Archive for March 2013
For this project, we’ll use a photo of the famous Sagrada Familia cathedral in Barcelona, Spain (you can download the RAW file from https://www.box.com/s/cq3uknqt54o3usf1jg3r). The photo was taken with a Canon PowerShot S90 camera, and the RAW file exhibits several obvious flaws, including visible barrel distortion, underexposed areas, and noise. In other words, this particular RAW file is perfect for tweaking in digiKam.
Before you start, make sure that digiKam is set to open RAW files in the 16-bit mode using the default settings. To do this, choose Settings → Configure digiKam and switch to the Raw Decoding section. Enable the Use the default settings, 16 bit option and press OK. Open then the RAW file for editing using the F4 key (or choose Image → Edit).
The first order of business is to fix the lens distortion. Since the LenFun library used by digiKam for automatic lens correction doesn’t have a lens profile for Canon PowerShot S90, you have to fix lens distortion manually. Choose Enhance → Lens → Distortion, then use the Main slider to set the correction value. Alternatively, you can enter the exact value in the field next to the slider. For this particular file, the -27 value should do the trick. Check the preview image to make sure that the distortion is properly corrected, and press OK to apply the correction.
Although the Canon PowerShot S90 did a respectable job of producing a well-exposed image, the photo still has slightly underexposed areas. The easiest way to fix this problem is to use the Local Contrast tool (Enhance → Local Contrast). The default values should do the trick, but feel free to experiment with different settings. But don’t try to push them too far, as the final result may look unnatural. Also, before you start modifying the default settings, save them as a preset using the Save As button. Later, you can restore the original settings from the preset using the Load button.
Next stop is the Noise Reduction tool (Enhance → Noise Reduction). While the default noise reduction settings work fine in most situations, you might want to adjust them to achieve even better results. When experimenting with different noise reduction settings, it’s a good idea to switch to the 100% crop, which gives you a much better view of the noise reduction effect. To do this, select 100% from the Zoom drop-down list. You can then use the scrollbars to view the desired part of the photo. Alternatively, you can use the Pan button in the lower-right corner of the preview window to display a thumbnail of the photo and pan by dragging the red square to the desired area in the image. To preview the noise reduction result, use the Try button.
Finally, the photo could use some sharpening, so choose Enhance → Sharpen, adjust the sharpness level using the Sharpness slider, and press Try to preview the result. Again, you might want to switch to the 100% crop for a better preview.
Need to quickly push photos in digiKam to a device on the same network? Provided the device supports DLNA, you can do this using the DLNAExport Kipi plugin. Choose Export → Export via DLNA to open the DLNA Export wizard. From the Choose the implementation drop-down list, select either HUPnP API or miniDLNA. Both options have their advantages and drawbacks. miniDLNA supports thumbnails and works with all DLNA-compatible devices. But it can’t handle hierarchical folders or virtual albums. Also, miniDLNA relies on the older UPnP 1.0.0 protocol. HUPnP, in turn, uses the latest UPnP protocol and supports hierarchical folders and virtual albums. The drawbacks include the lack of support for Sony devices and thumbnails.
If you choose the miniDLNA option, you have to install the miniDLNA package on your system. To do this on Debian and Ubuntu-based Linux distributions, run the apt-get install minidlna command as root. Once miniDLNA has been installed, press the Find button in the DLNA Export window and specify the path to the miniDLNA binaries (usually it’s /usr/bin).
Press then the Next button, and select the collection you want to export. You have three options here: you can pick the desired albums in the My Albums section, or select tags under the My Tags tab to export photos containing specific tags. If you already have saved searches in digiKam, you can select them in the My Searches section to export photos matching specified search criteria. Note that tags and searches cannot be used with miniDLNA, as it doesn’t support virtual albums.
Press Next again and hit the Start button to start the DLNA server. You can then access the shared photos from any device on the network using a dedicated DLNA client, or DLNA-enabled software.