Exposing + Native ISO

[Mark L. Pederson]

Does the ISO setting on Red actually boost the electrical signal coming from the sensor or does it simply redefine the relationship of the response curve to the scale?

Sure it does - to the monitor path only - but since we record RAW ... not to the recorded image. Make sense?

Wiki is not so up to date on the RAW world

And again, this is how every RAW camera works that I have touched. It's not bad terminology from RED.

 

[Scott Crawley]

:blink:

OK. Please define FLUT. Is it same, or different?

~and thanks a ton.

Sure it does - to the monitor path only - but since we record RAW ... not to the recorded image. Make sense?

Wiki is not so up to date on the RAW world

And again, this is how every RAW camera works that I have touched. It's not bad terminology from RED.

 

[Gunleik Groven]

FLUT = ISO (but in decimal increments)

FLUT +1 = (for example) ISO 400 -> 800

 

[Scott Crawley]

Sure it does - to the monitor path only - but since we record RAW ... not to the recorded image. Make sense?

Wiki is not so up to date on the RAW world

And again, this is how every RAW camera works that I have touched. It's not bad terminology from RED.

So when Graeme says that the old concept of ISO doesn't really apply to digital, what exactly does he mean do you think? (I don't know if I can find a link in the archive. It was years ago. I will look.) Was he just referring to the fact that the MX does not exactly test out to 320 ISO or is there a more fundamental difference?

FLUT = ISO (but in decimal increments)

FLUT +1 = (for example) ISO 400 -> 800

Thanks. That is what I thought.

I guess the A/D converter in my head is getting an overdue an upgrade. ;-)

 

[Gunleik Groven]

So when Graeme says that the old concept of ISO doesn't really apply to digital, what exactly does he mean do you think? (I don't know if I can find a link in the archive. It was years ago. I will look.) Was he just referring to the fact that the MX does not exactly test out to 320 ISO or is there a more fundamental difference?

as far as I can remember and understand (but Graeme could well jump in and correct me), he was refering to the fact that you do not change the sensitivity of a sensor.

Let's say that filmstocks have 16 stops with+8/-8 independent of ISO rating, an 800 stock will have an equal over/under distribution as a 400, but the 800 wil manage one more stop in the bottom than the 400 one more in the top. (these are theoretical stocks...)

While with a sensor, you do not actually change the sensor (stock), so it will always clip and always go black at the same photon-levels, independently of what "ISO" you rate it at. The ISO just changeswhere within that range you put middle gray, from let's say +8/-8 to +7/-9

So the term does not give the same result when referred to stocks as it does to sensors. Unless you think of the different ISO settings as "pressing" the same stock. But even in that analogy, it is not a very precise equation, as film and sensors "see/respond" to light in very different ways.

 

[Mark L. Pederson]

So the term does not give the same result when referred to stocks as it does to sensors.

Yes.

But ... for the purpose of an EXPOSURE METHOD - it is VERY common to use ISO the same way cinematographers & photographers have for the last 60+ years.

Just think of the sensor as the film stock.

If you are using a light meter as part of your exposure method - you are using ISO in your exposure method.

If you are using the Histogram on a RED camera as part of your exposure method - you are using ISO in your exposure method.

If you are using a monitor as part of your exposure method - you are using ISO in your exposure method.

 

[Gunleik Groven]

I agree with all the above Mark. In fact I agree with all I have read from you in this thread.

That is why I try to stay out

I was walking around thinking about linear vs nonlinear lightresponse and how that affects the "pressing of stocks", but my brain said: Don't go there!

Hahahaha

It is pretty much the same point of this and the false color thread, though.

And what I see too often, is that people think of changing ISO like changing stock.

I can see from these threads how what I think of as simple concepts, can be confusing...

I'll duck again now. Promise!

 

[Mark L. Pederson]

I agree with all the above Mark. In fact I agree with all I have read from you in this thread.

That is why I try to stay out

Don't stay out. Clearly some people understand some explanations better from some folks over others.

Again, I think the issues of confusion are not about the high level stuff like - linear vs nonlinear light response - I think it's about the fact the younger generations are getting powerful tools that can work for them without them understanding how they work. And without a solid foundation of very basics of photography - there will be confusion.

In the old days - you had to work so hard and learn first to get the right and/or opportunity to use the tool (film camera) - today you just pull out your amex and you are an owner/operator. That's not a bad thing at all - it's democratization of technology - it empowers creatives. Now you can own the same camera that was used to shoot Michael Bay's next blockbuster. That's CRAZY!

But just buying the camera does not equal an understanding of the fundamentals of cinematography/photography. And IF you want to go advanced - (linear vs nonlinear light response for example) - you NEED to understand the basics ... or you will be fucked.

