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Fighting the Blues
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Detail of the noisy area
I considered several noise reduction options (see the right side bar), but as I had to deal with multiple colour casts as well, in this particular case I decided to convert the photo into black and white and slightly tone it. More extensive retouching could have been undertaken - if someone likes it. I prefer to fiddle with the original as little as possible. This one needed some fiddling, though.
An attempt to use a straightforward Hue/Saturation adjustment or Channel Mixer to convert to B+W was unsuccessful because of very pronounced specks of noise, particularly on the Blue channel.
Noise on the Blue Channel
Even the Green channel, usually the cleanest, was noisy and unsharp. However, the Red channel was remarkably
clear, which indicated that the luminance channel in LAB mode was available to start killing those nasty blues.
Step 1. Convert from RGB Color to Lab Color mode (Image>Mode>Lab
Color). SinceLab Color space is wider than RGB there will
be no distinguishable colour shifts resulting from converting back and forth between
these two modes. It would not have bothered me anyway because I intended to end up with B+W image.
Step 2.
Check Luminance (Lightness) channel. If it looks good, proceed with deleting A and B channels.
If at this stage you decide to convert back to RGB Color Photoshop would not allow you to do it.
Step 3. Convert from LAB mode to Grayscale (Image>Mode>Grayscale).
Step 4. Now you can convert from Grayscale to RGB Color.
Step 5. After the last conversion you will end up with three pretty clean identical channels. Manipulate the Channel Mixer (Image>Adjustments>Channel Mixer...) to achieve a better contrast and more interesting range of grays. Check Monochrome box and adjust the sliders.
Step 6. Bring out Hue/Saturation dialogue box (Image>Adjustments>Hue/Saturation..), check Colorize box and add a little bit of sepia tone.
Step 7. Apply Unsharp Mask to you taste (Filter>Sharpen>Unsharp Mask...). Voila! Much better...
Final version
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There are many methods of noise reduction. Sometimes you would see an improvement in noise levels simply by blurring the offending channel with Gaussian Blur. Sometimes, converting to Lab Color and blurring either A or B channel would help. If it was not for the colour cast in this picture I would have probably just duplicated the cleanest RGB channel. Then I would have run a Find Edges filter and, after increasing contrast with Curves and a little Blur, loaded the Alpha channel as a selection and applied some Gaussian Blur to smooth the noise. If you are not into DIY, check out the shareware Neat Image programme. The free demo version is available from www.neatimage.com. If you happen to own a copy of Photoshop, you can buy a good noise reduction action from www.fredmiranda.com. Finally, search for "noise reduction" on www.dpreview.com forums, where this topic is discussed very often. Good luck! |
© Copyright 2002-03, Galina Walls