Where does noise come from in my workflow?

[bend the light]

Thnaks Rob. I wonder what the "native" iso for the 400d is?
An experiment is needed maybe?

An excellent response, and again, note3 being taken...I will nail this "problem",. iof indeed it is a problem and not a figment of my imagination.

[bend the light]

Well, here's an image that people have said is noisy...


And the RAW is hosted here...

http://www.mediafire.com/file/9cp4ep...y/_MG_8811.CR2

If anyone wants to have a go and process this anyway they like, THEY CAN. Any help in my processing would be appreciated.

[robski]

The file size of your jpeg might suggest high levels of noise but I don't know what compression setting has been selected. On the LCD screen at work I can see a bit of noise but hardly any on my aged CRT screen at home. Attached is my attempt which is 100Kb less than yours. This was saved with a setting of 10 in Photoshop.

The RAW appears to be over exposed if anything and lacking tonal range.

For this shot I used the auto option in CS5 ARC to get the levels in the right ball park and then tweaked as the change in black levels were over egged. Then applied some 30% noise reduction and sharpening at the RAW stage.

Does it appear cleaner to you ?

[Gidders]

Thanks for posting the RAW file ... I'll take you through how I would process this with a series of screen shots to see if that helps you.

Untitled-1.jpg
On opening the file in ACR the first thing is that as Rob says its got a very limited tonal range ... but its not over exposed - there are gaps at both ends of the histogram with no clipping

Untitled-2.jpg
Switching to the details tab, as a default ACR applies some capture sharpening 25/1.0/25/0 which I always accept - RAW files always need a bit of sharpening and this is a very modest amount

It also applies default noise reduction of luminance 0, colour 25 - this I do NOT accept as the amount of noise reduction required varied with ISO. I have a number of ISO dependant default noise profiles which I have built for my camera (Canon 40D) and I have ACR (or Lightroom) apply them automatically depending on the detected ISO of the image. For more information of how to do this see <<<this thread>>>

Untitled-3.jpg 200% zoom
Resetting the noise reduction to 0/0 for a minute and zooming in we can see that there is both some colour & luminance some noise present in this image ... which is to be expected shooting at ISO 400.

The sensor on your 400D is not dis-similar to my 40D so starting from my ISO 0400 preset of 15/5 I found it was still a little bit noisy so edge the setting up to 23/8. Noise reduction is always a balance between removing noise and softening details ... I tend to err on the side of leaving a bit of noise if necessary rather than sacrificing detail.

Untitled-4.jpg 200% zoom
This would be my starting point before any exposure or black level adjustments etc. In the next post we'll look at how adjusting these setting affects the noise ... if at all

[Gidders]

Ok now lets go back to the basic tab and adjust the exposure.

Holding down the ALT key while moving the exposure slide will mask the image and show us when clipping start to occur. In this image clipping begins at about +0.55 but I would accept a tad more clipping and kept moving the slider to +0.8. Doing the same with the black levels shows us that black clipping begins at about 30 but again I would accept a modicum of clipping and took the slider up to +45.

Untitled-5.jpg
This gives us a nice contrasty image with the histogram filling the scale ... but what has happen to the noise levels?

Untitled-6.jpg 200% zoom
OMG ... so that's where the noise comes from

Untitled-7.jpg
Looking at whether is the increase in exposure or increase in blacks we can see by comparing to the un adjusted image in the middle, increasing the backs tends to emphasise luminance noise and increasing the exposure increases colour noise.

Untitled-8.jpg
If we then apply a modest smart sharpen on Photoshop say 150% and 0.5 pixel radius it gets even worse Looking at your image it looks at though you have been considerably more aggressive with your sharpening - I'm guessing something like 200% & 2/2.5 pixel radius, possibility to try to compensate for the lack of depth of field. This will emphasise any noise HUGELY!!

... continued in next post

[Gidders]

Whenever I push either the exposure or blacks levels significantly I always revisit the noise reduction setting before opening in Photoshop.

Untitled-9.jpg
In this case increasing the luminance setting to 65 and the colour setting to 25 gives reasonable results I think.

Finally opening the image in PS, cropping and applying a modest sharpen again is about as good as its going to get - IMHO

Hope that helps

[bend the light]

That is a fantastic piece of work, Clive...thanks. I have had loads of good advice, here and in other places, since I asked this question, but this write-up is fab!

Many thanks.