 

[Scott Crawley]

Yes it is my understanding that the analogy applies. Each line of chip (M, MX, Dragon) has it's own response curve that defines it just as each film stock has it's own defining response curve.

You do not actually change the sensitivity of a film stock either. When I set the ISO on my old film Pentax, what I am doing is changing the way the internal light meter responds. My understanding is that this is the same with Red. The difference is that the ISO setting can also directly effect the way the captured values are displayed, which does not happen with film.

Am I still on track?

as far as I can remember and understand (but Graeme could well jump in and correct me), he was refering to the fact that you do not change the sensitivity of a sensor.

Let's say that filmstocks have 16 stops with+8/-8 independent of ISO rating, an 800 stock will have an equal over/under distribution as a 400, but the 800 wil manage one more stop in the bottom than the 400 one more in the top. (these are theoretical stocks...)

While a sensor, you do not actually change the sensor (stock), so it will always clip and always go black at the same photon-levels, independently of what "ISO" you rate it at. The ISO just changes the rating from let's say +8/-8 to +7/-9

So the term does not give the same result when referred to stocks as it does to sensors. Unless you think of the different ISO settings as "pressing" the same stock. But even in that analogy, it is not a very precise equation, as film and sensors "see/respond" to light in very different ways.

 

[Gunleik Groven]

But just buying the camera does not equal an understanding of the fundamentals of cinematography/photography. And IF you want to go advanced - (linear vs nonlinear light response for example) - you NEED to understand the basics ... or you will be fucked.

Could not agree more.

If I may... What seems to generate some confusion here, is that two issues are confused.

1. What does ISO mean on a digital camera
2. How is ISO used for exposure
(and as a possible actually unrelated 3.) What is "base" ISO of camera X

 

[Gunleik Groven]

Yes it is my understanding that the analogy applies. Each line of chip (M, MX, Dragon) has it's own response curve that defines it just as each film stock has it's own defining response curve.

You do not actually change the sensitivity of a film stock either. When I set the ISO on my old film Pentax, what I am doing is changing the way the internal light meter responds. My understanding is that this is the same with Red. The difference is that the ISO setting can also directly effect the way the captured values are displayed, which does not happen with film.

Am I still on track?

You are on track.

Well... Much of the same happens if you press a filmstock a stop and a sensor a stop. The noise/precission/color-renderition characteristics are changed. Thus if you edit a continuus "dialogue" scene where the DOP have used (let's say) ISO 400 for one person and 1600 for the other, it will probably cut quite badly, even though you have normalized the developed levels with ISO in a way that makes developed skin-levels "equal", the "character" of the images are not vaguely similar.

I frequently used to underexposure MX (ie: High ISO) to soften my images and get a different and "fatter" kind of colors...

It is fun that we have this conversation, as I am looking through images to put up on my website-to-be...

(this is one of my early Epic exposures...)

 

[Scott Crawley]

Again, I think the issues of confusion are not about the high level stuff like - linear vs nonlinear light response - I think it's about the fact the younger generations are getting powerful tools that can work for them without them understanding how they work. And without a solid foundation of very basics of photography - there will be confusion.

Sure, but it is not an age related thing. Speaking only of myself; I am not of a "younger generation". I do not have an advanced degree in photography or cinematography. I learned what I could in schools, through mentoring and independent study. I believe that I have a pretty solid understanding of film. What I and I believe many others are lacking is confidence in what we know and perhaps a completeness of understanding. In a word, mastery.

Correction Two words: Mastery and Certification, as I do not feel i have been thoroughly tested. Getting back to Mark's earlier point, Reducation could help with some of that.

 

[Mark L. Pederson]

If I may... What seems to generate some confusion here, is that two issues are confused.

1. What does ISO mean on a digital camera
2. How is ISO used for exposure
(and as a possible actually unrelated 3.) What is "base" ISO of camera X

Yes. And this is why I keep beating the term EXPOSURE METHOD because people use different methods for choosing an exposure.

I try to tell people:

The sensor doesn't care what the ISO setting is - but usually the person choosing the exposure cares very much. It depends on the method they choose to use to choose that exposure. And MOST of the tools are in fact, effected by an ISO choice - light meter, histogram, monitor path.

So ... it doesn't change what the sensor records - but it changes MOST methods for choosing the aperture, shutter, filters that DO effect what the sensor records.

I actually HATE when people say "it's JUST meta-data" - as if it's meaningless - when in fact - it's CORE to understanding the fundamentals.

