Thursday, November 5, 2009

Hype and Noise

First the hype. Adobe has a new Lightroom 3 beta up on its web site. In the hype pdf they talk about their great new noise reduction algorithm. So I downloaded the beta to see if the new program would be useful during the YSP project--with over 800 images on the disk it's moved from a shoot into a project.

The first thing I noticed when I tried to use noise reduction was half of it wasn't there. The slider for color noise reduction--the ugly blotches of color caused by the demoisaicing--worked. But the slider for luminescence noise--removing the actual noise--was grayed out. A closer reading of the hype on noise reduction--a marketing song and dance to hide the obvious--Adobe might have a gold metal algorithm somewhere but it ain't implemented yet.

So beta 3 isn't going to help the YSP project. Except that it has me looking into how hard I can push the camera using the Lightroom 2 noise reduction. Which may be a bit farther than I first thought.

During the first shoot, I took the first image at ISO 400, 1/125 sec and f5.6. It is, as you can see, a bit on the dark side-3 to 4 stops underexposed. You should barely see Sasha, the girl on the left, since she's in the spotlight. Whether you see Laura, the girl on the right, depend on how your monitor is adjusted.

In Lightroom I upped the 'exposure' 3 stops. for the second image. (what actually going on when you do this is worth a post sometime)

As long as you don't look close image two isn't a complete disaster. But if you do look close--image three, a closeup of Laura's head--you see the noise in all its glory.

But noise can be reduced. In image four I applied Lightroom 2's noise reduction routine.

It has softened and lost detail,an inevitable consequence of noise reduction. Click on the images for a larger view. Compare the hair for the softening and the sleeve and background for the noise reduction. It's not perfect but I've done worse.

So where are we now. If I use my 105mm manual lens wide open at f2.5 I've picked up 2.3 of the 3 stop of underexposure. Since ISO 800 won't add that much more noise, something I decided in the last post, this lens will give a decent exposure.

But now I have another lens I could use. My 55-200mm kit lens is an f4 at 55mm, f4.2 at 70mm and f4.5 at 85mm. So I would lose a stop or more by switching over to that lens.

But it is image stabilized. I could drop the shutter speed to 1/60 or 1/40 sec since I don't have to worry about camera shake. That would pick up the lost stop of exposure.

Time for more experiments. I will duplicate the theater's lighting at home with my variable power flash and start shooting away. With luck, ISO 1600, and noise reduction I might even be able to take onstage headshots at 200mm and f5.6.

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