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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!

Jarek Zabczynski

Jarek Zabczynski

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I've heard so many conflicting arguments on what the native Dragon ISO is and what we should be shooting at to achieve the cleanest images.
I have heard things as native Dragon ISO is 800, 1600 or even 250. (I'm aware Mysterium-X is 800)

So what is it? Or is there native ISO and recommended shooting ISO?
 
Not a simple answer, as the Dragon does not have a "native iso", atleast not that I know of. You shoot at whatever ISO will give you the results you desire. This is further complicated by the fact that there are two very different OLPF options. The skin tone optimized olpf seems to do best between 250-500 ISO, the low light olpf seems to do best from 800-2000 ISO. I have personally shot footage at 2000 ISO that is moderately under exposed using the LLO olpf, processed it in rcx with DEB and found the results an incredible improvement over the MX sensor. However if you want to shoot without lighting you will need to do manually what many other cameras do automatically...use noise reduction. Utilizing Neat Video I have no doubt the dragon could rock 4000 ISO...but I really can't think of I good reason why this would be a strategy and not an emergency measure.
 
I have developed a rather strong opinion about this chaos.

All of this terminology has become confusing for most shooters. Really confusing.


However, much of this is clearly explained in one of the RED:LEARN documents here:
http://www.red.com/learn/red-101/iso-speed-revisited

A very important quote/definition is this one:

With RED, the native ISO speed describes the recommended starting point for balancing the competing trade-offs of noise in the shadows and clipping in the highlights.
Click to expand...

One other useful bit there is this one:

With most other cameras, “native ISO” originally referred to the sensitivity which is able to saturate the sensor’s photosites. This is often also called the “rated” or “base” ISO speed of a camera. The native ISO is often near 100 or 200 with stills cameras; anything higher and white represents only fractional photosite occupancy, and anything lower and photosites become over saturated. However, this definition does not apply to RED because all ISO speeds use the full potential of the sensor.
Click to expand...


One main reason why this is such a totally wrong concept is that all of these cameras actually produce images in linear light, which is not a proper looking image. And there is indeed a "base sensitivity" of each sensor's potential light gathering abilities, however, that number isn't something that's typically useful for us humans in regards to linear light.


ISO info you want in 3 bullet points:

Cleanest Image - Much of what I've written in the Dragon Data Sheets regarding ISO, how it works, and general shooting practices is pretty spot on. If you want the cleanest image possible shoot at the lowest available ISO. This concept is also more or less true for all cameras. When talking Dragon, that's ISO 250.

Native ISO - Based on what is written above in relationship to those definitions Red's recommended Native ISO is ISO 800. Which is essentially what "Raw View" now defaults to with a gamma space of REDlogFilm. However, in testing and depending on who you are you may find that anywhere in the range of ISO 800-1280 is the "wheelhouse". In a bazillion tests and that interesting middle ground where there's an even measurement above and below Middle Gray I've found around ISO 1100 to be rather interesting. But more or less to simplify things the answer you want is ISO 800.

Recommended Shooting ISO - Red's recommended shooting range on Dragon is ISO 250-2000. Much like choosing a film stock's ASA speed this ISO rating has similar implications, though Dragon is cleaner per equivalent sensitivity in comparison to film. Cleaner Image = Lower ISO. Denser Image = Higher ISO (meaning access to more of the sensor's potential dynamic range when exposing from Middle Gray).
 
The truth is, the native ISO is the one you choose. You can light and rate at any ISO in the following range

With STH OLPF I agree with phil that it can be between 250- 1280iso.

with the LLO im comfortable rating from 320 up to 2000 ISO.

i had a really long drawn out discussion here with Mrk at offhollywood before I got my dragon, where I was insisting that one number had to be given, and the importance of that one number.

The actual fact is that I can treat dragon as different filmstocks with different characteristics. The nice thing about that is that it's like I have a whole range of working filmstocks and texture choices. What does that mean?

if I want that hyper lean look of a daylight 50iso film, I rate at 250 with the STH OLPF. If I want some texture (and I choose to call it texture not noise) on interiors, I might rate above 1280 on the sth.

If I want clean 2000 the LLO is the way to go.

