FIGHTING AGAINST NOISE or how to get all out of RED

[Kim Frank]

Hi Greame...
Speaking in terms of the ZONE SYSTEM, 18% grey should stay in Zone 5.
Is that also correct for the RED, or why do I often read, that one should
set the ISO of a lightmeter lower than 320?
Does that mean 18% grey stays in Zone 6 on a RED?

 

[Graeme Nattress]

You should aim to expose to the right. See Jim's thread for details.

You can't be dogmatic about where you put mid grey. Exposure is all about mapping the dynamic range of the scene (which is obviously totally dependent on what you're shooting) to the DR of the sensor. You should ensure that the most important tones in the image are exposed as brightly as possible (ie, ETTR) but being aware that you should not clip highlights unnecessarily. Getting that balance right, is the art of exposure.

Graeme

 

[Rich Schaefer]

Zone System Baby!!!!

http://en.wikipedia.org/wiki/Zone_system

Prost,
Rich

 

[DS Williams]

Can someone clarify..

is noise caused by random photons bouncing around in the sensor, or random electrons bouncing around in the electronics..

 

[Graeme Nattress]

Noise is not caused by random photons bouncing around the sensor.

Thermal noise is a source of noise, but a small one. There is also photon noise, but this is due to the random nature of the light hitting each pixel, not light bouncing around between pixels. Then there is read noise, which is the noise you get from the process of reading the value of a pixel.

Graeme

 

[DS Williams]

Noise is not caused by random photons bouncing around the sensor.

Thermal noise is a source of noise, but a small one. There is also photon noise, but this is due to the random nature of the light hitting each pixel, not light bouncing around between pixels. Then there is read noise, which is the noise you get from the process of reading the value of a pixel.

Graeme

Thank you Graeme, That other user confused me a bit. I'm glad you set things straight.

Anyway, is read noise generally caused by random electron movement within the sensor? I know it interferes with precision quantizing at a certain minimum signal level

 

[Graeme Nattress]

You're asking the wrong guy. I'm not a sensor guru - I only get to play one on television.

Graeme

 

[Antoine Baumann]

@Vigen: Doesnt a DPX file have less bits than a TIFF?

@mmost: I thought the sensor would record linear - more details in the highlights -
why should I compress them turning into DPX?

Tiff can be 8, 16 or 32 bit. Dpx is very oftently 10bit (although could be more, at least that's what I heard, but only ever used 10bit dpx) and is 10bit in red application, not sure about scratch. Tiff in red application is 16 or 32 bit.

Sensor record linear, but human vision system is kind of log, and we certainly see way more difference in the shadows-mid than in the highlights, that is way you "compress" them when going 12 bit to 10 bit, because that's where you won't see the difference.

cheers,
antoine.