ART someone explain digital iso values to me

Divided Sky

Active Member
Sep 24, 2002
14,537
USA
so on film, the iso is physically the size of film grain, am i right?
on digital, how is iso determined? pixel clusters?

also, how is it that companies are making higher iso's better and better every year so that this year's 6400 is the same as last year's 3200 and the year before's 1600. will it just keep climbing? will we see cameras coming out next year with iso 12,800 with the same noise as this year's 6400?

and last, what does it mean when iso is "expandable to 12,800/25,600". is this marketing with no real applicable use like digital zoom (as opposed to optical zoom)?
 

michael

Florida Man, Esq.
Dec 21, 2001
112,539
The ether
Addressing your 2nd paragraph:

Technological advancements...how do they work??

Better, more advanced technology yields more impressive results at either the same price-point, size, ease of use, etc. That's like asking how did computers go from the size of a room to being a handheld device..
 

Marix

OT Supporter
May 23, 2006
27,969
I'm not an expert, but I think I have a basic understanding. The sensor runs at a set baseline sensitivity - usually ISO 100 or 200

And each ISO setting is basically supplying more voltage to the sensor to amplify it - hence the noise, which is from electronic heating etc. (Also explains overheating, hot pixels etc etc)

Noise is then controlled by trying to optimise the signal:noise ratio and reducing noise with processing.

"Expandable" ISO are basically settings where the manufacturer is saying "quality might suck, but we're offering it anyway." Partly for marketing, I'm sure. And kinda as a warning too. But those settings are genuinely useful sometimes. Definitely better than digital zoom.

It will keep improving yes, but is limited by electronic efficiency.. circuits are always going to generate heat and noise. Though processors now are so much more efficient and cooler than before.

You also get expandable low ISO too - down to 100 or 50. There is basically undervolts the sensor. Instead of noise, the consequence will be less dynamic range. On my camera, the expandable ISO100 loses about 1 stop from the highlights.
 
TS
TS
Divided Sky

Divided Sky

Active Member
Sep 24, 2002
14,537
USA
I'm not an expert, but I think I have a basic understanding. The sensor runs at a set baseline sensitivity - usually ISO 100 or 200

And each ISO setting is basically supplying more voltage to the sensor to amplify it - hence the noise, which is from electronic heating etc. (Also explains overheating, hot pixels etc etc)

Noise is then controlled by trying to optimise the signal:noise ratio and reducing noise with processing.

"Expandable" ISO are basically settings where the manufacturer is saying "quality might suck, but we're offering it anyway." Partly for marketing, I'm sure. And kinda as a warning too. But those settings are genuinely useful sometimes. Definitely better than digital zoom.

It will keep improving yes, but is limited by electronic efficiency.. circuits are always going to generate heat and noise. Though processors now are so much more efficient and cooler than before.

[]You also get expandable low ISO too - down to 100 or 50. There is basically undervolts the sensor. Instead of noise, the consequence will be less dynamic range. On my camera, the expandable ISO100 loses about 1 stop from the highlights.[/B]
thanks man, you always pull through with the quality info

thats really interesting the way iso works on digitals, esp the part on expanding it down :cool:

other than getting more grain for light sensitivity, digital iso is really no parallel to film iso then (in terms of the way it works), sounds like they couldve called it a completely different unit of measurement
 

Marix

OT Supporter
May 23, 2006
27,969
Addressing your 2nd paragraph:

Technological advancements...how do they work??

Better, more advanced technology yields more impressive results at either the same price-point, size, ease of use, etc. That's like asking how did computers go from the size of a room to being a handheld device..

Yes, but there are still limitations. Physics will always dictate that adding more pixels, more circuitry and more voltage will increase heat. Until we develop 100% efficient circuits with no heat output, you'll always have noise.
 

michael

Florida Man, Esq.
Dec 21, 2001
112,539
The ether
Yes, but there are still limitations. Physics will always dictate that adding more pixels, more circuitry and more voltage will increase heat. Until we develop 100% efficient circuits with no heat output, you'll always have noise.
I didn't say that wasn't true or that we were at the best technology we're going to be at..TS asked how things are getter better over time.. i told him that's how it works: things get better over time (typically).
 

michael

Florida Man, Esq.
Dec 21, 2001
112,539
The ether
other than getting more grain for light sensitivity, digital iso is really no parallel to film iso then (in terms of the way it works), sounds like they couldve called it a completely different unit of measurement

this.

they shoulda just called it "SS" for sensor sensitivity or something
 

Marix

OT Supporter
May 23, 2006
27,969
thanks man, you always pull through with the quality info

thats really interesting the way iso works on digitals, esp the part on expanding it down :cool:

other than getting more grain for light sensitivity, digital iso is really no parallel to film iso then, sounds like they couldve called it a completely different unit of measurement

Basically yeah. I've seen people on web forums already talking of changing that system.

