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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 :)

Black shade temprature experiment.

In a strange way, this make sense. I am not sure how safe this is for the sensor (hence red's warnings) but consider the following.

If you blackshade this way, the sensor is running at temperatures closer to actual recording temperatures, not standby temps. So when you are recording images the blackshading is calibrated to a temperature closer to that. This is possibly why you are seeing cleaner recorded images than with a regular blackshading.

Does that make sense? If this were to be correct, perhaps one way to calibrate is by location or season test what the average rec temp is, then calibrate to a temp being something similar... Of course you may run the risk of damaging your sensor, so Red's approved method is always suggested for shoots, but it is food for thought nonetheless...

Cheers from TOkyo

Ivan
 
Well, I trust RED to have the point at which the fan kicks in automatically adjusted to a safe value. So, I don't think that such experiments will damage your sensor.

The interesting point is this: if you are using a high difference between shooting and cooling speed, the temperature is going up and down quite a bit. RED is obviously using the metal body as a temperature buffer, but it will float nevertheless. Since we can't calibrate while shooting, it would make sense to me to try the following procedure:

– Observe the temperature under typical shooting conditions after shooting for a typical amount of time and note it.

– Adjust the fan speed until you get to the same levels when not recording.

– Do your black shading.

– Set the fan back to what you used before.

This should get you better results than shading at different temperatures than shooting.

How much better? Well, there are so many other variables, like long or short takes, weather, time of day etc. that I'm not sure it's worth the effort for every production…

Maybe RED could give as a few more slots to save calibrations for a few different temperature levels, so we can prepare them in time and apply them when we observe temperature changes during our shooting. Another approach would be adjusting your fan to constant speed where environment and sound guys don't object. But if you keep the sensor to high levels constantly, I doubt you'll gain anything, since a hotter sensor is always more noisy. Sensors for astronomy are massively cooled, by the way.
 
IF this "overheating blackshade procedure" work and reduce noise, this is hardley the magic solution to noise. What you probably are doing is re-rating the sensor to lower iso and losing sensitivity. But if it looks coolt, it might be good for some project :)
..but Graeme have adviced against it and he built this, so it's probably not a great idea.
 
well we are gonna find out soon. im gonna post up some clips in an hour or so. B/Sing the "Normal" way right now. Just shot the Hotshade...

I'm Doing it against a still life of colored fabrics, the kind that really show off noise. The scene is lit with a 500w par, with a shadow cast across the left side of the frame. I intentionally under exposed by about a stop, so you guys can boost it up, and look at the shadows.
 
Satsuki Murashige said:
Lately I have been black shading at max temperature. My procedure: Set standby fan speed to 25%, wait 20 minutes until the fan kicks on at 74C. Wrap black jacket around the camera to further shade the port cap. Calibrate and go to lunch. Set standby speed to 75-100% and run speed to 37%. No complaints yet.
Click to expand...



I wouldn't go lunch during calibration more so if you push the camera to the limit 45/75C. The most important thing in BS is to get close to the targetted shooting temp. If you are shooting in cold it could be 25C.
The numbers 25/45 refers to 25 sensor and 45 core (or CPU). The important setting to watch for BS is the sensor temp. Usually the core gets the fan kik in before the sensor.
I would definitly follow this advice :


Graeme Nattress said:
The standard advice is to black shade at working temperature.

Graeme
Click to expand...


But it is interesting to ask RED : are the components in the sensor performing better with higher temp?

Pat
 
I can see why black shading at slightly higher than operating temperature could give lower noise at operating temperature, but if the temperature difference is too great you run the risk of uneven noise across the sensor, as Elsie found. However, if you check that noise is even at operating temperature at ISO 12800, then you should be OK when putting ISO to a more usual setting.

This probably only works well where ambient temperature is not changing much.
 
No, its more or less getting it to prepare for the "Worst case scenario" of a hot sensor, then running it at a normal cooler range, thus reducing the apparent noise.... ( in theory)...

I'm uploading the two clips in R3D now.
 
