slog color setting question

L

Lenilenapi

Carbonite Member
I am about to get my F3 back with SLog installed and am wondering about the color pre-sets. Is it still true in the most recent software that you can only choose Tungstun or Daylight and are locked out of all in between color temps as well as green/magenta adjustments?

If so - I am a bit confused as to why. I understand that in theory Slog would use all the available lattitude of the chip and so there would be nothing to gain by trying to adjust the base color . However in that case why is there a choice for tungstun or daylight. Emulating film is no reason to l;imit choices on an electronic camera.

Presumably the base chip is daylight sensitive so wouldn't a Tungstun choice reduce lattitude and or raise noise? This was true for the RED and so many people would filter it blue to retain all the lattitude.
As I recall isn't it now possible to color balance the Alexa in its version of SLog.

My concern is less with the final image actually than with the monitoring image (for client) and the back-up SxS recording. Any way to color correct those when shooting sLog?

Is there an advantage to shooting the F3 blue?

Lenny Levy
 
Thanks for asking the question, I asked essentially the same thing further down on the page on 2/20 and no one has said much so far. There are settings in the menu which allow changes to the colors in S-Log and I suspect this is the way to change the color balance, but there is not much information on it.

On the menu it is under Camera Settings/S-Log white adjust where changes are possible. I think you might be able to use this to white balance with S-Log??
 
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Its designed to be graded. Doing it in camera or in post is the saem thing. the camera chip is only 5600K. ( i suppose tungsten is in there as a convenience)

Use gels to control your lights.
 
lasikdenver,

I saw your post and that's what motivated mine so I guess its just us 2 showing an interest. Since I don't have my camera yet, what are the adjustments available in that menu item? Is it just white adjust + or - (which I assume would be color temp)? Or is there also a green/magenta or phase adjustment? Have you confirmed that it does actually change the color of the sLog image?

Timur, I realize its designed to be graded but I can't believe that changing the color balance from daylight to tungstun would not affect image quality or even how you might expose though the effect might be subtle - as in film negative where some people never bother to use an 85 in dayllght and others swear by precise color balancing. There is a point to trying to get your color as close as possible on the negative and I would imagine in sLog as well. That's certainly how I used to shoot film. Particularly if you are not involved in the grading - and for clients used to ordinary video. Just conjecture for me at this point though as i haven't used it yet.
 
Here is what I found on the Alexa sensor, I think it is a very similar situation with the Sony F3: There is an adjustment specifically for S-Log [camera settings/S-Log/White Adjust] for both Red and Blue % adjustment which seems to go along with this description from the Alexa site. I have not tried using this, since I am not using balanced daylight Kino Flo's but it seems that being able to use this could be very useful at specific times. While you can adjust color in post, and you can also use gels to change the color, the fixed camera setting of 5600 is most sensitive for the sensor, but still is a gain adjustment to the different channels. It seems likely that if one wanted to, they could white balance in S-Log by adjusting the red and blue channels. There would still be the need to de-log in post but perhaps the color balance would not require adjustment. While S-Log is flexible, it is not a true RAW image. I have found that I need a lot less light to shoot at 5600 than 3200 with the same power Kino Flo lights at different color temperatures, which demonstrates that the sensor is more sensitive here, but I would still think it is better to shoot at the color temperature that matches the overall lighting, that is I would not use 5600 in an incandescent setting. You guys are the pros, and I am just trying to learn more, so if this is wrong please set me straight.

This is from the Alexa site:

Since one can neither create a sensor for each color temperature, nor change them if one could, digital cameras have to cover a variety of color temperatures with one sensor. For any given color temperature, a sensor will deliver an unequal amount of red (R), green (G) and blue (B) signal. In order to balance the three colors for different color temperatures, digital camera manufacturers use different amplification settings for red and blue, while keeping green un-amplified. Let’s look at the actual settings ALEXA uses to illustrate this.

