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Blue Noise/Noise - Black Shading - Using RCX

Patrik Kisucky

Patrik Kisucky

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I was wondering, why do we need to black shade in the first place? I found it in the manual:

"Sensor calibration is a process where the camera generates a calibration map to correct for pixel defects and offsets based on current system and environmental settings."

I have a situation where it seems to me, that no matter what I do, I have a lot of blue noise, all over my darker colors, blacks on my footage, even after I do black shading. Now, I've searched about this issue, and come across 2 answers.

1.) If you have a lot of blue noise/noise, allow your camera to reach shooting temperature, and then do the black shading. It should go away, or improve the image (not my case).

2.) It's OK to have a blue noise/noise in your raw footage, you have to improve the image, in the post using RCX.

Can someone please explain, how do I go about achieving the cleanest footage possible. I understand the camera shoots raw, and has a wide Dynamic range, that protects clipping. But if you are seeing the same noise, what is your workflow, to have a very clean image at the end? Thanks.
 
Sounds you may be using a combo of a very low whiteballance/little light/high iso...

Could you send me a single r3d frame? (take snapshot in RCX)
to

gunleikgroven at gmail dot com

Cheers!
 
When you see the noise ...

Are you shooting at 2K resolution? Always shoot 3K or higher resolution, unless the highest varispeed is required.
Are you underexposing the sensor? - Expose to the right on the histogram, or just below clipping monitoring RAW or using the Exposure false colour assist.
Are you grading up the shadows in post? - Lighten up shadows with some fill light, then crush in post to get them nearer the intended black level.
Are you shooting in tungsten light? - Try to use bluer lighting.
 
Thank you Gunleik, and Eric for fast reply, I'll run test later with the advice, and will send you r3d later today Gunleik, Thank you for your time.
 
Do you see the blue noise in RAW? I find when you mess with the tint or white balance with low light you will get the blue noise you speak of.
 
Yes, also in RAW. yeah, it could be the low light, I'll check on that. But wouldn't you want black to be black in the low light? I know there could be different shades, but I know, I have to do something wrong, when I'm getting blue spots over my darker colors.
 
You need contrast to get blacks too... :)

If the shots are very underexposed, you have allmost no contrast to play with and you'll unevitably gain noise in the shadows to get the rest of the image visible.

A nice little rtest is to look at the image at both redlogfilm 320iso/5600 kelvin and with linear/320 iso/5600 kelvin

The linear is a nice way to see where the exposure landed in the sensors sensitivity range

redlogfilm is a good way to judge potential and noise. Redlogfilm @ 800 iso is fine too... (LOL Graeme! )


I'll have a look at the images and post my concrete comments to you in a couple of mails... :)

Cheers and have fun!
 
Additional note:Even though some cameras "can see in the dark" that doesn't help them much without contrast. Contrast is basically what paints an image and lighting is still crucial to draw with light/photography in general.

It is also good to remember that you lose a lot of tonality when you underexpose, even when you pull it back up. Underexposed images are cool, as long as they are intended to actually be dark... :)

and...FLUT/ISO/EXPOSURE/CURVE does not enhance "real" contrast, they just accentuate the contrast allready recorded... :)
 
Since this thread was started, I thought I'd ask a question as not to waste a new thread.

Is it proper to just do one black shading with the general option? Or is it best to do black shading with the "current frame rate" option?

Does it make much of a difference and why?

Thanks
Joe
 
If you use extreme frame rates (in particular very slow ones), it makes sense to do a separate black shading for it. This way you can switch back and forth.

Wit the R1 you needed to do another one when going back to regular.
 
I just redid my black shading with the frame rate option and it seems cleaner. Maybe my previous one was bad.

Or it's like when you wash your car, it seems to drive faster and smoother (all mental).
 
I can only do a succsesfull calibration with the default setup. But advice from Gunleik helped a lot. I was shooting an interview today, and my footage is a lot cleaner. Altough, I still need to run some tests with shooting mainly in the dark, and having only certain part of the screen lit. I'm hoping to get real black color, or clean shadows, without blue or any noise in my images.
 
