Originally posted by Ishpuini Very interesting question. I'm particularily interested in seeing the difference between ISO80 on the K-5, ISO100 on the K-5 and ISO100 on the K-7. Esp in terms of DR.
ISO80 being an extended mode, and ISO100 being the sensor's native sensitivity, makes me wonder whether ISO80 will have better DR or not. I would guess not. Overexposing by 1/2 stop compared to ISO100 would mean that full pixel capacity would be reached 1/2 sooner at ISO80, reducing highlight DR by 1/2 stop, no? Unless Pentax/Sony pulled a trick to artificially increase pixel capacity in ISO80?
For me ISO80 is about longer exposures for land/cityscapes, which generally have large DR and more specifically often feature highlights (the white of the foam in a waterfall, the headlights of cars in a nightly cityscape, ...). Having 1/2 stop less DR would make ISO80 less interesting for this than ISO100...
Looking forward to finding out...
Actually, according to GordonBGood, ISO80 is closer to the base/native sensitivity of the Sony Exmor HD APS-C sensor used in the K-5, and explains the better IQ at ISO80 vs. ISO100.
Since there seems to be quite a bit of interest in this topic, here is the conversation from the other forum (my apologies if linking like this is frowned upon):
Re: Stunning k-5...: Pentax SLR Talk Forum: Digital Photography Review
Reading further into Gordon's comments, the DR of the K-5 at ISO800 beats the K-7/K20D at ISO100 (this has been confirmed by him in a different thread).