Started a RAW Processor....

Started Oct 23, 2010 | Discussions thread
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Jolon New Member • Posts: 13
Started a RAW Processor....

My DP1s arrived this week from Cliftons in the UK. Overall I was quite underwhelmed by the colours. They seemed a bit 'mixed-in'. Blues contain a bit of green, greens contain a bit of blue, and reds contain a bit of green too. The SPP color adjuster doesn't seem to be able to fix it.

I've been thinking about why that is the last couple of days. Last night I decide to take some photos of solid red, green, and blue on my IPS computer screen. Sure enough the solid red also included about a third green but no blue. The other colours also exhibited similar traits.

Thinking about it, it seemed to me that each colour channel sensor was responding a fair bit to the other channels. Looking at the response curve in one of the Foveon white papers confirmed this:

So I wondered whether the colours could be better 'separated' using a simple approach.

So today I began to write a RAW converter but got stuck at the Huffman decoding for the DP1s, so instead worked with the 16-bit TIFF files produced by the excellent X3F Tools:

The first step was to apply 2.2 Gamma which yielded this result (one of the first photos I took with the camera):

I then investigated each of the red, green, and blue photos I had taken and looked at how much each colour channel was responding to each of the pure colours and used that to work out how much to subtract from each channel. I also adjusted exposure slightly and shifted the white balance slightly towards blue purely based on the RGB colour of one of the house roofs (sunlight white balance?). And came up with this result:

In comparison here is the best I could get from SPP:

I think my colours are a bit off, a little artificial, almost painted. However I'm quite impressed with the results, it certainly has achieved the colour separation I was after. My image is also a lot noisier than SPP's.

Here is another example:

And with SPP:

I haven't accounted for the colour violet yet which takes an extreme blue response and adds a bit to red to simulate the purple colours. I'm not sure how that will affect the final image.

I think the images have an almost slide film look.

Thought people might be interested to see what the Foveon sensor can do!


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