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Grain issue on ISO 800

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Slobodan Milivojevic

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Hi guys,

just want to have a final and correct answer, because I had a discussion with DP who shot a corporate for me.
He is saying that SCARLET's and EPIC's MX default ISO is 800 and shooting and light measurement should be worked around it.

I am saying that default ISO is 320 and that on higher ISO this cameras are giving very nasty grain.

The end result is on the link below. Yes, he shot on 800, there is grain, but he is saying its normal, acceptable and its ok.....

I was directing and finalizing this project, and I had to use NEAT VIDEO (which helped me a lot in post) to fix all grainy shots.

r3d frame export
 
In my experience, the native ISO is anywhere between 320 and 800 depending on the contrast ratio of the scene. If you're shooting an exterior with a ton of dappled highlight information, then shoot 800. If you find yourself in a very low contrast situation, i.e. an overcast day with a large amount of flat midtones, extended highlight detail is not as much of a concern and you can shoot at 320.

This is because, if I'm understanding correctly, the MX and Epic sensors have been engineered with a lower noisefloor than the original One. A stop and a half lower, to be exact. Which is why you can effectively underexpose your image by a stop and a half on the epic (rating it at 800) to preserve highlight detail. I feel choosing an ISO on a digital cinema camera requires a very different approach than with film, because on the Red and Alexa, the ISO you choose really depends on your tolerance for noise (high iso) and tolerance for non-correctable sensor overexposure (low iso). I have tested this by shooting 1280 ISO on a bright day to preserve the extremely high contrast scene I was framing. And in comparison to the same shot at 320 ISO, there is a massive difference in highlight latitude when viewed in RedCineX.

I'd like to hear others' opinions on this matter!
 
Its a scene I would have advised lighting to 320, not 800. Controlled light, very warm... (2000k ish)

Its conservatively exposed even at 800 too which compounds things, and as a result the blue channel's not being illuminated more than about 10-15%
 
Ramesh Jai said:
I use ISO 320 no matter what the experts say. 800 gives me grainy images. That's my official stand and I'm sticking to it :)
Click to expand...

I agree with you Ramesh.....I am not a DP, but I am director, and I always like to know and to be familiar with technical possibilities/limitations of the hardware......
I have personaly tested Scarlet, and regardless of Black shading done or no, ISO 800 gives a LOTS OF GRAIN, as in attached r3d file, while 320 gives amazing image without any grain.
 
ISO 800 just tends to make people expose lower - it protects highlights and in theory gives a nicer highlight rolloff (more bits allocated to highlights), but if there are significant shadow areas they will be underexposed resulting in noise.

ISO 320 does the opposite, but as long as you watch your highlight clipping, highlights are still protected as much as you want them to be, while maximising exposure of shadow areas, and hence minimising noise. That's my reasoning for always using ISO 320, unless it's so dark that I need the higher ISO just to see what's happening or to focus. But then I would say I need more light, not more ISO. Of course, if more light wasn't available, then needs must and NeatVideo can often save the shot.
 
Looking at this scene there is noise in the walls. The noise is there at 800 or 320. If you wanted to avoid the noise you needed more light. At 4K HD (sensor cropping) and 6;1 compression everything is correct, but the only way to beat noise is with light. If this scene was rated at 320 (interior tungsten) then the noise goalpost would have been telling you to add more light to fight off the noise, jacking the ISO to 800 only pronounces the problem.

There are two solutions to this "problem":

1. more light on the scene (therefore on the sensor)
2. Gel some tungsten lights toward the blue spectrum (a warm look can be achieved later with less noise)

I don't know all the circumstances, but a 320 rating on this scene would have asked for more light and therefore less noise. it is slightly underexposed. I don't mind the grain that much though.

It's not lethally bad or anything, but the same scene at rated 320 would have made sharper images.

David
 
For the past several months I've been getting very clean images by shooting low light/interior scenes at 320 ISO and day exteriors at 800 ISO. I should add that a lot of the time I'm recording straight to a HyperDeck Shuttle 2 which I believe gives you an even cleaner 1080 image.

