What is this fascination with iso6400?

Started Feb 11, 2013 | Discussions thread
dosdan Contributing Member • Posts: 534
Re: This is

mike703 wrote:

Pentax K-01, which has the same sensor as the K-30: it is a 12-bit version of the 14-bit Sony sensor used in the K5 series and the Nikon D7000 (amongst others).


I've got a K-5 & K-01.

Here are the 3 sensors mentioned:

http://www.dxomark.com/index.php/Cameras/Compare-Camera-Sensors/Compare-cameras-side-by-side/%28appareil1%29/811|0/%28brand%29/Pentax/%28appareil2%29/783|0/%28brand2%29/Pentax/%28appareil3%29/676|0/%28brand3%29/Pentax

www.sensorgen.info does not have a good coverage of Pentax sensors, but once you get up a bit above base ISO, the situation with 12-bit will be not that much different from the K-5.

I would suggest trying an experiment with the K-01.

Select a scene that has a bright source and darker stuff, say a shaded bedside lamp and stuff on a bedside table or wall.

Use a tripod if you have one.

Shoot in M mode.

Shoot in raw (DNG) mode.

Switch off Auto-ISO and set the ISO to ISO400

Use the E-dial to set the shutter speed.

Use the Ev-Comp button in conjunction with the E-dial to set the aperture.

Use the meter to bring the exposure up to the 0 level.

Say the shutter needed for this is 1/200s.

1. Take a shot (#1: EV0)

Now drop the shutter speed to 1/100s

2. Take another shot. (#2: EV-1). Normally you'd boost the ISO to ISO800 to compensate, but we'll underexpose 1 stop instead.

Drop the shutter speed to 1/50s

3. Take another shot (#3: EV-2)

Drop shutter speed to at 1/25s

4. Take another shot (#4: EV-3)

Drop shutter speed to 1/13s

5. Take a final shot (#5: EV-4)

Now load these 5 DNG files in RawTherapee. It's slow, but you need to perform these tests in RT because it provides a large adjustment range without "'optimisations" which will vary other settings in an unexpected manner.

Use the Exposure control in RT to boost the EV in PP going from 0 in #1 up to +4 EV in #5.

A. First round of adjustments: see if there's much difference in the noise in the dark parts of the scene after EV adjustment. I suspect #2 to #5 will be close. Probably #1 too.

B. Second round of adjustments: now play with the a custom Tone Curve and later, Highlight Recovery Amount & Highlight Reconstruction (Blend) to see how well you can portray the bright bits around the lampshade. I suspect you have more success in the more underexposed images. Don't just simply bring up the Exposure control as you'll saturate the highlights, which were captured OK, when rendering, but experiment with ways to render what's there successfully.

Dan.

 dosdan's gear list:dosdan's gear list
Pentax K100D Super Pentax K20D Pentax K-5 Pentax K-01 Pentax K-3 +1 more
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