We have a brand new blog which desperately needs some content before it can be launched and following our recent Canon EOS 50D review there has been quite a lot of discussion in the forums about the use of Adobe ACR as a RAW converter in our reviews. These, I thought, were two good reasons to get into blogging mode and write a brief article that explains why Dpreview is using ACR and not proprietary or other third party converters for its tests.
So why is it then that we use Adobe Camera RAW and not one of the other converters?
Firstly we aim to create a level playing field and to make results - as much as possible - comparable between cameras. For this reason we simply have to use a third party converter that can handle most of the many different RAW formats that are out there rather than a proprietary converter. ACR is used as a plug-in in Adobe Photoshop, Photoshop Elements and Lightroom and has the highest market share of all third party converters which makes it the obvious choice. More importantly though Adobe updates ACR very frequently (and we're involved in early releases) to include the latest camera models. This allows us to review a new model fairly promptly after its launch (we often get the cameras before anyone in the RAW development arena, including Adobe).
We know that Adobe Camera RAW applies different levels of sharpness to different cameras and because of that we use the following workflow when processing our box shots:
Load RAW file into Adobe Camera RAW (Auto mode disabled)
- Set Sharpness to 0 (all other settings default)
- Open file to Photoshop
- Apply a Unsharp mask: 80%, Radius 1.0, Threshold 0
- Save as a TIFF (for cropping) and as a JPEG quality 11 for download
Even by using this workflow we cannot entirely avoid any processing differences between cameras but it's certainly as good as it gets in terms of creating a 'level playing field'.
Secondly, especially when analyzing image noise, we want to show a camera's image output in its 'purest' form, i.e. as captured by the sensor and as little as possible altered by sharpening algorithms, noise reduction or any other forms of image processing. Again, ACR does a pretty good job in this area. To demonstrate this I have included example crops from two images which both have been processed from an ISO 3200 Canon EOS 50D RAW file, one in ACR 4.6, the other in Canon's Digital Photo Pro 3.5. Sharpening and noise reduction were set to zero in both converters, then we applied an identical unsharp mask to both images, so in theory we would expect pretty similar results.
Reality looks slightly different though. The ACR image is less sharpened and shows visibly larger amounts of chroma noise. That tells us two things. Firstly DPP is doing quite a good job at noise reduction and is probably the better choice for cleaning high ISO pictures of the 50D (ACR's NR can't match DPP's even if you turn it up). However, it also means that DPP applies at least some chroma noise reduction (and sharpening) even when NR is set to zero which renders the software pretty much less useless for our purposes.
Nevertheless, if you're interested in results that can be achieved with different RAW converters, you can have a look at the 'Software' page in our DSLR reviews where we usually post images of our resolution chart and the studio scene which have been processed in different RAW converters (if available at the time of the review).
