Archive for January 2011
Convert RAW Files to DNG with DNGConverter
digiKam comes with a nifty batch utility that allows you to convert RAW files to the DNG format. The question is, of course, why you would want to do that. After all, digiKam can handle RAW files without any problem, so what’s the point of adding one more step to your photographic workflow?
As you might know, RAW is not a file format, but rather an umbrella term that describes multiple file formats controlled by multiple hardware manufacturers. The RAW formats themselves are specific to digital camera manufacturers. For example, Canon cameras store RAW files in the CR2 format, while Nikon cameras use the NEF format. Besides being proprietary, RAW formats are often poorly documented and encumbered by patents.
The Digital Negative (DNG) format introduced by Adobe Systems, Inc in 2004 is designed to overcome these shortcomings by providing an open, well-documented universal format for storing RAW files. If you would like to know more about the DNG format, the DNG articles and links Web site provides a wealth of valuable information on the topic.
Being an open and well-documented format, DNG is suited particularly well for long-term archiving of digital photos. Of course, the CR2 and NEF and other RAW formats are widely adopted and supported, so they are not going away anytime soon. But there is no reason why you shouldn’t save your RAW files in the DNG format to be on the safe side. After all, storage is cheap nowadays, and the DNGConverter utility makes it supremely easy to convert RAW files to the DNG format.
Using DNGConverter couldn’t be easier. Launch the utility, add the RAW files, specify a few options, and hit the Convert button. For complete peace of mind, you might want to enable the Embed Original File option which embeds the source RAW file into the resulting DNG file.
Use the Levels Adjustment Tool in digiKam
When it comes to tweaking photos, Levels is the most important weapon in digiKam’s arsenal. This tool lets you adjust brightness and contrast by specifying the location of complete black, complete white, and midtones in a histogram, which makes it a perfect tool for fixing under- and overexposed photos as well as improving the overall tonal range of a photo.
You can access the Levels tool in the image editor by choosing Color | Levels Adjust. Select Luminosity from the Channel drop-down list, and press the Linear button.
The key element in the Levels Adjust pane is the histogram with the black point and white point sliders. Simply put, the black point slider controls shadows, while the white point slider controls highlights. So to darken shadow areas in the photo, move the black point slider to the right. Need to boost highlights? Move the white point slider to the left.
Instead of using sliders, you can let digiKam adjust levels automatically by pressing the Auto button. Using this feature is often hit and miss, but you can easily revert all changes using the Defaults button.
Three color pickers next to the Auto button provide yet another way to tweak levels. To adjust shadows, press the the appropriate color picker button and click on an area in the photos that should be black. In a similar manner, you can adjust midtones and highlight using the appropriate color pickers.
Adjusting levels in the Luminosity channel can help to increase contrast without affecting color saturation. To change the color balance, you can adjust levels in the Red, Green, and Blue channels (select the appropriate channel in the Channel drop-down list). This can be useful for boosting colors and fixing photos which suffer from unnatural color casts.
5 Splash Screens to Spice up digiKam
Every new version of digiKam features its own unique splash screen. But you don’t have to wait for the next digiKam release to get a new splash screen. Here are a few ready-to-go designs created by yours truly. To learn how to replace the default splash screen in digiKam, take a look at the Replace digiKam’s Default Splash Screen article.
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
Publish Photos on a WordPress Blog from digiKam
While digiKam doesn’t allow you to publish photos directly to a WordPress blog, you can work around this limitation. Enable the Post by Email feature on your WordPress blog, and you can use the SendImages Kipi plugin in digiKam to email photos directly to your blog.
To make this workaround work, you have to prepare your WordPress blog first. If you host your blog on WordPress.com, navigate to Dashboard | My Blogs and press the Enable button to activate the Post by Email feature. This will automatically generate a unique email address where you send your photos.
digiKam relies on an external email client to send photos, so before you proceed, make sure that you have a supported email program installed and configured on your machine. digiKam supports a wide range of email clients, including Thunderbird, Evolution, KMail, and Claws-Mail.
To send photos, switch to digiKam, select one or several photos, and choose Image | Email Images. In the Email Images Options window, switch to the Mail section and select the appropriate email client from the Mail program drop-down list. If you want to reduce the size and image quality of the selected photos before you send them, tick the Adjust image properties check box and adjust image settings. Hit the OK button, and digiKam automatically creates a new email with an attachment containing the photos using the specified email client. Add the subject and body (read more on how to format your email message for blog posting at http://en.support.wordpress.com/post-by-email/), then send the email to the unique WordPress address. Visit your blog, and you should see a new blog post with all the photos.
digiKam user? Read the digiKam Tricks book!
Cross-processing with digiKam
Although digiKam can’t rival dedicated image manipulation applications like the GIMP, it does have several essential editing tools which can help you to turn plain photos into striking images. For example, using the Curves Adjustment tool, you can apply the cross-processing effect to a photo. This effect is achieved by adjusting curves in three separate channels. In the Red and Green channels, you need to raise the red and green levels in the highlights, and to drop the red and green levels in the shadows. You have to do the exact opposite in the Blue channel.
In digiKam, open the photo you want to edit, and choose Color | Curves Adjustment. Select Red from the Channel drop-down list and use the mouse to adjust the curve. Repeat this procedure for the Green and Blue channels.
Instead of fiddling with curves, you can use a preset file created by yours truly as a starting point. Grab the preset file, press the Load button in the Adjust Curves window, and select the downloaded file. You can then tweak the existing settings to your liking. Once you’re satisfied with the result, save the modified profile by pressing the Save As button. So next time you want to apply the cross-processing effect, you simply load the saved preset file.
Do you have your own favorite presets? Feel free to share them with others.
digiKam 1.5 Released
The digiKam Tricks book version 1.5 is now available at Amazon US and UK. Here is what’s new in this release:
- The book now contains illustrations and screenshots
- Introduction to digiKam chapter added
- Cross-processing with digiKam tip added
Readers who already purchased the book will receive the new version free of charge. If you haven’t received your copy, please send me your order confirmation as proof of purchase to dmpop@linux.com and I’ll email you the latest version of the book.
The book is also available in the EPUB format upon request. Contact me at dmpop@linux.com for further details.
Happy reading!
