In the last two posts I presented data about how "successful" my picture taking has been and what common disasters immediately ruin a photograph. On this post I will address how non-catastrophic photo errors can be corrected in the post-processing phase or the "electronic darkroom."
Most snapshot photographers take a photo and allow the in-camera processor to create an image that can be viewed, shared or printed. Usually, these images are in a file format called Joint Photographic Experts Group or JPEG. JPEG is the most common file format used on the internet and is a compressed 8-bit file that has been around since the early 1990s. There are three concerns for serious photographers about capturing images in the JPEG format: 1) JPEG is a compressed format so much of the image data is thrown away during the compression in order to make the file size much smaller, 2) JPEG uses a lossy compression algorithm, meaning that every time the file is changed and saved it is re-compressed causing further loss of image data (the picture quality deteriorates), and 3) JPEG is (almost always) an 8-bit format that does not lend itself well to significant image manipulation in common software programs such as Adobe Lightroom or Photoshop. So what is the alternative to JPEG?
Digital cameras capture an image from the sensor in a RAW format. The RAW files contain luminance (brightness or intensity), redness, greenness, and blueness data from every single pixel in the sensor. This creates a huge 12 or 14-bit file that is not viewable without processing by additional software. The RAW data are compressed and converted to JPEG files for viewing in the camera and, depending on the camera quality and settings, are saved as JPEG, RAW, or both file types. Most advanced photographers save their images as RAW files so they can be saved and manipulated as needed without worry about data loss caused by file compression. The RAW files can be digitally manipulated over and over and the images will not lose data or quality. The RAW files have many different names depending upon the brand of camera used. Canon names their RAW files with the extension .CR2 and Nikon uses the file extension .NEF, in any regard, these are RAW files. I allow the editing software to convert my Canon .CR2 files into .DNG (digital negatives), a non-compressed, open-source file type that is common to almost all RAW processing programs. Conversion of any RAW file is necessary for viewing, sharing and printing and many file formats can be created from the RAW files. The common formats are JPEG, TIFF, PSD, GIF, and PNG. The differences in these formats are not important now.
So, the point of this posting was to overview the workflow that I use to prepare RAW images for viewing, sharing or printing. I use Adobe Lightroom for 90+ percent of my post-processing and use Photoshop for most of the last 5-10%. Lightroom is a database program optimized for photography. It catalogs the images so I can find what I want from more than 35,000 images in a few seconds but it is also a powerful image editing tool that is non-destructive and reversible.
When I import a file from the memory card of my camera, I follow a specific workflow to prepare the images for viewing. First, I rename the images to the day's photoshoot combined with the camera-generated file number, and, at the same time, I tag each images with searchable keywords that indicate the state, season, subject, and special tags for other processing. While this occurs during the image import, I look for the 5 causes of failures and delete these images on the spot. During the file import, I allow Lightroom to perform common "adjustments" to white balance, exposure, contrast, clarity, sharpening, and removal of digital noise - the same sort of things done to create a JPEG file in the camera but without compression of the file and loss of data. Digital cameras automatically capture the EXIF information for each image - this includes date, time, camera, lens, shutter speed, aperture, ISO, flash, copyright, and other information embedded into the image file.
After import and screening for 'bad' images, I view every image for 'first round' processing. I straighten the image and crop it if necessary. Next, I recheck the white balance and adjust the exposure and contrast to assure there is no 'clipping' of the whites or blacks that cause loss of clarity or detail in the image. Next, I add more specific keyword tags to selected images and if needed apply fine detail exposure and contrast enhancements to make the image 'come to life" more realistically as I saw it. Finally, I geo-tag the approximate location of the shot on Google Earth and back-up the files on the computer and re-format the memory card in the camera for the next day's shooting.
I put the images out of mind for a day or two and then revisit the image folder for the day to compare and eliminate duplicate (or near duplicate) images. I may refine the keyword tags and grade the images from one to five stars (still no 4 or 5-star images!) The starred images may receive additional cropping, exposure, or sharpening adjustments. Finally, a few images will go to Photoshop for advanced editing to remove artifacts or stitch together panoramas or high dynamic range images.
So there you have it, a lot of steps but much of the process is automated. The result is searchable, unique, refined images that are ready for conversion to JPEGs for sharing or printing. I will expand much of the post-processing information in later posts. But now it is time to start shooting again.