Last month (see Newspapers & Technology, March 2008, page 40), we took a look at one of the newest file formats in the digital universe; camera raw. The camera raw file is the uncompressed, unprocessed file that the digital camera sensor generates.

Why use the camera’s raw file instead of the more common TIFF or JPEG formats? A simple explanation is that you just might have a better idea about what you want your images to look like than does the engineer that designed your camera. After your camera software has delivered a finished JPEG or TIFF image to your computer, any detail or color gamut that has been lost is gone forever unless you have a great talent for retouching.

Color temperature, exposure, shadow detail, brightness, contrast, saturation and image sharpness can all suffer when camera software has at your images. But, if you work with camera raw images, you will find tools at your disposal that will allow you to modify each of these parameters. In addition, you will have the ability to work with 16-bit images instead of 8-bit images, and programs such as Adobe Photoshop can utilize these 16-bit images to provide smoother gradients, and improved tone separation.

Recognizing  raw files

It is not the easiest task to recognize raw files that might cross your desktop. This is because raw files can have all kinds of file extensions depending upon where they came from. For instance, Canon uses a .CRW extension, Nikon uses .NEF, Minolta .MRW, and Kodak might use either .KDC or .DCR.  Although Adobe does not produce cameras, it has come up with its own raw file format, the DNG, or digital negative format. It was hoped that all manufacturers would adopt this common file format but, so far, this has not happened.

Now, don’t abandon your attempt to work with camera raw files just because there is no standard file format. Luckily for us, Photoshop and other programs are smart enough to recognize all of these file types and will know what to do with them. Simply double-click on or use the file>open method to open a file in Photoshop and it will launch the camera raw module  (Figure 1).


Fig. 1: The Adobe Camera Raw interface provides you with extensive options to enhance your images before you even open them in Photoshop.
 

The title bar for the interface will display information from the metadata contained within the file such as camera model, speed, lens and exposure details.

Once the interface opens, you can look in the lower left hand portion (Figure 2) to begin the exploration. Here you can select which color space the final image will be converted to as well as the size, resolution, and the option to select between an 8- or 16-bit file. 


Fig. 2: The overall physical structure of the file can be specified using the menus in the lower left-hand portion of the interface.

The ultimate undo

In the upper left-hand portion of the interface you will find tools that can be used to zoom, crop, rotate and sample color information from your file. An important feature in working with camera raw files is that any changes you make in this interface will not alter the original file but will, instead, be used to modify the processed file you save from within the interface.

Here then, you can see another benefit from working with raw files; the ultimate undo. If you do not like the results of your manipulations, you can always go back to the original raw file and try again.

On the right-hand portion of the camera raw interface you will find the main area where you will do most of your image manipulation (Figure 3). On the Adjust tab you will find sliders used to modify fundamental settings for the image including color temperature, exposure, contrast, brightness and saturation. If modifying these settings appears to be a bit opposing at first, defer to the drop-down menus. The Settings drop-down menu allows you to select between default settings for the image, the camera raw defaults, or any custom settings you have previously saved.

Fig. 3: The settings panel is where most of the power
contained within using camera raw files resides.
 

Moving lower on this panel, you will next define the White Balance for this image. You can use the white point that was stored with the image by the camera or select from a list of standard light sources or use the sliders to build a “custom” light source.

Next up is the Detail tab. Here you can add varying amounts of unsharp masking to make the file appear sharper.  Adding Luminance Smoothing will help minimize the “grainy” look of an image that may occur if you used a high ISO setting on your camera. This grain appears as neutral-colored “noise.”  A cousin of this artifact is grain that appears to be colored rather than neutral. If you see this problem, the Color Noise Reduction slider tool is at your service to help reduce it.

Chromatic aberration is a phenomenon where different wavelengths of light will focus at different points on the lens.  Obviously a lens cannot be focused at multiple points in a single image and the resulting chromatic aberration will appear in images as color “fringing” which you may see in areas of high contrast such as edges.

Look to the Fringe sliders on the Lens panel to negate these artifacts.

Minimize vignetting

Vignetting, or the effect seen when light is not evenly illuminating the sensor, can also be minimized on this panel. This would appear as a darkening of the image around the edges. The midpoint slider controls how far into the image the falloff extends.

On the first tab, the Adjust tab, you have a control for contrast.  This is a fairly simple tool when compared to the control you have over contrast when using the Curve panel (Figure 4). From the drop-down menu you can select to add no additional contrast, the Linear option, or a medium or strong amount of additional contrast. By selecting the custom option you will be able to modify the curve just as you would any curve in Photoshop by adding and modifying anchor point position along the curve. 

Fig. 4: You can fine-tune the contrast adjustment set on the Adjust panel by using the curve found on this panel.
 

The camera raw comes programmed with the color characteristics of many camera chips and these characteristics are used when converting the image into your desired color space.  The Calibrate panel allows you to overrule the default settings to fine-tune the color balance of the image. The shadow tint slider will shift shadow areas of the image by adding green or magenta depending upon the position of the slider. If used on a low-key image, it will appear to modify the entire file rather than just the shadow areas. The additional red, green and blue hue and saturation sliders will give you wide latitude in finessing the color balance in a somewhat selective manner.

Located at the top of the interface are buttons that can be used to show, through the use of a colored mask, whether any clipping is occurring in these areas, which will effectively destroy any detail in these areas. If you determine that the detail indicated is important to the image, modify the sliders on the adjustment tab to retain it.

Clicking on the small arrow located just to the right of the Settings drop-down menu will bring up a panel that you can use to save the current settings that you have modified.  It is common that you will apply the same settings to multiple images and this feature should prove to be a great time saver.

As you can see, Adobe has elected to provide digital photographers an extensive set of tools they can use when dealing with camera raw files. Being able to go back to the original file at any time and reprocess it with modified settings is a great safety net. But remember: It can only be used by photographers who decide to take advantage of shooting raw.

Give it a try. You might find that the trade-off in a larger file size and reduced shooting speeds may just be worth it.

John Nate is a senior color specialist for Chromaticity Inc. He can be reached at jnate@chromaticity.com, or 616.988.6119.