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Old May 2, 2008, 2:33 PM   #1
Barry in Dallas's Avatar
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Having just upgraded from the k100d to the new k200d, I'm still curious why Pentax took away the ISO 3200 setting and replaced it with the lower ISO 100, they should have had both on this model. The k100d took some amazing printable shots at 3200,best I've seen.I do like like sharpness in my pics and ISO 100 is most welcome but Pentax, give us the best of both worlds without shelling extra bucks for a K20 . I'm not a computer programmer but could this be corrected with a firmware update?
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Old May 2, 2008, 4:22 PM   #2
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Hi Barry,

I'm no engineer, so this explanation might have some (or a lot) of technical mistakes, so take it for what it's worth.

ISO sensitivity range is tied to the sensor. The lowest sensitivity value is almost always the "native" value of the sensor, and will give you the best IQ. The Sony CCD used in the K200 is the same as was used in the K10 with a native ISO of 100, and the higher values are "pushed" by amplification of the signals from the "native" output. The highest value is the farthest that the designers can push the sensor and still retain a minimum level of IQ that they have established (where noise is generally viewed as at a level that is only acceptable in "emergencies").

The 6 MP Sony CCD sensor of the K100 has a native ISO value of 200, and could be pushed to 3200 (four stops) before noise reached a level that bordered on totally unacceptable. This amplification is done in the A/D (analog to digital) converter, and is then processed by the image processing engine in the camera.

A CMOS sensor like the Samsung in the K20 is different in that it has additional processing circuitry built into the sensor chip for each individual photo site. The variations in photosite output when amplified (noise) produced by pushing the sensitivity is a bit more easily controlled in this techology, so it can be pushed about one stop farther before the noise becomes unacceptable. The native sensitivity is 100 and the highest "normal" push is to 3200 with 6400 available for emergency use. AFAIK, this 6 stop range available in camera is about as wide as you'll find in an APS-C sized sensor.

You can, however, push your camera further as bahadir showed in this thread:


where he deliberately underexposed his K10 ISO 1600 shot by 2 stops, then used editing software to brighten the image and noise removal software to clean up the image. This gave him an effective sensitivity of ISO 6400 with pretty good results. I think it's pretty safe to say that this cannot always be counted on to give an acceptable result, as each image has its own characteristics, but it can always be tried in a pinch.

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Old May 2, 2008, 10:28 PM   #3
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What Scott said (at least that's my understanding).

I wasn't surprised that they didn't put ISO3200 on the 10 mp sensor - in general when you increase the number of pixels, you also increase the noise (my 5 mp Sony F717 had much less noise than the 8 mp (IIRC)Panny FZ30 I bought to replace it). As Scott pointed out, CMOS sensors operate differently and have less noise.
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Old May 2, 2008, 10:40 PM   #4
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Thanks Scott and Mtngal,
I made the switch from being a full fledge Fuji supporter to Pentax after I seen what Fuji has done over the last few years. My last cam (an s8000fd) seemed great at the time, it had everything I wanted..a large 18x zoom and the ISO went up to an amazing 6400 all in a small easy to hold package. I should have waited for the reviews, noise was apparent at even 200 ISO and 1600 and up was almost useless, you can't even add filters..UGH.
I had my heart set on getting the new Fuji s100fs with it's 14x zoom and 14MP. But after seeing review after review pointing out it's horrible CA and PF, I said no way especially after sticker shock set in ($795) I got my k200d with a Sigma 70-300mm zoom for about the same price at Amazon. No more bridgecams for me

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