Eventually, when ISO is excellent, we probably won't have ISO controls on cameras any more. Choose aperture and shutter, since they are the things which alter creativity of the shot and everything will be auto-ISO, which won't matter because you won't see noise anyway.
 

michael

Florida Man, Esq.
Dec 21, 2001
112,539
The ether
Basically yeah. I've seen people on web forums already talking of changing that system.

Eventually, when ISO is excellent, we probably won't have ISO controls on cameras any more. Choose aperture and shutter, since they are the things which alter creativity of the shot and everything will be auto-ISO, which won't matter because you won't see noise anyway.
liquid nitrogen cooled camera sensors :eek2:
 

MSIGuy

om nom nom nom!
May 30, 2005
4,705
And each ISO setting is basically supplying more voltage to the sensor to amplify it - hence the noise, which is from electronic heating etc. (Also explains overheating, hot pixels etc etc)
Not exactly. While heat is one part of the equation the real reason you see noise is the low signal to noise ratio recorded by the camera. Think about it this way, at insane ISO's you're recording a VERY small amount of light, that light is recorded from the sensor via an analog to digital convertor. The less light, the less signal there is for the ADC to convert to a signal, and within all electronics there is a certain level of electronic noise that's produced, and picked up by the ADC. That's why FF sensors tend to have better noise performance (other than the a850/a900 :mamoru: j/k) larger photosites, more light captured, more signal for the ADC to convert, higher signal to noise ratio.

The better the ADC's the better the higher the signal to noise ratio, the less noise. Reducing noise levels inside the camera will decrease noise levels too.
 

michael

Florida Man, Esq.
Dec 21, 2001
112,539
The ether
MSI: does the level of noise increase w/ the size of the sensor? and if so, I'm guessing the signal produced by the larger sensor increases at a higher rate than the noise does, otherwise you'd just continually get a larger image with the same proportion of noise since the signal:noise ratio would increase at the same rate.

so..if i'm right and the signal increases at a higher rate than the noise does, on a larger sensor, if they make sensors considerably larger than FF's, the SNR would continue to decrease and the "ISO" performance would get better and better..

yes? :embd:

just googling around, the Leica S2 with a sensor that's 56% larger than a standard FF..does it have better high iso performance?

clearly the efficiency, heat, ability to quell electronic noise will have an effect on picture quality..changing any of those variables for the better, while the other two remain the same should make for better photos in low light..


or the canon one that's 40x bigger than a 35mm ff.. http://www.thedigitalnewsroom.com/E..._40_times_larger_than_a_Full_Frame_sensor.htm
 
Last edited:

koolaids

OH YEAH
Jul 21, 2006
11,318
You also get expandable low ISO too - down to 100 or 50. There is basically undervolts the sensor. Instead of noise, the consequence will be less dynamic range. On my camera, the expandable ISO100 loses about 1 stop from the highlights.

i didn't know this :o

i always end up shooting at iso50 when i want to get the aperture as shallow as possible :o
 
TS
TS
Divided Sky

Divided Sky

Active Member
Sep 24, 2002
14,537
USA
Not exactly. While heat is one part of the equation the real reason you see noise is the low signal to noise ratio recorded by the camera. Think about it this way, at insane ISO's you're recording a VERY small amount of light, that light is recorded from the sensor via an analog to digital convertor. The less light, the less signal there is for the ADC to convert to a signal, and within all electronics there is a certain level of electronic noise that's produced, and picked up by the ADC. That's why FF sensors tend to have better noise performance (other than the a850/a900 :mamoru: j/k) larger photosites, more light captured, more signal for the ADC to convert, higher signal to noise ratio.

The better the ADC's the better the higher the signal to noise ratio, the less noise. Reducing noise levels inside the camera will decrease noise levels too.
:cool:
 

Wheezer

OT Supporter
Jul 1, 2002
1,621
Houston
so on film, the iso is physically the size of film grain, am i right?

Since everything else was answered. ASA (film speed) is the films sensitivity to light. Grain is a byproduct of higher speed films (or pushed film).

other than getting more grain for light sensitivity, digital iso is really no parallel to film iso then (in terms of the way it works), sounds like they couldve called it a completely different unit of measurement

They did, it was called ASA in film.
 

charles foster kane

New Member
Feb 14, 2007
93,467
Croatia
thanks man, you always pull through with the quality info

thats really interesting the way iso works on digitals, esp the part on expanding it down :cool:

other than getting more grain for light sensitivity, digital iso is really no parallel to film iso then (in terms of the way it works), sounds like they couldve called it a completely different unit of measurement
It's called the same thing because it's a standard, not a measurement, of light sensitivity

F/8 1/60th @iso100 is f/8 1/60th @iso100 on film or digital



In theory
 

Marix

OT Supporter
May 23, 2006
27,969
i didn't know this :o

i always end up shooting at iso50 when i want to get the aperture as shallow as possible :o

Me too! It doesn't matter so much- it just doesn't work *quite* as well for landscapes etc. I get more blown out highlights at the extended low ISO settings for the same exposure as ISO200 (which is the baseline ISO for my camera).
 

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