One of the main reason for the lack of acceptance of the Sigma camera is the inability to open and work on the RAW file outside of Sigma’s proprietary software, the Sigma Photo Pro. Based on numerous reviews and user feedback, the performance and stability of the Sigma software is highly questionable, especially on the Mac OS X. That said, the conversion quality is really second to none.
When I started using the camera, I had to change my workflow to accommodate the extra step needed to perform the RAW conversion. Users around the world have been asking for the universal RAW support via Adobe DNG to ease the workflow, and now Sigma has finally done it! Previously, an independent effort was initiated to code a small converter software to convert the X3F format to DNG, kudos to Roland Karlsson and highly dedicated team (Refer to this article at DPReview). When I met Mr Rudy Guttosch (VP, Foveon Inc. USA) in Shanghai back in March, he asked me if this (DNG) is really important….I said “YES!!!!!”. I don’t want to claim credit for this but we thanked Sigma for attentive to their customers’ needs and feedback. I believe the request was made for year, but in this case, it is better late than never.
The DNG support was incorporated into “H”. Sigma has stated that they will port this over to the sd Quattro and all dp Quattros through a firmware update although no specific date was given. Sigma implemented this as a 12-bit RAW DNG, which means it only has 4,096 levels of tonal resolution per channel. The native X3F is a 14-bit (total 16,384) RAW file which has approximately 4 times more information and tonal resolution.
Opening the DNG file is a standard affair as opening any other RAW files supported by Adobe. In this example, I opened it in Adobe Photoshop CC, and was greeted with the same Camera RAW dialog.
A point to note, when the user select a particular Color Mode and Aspect Ratio in the camera, the DNG file will be tagged with those information. For Color, you can still change it to other settings through Camera Profile in ACR (Adobe Camera Raw), but the aspect ratio is permanently set without any way to resort to the original ratio of 3:2. I have send my feedback to Sigma on this, and am waiting for their official reply. Given that this is a RAW file, it should be well….raw, and not half-cooked. Meanwhile, please take note of this behaviour if you chose to shoot in DNG. The native X3F file does allow you to change back to the original ratio in Sigma Photo Pro 6.5.
What is exciting about the DNG file is it provides an avenue to make a custom camera profile through tools like X-Rite ColorChecker Passport (ref: X-Rite). I will try to make one this week, weather permitting. Profiling the camera is often an overlooked process within the workflow…but it is also the hardest to make. A good camera profile increases color accuracy which is often mandatory for color critical work and applications like art reproduction and other copy work.
The 12-bit does limit the editing headroom, especially on highlight recovery. Shooting with ETTR can be a challenged. It is also not known if the dynamic range of the Foveon sensor has a non-linear relationship with the distribution of tonal resolution (bits) as in any other conventional sensor, but in my shooting experience even now my DNG test, the ability to recover shadow seems easier than highlight. My recommendation is to shoot with a slightly underexposed metering.
The benefit of using the DNG file in the Adobe workflow (ACR/Lightroom) is both speed and familiarity coupled with the ability to use far more advanced adjustment algorithms including shadow/highlight recover (to replac X3 Fill in SPP), Clarity, DeHaze (in CC), Lens Correction, better Chromatic Aberration and Noise Reduction adjustments, etc. Personally I am not a big fan of ACR for RAW conversion because there are better RAW converters out there but I must admit I enjoyed the ease of use and speed of editing the Adobe software provides especially in Lightroom. I have tried opening the DNG in Capture One 10; while the conversion quality is noticeable superior to ACR, I could not change the Color Mode (profile) of the image which means if the shot was taken in Mono, it will remain in Mono. Ditto for aspect ratio.
I was initially tempted to do a comparison between the X3F and DNG, but practically it makes no sense. My reason for not doing it is because those who don’t find fault in SPP and can accept it as it is (SPP 6.5 has improved in performance due to the GPU support) may continue to use SPP, but those who hated it will switch to DNG anyway. Also, did I mention that a color image in DNG is approximately 150MB each?! A monochrome file is approximately 100MB. It takes a longer time to write to the SD card compares to writing a X3F,
There is a quantitative and qualitative differences in each RAW file format, but each has its own value proposition and advantages. At the end, it has to fit into your workflow. I can work with either or both, at least know we have a CHOICE!