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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 :)

Native Dragon ISO…once and for all!

It's already been said higher up in the thread and I think it's a really good refresher for many RED shooters:

There is a major difference where on a non-raw camera with gain amplification you SET the GAIN (actually boosting the signal), whereas on a raw camera like RED you RATE the GAIN.

People who don't understand the difference/implications between setting and rating will have trouble with RED.
 
Can someone explain simply this concept of low ISO for dark and high ISO for light because this seems really counterintuitive for me and pretty much
seems to destroy the use of ISO as a way artificially enhancing a low light image.
First of all I thought as you were shooting ISO was metadata and so whether you use higher or lower ISO it doesn't matter to the
end product.

So lets say you're shooting a documentary; natural light in a dark environment and you're stopped open all the way, in your monitor the ISO
that looks right is 1600 but according to the advice here you would have to drop down to say 250 ISO so now it looks several stops under exposed and ISO
aside you have no other way of seeing more than you can..., how are you supposed to make the image work if in order to get the best quality the ISO works
in the complete reverse of what you're used to. What happens when you get to the grade?
 
David Ellison said:
Can someone explain simply this concept of low ISO for dark and high ISO for light because this seems really counterintuitive for me and pretty much
seems to destroy the use of ISO as a way artificially enhancing a low light image.
First of all I thought as you were shooting ISO was metadata and so whether you use higher or lower ISO it doesn't matter to the
end product.

So lets say you're shooting a documentary; natural light in a dark environment and you're stopped open all the way, in your monitor the ISO
that looks right is 1600 but according to the advice here you would have to drop down to say 250 ISO so now it looks several stops under exposed and ISO
aside you have no other way of seeing more than you can..., how are you supposed to make the image work if in order to get the best quality the ISO works
in the complete reverse of what you're used to. What happens when you get to the grade?
Click to expand...


I'm not a huge fan of this generalization and method as it's a bit off of how I personally work, however it does serve two logical advantages under the described shooting conditions.

- "Darker" shots often contain more shadows and midtones across the frame, especially when dealing with Low Key lighting scenarios. Since the content in frame floats in that mid to dark tonal range texture is more apparent and visible when viewed. Thus a lower ISO rating would produce a cleaner image.

- "Brighter" shots often contain more midtones and highlights and might as well contain a decent transition from shadow. In High Key lighting scenarios where more of your values tend to float in midtones through lighter tones noise won't be as apparent. Also, based off of how Dynamic Range is distributed when rating your ISO higher you get more "highlight retention/protection" when exposing with a Middle Gray exposure technique. That comes in handy if you have a contrast scene or an intense light area that you want to hold within range.

In this method what you are protecting mainly against is "perception of texture" when the footage is watched based off of the content/values in frame.

ETTR (exposing to the right) is another method that's popular to utilize as you favor a histogram that is weighted away from shadow and in post bring the ISO rating down to the image you are hoping to create. The issue with ETTR is often consistency both in exposure practice and general image texture.


I work in the more "film style" method of exposing where you choose an ISO Rating and work from there. Sometimes selecting a new ISO Rating on a per scene basis. Most of the time however I try to keep my ISO consistent across a project as much as possible.

The shorter version of all of this is if you want cleaner images you want to be shooting at lower ISOs. This isn't anything new and it is true for all cameras. There's no real reinvention of the wheel here. Where people tend to get in the most trouble is having shots that are woefully underexposed and attempt to "dig out" a salvageable image. However, boosting an ISO 800 image 2 or 3 stops (which result in ISO 3200 and 6400 exposures) isn't exactly the best way to work really and that's what needs to get hammered home.

Accurate exposure is actually the answer. Accurate exposure and knowledge of the texture and capabilities of of each ISO rating is pivotal.
 
