DigitalPro Shooter Volume 2, Issue 7, March 24th, 2003

Welcome to DPS 2- 7. Judging by the mail we receive and the posts on many websites around the net, choice of file formats is one of the hottest issues facing digital photographers. But what are the real differences and how should you choose a format to use? Too many of the conversations on this topic turn into tirades by one side  promoting their point of view for a business or other selfish reason without taking into account the needs of those listening.

In this issue we've pulled together for the first time a broad model of how you can think about Raw and JPEG and some rules of thumb for making the choice. We'll also bust some of the myths about file formats.

Raw vs. JPEG: Style or Substance?

The very first thing to know about Raw, TIFF, and JPEG is that if you have a pro quality D-SLR (this includes at least the Canon D60, 10D, 1D, 1Ds and the Nikon D100, D1, D1X and D1H) you can take high-quality publishable photographs in any of the 3 file formats (although you'll want to be using the highest quality settings and highest resolution available for whichever format you choose). All D-SLRs have hundreds of dollars worth of electronics--that you paid for--which are dedicated to taking the raw sensor data and turning it into a useable finished image in a fraction of a second. This is probably the most remarkable miracle of modern digital camera technology. If your camera vendor claims you need to shoot Raw format to get the best quality from their camera, ask them if that means you've wasted $500 or more paying for all those extra circuit boards to do in camera image processing:-) Or if they don't have confidence in their own camera to produce a finished image. Frankly, its just as likely that they have a vested interest in locking you in to their proprietary file format and image processing software system. We'll come back to the quality issue, but first we'll look at the broader issue of shooting Raw vs. JPEG.

If we clear away all the computer jargon the Raw vs. JPEG discussion is really the same as one that has been going on in photography for decades. Basically it has to do with when your photograph is finished. Any one who shot chromes, particularly for editorial submission or projection, was used to the image being complete at the moment the shutter was pressed. As long as the light was within the range of the film and the metering was set the way you wanted, the photo was finished. If you needed to print a slide you could send it off to a lab and the lab tech worked to match the chrome. By contrast, many photographers who shot with negative film were used to an extended creative process that might involve hours in the darkroom working to finish the image that they started in the camera. The greater latitude and resulting lower gamma (contrast) of negative film meant that an extra creative step was needed to print the final image. And since negatives can't be viewed directly there wasn't any single "right" way to visualize the image contained on a negative. Obviously the most famous example of the importance of printing were the many famous Ansel Adams images that were of only passing interest until reprinted many years later in a way that caught the viewer's attention.

Today we are witnessing a replay of this same phenomenon with digital. Depending on your job requirements or your style, you may work to create the image in the camera. If so, then the camera's extensive image processing circuitry is your best friend. It'll will turn the light you capture into a finished and viewable image practically before you let up on the shutter. Just as with chromes, your image is complete and ready to use. Of course this assumes you've got the lighting, exposure and white balance just the way you want them before you press the shutter. On the other hand, if you think of the scene in front of you as the raw material and yearn for the time you spent performing your special magic in the darkroom then Raw files give you back that same flexibility. You can remap the 12-bits of information captured by the camera into the final 8-bits needed for output. You can change the white balance to your heart's content and you can even alter the exposure by several stops without ruining the image. You can do some of that with JPEGs, but not as well or as extensively.

If everyone was willing to just leave the choice at that life would be fairly simple. Raw files allow you to create a digital darkroom and fulfill your creative yearnings at the computer while JPEGs complete the image at the time of capture and recreate the freeing feeling of chromes when your image is finished at the time you click the shutter. But in the interests of selling seminars or software, or just promoting their workflow there is a steady siren's song that claims you need to shoot Raw files to get the most from your camera. Frankly, that's bunk. Sure, if you live in the world of numbers, there is good, solid math that shows you can tweak more decimal points out of a Raw file after the fact. That 2GHz Pentium and enough of your time can do a technically superior job when compared to the VLSI in the camera and the 100 milliseconds it has to do its work. But that comparison completely ignores your skill as a photographer, your needs as a working pro, and the value of your time. If you are familiar with your subject and the lighting conditions, you can often capture the image so that it can be directly processed into a JPEG without losing anything you wanted it to communicate. And if you are paid to produce quality images, the increased size of Raw images and the increased processing time required will decrease your productivity. That's fine if you need Raw images to create your final result, but if you don't then Raw files are just slowing you down. Finally, your time. If you enjoy working with your images, just like you enjoyed working in the darkroom, then great. But if not, then let the camera you paid all that money for do the work rather than making you do it! If you can live with the larger file size, Canon's Raw+JPEG option is a very creative approach to providing the best of both worlds. Kodak's ERI format is as well. Nikon's attempt to emulate this capability by adding JPEG creation for Raw files in Capture is nice in theory but defeats the entire point of having the image finished in the camera by requiring the purchase and use of their software to create the JPEG. (Note: Unfortunately with the Canon 10D, it appears that special software support is now needed to extract the JPEG image from the Raw+JPEG file. This removes much of the advantage of having the JPEG there in the first place.)

