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01-10-2007, 07:54 PM   #1
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Native ISO in the K10D

I just read an article about ISO in digital cameras. It explained that each sensor has a native ISO and when we increase it we are just turning up the gain and therefore introducing noise. Well we all kind of knew that. The part I found really interesting is that when we shoot below the native ISO of the sensor the camera throws out info in post processing of the data. That is data from the sensor enters the image processor and is lost to make the lower ISO. The article goes on to suggest that because of this, the lower ISO settings (below native ISO) don't really produce a good an image as the camera is capable of. They suggest shooting at the native ISO and not going to much above that.

My question is what is the native ISO of the sensor in the K10D. As most of my shooting is done with studio lights, I can shoot at that ISO with out any concern for lack of light.

01-10-2007, 08:09 PM   #2
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i am reasonably certain the k10 is iso 100 and the k100 is iso 200.. i dont think u get the option of going below native..

trog
01-10-2007, 08:09 PM   #3
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QuoteOriginally posted by Michael Rothman Quote
I just read an article about ISO in digital cameras. It explained that each sensor has a native ISO and when we increase it we are just turning up the gain and therefore introducing noise. Well we all kind of knew that.
I think that is pretty much true.

QuoteOriginally posted by Michael Rothman Quote
The part I found really interesting is that when we shoot below the native ISO of the sensor the camera throws out info in post processing of the data. That is data from the sensor enters the image processor and is lost to make the lower ISO. The article goes on to suggest that because of this, the lower ISO settings (below native ISO) don't really produce a good an image as the camera is capable of. They suggest shooting at the native ISO and not going to much above that.

My question is what is the native ISO of the sensor in the K10D. As most of my shooting is done with studio lights, I can shoot at that ISO with out any concern for lack of light.
I don't understand how you can shoot below the native ISO of the sensor. If your sensor natively has a sensitivity of ISO 100, and you shoot at ISO 50, you are going to dump 2x the light into the sensor vs. what it can handle. That means you're going to fill up all the CCD cells with 2x the photons that they can handle, and every photon that doesn't fit will get lost (clipped). So I don't think it's possible to shoot below the native sensitivity of the sensor without blowing out all the highlights.

Can you point us to the article in question so that we can see what you're referring to? I must be missing something.

-- Michael
01-10-2007, 08:16 PM   #4
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Lowest ISO by definition. For K10D that would be ISO 100. The article was probably talking about simulating lower sensitivity, which no DSLRs are doing as far as I know. The problem is that you reduce dynamic range since sensor gets overexposed for all lower than native ISO, which is also reported by Pentax engineers in their explanation on why ISO 50 has not been implemented (although initially supported in K10D).

The part about high ISO is correct: it is increased amplifier gain or software ISO boost which I have proved by doing several experiments I called "digital push processing". See more details if you are interested here:

ISO 200 push processed to ISO 1600:
http://i16.photobucket.com/albums/b26/iglisin/linked/ISO200to1600.jpg

ISO 200 push processed to ISO 3200:
http://i16.photobucket.com/albums/b26/iglisin/linked/ISO200to3200.jpg

01-10-2007, 10:12 PM   #5
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The article is in the May June '06 Digital Photo Pro. Page 130. by Mike Stensvold

"If you set a lower ISO than the sensor's native sensitivity, the camera's image processor adjusts the image data after the A/D converter converts it to digital form. In the process, the dynamic range is reduced. So it is best to shoot at the sensor's native ISO whenever possible."

This is what i.glisin stated about the dynamic range, but I do not think the lowest ISO listed on the camera is the native ISO, just what the processor will lower it to.
01-11-2007, 05:44 AM   #6
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QuoteOriginally posted by i.glisin Quote
Lowest ISO by definition. For K10D that would be ISO 100. The article was probably talking about simulating lower sensitivity, which no DSLRs are doing as far as I know. The problem is that you reduce dynamic range since sensor gets overexposed for all lower than native ISO, which is also reported by Pentax engineers in their explanation on why ISO 50 has not been implemented (although initially supported in K10D).

The part about high ISO is correct: it is increased amplifier gain or software ISO boost which I have proved by doing several experiments I called "digital push processing". See more details if you are interested here:

ISO 200 push processed to ISO 1600:
http://i16.photobucket.com/albums/b26/iglisin/linked/ISO200to1600.jpg

ISO 200 push processed to ISO 3200:
http://i16.photobucket.com/albums/b26/iglisin/linked/ISO200to3200.jpg
I believe that one (or more?) of Canon's very expensive high end cameras can be shot under it's native sensor of ISO 100.
I can't remember where I read it, but the conclusion is that there wasn't any advantages to going under ISO 100

randy
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