When using ALEXA to capture a grey card lit with a tungsten source (3200 K), the signals from the red and blue pixels have to be amplified by the following amounts to make a neutral grey:

R - 1.13x

G - 1.00x

B - 2.07x


Shooting the same chart, but now lit with a daylight source (5600 K), will put more blue and less red light on the sensor. So we can apply less amplification to the signal from the blue pixels but need a little more amplification for the signal from the red pixels:

R - 1.64x

G - 1.00x

B - 1.37x


So, for tungsten ALEXA uses a little more amplification in the blue channel, and for daylight a little more in the red. And for those who are still reading and want more: even though the red and blue amplifications are equal at 5000 K, daylight (5600 K) has the mathematically lowest overall noise gain, measured as the square root of the sum of the squared gains.
 
lasik,
Thanks, that's exactly what I figured was going on and its nice to know there is an adjustment if I want it.

Timur, Of course you can light to 3200 or 5600 but that's if you are in a fully controlled situation. But I don't understand the reluctance to accept that many shooters like to control their color at the camera as well as with lighting.

In mixed light I often gel my lights to match or abet the ambient or sometimes go available. I like blue windows and tungstun keys and that often means playing around a bit to find the best mix. Likewise I often find it easier to warm or cool a scene lit with a number of instruments in the camera rather than gelling every light.
Nothing any different than what most shooters do - and it would simply be nice to have that look be what the camera starts out with and what the client sees if I'm not grading. Some measure of security when lighting as well.

It sounds like that will be available though and one could carry a little magenta or a Floro filter for heavily green flourescents which I encounter fairly often on industrials in older buildings like banks.
 
On the Camera Set Menu, there is a choice for S-Log White Adj+ . This will let you choose an offset for R and B. I believe this is what you are speaking about.

The Alexa settings wouldn't work if for no other reason than the Alexa has an option for R G and B offsets. This feature was introduced to the F3 with the 1.2 firmware. I would personally only adjust those offsets with on-set access to WFM and DSC color chart. But it can be done.

Otherwise, shoot 5600K (and remember that you have to press the 5600K button despite the fact that the sensor is a native 5600K sensor) or 3200K and gel or just fix it in post. As Timur says. Timur rules.

In Lenny's mixed light situations, it might not be a bad idea to experiment with those offsets-- with caution.

Ned Soltz
 
Thanks Ned,
Good points. +Red and +Blue don't sound like they are the same as color temp offsets in the F3, so careful testing would be in order. Hopefully i'll have something to add next week.
It would be interesting to investigate whether there is a difference in noise and latitude between 5600 and 3200.
Don't mean to be negative Timur as your insight is always very much appreciated.
Lenny
 
Lenilenapi said:
Thanks Ned,
Good points. +Red and +Blue don't sound like they are the same as color temp offsets in the F3, so careful testing would be in order. Hopefully i'll have something to add next week.
It would be interesting to investigate whether there is a difference in noise and latitude between 5600 and 3200.
Don't mean to be negative Timur as your insight is always very much appreciated.
Lenny
Click to expand...

It's amplification that causes noise, and most sensors take the least amplification at 5600k. I'd bet the F3 is the same. Currently I use 5600k and lights that are between 5400k and 5600k. I haven't taken a gel out in months.

On a side note I just shot all night in the woods with LED lights on batteries. First note, we shot from 6:30pm to 1 am (6.5 hours) on one battery. (High effeciency lights. I'm suprised by the light output and battery life.)

Second note, I used 5600k on the camera. Third note, I'm going to leave the S-Log ungraded as its very close to what we used to do on film called bleach by-pass, a washed silvery look.

I'm very happy with the results.
Duke
 
Im just saying thats not what slog is designed for. Its a pure cinema system, with luts and 444 capture in mind.

Its like taking a ARRI 435B, to shoot news. Its not ment for that. Why would they design it to do so. Slog comes from the pedigree of the F35.
 
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