Friday, 2 April 2010

GH1: Use RAW and gain 1% megapixels

The Panasonic Lumix GH1 has a 14 megapixel multi aspect sensor, with around 12 megapixel output at three different aspect ratios: 4:3, 3:2 and 16:9.

At 4:3, the JPEG image is 4000x3000, which is easily calculated to 12 million pixels. The corresponding RAW file, on the other hand, yields 4018x3016 pixels, or a total of 12.118.288 pixels, which is 1% more megapixels than the JPEG output.

The same goes for the other aspect ratios. At 16:9, the JPEG image is 4352x2448, or 10.65 megapixels. The RAW file has a 4396x2464 resolution, 10.83 megapixels, a difference of 1.7%.

Of course, an increase of 1-2% of the resolution is hardly significant, and no real reason to use RAW alone. But there could be situations where you need a little bit extra details around the edge, and then looking at the RAW file could help you.

Here is an example exposure in two versions, developed from RAW (top) and JPEG (bottom):

From RAW, 4396x2464

From JPG, 4352x2448

It is hardly possible to notice any differences between the two images, when shown scaled down like this. However, when looking at a 100% crop from the right hand border, the differences are obvious:

We are losing a little bit of details in the borders when using JPEG, as opposed to RAW.

Appendix

The lens used here was the Four Thirds Olympus 9-18mm f/4-5.6, with the Panasonic DMW-MA1 adapter. The lens was used at 9mm, f/4, ISO 100. In the image above, you can see a typical example of chromatic aberration (CA). This is noticeable as the purple and green fringing along areas of high contrast, where black and white paint meet.

I have been using UFRaw to convert RAW files in Linux.

1 comment:

  1. As far as I know these additional pixels are used to correct distortion of the mFT Lenses. Interesting that it also has an effect using FT Lenses...

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