This image of a Bald Eagle works as is, shot with a White Balance of 6510K. If I'd wanted the Eagle to look as if it was in front of a perfect blue sky I could have shot with a lower color temperature setting.

But since the image is a NEF file I can easily change the White Balance after the fact in Adobe Camera Raw to create the classic blue sky look if I change my mind later. The image isn't any better as a result, but I do have more freedom to make choices "in the darkroom" instead of just behind the camera.

Okay, so by now you're saying, "But I heard that you need to shoot Raw to get the best images". Let's talk about that in more detail. The first thing you've probably been told is that Raw files are 12-bits and JPEG files are 8-bits so they're "better". However that is apples vs. oranges. The 12-bit CCD is a linear encoding of light. Each of the 4096 levels represents an equal number of photons. The human visual system's response to light isn't linear though. Humans are sensitive to percentage changes in light, not absolute changes. So at the high end of the 4096 values there is "too much" information (the brightest stop of light is represented by 2048 separate values, from 2048 to 4095) while at the low end of the 4096 values there is "too little" information (the darkest stop of light is represented by only 2 values, 1 and 2!). Nikon itself uses this fact to create visually lossless compressed NEFs. The compressed NEF format uses just over 500 values (a little over 9-bits) to encode all the data in a NEF file by spreading the values out in a way that more accurately reflects the sensitivity of the human eye. The camera uses a tone curve (essentially a modified gamma curve) to push that a little further, into an 8-bit (256-value) encoding. Sure there is some small loss of mathematical detail, but if the tone curve is the right one for the image and you don't need to move the exposure after the fact you'll be hard pressed to see the difference. And since essentially every output device in common use is 8-bits or less per color, your software is going to need to do convert the image to 8-bits per color at some point in any case. The only advantage of doing it on the computer is that you can change your mind or re-purpose the image after the fact by doing it several different ways.

A very similar argument is also heard about JPEG compression. There is a gnawing fear that somehow because JPEG is a "lossy" compression algorithm you'll be throwing away that vital pixel. The truth is that modern JPEG compression--when used with the High quality settings found in modern D-SLRs or Photoshop--is essentially visually lossless if used only once or twice on an image. There is a detailed comparison of different levels of compression and how they specifically affect pixel values in the D100 and D1 Generation Update eBook if you're interested in the gory details. There is no question that by forcing the choice of exposure, tone curve, and white balance at the time of capture JPEGs limit your options to change your mind after the fact--just like slide film did. But that doesn't mean that slides aren't as good as negatives or that JPEGs aren't as good as Raw files. It means you need to decide on your goals for your photography and about which format fits your shooting needs and style.

For me personally, the decision is normally easy. I spend too much time in the office or on the computer as it is. I'd rather invest my effort in learning how to capture the image the way I want it when I press the shutter than in perfecting my digital darkroom technique. And photographing wildlife brings in a whole other dimension. The constant activity of the subject means that JPEG offers the substantial advantage of letting me capture more of the action more of the time. Any image I capture is of course better quality than one I don't! But, in case you think we don't spend enough time with Raw files to truly appreciate their beauty, in the process of creating DigitalPro my co-developers and I have shot and built decoders and viewers for over a dozen different variants of Nikon and Canon Raw file formats, so we a solid understanding of what those file formats offer and how D-SLRs and computer software alike render them into completed images.

But, as my daughter says, "Make your own opinion". There are as many opinions out there as there are photographers, but only yours matters. What's important is that you have confidence in your ability, your equipment and your workflow to help you produce the images you need when you need them. Have fun and good shooting!--David

We'd love to hear your opinion, as well as what format or formats you shoot and how they help you creatively and in your business. Please join us on the DigitalPro forums and let us know!

DigitalPro Tip of the Week

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DigitalPro2 Preview 4 available

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