I am not sure blackshading is part of the OPs issues, but you can have 2 blackshades installed. One "standard" and one for varispeed would make sense...

Joseph S. said:
Since this thread was started, I thought I'd ask a question as not to waste a new thread.

Is it proper to just do one black shading with the general option? Or is it best to do black shading with the "current frame rate" option?

Does it make much of a difference and why?

Thanks
Joe
Click to expand...
 
Patrik Kisucky said:
...I still need to run some tests with shooting mainly in the dark, and having only certain part of the screen lit. I'm hoping to get real black color, or clean shadows, without blue or any noise in my images.
Click to expand...

Patrik, the problem is that against your gut you should raise ISO when shooting in bright high-contrast environments such as sunny parks, and decrease ISO when shooting in an environment that holds not much contrast, such as a dark low-light scene.

Estimating contrast is fairly easy. Start with Red's proclaimed 800 ASA and check your histogram. When it spreads from the left to the right across the whole range your scene has a lot of contrast and a higher ISO is recommended. ISO 800 will do the trick here. When the opposite is the case, e.g. the histogram is half the range wide, lower the ISO. ISO 500 or 320 will be fine here.

Remember that the sensor is natively rated (not the best term actually) at ISO 320. ISO 800 already takes some underexposure in account to protect highlights.

Even if you are shooting in a low-light environment you aim should be, as always, to fill the sensor with as much light as possible. Either you choose a particular fast lens or add some light. Increasing ISO - and ISO 800 is actually 1 stop and a bit more than the native ISO 320 - will do the opposite and introduce noise. For clean nigh exteriors I set the camera to ISO 500 and make sure that the bright parts of the skin tones are exposed on the fat side. Epic or Scarlet for that matter are NOT cameras that see in the dark when noise is of any concern.

Leveling out noise is alway a walk on the edge. It's dependent on your subjective taste and how much you will oversample the footage. Shooting in 4KHD will accept just about 1/4 stop less light than 3K for instance when 1080p is the target resolution and the noise level should be the same.



Hans
 
Great read, Gunleik, Thanks for posting. Graphics added to the article, would be fantastic. I know, I'll read a few more times too.
 
Hans von Sonntag said:
Patrik, the problem is that against your gut you should raise ISO when shooting in bright high-contrast environments such as sunny parks, and decrease ISO when shooting in an environment that holds not much contrast, such as a dark low-light scene.

Estimating contrast is fairly easy. Start with Red's proclaimed 800 ASA and check your histogram. When it spreads from the left to the right across the whole range your scene has a lot of contrast and a higher ISO is recommended. ISO 800 will do the trick here. When the opposite is the case, e.g. the histogram is half the range wide, lower the ISO. ISO 500 or 320 will be fine here.

Remember that the sensor is natively rated (not the best term actually) at ISO 320. ISO 800 already takes some underexposure in account to protect highlights.

Even if you are shooting in a low-light environment you aim should be, as always, to fill the sensor with as much light as possible. Either you choose a particular fast lens or add some light. Increasing ISO - and ISO 800 is actually 1 stop and a bit more than the native ISO 320 - will do the opposite and introduce noise. For clean nigh exteriors I set the camera to ISO 500 and make sure that the bright parts of the skin tones are exposed on the fat side. Epic or Scarlet for that matter are NOT cameras that see in the dark when noise is of any concern.

Leveling out noise is alway a walk on the edge. It's dependent on your subjective taste and how much you will oversample the footage. Shooting in 4KHD will accept just about 1/4 stop less light than 3K for instance when 1080p is the target resolution and the noise level should be the same.



Hans
Click to expand...


This is one of the better and more clear commentaries that I have seen on the subject of RED exposure. Thanks! :thumbsup:
 
Thank you Hans, very true, about raising the ISO in a bright scene. The other day I raised it to 800, based on my histogram, not what my eyes were telling me looking at the LCD picture.
 
When raising ISO or lowering ISO, my histogram reading changes. Clipping stays the same. So it does appear like this is just visual and the camera is not changing, just my histogram.

If ISO is metadata only, shouldn't the histogram stay the same?
 
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