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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 :)

RED Scarlet-X - intense noise in blue channel

Just make sure to call beforehand and ask ... It's a small crew :)
Maybe there's a RED workshop planned for your university, too. Ask Kristin about it.
 
I believe you can remove the blue noise as well. What I haven't seen like that though is the blue in patches like that. Have you?
 
David,

before you take action do some more test. Gunleik's comment (see post #10) about exposure is right, of course. The Epic/Scarlet is in general is light hungry. If you let the sensor starve - and that what you essentially do in your example - the camera starts to exhibit noise. IMHO, the noise is too bluish for a healthy BS but you used tungsten light which is again not the best way to generate noise-free pictures.

My advice is to shoot badly underexposed shots, even shoot with the lens cap on and then let the pros her check the material.

If you talk to seasoned DPs you will find that they all tend to rate the Red MX to 400-500 ASA. 800 ASA is the setting when you environment is very constrasty such as a sunny park and your aim is to squeeze as much DR as possible out of the camera. An environment with flat, dull light, such as in your example, needs low ASA for decent noise. 320 ASA would not be wrong. If your histogram shows the hump much to the left such as in your example, you have to turn on the light or live with noise.

However the noise looks a bit too colourful.

Sometimes the BS does not work properly. If this is the case it's time for a break and the camera needs a trip to California. Had this 3 times since 2008.



Hans
 
I guess he chose a bad example, too. Because he said that the blue patches appeared in better lit images, too.
Noisy it is. I tried a similar image and underexposed it. Didn't show the patches. Lot of noise, yes. But not like that.
 
I absolutely agree with your opinion: since we shot the sceneries in low light, there needs to be noise (that is part of the game). However, the noise does not look typical (very bluish and patchy). Once we shot a scenery in normal light conditions and exposed to the right, the noise decreased but it did not disappear and it still looked that bluish/patchy.
 
David, there is no problem at all in the camera. The problem is within the cameraman poor knowledge of camera work.
Scene is poorly lit and probably by a bad source.
You could have done a couple of things:
Replace bulbs with higher wattage tungsten ones
Bring a stupidly cheap redhead and bounce it somewhere
Don't underexpose bad, flat light
Shoot/expose lower ISO when scene has flat, poor light.

On you're actual footage a noise remover helps (supposing you have somebody who knows how to use it or at least you have time to experiment on different parameters)
 
Alvise Tedesco said:
David, there is no problem at all in the camera. The problem is within the cameraman poor knowledge of camera work.
Scene is poorly lit and probably by a bad source.
You could have done a couple of things:
Replace bulbs with higher wattage tungsten ones
Bring a stupidly cheap redhead and bounce it somewhere
Don't underexpose bad, flat light
Shoot/expose lower ISO when scene has flat, poor light.

On you're actual footage a noise remover helps (supposing you have somebody who knows how to use it or at least you have time to experiment on different parameters)
Click to expand...
The scene I attached to my post is a test file which should just show the bluish/patchy noise - so it is nothing we shot on set. Since the DP (and the 1st AC as well) shot several award-winning feature films and commercials, I would not agree with you that there has been not enough knowledge about the RED Scarlet-X on set. Just two days ago, the 1st AC shot a high-end commercial with the head manager of the german soccer team which has been in similar light conditions: noise is there also visible but it is not bluish and patchy.
 
There is a similar thread in the DRAGON forum (http://www.reduser.net/forum/showthread.php?113430-Dragon-Noise-Confirmation) and the punchline is the same: counter-intuitively, you should rate the ISO of the camera opposite to the lighting conditions of your environment. If you are in a bright environment with tons of highlights, rate it at ISO 800. If you are in a dark interior environment with lots of shadows, rate it at ISO 500 (with daylight-balanced sources) or even ISO 320 (the true ISO of the camera, with tungsten-balanced sources). And watch the goalposts (which don't change according to ISO, they truly show whether the sensor is clipping or being starved).

