Sunday, January 16, 2011

HS10 – RAW Vignetting … A Problem

RAW on the HS10 is not quite the image quality savior that I had thought. Vignetting gets pretty bad when the camera screws up the white balance, and sometimes the images become unrecoverable.

Now let’s be very clear on this: the image is exposed adequately, the lighting is consistent, but the camera gets the white balance wrong.

Example 1 is a toy Donkey (from Shrek) that I shot at 3200 ISO in a room with a older Halogen light. I wanted to test the detail retention at high ISO, and found it to be surprisingly good.

But what stands out is the poisonous vignetting. It might  be possible to fix the vignette on the right with heroic efforts, but the left side of the image is worse and it is all over the subject. This image is pretty much fatally wounded.

Example 2 is more subtle and thus more interesting. I was out today trying to capture winter images for the Cameras Across Canada contest (separate article coming), and when I got back and started processing the RAW images I was surprised to see how bad the default white balance turned out on many of the images. Typically, small subject with lots of surrounding white (this was in a snow storm) and you get a blue image.

Even after exposure correction in ACR (i.e. to get a nice bright snow field) there is residual vignetting. Now, Jon says that he does not notice it all that much, so perhaps it would be tolerable … I don’t really know as it really bugs me.

But it’s the correction process that is just brutal. The pattern is not consistent because it appears that the colors can be somewhat variable, so this is not just a luminance correction. And sure enough, trying to correct it in ACR and PTLens were both inadequate to get a nice, smooth snow field. It should be perfectly uniform … it’s a fricken snow storm!

I created an animated GIF to show you how this looks after ACR exposure correction and then before and after white balance correction …

Very difficult to work with … be warned. No idea yet how to mitigate it …

I’ll be posting a series of the images form today’s shoot soon (it’s really late) and you will see that I had to go black and white a lot to save some of the images I really liked.

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