I've been using Aperture for many years and have recently learned something useful about how to tweak the RAW conversion settings. Until recently I just left them at the default settings for my camera, a Panasonic GH2.
Anyhow I've not been entirely happy with shadow noise (otherwise I reckon it's a great camera). Many web sites say that a degree of shadow noise is normal for this camera, so I didn't figure mine was any different. I tried a variety of noise reduction approaches but none really made a worthwhile improvement.
Until a few days ago when I tried tweaking the 'Raw Fine Tuning' settings - and I found a way to make things *much* better.
Please note that the following comments may only be relevant to Panasonic RAW files, and maybe only for the GH2. I don't know if they apply to other cameras (though I think they may.
It turns out that for the GH2, the default 'Raw Fine Tuning' setting includes 'Sharpening' of 0.78 and 'Edges' of 0.79. This is fairly aggressive sharpening, but I didn't really realise what it was doing to noise until I discovered that was significantly increasing shadow noise -even at base ISO!
If I set these both the sharpening sliders in the Raw Fine Tuning section to '0', the 'grain' in the shadows is much smoother - a massive improvement.
But, of course, the image is a bit less 'sharp'. Well, this isn't much of a problem with 16+ megapixel cameras. Unless you are making huge enlargements from originals, and really look closely at the finest details at 100%, it makes very little difference if you give up this 'sharpness'. But the reduction in noise is actually very obvious indeed. It's much better!
Most of the sharpness I need on these less noisy images can easily be added by including the 'Edge Sharpen' adjustment, either at the defailt settings, or marginally toned down a bit. I'm currently using Intensity 0.7, Edges 0.3 and Falloff 0.4. This leaves most smooth areas untouched, so the 'noise' or 'grain' in smooth areas is as it comes from the sensor. By toggling the Edge Sharpen on and off, I can easily confirm no change in 100% or 200% loupe views.
That level of edge sharpening is a bit subtle, but actually achieves most of what I got from the Raw Fine Tuning sharpening sliders. It will be applied only to in-focus contrasty things like eyelashes or hairs or other defined edges, and very nicely.
So I'm sharing this in case other people also find it helpful. I strongly suggest removing the default sharpening entirely, and only using the Edge Sharpening slider in a cautious manner if you want to enhance sharpness.
Some related web pages:
PS - there is a different issue with the default Raw Fine Tuning 'Boost' and 'Hue Boost' sliders, both of which are set to 1' by default. It turns out that these introduce a very large amount of contrast and exposure gain - turn them down to zero and the image goes quite dark and flat! The Aperture user guide says something about Hue Boost changing colours when Boost is set to '1' and this is the case. So I've experimented with turning them both to zero, and instead using a custom curves adjustment to achieve a similar level of exposure and contrast to the default conversion and the camera's default JPG image. By fine-tweaking the curves one can get better control of blown highlights and the overall contrast. I'm not sure if the colours are 'better', but I think so. I am fairly sure that I get smoother transitions in the mid-tonal ranges with this approach rather than just using Apple's default settings. Maybe they are a but strong for my liking. Certainly I can make curves that rarely require the 'Recovery' slider to fix over-boosted highlights. Anyhow, you may also find that this tweak helps a bit. Interestingly on a Canon RAW file the effect is not nearly as great in exposure terms, but there is also a definite colour change.
PSS - the end result is that I have set my camera preset for RAW fine tuning to zero settings for boost, hue boost, sharpening and edges. I then add contrast as needed using curves, and sharpen only with a little edge sharpening. I've then saved a few Presets with slightly different contrast curves and all with a little edge sharpening. I can very quickly select the level of contrast needed, and I am very confident that my results are quite a bit better, with better tonal gradations and much less noise.
Hope this helps