This can never be answered precisely since everyone rates Dragon as having a different dynamic range. If middle gray falls 9 stops below white at say 1200 ISO (and the DP assumes 18 stops of usable sensor data) then it would be a 1200 ISO sensor. If middle gray falls 7 stops below middle gray (assuming 14 stops usable sensor dynamic range) then the same captured image would be rated as 300 ISO. It gets even more complicated when "White" is also a moving target. If you have truly white light and the sensor is about 5600K native then all the channels will clip about the same place. But if you have your 14 stop 300ISO sensor and you're in tungsten then the blue channel is a stop darker so you would want to over expose at least a stop and you're down to a 6.5 stop below 1-stop-over-exposed-red/green-and-100%-blue-white. In that case you're now using 1 less stop and you're one half stop lower on the sensitivity rating so you are down to 212 ISO.

With the exact same hypothetical sensor you could be 1200 ISO or 212. It all comes down to the conditions and the opinion of the decision makers on how much noise they tolerate. Personally I just give the sensor as much light as it can take before something important clips. Usually that's in the 300-400 ISO range for Dragon. The further my image is away from the noise floor, the cleaner it'll be.
 
Ah, so it's more about lower and higher contrast environments than actual light level.... Lower contrast reacts more favourably to higher ISO's because of it's benefits to midtones and lower ISOs react better to sharper changes in shadows and highlights....?
 
David Ellison said:
Ah, so it's more about lower and higher contrast environments than actual light level.... Lower contrast reacts more favourably to higher ISO's because of it's benefits to midtones and lower ISOs react better to sharper changes in shadows and highlights....?
Click to expand...

Lower ISO is utilizing more of the Dragon sensor's total Dynamic Range in the dark through shadows.

Higher ISO is providing more Dynamic Range for the lights through highlights.

Dragon at ISO 800-1280 gives you the approximate even tonal range in stops above and below Middle Gray. The variance there is more or less what Gavin stated above and will vary depending on your tolerance/preference for noise character.
 
I think the problem here is the term, "shooting at" XXXX given ISO.

If the scene is dark and you simply move the ISO in camera from 800 to 1600 then you are Now shooting the scene at 800iso and you have digitally pushed the in camera monitoring by 1 stop.

lets use ISO 800 and a typical no light scenario as an example.

Factory setting
1. You walk into a run and gun situation fire up the camera open up your lens to f2.8
2. "gee, that's a bit dark", you say and the histogram is to the left.
3. you then move the ISO to 1600 and say "that looks about right"

In the above scenario you did not "shoot" the scene at 1600 ISO, you probably shot a scene at 400ISO and applied digital gain to the tune of 2 full stops. Now you get back to the shop and you think, "gee, that was really dark, even at 1600iso" so you push it to 3200iso in rcx and you think, "shit, that is a bit to much noise".

you just shot a scene wide open

it's noisy because it is exposed one stop under factory and pushed 3 stops.

Same scenario

1. You walk into a run and gun situation fire up the camera open up your lens to f2.8
2. "gee, that's a bit dark", you say and the histogram is to the left.
3. You put a 1x1 led light panel up and bounce it off the ceiling as a base light and say "that looks about right". histogram is more toward the middle. Or you open up to f2.0 or better yet 2 stops to f1.4 (adding 4x more light to the sensor)

now you come back and you push it one stopin post from to 1600 and the scene feels so much cleaner and you are getting a bit of pop to you images. Makes sense, you've hit the photo sites with more light, so when you push a stop or a stop and a half everything seems much better and ok.

even if you just put a mini lite panel with a heavy frost on top of your camera, just to push in that little extra light, your scene would benefit greatly, why? Because you shot it closer to 800ISO, even if you added only enough light to get the base light level of that scene from 400 to 640 ISO, you'd be far better off.

so if you left your camera set to 400 ISO and added light or opened the aperture or adjusted the shutter until you move the histogram to the middle, the you would know that you have enough light on the scene to get those noise free exposures.

Even an the darkest scenes are "lit" in one way or another.

battistella
 
David Ellison said:
So lets say you're shooting a documentary; natural light in a dark environment and you're stopped open all the way, in your monitor the ISO
that looks right is 1600 but according to the advice here you would have to drop down to say 250 ISO so now it looks several stops under exposed...
Click to expand...

David Battistella said:
This has been preached around here endlessly as well as the fact that ISO has no effect on exposure (unless you use it as part of your rating and exposure toolkit).

