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Author Topic: Noise levels on Sony Alpha and Canon 5DII  (Read 7445 times)

madmanchan

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Noise levels on Sony Alpha and Canon 5DII
« Reply #20 on: December 08, 2008, 08:38:17 am »

Nick, all the Canon files are losslessly compressed with the result being that smooth images are small and high-variance images are big. At ISO 100, an image of tree bark (lots of fine detail) will be much bigger than an image of blue sky. For a fixed subject, the variance goes up with higher ISO, so the file size goes up too. i.e., in general higher ISO --> bigger files.
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Eric Chan

douglasf13

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Noise levels on Sony Alpha and Canon 5DII
« Reply #21 on: December 08, 2008, 11:47:17 am »

Quote from: Max Penson
I've tested the numbers between D300 12 bits and 14 bits. As expected, there is a difference. You have naturally less noise with 14 bits and a bit more DR, which is probably insignificant with basic image processing. But, noise reduction on 14 bits apposed to 12 bits could make a big real world difference. Also, algorithms like shadows/highlights will show better toning on 14 bits. Anything the does extreme processing will benefit from 14 bits, even less noise after basic gamma.

Those results aren't in question.  The issue is that it may not have anything to do with 14bits, but rather it's just an oversampling, and that's why it's cleaner(and why it takes longer to process.) Emil can weigh in here for a techical explanation of what I'm referring to
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Panopeeper

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Noise levels on Sony Alpha and Canon 5DII
« Reply #22 on: December 08, 2008, 02:23:18 pm »

Quote from: Nick Rains
What's odd here is that the A900 files are ALL about 25mb. The Canons vary a lot more, my 5D can be between 9 and 15mb depending on subject matter. When I tested the A900 a few months back I was surprised to see how they varied in size by only about 1mb must be a very different compression algorithm.
Of course the file sizes are almost equal. The only difference in the file size comes from the embedded JPEG, which is around 500 KB for the A700, depending on the scenery and noisiness.

The A700/A900 lossy raw data is not compressed, thus its length is always 4288x2856 bytes for the A700 and 6080x4048 for the A900. The compression of the original raw data is achieved by just the lossiness. This is in contrast to the Nikons, which compress the lossy data as well (but the lossiness is much less with the D3 and D300 than with the A700 and A900).
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Gabor

Plekto

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Noise levels on Sony Alpha and Canon 5DII
« Reply #23 on: December 08, 2008, 04:36:55 pm »

Still, it isn't exactly a clear-cut case as I noticed that the Sony has less jaggies/pixelation on the edges of objects(as would be expected).  Also, ISO3200 isn't something that I'd use more than once every few months.  But I do desire more resolution more often, so there has to be a weighting towards the higher resolution image, IMO.  

Yes, it would be better if it were 14 bit, but the colors are very good and when you come back down to ISO 800 or lower, it looks very nice.

http://www.cameralabs.com/reviews/Sony_Alpha_DSLR_A900/
This site has some examples of the NR on it - and you can see how great a difference it makes at each level.  I actually prefer the NR on the highest setting myself(usually I don't - go figure).

« Last Edit: December 08, 2008, 04:48:25 pm by Plekto »
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Max Penson

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Noise levels on Sony Alpha and Canon 5DII
« Reply #24 on: December 09, 2008, 03:56:44 am »

Quote from: douglasf13
Those results aren't in question.  The issue is that it may not have anything to do with 14bits, but rather it's just an oversampling, and that's why it's cleaner(and why it takes longer to process.) Emil can weigh in here for a techical explanation of what I'm referring to


Well, I guess that by oversampling you mean that Nikon simply maps 12bit data from the ADC to 14bits. Right? Based on the fact the D300 drops frame rate when set on 14 bit to 2.5 FPS, I'd say it is true 14 bits out of the ADC.
« Last Edit: December 09, 2008, 03:58:35 am by Max Penson »
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Slough

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Noise levels on Sony Alpha and Canon 5DII
« Reply #25 on: December 09, 2008, 08:18:47 am »

Quote from: Max Penson
Well, I guess that by oversampling you mean that Nikon simply maps 12bit data from the ADC to 14bits. Right? Based on the fact the D300 drops frame rate when set on 14 bit to 2.5 FPS, I'd say it is true 14 bits out of the ADC.

I don't understand what is meant. As I understand it, a film scanner can perform multiple readings of the same region (i.e. pass light through again and read the signal) and averaging these readings will reduce the random noise.

I doubt the D3x camera repeatedly re-exposes the sensor. So presumably the sensor is exposed, and charge builds up. Then maybe they try reading the charge in each sensor pit 4 times in order to halve the noise associated with the read path. So maybe a 12 bit read path but read multiple times to reduce noise. Who knows.
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