May 2007 HelpLine

Making Workflow Work
Making Workflow Work

    • Raw File Processing
    • The “Oh-Really?” Factor

RAW File Processing

Q) I don’t know what’s best when working with RAW files-opening and working on the RAW file and then saving it as a TIFF  or first converting it to a TIFF and then working on it? Does it make any difference? I intend to save the TIFF files with the best quality.
Pierre Michel
Via the Internet

A) A lot depends on what you mean by “working on it.” Should you do all of your work in a RAW image-processing application? Or should you do some work in RAW and then move into an image-editing program? Both of these questions deal with an ever-popular term in digital photography: workflow.

From capture to output, there are myriad ways of moving your images through the digital darkroom. At times, it seems that each photographer has his or her own special workflow that works best.

As your question implies, however, you need to consider the technical aspects of the way you work on your images. But don’t get too caught up in someone else’s explanation of the perfect workflow. Your workflow should work for you.

I’d recommend that, in a RAW workflow, you try to use as many of the tools available in your RAW image processor as possible. There are two reasons for this.

First, when editing a RAW file, you’re not changing pixels; you’re just creating a set of instructions to tell the software how to process the file. So even if you crop, resize or make the image black-and-white, you can still reset the instruction set and get back to your original RAW image. This gives you a lot of flexibility and allows you to always maintain high quality in the processing. (Adobe Lightroom offers this capability for JPEGs now, too.)


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.


One thing to remember throughout these last steps is to pay attention to when you use “Save” and when you use “Save as.” As you move through images, it’s easy to get accustomed to using Ctrl/Cmd + S for Save, accidentally saving over a file.

Of course, you’re not through with your workflow. But I’m curious what readers think. What’s the last step in the workflow that I’ve left out? Send an e-mail, with “workflow” in the subject line, to HelpLine.

The “Oh-Really?” Factor

Q) Okay, I’m confused! I bought my son a Nikon D50 D-SLR. I understand that there’s a 1.5x lens factor when using “film” lenses because the sensor size is smaller than 35mm. The real confusion comes into play when we start talking about the Nikon DX series of lenses. I’m told that they’re optimized for the APS-sized sensor, so does that mean that the 1.5x factor no longer applies? Most salespeople and ads say “yes” but a few say “no.” What’s the real answer here?
Joe Pasquale
Lancaster, Pennsylvania

A) Before we get into lens “factors,” let’s talk about sensor sizes. There are “full-frame” sensors that are equivalent in size to 35mm film. There are also smaller sensors, which you’ve referred to as APS-sized. Actually, APS was a new consumer film format developed just before digital started appearing in the marketplace.

Before I go much further, let’s deal with the term “lens factor.” People have used all sorts of shorthand to talk about it, including “magnification factor,” “focal length multiplier,” “cropping factor” and, simply, “lens factor.”

The key thing to remember is that the focal length doesn’t change. The act of putting a lens on a camera body doesn’t magically change the focal length. I can go on explaining how the field of view changes or how an object will appear larger in the frame, but no matter what I write, there will be those who will argue about one term or another.

I’d rather see people accept the fact that we’re talking about different formats. There’s a 35mm format and an APS-C-sized format. There are also 4×5 and 645 formats; someday there may be other formats.


When talking about 4×5 and 645, do photographers say 645 is a cropped version of 4×5? No. Are we cropping the image format? No. To say we’re “cropping” when we don’t talk about cropping with other formats is inconsistent.

To say that we aren’t magnifying doesn’t address the fact that the same subject shot with the same lens but in a different format, does appear larger. As photographers, do we want to talk about the size of an object within the image area or some abstract idea about focal lengths?

Another way of talking about this issue is field of view. People are accustomed to the field of view (also called angle of view) of lenses on a 35mm film camera. So when you put a 100mm focal-length lens on a 35mm camera,
it gives you a certain field of view. When you put a 100mm lens on a different-format camera it will give you a different field of view.

But the key point worth repeating here is that the focal length still doesn’t change; the image within the format does. This is where the 1.5x factor you asked about comes from. The lens on an APS-C-format camera acts as if it has a focal length 1.5 times what you’d expect from the 35mm format.

This applies to any lens. When a lens is designed or “optimized” for a certain sensor, that simply means the lens only covers the area of the sensor and nothing larger. The focal length doesn’t change-only the circle of coverage.

All lenses have a certain circle of coverage that affects the format with which they can be used. If you have a 4×5 camera, for example, you must have a lens that can cover the whole 4×5-inch negative. On the other hand, if you’re dealing with a small, compact digital camera with a sensor only a quarter-inch across, you can use a small lens with a small coverage, even though the focal length, again, doesn’t change.

If you have questions, please send them to HelpLine, PCPhoto Magazine, 12121 Wilshire Blvd., Ste. 1200, Los Angeles, CA 90025 or helpline@pcphotomag.com.

 

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