The SFD mode is one of the most important features introduced with the Sigma sd Quattro. It is a kind of multiple exposure feature, which captures 7 X3F files, which then get converted into a single X3I file. Just like X3F files the X3I file can be developed in Sigma Photo Pro, whereby you can adjust all the usual sliders and settings, among others exposure, white balance, contrast, sharpness and X3 Fill Light.
Some pieces of info, before we begin:
- I used identical settings to shoot both X3I and X3F files. The only thing I changed between the shots was the mode.
- The X3I crops in the comparison images are always left; X3Fs are right.
- Where it was possible or necessary, I tried to adjust the settings in SPP in such a way, that the resulting images look as similar as possible. It wasn’t easy because X3Is are less contrasty and brighter and have different colors.
- You can find all of the photos shown here and view them in full resolution in my Flickr
What does an X3I file look like?
X3I files are something like pimped out X3F files, which have very low contrast. They are akin to HDR images without tone mapping. Below I have included two images for you to compare – the first one is a JPG created using an X3I file, while the second JPG was created using an X3F file. Neither of the two photos was edited.
Dynamic range and highlights recovery
The fact that X3I files look dull is no coincidence. This is due to their much higher dynamic range, which allows for far greater post processing headroom. The first JPG was created without editing using an X3F file, which was shot for comparison purposes, and shows what the scene looked like quite accurately. The small part of the building front is clearly overexposed.
When editing both the X3I (left) as well as X3F (right) file I tried to recover all the highlight detail. This didn’t work as well with the latter file as it did with the former.
What becomes apparent immediately is that the crops look different. This isn’t due to different settings – the settings were the same – but rather due to sliders in SPP having a different effect, depending on whether an X3I or an X3F file is being edited.
Even in the photo of the construction site, which was included in the beginning and which doesn’t contain really deep shadows, there is an obvious difference. The X3I file (left) has a huge advantage in regard to luminance noise and color blotches.
What’s also interesting is that the sky appears to be much cleaner in the JPG created using the X3I file.
In some of the food photos I shot for the purpose of this comparison, the X3I files seem to offer an even greater advantage in said areas. This is due to deeper shadows and stronger noise in the X3F files.
Micro contrast and sharpness
I’m not sure what the reason behind it is, but X3I files seem to have a tad higher micro contrast and sharpness as well. Whether this is due to lower luminance noise or my tripod, I cannot say. Below are the same two food photos, but this time with two different crops.
As one would expect from a shooting mode, which is based on multiple exposure, the SFD mode is not suitable for moving subjects. The following crop of a crane from the photo of the construction site embedded at the beginning of the article, shows what happens if something is moving in the frame during capture. It is to be expected, that the effect would be even stronger with faster moving subjects.
I didn’t expect much before I began experimenting with the SFD mode. I was therefore positively surprised by the vast improvements in regard to dynamic range and noise performance it brings to the table. Higher micro contrast and sharpness are a nice bonus, which wasn’t really necessary considering Foveon’s already high level of sharpness. It is really unfortunate, that this mode isn’t usable for moving subjects.