What I mean by that is this. If you, as the cinematographer assign an ISO rating to the scene and light and expose according to that rating. This will have a huge effect on the RAW image data (just as it would with film.

So. If I rate an exterior scene at 2000ISO and use ND, shutter and IRIS to "expose" that way, the RAW data will be underexposed but it could be a creative choice. If I rate the same scene at 250ISO chances are I will have a MUCH MEATIER RAW negative.
...
You're advice (and others) is correct, when you get into low light situation the best thing to do would be to take your ISO down to 500 or 400 or 320 (for montioring).
Battistella
Click to expand...

Still not clear if ISO has any effect or not in the situation when you are NOT able to add additional light (like in the documentary situation mentioned above) and the available light is very low, and you don't want to mess with the shutter for other reasons, and you are already fully open at a T1.5.

In that case, setting the ISO to whatever high value you need to, so you can see enough in the monitor to compose the shot, is the best thing to do. Correct? I don't think anyone is saying that in this situation, you should set the ISO to a low value like 250 etc.
 
David Ellison said:
Can someone explain simply this concept of low ISO for dark and high ISO for light because this seems really counterintuitive for me and pretty much
seems to destroy the use of ISO as a way artificially enhancing a low light image.
Click to expand...

The way I explain it to people is if you use a lower ISO more light is hitting the sensor because you're going to compensate by opening up the iris or adding more lighting. And, obviously, if more light is hitting the sensor, then more light will be in the shadows which means less noise. If you're wide open and you can't add more light then changing the ISO does nothing (except gain up the image).

The other guys have the technical explanations well covered :)
 
Nikhil Kamkolkar said:
Still not clear if ISO has any effect or not in the situation when you are NOT able to add additional light (like in the documentary situation mentioned above) and the available light is very low, and you don't want to mess with the shutter for other reasons, and you are already fully open at a T1.5.

In that case, setting the ISO to whatever high value you need to, so you can see enough in the monitor to compose the shot, is the best thing to do. Correct? I don't think anyone is saying that in this situation, you should set the ISO to a low value like 250 etc.
Click to expand...

If you cannot add light, you'll "see the scene" by adding gain/setting higher ISO. That will inevitably lead to a more noisy scene though. And it would be good advice yo use optical/exposure techniques to get as much light as possible to the sensor before compensating with gain/ISO.

Those would be:
Adding light
Opening up on the lens (lower T/F-stop) (will maybe change DOF character in an unwanted way)
And sometimes, when applicable: Longer shutter (will change motion-blur character)

But of you don't have the possibility to add light, you don't.

What we see a bit here is people shooting at high ISO with a high F/T-stop or maybe even with NDs to control a low T-stop at high ISO.
Unless you want that characteristic of the image, that is basically: Adding unwanted noise and lower precision to an image.

There is nothing called "artificial light". Gain, denoised or not, changes the character of an image.
 
ISO is digital gain.

RATING at specific ISO is using ISO as a lighting tool. That is to say you are using ISO ona light meter as a basis for your lighting ratios.

if I rate at 250 ISO (I'm talking metered scenes here not run and gun, then I am bringing in the combination of light, aperture and shutter to move a histogram (a fat wide histogram for that rating) and more light hitting the photosites.

i can also rate at 800iso and set my meter to that rating. Then it's a different combination of light aperture and shutter to get that SAME fat histogram BUT (less light hitting the sensor)

i can also rate at 3200iso, still a different combination of light, shutter and aperture BUT (far less light hitting the sensor)

Less light = more noise

more light = less noise

moving ISO to "see" better is like turning up the monitor brightness. IT HAS NO EFFECT ON EXPOSURE WHEN USED IN THIS WAY

(You could use the brightness or exposure controls to accomplish the same thing)

if you don't have a meter and don't assign a scene a rating, then you are lighting by eye or available light and using ISO as a monitoring tool and not an exposure tool.

Battistella
 
Brandon J.F. said:
The way I explain it to people is if you use a lower ISO more light is hitting the sensor because you're going to compensate by opening up the iris or adding more lighting. And, obviously, if more light is hitting the sensor, then more light will be in the shadows which means less noise. If you're wide open and you can't add more light then changing the ISO does nothing (except gain up the image).

