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Applies to ver. 5.5.3.

Sigma Photo Pro is the only software that is able to deal with the Foveon X3 RAW files (.X3F) on Windows. Mac users can give a try to Iridient Developer (not tested).

SPP is a simple RAW converter with everything one needs to adjust a RAW file, but with a few quirks. Processing is slow, so much that a progress bar appears each time a setting is tweaked, to inform the user about the ongoing operation progress.

Workflow

First, set your general preferences, located in the top menu of the software (and not in the editor itself), under File. Set especially the color space and the default adjustment parameter the software will apply when opening an X3F file.

By default, a lighter version of the picture is displayed, to reduce processing time. Even then, it’s far from what one would call “fast”. Anyway, I never click on the Full Res button before making my adjustments. Also by default, the histogram is not displayed. Clicking on the discreet “Guide button at the top right of the editing window to make it pop up. I activate the alert mask in the Adjustment section of the top menu. It’s now ready for processing.

The following is what works for me after having dealt with hundreds of Foveon X3 images. Some of these points are developed thereafter.

What I always do

  • I adjust exposure to get a complete histogram, or leave a bit of margin to have more processing latitude later on.
  • I adjust white balance.
  • I convert the X3F file to a 16-bit TIFF file for final editing in Photoshop.

What I do case by case

  • I tame down the highlights/open the shadows.
  • I disable noise reduction for pictures shot at ISO 100 or ISO 200, and I tweak the banding reduction option if needed, as this phenomenon can occur even at ISO 100 in some rare cases.
  • I fix lateral chromatic aberrations.

What I leave default

  • Sharpness. Sometimes, I even pull it down if there is aliasing or an inadequate crunchy look. Viewing at 100% is required for critical sharpness assessment.
  • Saturation. It offers only rough adjustment possibilities, and this parameter can be adjusted finely afterwards with the TIFF, if needed.
  • Color profile. It’s left on Neutral, as shot – best balance and latitude.

 

White balance

Setting the correct white balance can be so tricky with the Foveon X3 sensor and Sigma Photo Pro that it requires a section on its own.

You can set white balance the coarse way, using one of the presets. I’ve never used anything else than Auto, Sunlight, Shade, Overcast (the others have never been convincing). However, I often remained unsatisfied with the results – presets are limited by essence, and not as easily predicting with Foveon images as with regular images from Bayer-pattern sensors. As I told before, fine tuning by color temperature is lacking in SPP. It’s not an oversight though. Foveon images don’t have a linear response to color temperature, as it’s the case with images generated by conventional sensors. That means, if you need to make an image colder for instance, setting a cooler white balance will cool down some colors and make them look right, but some others will shift or saturate/desaturate, making them just as wrong as before.

To avoid this, Sigma has dismissed the usual color temperature setting, and has implemented a CMY circle to bias color manually according to what your eyes see, simply by clicking inside it.

It’s not ideal at all, due to precise adjustment requiring pin-point clicking (the circle is so small!). As the circle is clicked, the corresponding bias appears on the left, in Cyan-Magenta-Yellow values. This way, control over white balance is total.

Alternatively, white balance can be set by using the white point tool, but I have found out it does not work well for all pictures.

Examples – White balance presets and color circle

Auto Auto
Sunlight Sunlight
Shade Shade
Overcast Overcast

Auto is on the cold side, Shade gives dead greens and a pinkish orange tint, and Overcast oversaturates the pumpkin while making the greens too warm. Here, the Sunlight preset gives the most true-to-life result overall (although the sky was overcast), but the greens are a bit off.

Changing the preset not only changes the color temperature, but the tint and the saturation as well. This makes for unpredictable results, so one has to try each setting to determine whether there is a suited preset or not.

The color circle gives more control over white balance, but is a pain to use.

Auto Auto
Auto with 2M+12Y on the color circle Auto with 2M+12Y on the color circle
Sunlight Sunlight

After several tests, I found that a 2M+12Y bias gave rather satisfying results, similar to those from the Sunlight preset but with slightly better greens.

