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5 Days Ago   #1
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ISO invariance for Pentax DSLR cameras?

Are the Pentax cameras with invariant ISO or not? What are the native ISO values and what are the simulated ones?
It would be interesting to know for KP, for example, a camera with APS-C sensor that performs at high ISO values.

5 Days Ago - 1 Like   #2
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The Sony Exmor sensors are ISO invariant. Here is a discussion on the topic (with a number of good links) - not necessarily with respect to the KP.
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Thanks for the links, useful information though I am not passionate about astrofotography (still ).

I'm still curious about KP what ISO values are "real" and what are "simulated"?
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My K01 and my K1 are certainly Iso invariant. Now almost all the time my K1 is set to base Iso (100).
Iso invariance - PentaxForums.com

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QuoteOriginally posted by edri Quote
I'm still curious about KP what ISO values are "real" and what are "simulated"?
I am not sure what the relevance of this is to a truly Iso invariant sensor?
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QuoteOriginally posted by edri Quote
I'm still curious about KP what ISO values are "real" and what are "simulated"?
Setting ISO is basically telling the camera's processor how much to mathematically amplify the digital output from the sensor's processor. The sensor itself is supplied a variable bias voltage to compensate for different light intensities and the bias voltage is determined by the sensor's processor according to instructions from the camera designers. Like any electronic device, analog performance is not perfectly constant, but the sensor's processor can compensate for that and in effect all ISO settings are artificial.

The people designing Pentax cameras know more about the performance characteristics of the both the light meter and image sensors put in their cameras than any of us do. Extending the range of allowable ISO settings involves tradeoffs, at the high end a decision is made as to how noisy acceptable images can be (and with the KP's special in-camera noise reduction processing, how much detail can be lost while still being acceptable) and at the low end, in order to offer lower ISO settings, either losing details (by "compressing" the sensor's output) or making high ISO settings noisier than they would be if the "base" ISO was higher. Either way, it's a marketing decision implemented by engineers.

The programming of the sensor and the camera combine to produce the best results at the ISO settings that the camera designers decide should produce the best results. Different cameras using the same sensor will perform differently, depending on how well the programmers compensate for varying physical characteristics of the image and light meter sensors, as well as the decisions made regarding tradeoffs of details retained versus minimum and maximum ISO settings. What are "real" and "simulated" ISO values is subjective and if you don't find images taken at certain ISO settings to be acceptable, don't take images at those ISO settings. Unless you can manipulate instantaneous light intensities, selecting preferred shutter speeds and apertures should come before selecting preferred ISO settings, because the alternative is not taking an image, period.
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