The other guys have the technical explanations well covered :)
Click to expand...

While I've already been soaking this up. THIS explanation really sells it for me. Thanks!
 
Alexandros Tsoupras said:
Here is what DXOMARK say in test that they make with the old version of the LLO OLPF.
''It’s also worth noting that the Epic Dragon only has one ‘native’ ISO setting (ISO 250 which is measured at 104), the others are achieved by applying digital gain.''
http://www.dxomark.com/Reviews/RED-...xOMark-sensor-score-barrier/In-Depth-Analysis
Click to expand...

I dunno. I've read the whole thread and the confusing comments Mr. Nattress made in Alexandros' other linked thread. Here's what it sounds like to me:

1.) The real answer to OP's actual question, "What is Dragon's native ISO," is, as Alexandros quotes, quite simply "250 [actually 104], because that's actually its only ISO."

2.) The interesting discussion that has followed has actually been an answer to a different question, "So it sounds like ISO setting on the Dragon actually just sort of acts as an exposure guideline (sorta like a very advanced zebra) and ISO setting in RedCine is just sort of an "exposure"/"curves" slider. What are the best ways to make use of these tools?"

Doesn't make the thread any less useful, just kind of find it interesting.
 
I might have other "unresolved issues" with RED that keeps me from being an owner, but I think the camera is beautiful in its honest approach with just a shutter and aperture. ISO actually isn't there. You've got the light you've got and you have the goal posts showing you how much light is hitting the sensor. In low light, you can open up the aperture or change the shutter. Or bring your own light. That's it, in terms of feeding the sensor with light.

To me, that is very straight forward photography and it speaks to me a lot.

I think it's fair to say that "what you get between the goal posts, is the light you bring home". And, correct me if I'm wrong, no matter what ISO you set in camera, the histogram between the goal posts remains constant and shows the de facto light amount on the sensor.
 
the stoplights and goalposts are from linear-light "raw". the new "zone" tool, as well, as far as i understand (haven't used it yet)

i do btw agree that the histogram should be choosable. and I can see why red have made the choice they have.
 
Last edited:
David Ellison said:
Can someone explain simply this concept of low ISO for dark and high ISO for light because this seems really counterintuitive for me and pretty much
seems to destroy the use of ISO as a way artificially enhancing a low light image.
First of all I thought as you were shooting ISO was metadata and so whether you use higher or lower ISO it doesn't matter to the
end product.

So lets say you're shooting a documentary; natural light in a dark environment and you're stopped open all the way, in your monitor the ISO
that looks right is 1600 but according to the advice here you would have to drop down to say 250 ISO so now it looks several stops under exposed and ISO
aside you have no other way of seeing more than you can..., how are you supposed to make the image work if in order to get the best quality the ISO works
in the complete reverse of what you're used to. What happens when you get to the grade?
Click to expand...
Nikhil Kamkolkar said:
Still not clear if ISO has any effect or not in the situation when you are NOT able to add additional light (like in the documentary situation mentioned above) and the available light is very low, and you don't want to mess with the shutter for other reasons, and you are already fully open at a T1.5.

In that case, setting the ISO to whatever high value you need to, so you can see enough in the monitor to compose the shot, is the best thing to do. Correct? I don't think anyone is saying that in this situation, you should set the ISO to a low value like 250 etc.
Click to expand...

The real answer to this question, which no one has exactly given you yet [unless you read between the lines fairly hard] is that basically this thread doesn't apply to you. What they've been talking about here is controlled/artificial lighting. When they say "dark" scene, they mean "low key," not "underexposed." In other words, they're comparing how image quality and tonal balance changes when you, for instance, increase ISO by 2 stops AND correspondingly turn your lights down 2 stops (so that exposure remains "the same").

Available light shooting is different. You don't have the luxury. You have to apply the gain you have to apply to, you know, see stuff. As Nikhil says, it's a different situation in which gain has to be used the same way it would be on any other camera (even if that's not ideal).
 
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