The fact is the sensor responds to how much or how little light you throw at it. I find that when you meter and light a scene you can expect better results than film stocks, but the same reaction. Like if I push an 800iso film stop one stop I expect it to be noisier. If I meter and light a 50daylight stock and expose the shadows a 1/2 stop over then it's all there.

You get the creative choice to work within the ISO range that you want to expose your images, the sensor responds accordingly. You want super clean, well, lower ISO and more light, you like a bit of texture, higher ISO and a bit more texture.

The sensor responds much like a range of film stocks, if you understand that, you understand that inside your dragon camera lies a variety of film stocks and combinations, like flipping through the kodak or Fujifilm catalog. :)

recapping. Don't think native as a hard number, think of it as a working range.

When i got my head around this after testing, I was a happy camper. I really understood what mark was saying and phils testing (and my own) really helped confirm this.

Battistella
 
For a rule-of-thumb, there might need to be:

Sensor: Optimal ISO with no OLPF
DEB : Multiplication_factor for ISOs above xxx
ADD : Multiplication_factor
STH/LLO/H20/Middle-of-the-road : Divide_by_factor representing S/N reduction for the OLPF

AJ
 
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
And here is what Graeme Nattress says about that:
http://www.reduser.net/forum/showthread.php?118223-ISO100-Color-Science
Personally i like to rate the STH OLPF at 800-2000 ISO range because of the texture/noise. I'm a film guy and the DRAGON is more like film to my eyes.
 
Been a while since I checked if this is still true, but "reference ISO for Dragon" seemed to be 250 a while back (as opposed to 320 on MX). That doesn't mean "native", but what the tools are tuned from.
 
reference = expected response@xxxxISO

expected response (amount of noise, grain, texture, stops over and under,ecc) = personal taste

can also mean

reference= predictable response@xxxxISO

predictible response (amount of noise, grain, texture, stops over and under,ecc) = ISO rating

In other words.

To get predictable responses that mesh with personal tastes you do have to do some testing. This is going to vary from person to person but Phil's testing confirms how this sensor responds (in a general way) to light.

The he next question might be whether if a manufacturer gives it a number makes it "official" or not as many people did not treat all film stocks according to the way they were rated by the manufacturer.

So, it's subjective and needs to be selected from a variable range set by the manufacturer (or users based on tested) leaving other users the creative exposure option.

Solving exposure challenges is the work of cinematographers.

battistella
 
Phil Holland said:
I have developed a rather strong opinion about this chaos.
Click to expand...

And a rather good one, too!

[...]

ISO info you want in 3 bullet points:

Cleanest Image - Much of what I've written in the Dragon Data Sheets regarding ISO, how it works, and general shooting practices is pretty spot on. If you want the cleanest image possible shoot at the lowest available ISO. This concept is also more or less true for all cameras. When talking Dragon, that's ISO 250.

Native ISO - Based on what is written above in relationship to those definitions Red's recommended Native ISO is ISO 800. Which is essentially what "Raw View" now defaults to with a gamma space of REDlogFilm. However, in testing and depending on who you are you may find that anywhere in the range of ISO 800-1280 is the "wheelhouse". In a bazillion tests and that interesting middle ground where there's an even measurement above and below Middle Gray I've found around ISO 1100 to be rather interesting. But more or less to simplify things the answer you want is ISO 800.

Recommended Shooting ISO - Red's recommended shooting range on Dragon is ISO 250-2000. Much like choosing a film stock's ASA speed this ISO rating has similar implications, though Dragon is cleaner per equivalent sensitivity in comparison to film. Cleaner Image = Lower ISO. Denser Image = Higher ISO (meaning access to more of the sensor's potential dynamic range when exposing from Middle Gray).
Click to expand...

There's a crucial fourth bullet point/rule of thumb (which does not contradict any of the above, but has been my foolproof way of following the above):

Lower ISO for darker scenes, Higher ISO for lighter scenes - It seems counter-intuitive, but it will save you from ever posting another "my dragon has too much noise" thread.

Here's how I put it into practice. I start with ISO 800, my preferred (or available) lens aperture and my preferred (or available) shutter angle and look at my histogram.

If the scene is mostly dark scene (i.e., the center of the main hump in the histogram is left of center at all and/or low-side noise is at 50% or more), I compensate by shooting at the lower end of the preferred ISO (320 for STH, 640 for LLO) and I adjust my lighting, aperture, and shutter angle accordingly.

