color temperature at higher temperatures? You can rather easily see a difference of 300K when around 3000K, but at 5 or 6000 it's quite hard to notice such a change...

 

Regards, Dave

[David Mullen ASC]

I got my math wrong, I think I took the MIRED shift from daylight to tungsten, divided it in half... but divided it in half again by accident.

 

The MIRED shift for 1/2 CTB and halfway between daylight and tungsten would be -68, or around 4100K.

[Rob Vogt]

Thanks guys I think I'm going to go with Sastuki's recommendation (I didn't even know the Vivid 500 existed, I thought it was only 160) but I will try to get my hand on some of these filters for my test b/c I have to test the cross processing anyway so I might rent a 1/2 CTB filter or the 82 series.