I have black-shaded my DRAGON and find that when I crank up the ISO to 12800, there is intrinsic noise in all channels--with the blue channel smearing quite far along the bottom of the histogram. I don't see this as a defect per se. I see this as just evidence that the camera isn't really designed for such things, and that if it's going to be pushed to absurd limits, the footage is going to need extraordinary help in post.
 
Michael Tiemann said:
There is a similar thread in the DRAGON forum (http://www.reduser.net/forum/showthread.php?113430-Dragon-Noise-Confirmation) and the punchline is the same: counter-intuitively, you should rate the ISO of the camera opposite to the lighting conditions of your environment. If you are in a bright environment with tons of highlights, rate it at ISO 800. If you are in a dark interior environment with lots of shadows, rate it at ISO 500 (with daylight-balanced sources) or even ISO 320 (the true ISO of the camera, with tungsten-balanced sources). And watch the goalposts (which don't change according to ISO, they truly show whether the sensor is clipping or being starved).

I have black-shaded my DRAGON and find that when I crank up the ISO to 12800, there is intrinsic noise in all channels--with the blue channel smearing quite far along the bottom of the histogram. I don't see this as a defect per se. I see this as just evidence that the camera isn't really designed for such things, and that if it's going to be pushed to absurd limits, the footage is going to need extraordinary help in post.
Click to expand...
Here is a link to an 100% crop of an image we shot on location. I am not that familiar with REDs color science and imaging processing, but that bluish/patchy pixels (especially in front of the brighter green screen) does not look "healthy" to me. I think RED would not be that popular if those bluish/patchy pixels are normal once you are at ISO 800 and underexpose a bit - or am I wrong?
 
David Strüning said:
Here is a link to an 100% crop of an image we shot on location. I am not that familiar with REDs color science and imaging processing, but that bluish/patchy pixels (especially in front of the brighter green screen) does not look "healthy" to me. I think RED would not be that popular if those bluish/patchy pixels are normal once you are at ISO 800 and underexpose a bit - or am I wrong?
Click to expand...

Having seen the image - I am now suspecting your monitor - in particular the calibration of your monitor. It could be just that blue is exaggerated on your colour profile - the image looks completely normal to me (for an underexposed shot) if that's indeed 1:1 crop.
Try to see the same link you have posted above on a some standard device - such as iPad and compare it to what you see on your monitor. Does it look the same?

fm3whc.jpg


:sifone: Peter
 
Peter Majtan said:
Having seen the image - I am now suspecting your monitor - in particular the calibration of your monitor. It could be just that blue is exaggerated on your colour profile - the image looks completely normal to me (for an underexposed shot) if that's indeed 1:1 crop.
Try to see the same link you have posted above on a some standard device - such as iPad and compare it to what you see on your monitor. Does it look the same? ...
Click to expand...
Do you not see those bluish/patchy pixels? Since we checked the footage on different monitors and always saw that effect, I do not really expect the monitor to be the reason for this.
 
David, it looks like you walked into a few of the RED gotcha's.

1. 800 iso is all well and good if you ETTR as I do. if you are trying to light 'moody' and judging exposure from how it looks on your monitors you will be in trouble. if you want to work this way then use 400 iso or so.

2. This is doubly true if using tungsten light. As a rule do not use tungsten balanced light if you can avoid it (I know its not always possible esp. on location but in a studio you should gel lights with at least 1/2 ctb or put an 80 (insert letter here) on the camera and WB to taste.)

Just looking at the JPG, even if you followed the above your green screen is under-exposed quite severely. Light like that on a blue screen and see how splotchy it would be! (FYI never use blue screen with a RED camera or any other Digital cinema CMOS camera.)
 
A quick review of other threads teaches that tungsten lights are about 4x-5x shy in the blue channel compared to daylight, so if you are rebalancing the camera from its native 5000K color temp to 3200K, you are losing two stops in the blue channel (that are made up by gain). That makes your ISO 800 really ISO 3200 in the blue channel.
 
Thanks a lot for your extensive support and detailed clearing of this effect. I will definitely do some tests in order to reproduce your advises. Anyway, to prove that this problem caused in an operating error and not in an internal camera damage, the RED Scarlet-X has been send to RED. I will keep you updated.
 
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