ISO ranges and low iso, techies please look.

Gooshin · 09-09-2009, 07:13 AM

I am not an engineer and therefore do not know

but why do many cameras limit themselves at ISO100, or even 200.

Why is it that our sensors cannot match the ISO equivalent of 25, or lower?

is there a technical/physical limitation?

my friend mentioned something about a sensors range of possible sensitivies, and that if you make the native sensitivity too low, amplyifying it for a higher iso would become difficult. And since the majority of people up the iso rather than lower it, it only makes marketing sense.

but there ARE times when i would like to drop down to 50 or 25 (broad daylight + wide open lens)

I understand that a very simple solution is to get an ND filter... but i'm just curious about the "why".

thanks,

**DAZ** · 09-09-2009, 08:07 AM

It has to do with noise. Most camera manufacturers’ list the lowest ISO that is the closest to the standard ISO with the lowest noise (with some measurement error and fudge factors). To go lower just gives more noise. Yes a higher ISO gives more noise but there is not really any other way when you what more sensitivity but to go lower you can use a ND filter and not get any more noise.

DAZ

Marc Sabatella · 09-09-2009, 08:11 AM

A sensor has one and only one "native" ISO - that is, it only actually collects photon at one given rate. All higher ISO's above that are created by amplifying the results collected at the native ISO. The more amplification, the more noise. A lower native ISO means more amplification is required to get to, say, ISO 1600. Meaning it's likely to be noisier at ISO 1600 than an otherwise-similar sensor with a higher native ISO.

And there's no good way to "de-amplify" the results collected at native ISO in order to simulate lower ISO. A shutter speed slow enough to get a good exposure at ISO 25 would clip at the native ISO of 100 or 200. I gather some cameras have implemented some sort of magic to get around this, but it's probably more work than it's worth given that a ND filter solves the problem nicely.

audiobomber · 09-09-2009, 08:27 AM

So then the K100D has a native resolution of ISO 200 and the K20D has a native resolution of ISO 100?

Personally I'd give up ISO 100 for better high ISO performance on my K20. If I'm using auto ISO, I usually start it at ISO 200 anyway, because I want to keep the shutter speeds up. I've not noticed a difference in quality between ISO 100 and 200.

**DAZ** · 09-09-2009, 08:53 AM

Originally posted by audiobomber

So then the K100D has a native resolution of ISO 200 and the K20D has a native resolution of ISO 100?

Personally I'd give up ISO 100 for better high ISO performance on my K20. If I'm using auto ISO, I usually start it at ISO 200 anyway, because I want to keep the shutter speeds up. I've not noticed a difference in quality between ISO 100 and 200.

The difference in noise and DR between ISO 100 and 200 is small but measurable. To some it is an issue to others it is not.

DAZ

Gooshin · 09-09-2009, 09:15 AM

according to DxO, the K20D has the most DR at 100, dropping by nearly one point at 200.

however you wont see this unless you are shooting outside.

audiobomber · 09-09-2009, 10:45 AM

Originally posted by Gooshin

according to DxO, the K20D has the most DR at 100, dropping by nearly one point at 200.

however you wont see this unless you are shooting outside.

If there's a lot of sky in my photos, I use the extended DR setting, which loses ISO 100 anyway.

Damn Brit · 09-09-2009, 07:37 PM

Moved to Everything Else.

09-09-2009, 07:13 AM	#1
Gooshin Veteran Member Join Date: Sep 2007 Location: Toronto, the one in Canada. Posts: 5,610	ISO ranges and low iso, techies please look. I am not an engineer and therefore do not know but why do many cameras limit themselves at ISO100, or even 200. Why is it that our sensors cannot match the ISO equivalent of 25, or lower? is there a technical/physical limitation? my friend mentioned something about a sensors range of possible sensitivies, and that if you make the native sensitivity too low, amplyifying it for a higher iso would become difficult. And since the majority of people up the iso rather than lower it, it only makes marketing sense. but there ARE times when i would like to drop down to 50 or 25 (broad daylight + wide open lens) I understand that a very simple solution is to get an ND filter... but i'm just curious about the "why". thanks,

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09-09-2009, 08:07 AM	#2
DAZ Loyal Site Supporter Join Date: Sep 2006 Location: Everett, WA USA Photos: Gallery Posts: 744	It has to do with noise. Most camera manufacturers’ list the lowest ISO that is the closest to the standard ISO with the lowest noise (with some measurement error and fudge factors). To go lower just gives more noise. Yes a higher ISO gives more noise but there is not really any other way when you what more sensitivity but to go lower you can use a ND filter and not get any more noise. DAZ

09-09-2009, 08:11 AM	#3
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	A sensor has one and only one "native" ISO - that is, it only actually collects photon at one given rate. All higher ISO's above that are created by amplifying the results collected at the native ISO. The more amplification, the more noise. A lower native ISO means more amplification is required to get to, say, ISO 1600. Meaning it's likely to be noisier at ISO 1600 than an otherwise-similar sensor with a higher native ISO. And there's no good way to "de-amplify" the results collected at native ISO in order to simulate lower ISO. A shutter speed slow enough to get a good exposure at ISO 25 would clip at the native ISO of 100 or 200. I gather some cameras have implemented some sort of magic to get around this, but it's probably more work than it's worth given that a ND filter solves the problem nicely.

09-09-2009, 08:27 AM	#4
audiobomber Veteran Member Join Date: May 2008 Location: Sudbury, Ontario Photos: Albums Posts: 6,806	So then the K100D has a native resolution of ISO 200 and the K20D has a native resolution of ISO 100? Personally I'd give up ISO 100 for better high ISO performance on my K20. If I'm using auto ISO, I usually start it at ISO 200 anyway, because I want to keep the shutter speeds up. I've not noticed a difference in quality between ISO 100 and 200.

09-09-2009, 08:53 AM	#5
DAZ Loyal Site Supporter Join Date: Sep 2006 Location: Everett, WA USA Photos: Gallery Posts: 744	Originally posted by audiobomber So then the K100D has a native resolution of ISO 200 and the K20D has a native resolution of ISO 100? Personally I'd give up ISO 100 for better high ISO performance on my K20. If I'm using auto ISO, I usually start it at ISO 200 anyway, because I want to keep the shutter speeds up. I've not noticed a difference in quality between ISO 100 and 200. The difference in noise and DR between ISO 100 and 200 is small but measurable. To some it is an issue to others it is not. DAZ

09-09-2009, 09:15 AM	#6
Gooshin Veteran Member Join Date: Sep 2007 Location: Toronto, the one in Canada. Posts: 5,610 Original Poster	according to DxO, the K20D has the most DR at 100, dropping by nearly one point at 200. however you wont see this unless you are shooting outside.

09-09-2009, 10:45 AM	#7
audiobomber Veteran Member Join Date: May 2008 Location: Sudbury, Ontario Photos: Albums Posts: 6,806	Originally posted by Gooshin according to DxO, the K20D has the most DR at 100, dropping by nearly one point at 200. however you wont see this unless you are shooting outside. If there's a lot of sky in my photos, I use the extended DR setting, which loses ISO 100 anyway.

09-09-2009, 07:37 PM	#8
Damn Brit Guest	Moved to Everything Else.