 

[Mark L. Pederson]

Sure, but it is not an age related thing. Speaking only of myself; I am not of a "younger generation". I do not have an advanced degree in photography or cinematography. I learned what I could in schools and through mentoring and believe that I have a pretty solid understanding of film. What I and I believe many others are lacking is confidence in what we know and perhaps a completeness of understanding. In a word, mastery.

Understood it's not about age - the generation comment was more based on what people have access to now vs. when I was young and wanted to make movies.

I am certainly NOT saying anyone needs "an advanced degree in photography or cinematography" in fact - I'm saying the opposite. You need to understand the very basics.

Setting Aperture / Shutter Speeds / Depth of Field / FOV / ISO / using a light meter / dynamic range / contrast ratios, etc. - and what all them do and effect.

You can't get to the mastery if you don't truly understand the basics. I'm sure that you do - but it is clear to me that a good number of folks are missing an understanding of at least some of the basic things.

 

[Elsie N]

...
I frequently used to underexposure MX (ie: High ISO) to soften my images and get a different and "fatter" kind of colors...

...

Gunliek, are you referring to the thickness of the histogram when you say fatter? I've noticed that sometimes I get a very thick readout and other times it is very slim. I always assumed it had to do with the amount of light hitting the sensor but your statement suggests it may have to do with ISO?

 

[David Battistella]

You know what is weird.

Since the very first day of owning a red (early adopter 758) and right up until today, the only place to see RAW view is in the camera.

You can not see raw view (or the specific RAW view lut) on anything other than the camera or camera monitoring devices. That means a DP uses that image as a reference image and will never have the chance to his reference image it again.

so maybe that needs to change, maybe it doesn't .

discuss...


battistella

 

[Gunleik Groven]

I agree with all that.

I try (knowingly) to distinguish "ISO" from "exposure" in what I write as
Exposure = photon hitting the sensor
ISO = interprets the sensor data into something viewable (part of that chain, I know, but an important one)

When I see all the requests for ISO tests, I get a bit pissed at times. Because I can make a noisy or noisefree image under "any" ISO, just by controlling the exposure.
One thing I want to do with the Bristol files, unless Geoff does that, is to normalize all the exposure in 1-stop increments to the base-exposure with ISO operations.
That way people can see what noise you get "a given ISO".

I am reluctant to do that though, because I can foresee the responses to the results. Because in doing that, high-ISO images will be noisy...
And people do not WANT the 6400 exposure to have more noise than the 200. And using all that energy telling people that this is actually "fantastic" and "proof that things work like they should", and that this does not make "Dragon bad in lowlight", is sometimes a drag...

They could download the files and postulate the results easily themselves, but I think it could be a useful thing to do, for those who can interpret the data.

Likewise I think it would be cool to do resampling tests to UHD and 1080, but some people do not get that "smoother" does not equal "noiseless".

Graeme had a nice little post on read-out-noise, which was very enlightening to me.
Read-out noise is equal at all exposures, but becomes a higher percentage of the total image at underexposures than "good" exposures.

Another thing that people do not seem to think too much about either is how the color hue/saturation-characteristics can change drastically under different exposure levels, even under the same light.


I would say I HATE when people say that ANY metadata is "just metadata".

Back when the R1 M came out, many used it as a video-cam. Even film-photographers. And I had files sent to me, being the "RED-geek".

One example I always remember was from a big-film set with enough lights and a 100 KW truck. They were filming an indoor night bar-scene. Typical cliches with dancing girls and all, and they wanted the scene to be blue.
They started off with WB'ing the camera (as they had tungsten-lights, right+), and then lit from the monitors.

They had all the gels and power in the world, but still they managed to seriously underexpose the blue-channel in a blue scene with more than enough lights available, because of metadata (in this case WB and ISO) misleading them in their exposure decisions.

This is vastly improved with the Dragon. It allows for a lot more "stupidity", but still intent wins over accident. And even though the files are incredibly more "better", you get further by doing it "right for your scene according to camera".
But for intent, you have to understand how it works...

Rant off...

 

[Gunleik Groven]

Gunliek, are you referring to the thickness of the histogram when you say fatter? I've noticed that sometimes I get a very thick readout and other times it is very slim. I always assumed it had to do with the amount of light hitting the sensor but your statement suggests it may have to do with ISO?

Nope.

i was referring to how the channels saturate.

The example posted above is an example of serious underexposure...

 

[Scott Crawley]

That means a DP uses that image as a reference image and will never have the chance to his reference image it again.

Load the shot back up into a mag and playback on the camera if you need to, though I am unsure why you would need to.

 

[David Battistella]

Not to practical three months later in a DI.

battistella

Load the shot back up into a mag and playback on the camera if you need to, though I am unsure why you would need to.