Sunday, April 1, 2007

May 2007 HelpLine

DPMag Published in HelpLine
May 2007 HelpLine

The second reason for staying in RAW is that the RAW color workspace has a large bit depth. Think of bit depth as the digits to the right of the decimal point when adding numbers on a calculator. If your calculator only displays two digits to the right of the decimal point, then when you add 2.0098 plus 1.0001, your calculator (depending on how it rounds) will display 3.00 or 3.01. Neither is the correct answer, so a little rounding error creeps in with each calculation.

Believe it or not, when you adjust levels in your image, you're doing math. There are thousands of calculations occurring with the millions of pixels that you're dealing with. Since your bit depth is large in your RAW-processing program, you have more room to work with when doing calculations on the pixels—2.0098 plus 1.0001 = 3.0099.

Now, it's true that you can work in a large bit-depth space in Photoshop. In your RAW program, however, you're working with pixel information closer to the original file as captured by your camera. There are some quality advantages to that (such as the ability to more easily bring out detail in highlights).

Moving on with the workflow, next, you can bring the file into Photoshop or any other image-processing program and continue to edit the image there. Here, you can do things that aren't possible in the RAW-conversion program, such as cloning or selective adjustments to specific areas in an image.

While editing in your image-processing program, I'd recommend that you save the file in the native file format for the program (such as .PSD for Photoshop). This preserves the layers and history of the file so you can return to the image and make other adjustments (or remove adjustments) at a later date.

You mention wanting to use TIFFs. I'd wait and use the TIFF file format for saving output files. Let's say I have an image that I want to print at a large size and a small size and also post on a Website. In this situation, I could work several different ways, but I'd want to end up with four different files: the .PSD master file, two TIFF files for the two sizes for printing, and a JPEG for use on the Web.

This is where I'd sharpen. First, I might apply an appropriate amount of sharpening for the large file and then save it as a TIFF named "photoLG.tiff." Then I'd resize the master and sharpen for the small size and save it as "photoSM.tiff." If the sharpening is still appropriate for Web display, I'd save a JPEG called "photoSM.jpeg." I might also consider saving a thumbnail, depending on the application on the Web.


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