Highlight correction

Set Show Warnings in the Adjustment menu first, to have the pinned blacks and clipped whites (you’re likely to see more of the latter) highlighted on the image.

There are several ways to deal with highlights in Sigma Photo Pro, and it’s a good thing as long as one knows their respective effects. It’s not obvious from their designation alone, as you will see.

“Highlight”

Default is 0 and it goes from -2 to +2. Bright tones of the image can be tamed down with this tool to give it more punch and make it more balanced, but it’s of no help for areas marked as clipped.

Highlight set to 0 Highlight set to 0
Highlight set to -2 Highlight set to -2

“X3 Fill Light”

One of Sigma Photo Pro’s most powerful tool. Useful on a scenery with a bright sky and a dark landscape and backlighting scenes in general, because it combines highlight darkening and shadow brightening. A slight move to the right is enough to recover details in highlights and to brighten the darkest areas efficiently. It’s easy to overuse though, so watch out for noise in brightened areas and make sure the scene does not look unnatural. Arguably, Photoshop and its shadow/highlight tool does a great job with more control, but you may want to benefit from all the info packed in RAW.

X3 Fill Light set to 0 X3 Fill Light set to 0
X3 Fill Light set to +0.5 X3 Fill Light set to +0.5

“Highlight Correction”

An oddity. It’s not part of the Tonal adjustments tools as the previous ones. The cursor goes from 0 (Neutralize) to 1 (Restore). It’s not clear what Neutralize and Restore are meant to do respectively, as the semantic difference between the two words is not obvious here. After tweaking, the difference is most often inconspicuous. The strongest effect I have seen is a whitening of the brightest areas of the image when set to Neutralize (default setting is Restore), as seen below.

Restore Restore
Neutralize Neutralize

Chromatic aberrations

CA fixing tools are considerably more effective in Sigma Photo Pro 5.5 than in previous versions. Two sections, with distinct tools, are available.

“Chromatic Aberration Correction”

Fixes lateral chromatic aberration. Checking the box corrects automatically using the embedded profile of the lens. Easy, effective, and configurable if needed. Doing it manually enables separate fixing of each color fringe.

Uncorrected Uncorrected
Corrected Corrected

There is more lateral CA near the bottom of the frame.

“Fringe Correction”

Fixes longitudinal chromatic aberration (primary and secondary spectrum), although the word fringe usually refers to lateral CA.
LOCA is always more tricky to fix, and the use of the dedicated tool is more delicate accordingly. A high Hue range value is useful to remove LOCA efficiently but a high Amount value tends to kill the corresponding hues over the whole frame. Keep it low, especially for the green, or your leaves will become washed out. It’s a matter of balance here – it’s not worth screwing the whole image to fix faint LOCA.

Green
Uncorrected Uncorrected
Corrected with Hue range and Amount set to 1 Corrected with Hue range and Amount set to 1
Magenta
Uncorrected Uncorrected
Corrected with Hue Range and Amount set to 1 Corrected with Hue Range and Amount set to 1

Note there is barely any LOCA on this sample (just faint traces in the slightly out-of-focus areas of the leftest tree), but they show the effect such a correction can afford to an entire image.

Black and white

Sigma is aware that Foveon X3 images have a high potential for vibrant black and white imagery, so it was given special attention in Sigma Photo Pro 5.5, with advanced features.

Clicking on Monochome instantly converts the opened image in black and white. SPP then displays the usual adjutment tools, but also a few unexpected settings to help you get the best black and white rendering.

Pushing the Grain film cursors affords a vintage look with a gritty feel, and a dedicated RGB circular color chart enables to give the image a suited tonality. Again, there is no preset as found in Photoshop, so trial and practice are essential to get the best from these tools.

Most of this can be achieved using a third-party software from a generated TIFF image, but you may want to benefit from all the information packed in RAW.

A simple click on Color recovers the original image.

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