Sigma X3F TIFF Conversion Issues For Blown-out Skies

The Sigma Photo Pro (SPP) software, which must be used to open X3F files, has trouble exporting to TIFF, clipped or blown-out parts of an image, like a cloudy sky, unless you manually adjust exposure and fill.  If you let SPP export in “auto” mode, there is a high risk that you will not be able to recover highlights, from the TIFF, in Photoshop(PS) or other editing software.

A long-time Sigma user pointed out that Foveon sensor files are more diifficult to work with because “They (Sigma) have two problems. (1) The layers have strongly overlapping color response that is not matched to the color theories used for RGB color management. (2) the third layer is very noisy.”

At this writing, there is no X3F to DNG converter and I doubt, for long-winded technical reasons, there ever will be.

If you must have details in the blown-out areas of the image, you must export for that (adjust exposure in SPP for the clouds), then, in PS, bring up the exposure in the part of the image that had it’s exposure reduced to bring out the sky.

Adobe Camera Raw does a significantly better job with bayer sensor images, good enough that one can often use the “raw” TIFF (many even work with JPGs) to post process with little loss of image information.  However, if one can, only usually loads the image into Photoshop through Adobe Camera Raw (ACR)

The root problem is that you can open RAW files in Photoshop from just about any camera but the Sigma.  This means that you have to convert Sigma X3F RAW files to TIFF files first, if you’re going to use other image editing software.  Or put another way, you have to adjust exposure and fill twice.  First in SPP, then in PS.  For Sigma images, the TIFF becomes the “RAW” file for PS.

Although a Bayer / Photoshop workflow is much easier than working with Sigma images, I still prefer Foveon. As nice as the D600 is, there is a 3-dimensional look to Sigma images that, IMHO, it just can’t replicate.  That said, the dp1m is not the best choice for low-light or fast photography.

Here are some images that I hope illustrate these issues.

First, a Sigma DP1M photo.  This is a JPG copy of a TIFF created by Sigma Photo Pro, at its default setting (that is, no auto or manual adjustment)


Second, a photo from a Nikon d600.  A TIFF was created by Photoshop’s Camera RAW filter, again, no adjustments


Here I reduce the exposure on the dp1m image by 1 in PS.  


Yes, doesn’t seem bad. Now I do the same for the Nikon version (I’m quickly selecting using a wand, so excuse the jaggy nature)


Dropping the exposure doesn’t give me an image I want, for either camera.

Now, here is the Sigma where I have tried to adjust the sky using a curve, to suit my taste.


Doesn’t get me where I want to go.  Now here I do the same thing with the Nikon TIFF


As you can see, I am able to recover the sky pretty well in Adobe’s default TIFF creation.  The bottom line is the Adobe camera RAW created a much better TIFF in default mode than Sigma Photo Pro did with the X3F file.

What if I try to do this with the X3F generated TIFF?


No matter what I try, I can’t get the clouds to look healthy.

However, I can get a good image from the dp1m image, by adjusting the X3F’s exposure in SPP to favor the sky then bringing up the houses with curves in PS (reverse selection to sky).  In the end, I can get to where I want to go, but I can’t sleep-walk through RAW processing with Foveon images like I can do with bayers.  Probably for the best because I should pay attention anyway!


Here is what the TIFF looked like


I believe I may be able create better “default” TIFFs by generating two sets from SPP, a normal, and one with the exposure set down 2 stops.  I can then let Photoshop merge the images and get the best of both worlds.  For another day…

In the meantime, here is Ted’s workflow, as explained on a DPReview forum:

I use SPP to produce a neutral image adjusting only the exposure comp. slider to get the histogram as wide as possible, checking each color in turn. Some might leave a little space each end, others might not. Very important, IMHO, to use ProPhoto working space for the review image. Some back off SPP’s sharpening as it does sharpen at zero setting, particularly visible at sharp edges. I also back off the saturation slider a smidgeon. The aim here is produce a neutral image, not one that pleases the eye! Then save as a 16-bit TIFF, still in ProPhoto color space.

So, for me (SD9, SD10, SD14, SD1), all SPP 3.5 sliders at zero, except:

Exposure comp: as required

Saturation: -0.3

Sharpness: -0.7

Any proper editor has much better tools for tone curves, color adjustments, sharpening, re-sampling and conversion to color spaces other than ProPhoto.

If you don’t already, you might want to try editing in PS, but staying in 16-bit ProPhoto, until the time comes to ‘save as’ (for me) sRGB JPEG. A 16-bit neutral TIFF in ProPhoto color space is the best for flexibility, IMHO.

5 thoughts on “Sigma X3F TIFF Conversion Issues For Blown-out Skies”

  1. Many thanks for that post.
    Yes, indeed, it is important to know, how Sigma Photo Pro works with the X3F-file. Your workflow seems to be very helpful and gives an outstanding image by finishing in Lightroom or CameraRaw from Photoshop.
    And gives more detail back from sky! More than D600! Wow!

  2. Thanks! Only looks like more DR than d600 in the example because looking at Sigma processing limitation. I now believe the d600 has more dynamic range. The Sigma has a better mid-range image, IMHO, so it’s not about DR to me, but getting sufficient DR in challenging situations. That is to say, though the d600 provides more DR, it doesn’t have the color-richness of the Sigmas so I must be more careful when shooting Sigma, then the d600. Both are great cameras! Also, I don’t run into many challenging DR situations like the above, so don’t feel the Sigma is lacking.

  3. An inexperienced DP2M user here.
    TIFF file size from SPP conversion seems so big, close to 100MB , I used to think it would contain more of less all information from a X3F file, but you are suggesting otherwise right?

    So are you suggesting, 1.) to use SPP to lower the EV to get the highlight. 2. ) export as TIFF 3.) pull up shadow by LR/PS?

    Why do you not want to pull up shadow by X3 fill light? Is it because the X3 fill light are too primitive without curve control?


    1. Yes, the extreme wide range of Fovean RAW data values means that most software, like Photoshop, is not designed to handle it; that is, Sigma software can manipulate Foveon RAW data outside of normal gamuts better than can be done with a TIFF (that as far as PS is concerned, is debayered and within gamut). So yes, what I’m suggesting, or what I understand others to suggest, is that if you have a very wide dynamic range in your Foveon RAW image, use SPP to get the RAW data into the gamut/dynamic-range you want to use, and then do tweaking in LR/PS.

      Personally, I find X3 fill a bit artificial, but I’m not an expert in this. I use it a little. Hope this answers your question.

  4. Max thanks for you response.
    I still find SPP too tedious to work with , so I now bath convert all my photo to TIFF with SPP and do the rest of my work with LR. I would however, still go back to SPP to tweak any photo that has meet their limit in Lightroom. ( I do street photography with my DP2M , hence I always ended up with hundreds of photos to review, making SPP impossible to me)

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