If the scene is mostly light scene (i.e., 80% of main hump in the histogram is right of center and/or high-side stoplights are clipping) compensate by shooting at the higher end of the preferred ISO (1000 for STH, 2000 for LLO) and I adjust my lighting, aperture, and shutter angle accordingly.

If the scene is somewhere between those two, I shoot in the middle range of the preferred ISO (down to 500 for STH, up to 1280 for LLO, or just leave it at ISO 800) and I fine-tune my lighting, aperture, and shutter angle accordingly.
 
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One thing not to forget is that there are only 2 ways to change the amount of light hitting the sensor: iris (and I'll consider ND's under that category) and shutter speed.
ISO has no influence, zilch, nada, about how much light hits the sensor. So it also stands to common sense that if you are in a dark situation, you set the camera with ISO 2000, if the scene for some reason seems too bright, DO NOT close down your aperture! just lower your ISO. As long as you're not clipping, you'll be fine.
I know that seems like a given to most here, but you jhave no idea how many people I have spoken with that have done that mistake and starved the sensor of light and then complained about noise in the picture.

Reality is that most DP's that are not used to RED, can't wrap their heads around the different way you expose these cameras and end up getting bad results and blaming the camera...
 
This is probably the single greatest exposure problem I have seen here on reduser Daniel.

Using ISO settings as a DOF tool in low light and starving the sensor. Not good.

ISO does have no bearing on exposure, until people use it as an exposure tool, which is pretty common in dslr land, but one of those things that should not nessisarily transfer to motion picture concepts.

Battistella
 
Daniel Stilling said:
One thing not to forget is that there are only 2 ways to change the amount of light hitting the sensor: iris (and I'll consider ND's under that category) and shutter speed.
Click to expand...

Actually there is a third way: use (more (powerful)) lights.
 
Michael Tiemann said:
Lower ISO for darker scenes, Higher ISO for lighter scenes - It seems counter-intuitive, but it will save you from ever posting another "my dragon has too much noise" thread.
Click to expand...

That does make sense in one way, but in the other way makes you go wtf?

I totally understand low ISO and more lighting will produce a cleaner image, especially in dark situations. If you can get more lights, great. I guess the other is little more difficult to grasp. That in bright situations shoot at a higher ISO than you would the dark. Seems like you would intuitively just want to shoot at the lower ISO where ever possible.

I feel like I understand but my brain doesn't want me to commit to such thoughts lol!

I guess I'm gonna have to wait and see for myself and do some testing when my camera gets back from RED. Just trying to get a head start on my train of thought on all this!
 
Jarek Zabczynski said:
That does make sense in one way, but in the other way makes you go wtf?

I totally understand low ISO and more lighting will produce a cleaner image, especially in dark situations. If you can get more lights, great. I guess the other is little more difficult to grasp. That in bright situations shoot at a higher ISO than you would the dark. Seems like you would intuitively just want to shoot at the lower ISO where ever possible.

I feel like I understand but my brain doesn't want me to commit to such thoughts lol!

I guess I'm gonna have to wait and see for myself and do some testing when my camera gets back from RED. Just trying to get a head start on my train of thought on all this!
Click to expand...


I'll take a stab at this. To the best of my knowledge...

Keep in mind that changing ISO changes the distribution of where the stops fall within the total dynamic range in relationship/when exposing to middle gray. ISO 800 or thereabouts gets you fairly even on both sides.

Lower ISOs distribute more stops below middle gray and higher ISOs place more above middle gray. Darker scenes rated at low ISOs, when exposed correctly, benefit from both more light on the sensor (from adding more lights, opening the lens, increasing shutter angle) and the greater concentration of stops dedicated to shadow detail.

Bright scenes, which usually have less intense shadow areas, benefit more from the greater overexposure latitude of higher ISOs. This way, you're not wasting stops in the shadows, where you don't need them as much, and putting them where they'll do the most good, at the top.


This handy-dandy chart from Phil Holland illustrates this very well:

phfx_redDragon_ISOExamples.jpg



You can also get more helpful information about this from the sticky in the Dragon section:

http://www.reduser.net/forum/showthread.php?92999-Red-Dragon-Info-and-Data-Sheets


As well as this tutorial on RED's website:

http://www.red.com/learn/red-101/iso-speed-revisited
 
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Me thinking... ISO on these and most digital cameras = digital gain...

