10D: Lower noise from jpg than raw at high iso levels?

[mike kelly]

The current UK edition of Photography Monthly magazine has a review of the 20D that

includes a chart of noise levels for both RAW and JPEG files at different ISO settings for the

20D, 10D and 1D. What is most noticeable is that RAW produces consistently lower noise

levels than JPEG at ISO 100 > 800, but massively more noise than JPEG at ISO 1600 and

3200 (on the 10D in particular).

 

This surprised me, but I took a chance shooting football photos at ISO 1600 in poor light

conditions this weekend and went with JPEG. I was surprised by the low noise levels

compared to a similar event last year when I shot RAW and converted through C1.

 

Is this a well known effect that I was unaware of? Any other experiences from the floor?

[digitmstr]

Very interesting. For some reason, I have only been using raw with lower ISO 100-400 anyways. Mostly, I guess, because if I did a shoot that "neede" RAW conversion it's usually been a slower, more deliberate type of Studio or interior shoot.

 

I will have to try what you suggest and see if I get the same results as you did with C1 PRO. I can't think of why the program would increase the noise levels though...

[charlie_vigue]

Maybe the DCT compression throws away the high frequency noise? It is lossy, after all.

[mike kelly]

The article says the test they did was baased on a 30 second exposure in total darkness,

then noise assessed using the Photoshop histogram feature.

 

My guess is not that C1 would increase the noise, but that the in-camera jpeg algorithm is

effective at reducing it.

[david_kieltyka]

The amount of noise in a RAW conversion is controllable by the converter. The magazine

in question could simply apply more NR during conversion if they wanted to. Note that the

JPEG is converted from the same RAW data...there's noting inherently less noisy about a

high ISO JPEG compared to a high ISO RAW. The JPEG has just been processed more

aggressively.

 

-Dave-

[jbq]

What are the "RAW" files that they compare? A fair comparison would be to compare JPEGs of the same size, to measure the difference between pictures compressed in-camera and on PC, and to couple the noise measurements with MTF measurements.

[todd_west]

<p><i>The JPEG has just been processed more aggressively.</i></p>

 

<p>Yep. Specifically, what JPEG does is take 8 by 8 blocks of pixels and drop the high frequency information. Given sufficent noise, JPEG will result in a net rejection of noise rather than injecting it.

 

<p>If you think this is a oversimplification of energy compaction and coding weights of a cosine basis, you're right. But then, you didn't need to read this explanation, did you? :-)

[x]

And in addition to what's already been said, as more aggressive noise reduction takes place you lose an increasing amount of detail, plus on top of that the Jpeg removal of detail. Far better to use say, the PC CS Raw converter with minimal noise reduction to create a TIF file. Then use Noise Ninja to take the noise out. Then use PS to put the final image together. I find that the best solution is a blend of the noise-reduced and original images. Sometimes you need a little noise to give apparant texture to certain areas of the picture otherwise the noise-reduced image on its own looks "wrong".