Mike
 
Grain didn't look too bad - but it is underexposed, and the blue channel is seriously lacking. I'm always @800ISO, but I have learned how to light a scene at that ISO and read the available scopes / histogram/ etc to get a clean properly exposed image. Just as easy to do @320 if you know your gear and your craft… No right answer to this; but plenty of wrong.
 
Yes, your color temperature is quite low. You could use a D80 filter and increase the overall light or open up the lens more. As you expose now you use about 20% of the sensor in the blue channel... So when you then up the blue by using a lower temp you let the noise of the starved sensor show.

First option:
Use balanced light.

2nd Option:
use a ballancing filter.

Third option:
Bring up your exposure so you do not have such weak blue channel and then bring down the light in post.
 
320 is where I get the cleanest, grain-free images generally speaking. I use Schneider 1/8-1/2 CTB's for some tungsten int.'s relative to the scene. 1/2 CTB is a 1-stop loss in this set.
 
Timur Civan said:
Also, what are you watching your footage on? On my calibrated monitor it looks perfectly fine, but underexposed.
Click to expand...

Hi, watching it on 1 HD calibrated monitor (TV LOGIC) and external calibrated LCD TV, and the grain is terrible on RAW footage....
Even, I can notice it on my downsampled JVC SD reference monitor.
Playback card is BLACKMAGIC EXTREME HD.
 
But you need to get more exposure you are at the most about 20% in the blue channel you need to be around 805 to get a perfect image.. you are starving the sensor basically. mostly in blue channel wich is also the weakest so for that reason you are experiencing noise.
Expose more and / or use a filter that brings your lights more towards a balanced 5600K As if you now look at your image in 5600K then you do not have noise, correct? But your image is rather warm, thats how you shot it, Simply twisting a warm under exposed image back to cold or neutral is not the best practice to avoid noise.
 
Hungry sensor! This scene looks like it was lit for 800, not 320. I steer people clear of ISO320 all the time, it gets them into trouble.

The reason they call the EPIC a native 800 camera is because there is an even number of stops above and below 18% grey at 800 ISO.

Now, the above portion has a hard stop at clipping but the below is a little more fuzzy. It is usually defined as "acceptable noise".

So your tolerance for noise is lower than mine - but - The mistake I see most often is when people rate at 320 and grossly over expose because the histogram is artificially cutting off before the top. It will do the same with any SDI waveform. Granted, they should know better when looking at a WFM but we're talking about DP/Operators who are in the heat of battle.

At 800, they always protect those highlights. I think everyone would rather have some noise than premature clipping.

I think the noise looks acceptable, certainly by 35mm film standards, but more light is the real answer if you want to live at 320, just watch those highlights!

BTW, blue filtration would also be ideal, RED doesn't like a lacking in the blue channel, it shows up as ugly noise.
 
Your shooting setup 4K HD 3860x2160 is smaller than super35 and 35mm (noise magnification). The level of noise which you are getting under tungsten is normal (nothing is wrong with your camera).
Grab an EPIC and shoot in 4.8K at 3-4:1 compression ratio, you might be more satisfied and your 1080p output might be crystal clear.
 
I pretty much agree with what everyone's saying. Even at 800 ISO, the scene looks pretty under-exposed. In particular when we shoot Tungsten, we generally shoot at 320 to be safe. We look at our wave-forms pretty religiously and try and make sure everything looks as "healthy" as possible.

In your case, you def would have needed more light, or to have opened up the lens a stop or two.
 
ericyoung said:
ISO 800 just tends to make people expose lower - it protects highlights and in theory gives a nicer highlight rolloff (more bits allocated to highlights), but if there are significant shadow areas they will be underexposed resulting in noise.
Click to expand...

This is exactly right. The choosing of ISO should be made after observing the contrast ratio in your scene. 800 asa is by no means the native ISO for all situations. You have to think about where you're placing your exposure within the linear bits.
 
I prefer to look of Epic footage at 800 ISO; it gets too clean and snappy at low ISO's and looks more digital to me. It only makes sense if you need a really clean signal for chromakey work or something. Otherwise I don't see a problem with a very mild level of noise if it's not distracting.

But I think if someone has a tendency to underexpose, they are safer working at a lower ISO rating. And if someone has a tendency to overexpose, then they are safer working at a high iSO rating. Know thyself!
 
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