Foveon workflow: Blue Channel trick for Quattro cameras by using X3F Tools?


deutsch_s1

Since the blue channel trick doesn’t work with Quattro X3Fs, I tried to find out last week if there’s an alternative to SPP and that particular workflow. Just as a reminder: The blue channel trick is a workflow in SPP used for the conversion of Marrill X3F into black-and-white in order to reduce noise. This workflow, in which only the image information of the surprisingly noiseless blue channel is used, doesn’t achieve the desired result with Quattro X3Fs. As expected there’s a change in the tonal range, however, noise won’t be reduced.

Farbmischer-Blaukanal

Last week I tried to find out if it works somehow with RawDigger – a RAW-converter with very interesting features. With RawDigger I could extract the blue layer and save it as a TIFF file but the result wasn’t convincing. Even though noise in the medium gray tones was less pronounced, very bright luminance noise was visible in particularly dark areas, which was confusingly similar to the noise in long-exposure photographs taken without dark-frame subtraction. As such bright noise can be detected in the deepest depths by the immense difference in contrast much more easily than the fairly contrast-less noise in the medium tones, I concluded that the images developed in SPP look better in total.

In the meantime, I took a closer look at X3F Tools 0.54 aka Kalpanika. Interestingly, this RAW-converter also has a function that extracts a Quattro X3F’s blue layer and saves it as a TIFF file. The command chain you need to enter in the Windows command prompt is: x3f_extract –qtop –tiff and then, depending on whether you’d like to extract the blue layer from singular X3Fs or all X3Fs in the folder C:\user\username, either filename.X3F or *.X3F and then execute by pressing Enter. The result, when opened in Lightroom, looks as follows:

X3F-Tools-Blaukanal

In case you haven’t read my blog entry from last week, I’d like to point out a curious thing, and that’s the fact that what X3F Tools produces can’t be the blue channel. The image should be colorless and very dark, like the TIFF files saved with RawDigger which only contain the image information from the blue channel:

Lightroom-Screenshot

In both cases it’s the same X3F file taken with ISO1600.

Like last time I pushed three Quattro X3Fs (ISO1600, 3200 and 6400) through SPP and X3F Tools 0.54 and imported them into Lightroom, where I adjusted the TIFFs from X3FT to the unprocessed TIFFs from SPP. You can find the settings applied in SPP in last week’s blog entry. You can also take a closer look at all full-resolution images (from RawDigger, SPP and X3F Tools) on Flickr.

Now let’s look at the crops of the photos (TIFFs) developed in SPP 6.3 (left) and X3F Tools 0.54 / Lightroom (right).

SPP-vs-X3F_Tools-ISO1600

ISO1600

SPP-vs-X3F_Tools-ISO3200

ISO3200

SPP-vs-X3F_Tools-ISO6400

ISO6400

Like last time the comparison clearly favors SPP this time as well. The following can be summarized:

  • In X3F Tools-generated TIFFs there’s less noise in the medium tones, but more noise in the shadows. But the difference isn’t as big in both ways as when comparing RawDigger with SPP. This means that when it comes to noise, it doesn’t matter if you develop your X3Fs in X3F Tools or in SPP.
  • Still I’d prefer SPP to Kalpanika, as with the former application you’re much more flexible when it comes to highlights. Kalpanika only exports a TIFF file you can continue to edit in Lightroom or another image processing application. However, TIFF is not a RAW format, which means that highlights can’t be restored if the image is overexposed. As you edit an X3F file in SPP you can still fix the overexposed image provided that it isn’t hopelessly overexposed.
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