[wim]

Hi Serkan,

[quote name='PuxaVida' date='18 July 2010 - 04:11 PM' timestamp='1279462319' post='1095']

AFAIK, the noise issue has many aspects in digital photography. There's more behind the fact that most of us know; area of photosites, which effects the result in raw data. Of course it begins with the light sensitive area. Think of pixels as buckets to collect photons from rain of light. [/quote]

Except that these buckets are leaky, as in, having holes on the sides, IOW, partly spilling into adjacent buckets. This is one of the areas of great headaches, I think. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='' />

If the bucket is big and there are enough number of photons in it, you start the high ISO race with an advantage. But then the A/D converter must count them correctly and try to find the (almost) perfect RGB value for each pixel (interpolating / demosaicing). If the quality of count and finding correct values is not ok, then this usually leads to noise in the raw data. I believe that 14 bit A/D converters can be more helpful than the 12bits, but in the end most of the images are published as 8 bit JPEGs. So if you have high gamut monitor and you don't like sharing your images on the net, go for the high bits and see them in your terrific monitor.

This is where Zone-system type photography and/or HDR comes in. It does require a lot of learning and a lot of extra work, however <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='' />

The D3 and 5D MKII are the best examples regarding the facts mentioned above. Noise in the final raw data has many dependencies, and only some of them are known to us "regular users".

Agreed.

PS: In the astrophotography, Thom Hogan thinks that the Canons has the advantage because of the even distribution of noise values (like bell-shape around value zero) by the A/D converter. So the noise is distributed equally to either side of 0 value. According to him, this allows proper stacking of multiple images to extract the real image. OTOH, Nikon truncates the noise through its A/D converter, so that an uneven distribution is produced... I don't know why Nikon does it and how are the actual effects but this info comes from a Nikon speacialist.



Best regards,



Serkan

Well, it does look like the in-camera Nikon AD conversion process sets values below a certain threshold to zero, thus eliminating a lot of noise, and thus distorting the noise distribution curve, but also wiping out a lot of very fine astro-information in de case of astrophotography, and of course simultaneously increasing the DR in a fashion that to me looks rather artificial. Setting, e.g., the lowest two bits to black (zero value), provides a seemingly two stop noise and DR advantage immediately <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='' />. The exact process and how it is done, and what the actual algorithm used is (more complicated for sure than the simple form I mention here) I don't know either, obviously <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='' />. I think it is very clever, just a pity that it is done prior to saving the Raw file, rather than as a very effective noise reduction method for jpeg generation.



Kind regards, Wim