So the question here is "Native Dragon digital gain once and for all...?"

Well to me there can not be a straight answer to that question. The real question would be something like how much digital gain can we add to dragon footage before it looks bad?

To me the answer to that question is: It all depends on 1. perception. and 2 what end of the sensor spectrum the footage is captured. If it's captured right at the noise floor of the sensor I would say that you can not add any digital gain at all... and if it's captured at the upper third part of the spectrum, bellow clipping point, I would say you can add infinite digital gain and it would still look clean/good, even though your image would for sure go completely white at some point long before you get to infinite digital gain....

Then there is the discussion of middle gray, well that goes back to the above... basically that's just a point in between white and an acceptable noise level. whats an acceptable noise level would be is hard to set and can not be done once and for all. it's again depending on a lot of things, taste, light balance, mastering resolution etc. etc.

So personally I think it's better to ignore the iso debate all together.... even though I realize I'm diving right into it now :)..
Instead to expose well try look at your histogram and goal posts. When in raw I my personal reference goal is that none of the color channels should land in the bottom quarter of the histogram and none should peak. Then to I try to stay within the same part of the histogram trough out the project or better. In other words if one scene lands far above the others that's fine, I can always add texture to it in post. And for me personally I like to think noise reduction does not work. or at least should be avoided. Then the goal posts, try to make them never to show, of course if you shoot right into a heavy light and the rest is close to pitch black you might have to choose your battle but with dragon there is not much of that sort of sacrificing that has to be done..
 
The issue is really more about what is now referred to here on Reduser as "usable dynamic range" than any sort of voodoo concerning a base sensitivity mark. The reason some seasoned RED shooters use "counterintuitive" exposure methods as stated above is because of limited DR in extremely high contrast scenes. If your scene DR is small like in a night interior it is better to overexpose (lower ISO like 320) to reduce noise. If you are shooting a high DR scene like a bright and contrasty day exterior it is better to underexpose (higher ISO like 800+) to be able to capture as much of your scene DR as possible. The "EPIC Native ISO" thread is a helpful read to get your head around what is actually happening:

http://www.reduser.net/forum/showthread.php?86485-Opinion-POLL-EPIC-native-ISO-800-or-ISO-320

From my work with the Dragon in terms of ISO, exposure, and dynamic range I've found the new camera to behave very much like the old. I have found better DR all the way around, especially in the highlights as the "rolloff to white" is smoother. However, it's "Native ISO" feels very similar to the EPIC. I have not seen a drastic change in base sensitivity like I do when I pull out my A7s.
 
Adrian, I think you're spot on as to the HLO OLPF. The original (and thus probably also the LLO) had a bit of more sensitivity, but the HLO seems to me to be exactly the same as the MX, but with much better colors, "nicer" noise and all the extra DR in the top, where I most often need it.
 
Well when I think of ISO with R3D I think that I am designing my shot for the DI and I am using a algorithm to move to a lower pixel width.
So these are my current test settings while shooting 6k with red code 5, depending on the output format :
6k EXR & DPX (split) - 400 ISO ( i find i really need to have some pressure on every sensor to get low noise) basically it's real hard to do processing when you need 6k without getting some blurring
4k dpx : 800 ISO - this to me is the sweet spot of doing simple processing to get really nice blacks and great highlights, I have not worked out a nice algorithm to remove noise in the mid's but have some that are pretty good
2k dpx : 1000 to 2000 ISO - i find i can really push when moving from 6k to 2k (i'd think 2.5k i think i'd lean more to 1000 ISO)
1080p : 1000 to 5000 ISO - for something that's going to be compressed, I find i can really crank the iso if i average out & cluster the color map (which i'm sure is happening in these high iso camera's), also i can really boost the red code number.


Would be nice to have standard processing nodes and/or layers people could download for programs like nuke or AE, for moving to the DI, I'm sure they would be used a lot.
BTW I don't like to do the processing to the DI in the r3d converter (i.e. the library RED provides to vendors, i.e. A.D.D.), since i like normally to have a bit more control.

Edit: I do everything with the skin tone OLPF btw
 
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