K5 - how high do you set "Auto iso"?

Just getting to grips with the K5 and for the first time ever of owning a Pentax I have the confidence to use the "Auto Iso" setting - I've never used it previously in the K10D or K20D as I always preferred to keep a good eye on the Iso setting.

Having just done a couple of rough & ready tests, nothing scientific, I'm certainly comfortable with setting it at 12800. Obviously if it's underexposed a bit of noise creeps in but with decent exposure I'd be pretty happy with it straight from the camera. 25600 definitely needs noise reduction but I think would be ok for smaller prints whilst I don't think 51200 is very useable, perhaps for an absolutely must have shot and it would need some heavy noise reduction.

On this basis I'm going to start with a max iso of 12600 until I get chance to do some "real world" testing. I'm interested to hear others thoughts on this?

Simon

It depends on what mode. I base my settings on DXOMark tests since I do RAW almost exclusively.
Portrait: 5000 (keep Color Sensitivity above red dotted line)
Action: 8000 (SNR above red dotted line)
Normal: 12800 (Tonal Range above red dotted line)
Landscape: 2500 (DR above 8 bits; < 8 bits = may as well do JPEG) but most of the time fixed at 80

I think it's wise to set the MAX auto ISO to the highest ISO where you find the noise acceptable.

I now have mine set as 80-3200 that is good enough for most condition.

Also the the sensor doesn't go higher as 3200 ISO i believe so the other ISO settings are done by the firmware/software of the camera and not the sensor.

I only just have mine K5 but would like to test if you can get a 2 stop under expose ISO 3200 photo to look like a normal expose ISO 12800 photo with the help of software on the computer.

I believe ISO 3200 is ISO 1600 pulled up by 1 stop by "software". There's probably a reason Pentax performs RAW noise reduction (which cannot be turned off) only from ISO 3200.

Whilst it's great to have the confidence of using auto iso at last I'm only likely to use it for general use anyway so my initial impressions are that Iso 12800 shouldn't have too negative an effect on the shots I'm likely to be taking (travel photos etc), for tripod mounted landscapes I'll always be using Iso 80 for maximum DR and whilst hiking and using a monopod I'll still prefer to control it manually to keep it nice and low.

I did try a few shots @3200, 6400 & 12800 which were deliberately underexposed and when corrected in Photoshop only the 3200 shots were acceptable - as ever it's still going to be important to achieve good exposure in order to avoid unsightly noise - the K5 sensor is good but it's no miracle worker!!

You should go back in time 6 years of show with the k5, i'm sure they will find it a miracle worker...

I leave mine set to max range - 80 to 51200.

If I encounter a situation where I need to specify the ISO to avoid it going too high I do so.