Hot Shade:
So, I set the standby speed to 40%. Left the camera for about 30 minutes. It warmed up to 39/69C.
Once the black shade completed at that temperature, I set the fans to 70% standby 40% recording. the Camera cooled to 34/47C, then i shot the still life.
Here is the footage. R3D 3:1 Compression F5.1 on a Canon 50mm. 5k Full frame. about 500MB.

HOTSHADE.jpg


After switching back to 70%
NORMALBSsettings.jpg


http://timurcivan.com/downloads/HOTBS.R3D



Normal shade:

Set the Camera to 70% standby 40% Record and left it alone for about 30 minutes. The temperature settled at 34/46C, then i performed the Black Shade, with the Standby fan at 70% and the aforementioned temperature.
NORMALBSTEMP.jpg

Here is the footage. There was no change in the lighting setup from the previous shot.

http://timurcivan.com/downloads/STANDARDBS.R3D

Conclusions guys?
 
donwloading now timur. I did some of my own tests here in tokyo... I am testing at in between settings as well as most takes we do are generally only a few minutes... I consider that standard recording temp...
 
It seems that blackshading at a hotter temperature made the image much darker according to your images. In fact to get the levels to match I had to push up the FLUT on the HOT B/S to 0.3 to actually get it to match to the STANDARD, and at that point the grain structure was not really discernible, even pixel peeping into the shadows/blacks and over the blue bag.

In fact i noticed slightly MORE grain in some places on the HOT b/s
 
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Me too Tehben,

That would be really nice.

Tehben Dean said:
I'm still hoping for the ability to store several Black Shade presets to be implemented soon.
Will be really handy for going from shooting inside to 15degrees below freezing outside... :)
Click to expand...
 
Thanks Timur,

I do prefer Standard...

I had to color match the HotBS to get close to Standard. Standard has more info in the blacks.

Here a H264 for download (if it can tell anything...)

http://dl.free.fr/icSxRiLJM

Pat
 

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What if RED gives us a new option for black shading?

Input the desired sensor temperature (that you anticipate shooting with), and RED will adjust the fan speed to keep that temperature constant to that temperature during black shading?

I suggested to RED months ago that it would also be useful to be able to input a sensor temperature, and have the recording fan speed modulated to keep the sensor at that temperature while shooting.
 
Not sure how useful that'd be in practice though... I mean, as it stands, the thermal monitoring and fan control (auto) is there to ensure the camera doesn't overheat (72c-75c)... Any less than that, and it remains as quite as possible on Auto. In other words, what would be the benefit of being able to make it run hotter and/or louder than necessary? Furthermore, could you not do the same thing with manual settings?

Timur, did you confirm if the settings were the same? I haven't gotten the clips yet, but what does the metadata say?
 
No free lunch

No free lunch

I have to wonder if the black shading calibration process essentially fine tunes the response of each pixel by precisely defining the level of voltage required to go from zero to the lowest luma value. I think of it as suppressing false positives.

If I have this right, then a black shading pass at a temperature that carries more noise causes the calibration routine to up the minimum value for those pixels to respond to photons. If this theory is correct, then shooting at a lower sensor temp than the calibration temp would be less noisy but also less sensitive - lowering effective ISO by requiring pixel "X" to get hit by more photons before responding.

FWIW I think its far easier to wrap your mind around things like this if you stop thinking in terms of ASA/ISO, DR, or latitude and cut right to the chase - signal to noise ratio. Assuming RED has engineered the black shading process well, then their advice to calibrate under conditions as close as possible to shooting conditions should maximize the S/N ratio. Calibrating at higher temps to lower the noise floor isn't really getting you anywhere if the signal levels adjust in unison.

I can see how particular image processing pipelines might arrive a less noisy result via this technique but I contend you can easily get essentially identical results with the most basic of grading tools. I'd rather have the best possible genuine signal to noise ratio the device is capable of under given conditions and then crush any noise that bothers me with a couple of clicks in RCP-X (or Scratch, Baselight, etc.). YMMV.

Cheers - #19
 
Timur, this sounds too good to be true, but I couldn't resist getting excited at the idea of getting no noise at 1600 ISO. Wow

But then I read Blair's post and it re-confirms how we should think of Black Shading. It makes sense. He is truly the 4K Ninja
 
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