The Real Truth About JPEG images

This article originally appeared in Outdoors Unlimited, the publication of the Outdoor Writers Association of America.

The Real Truth About JPEG images

by Michael Furtman

One of the great myths in digital imaging – adopted as gospel by both photographers and editors – is that JPEG images are so inferior to RAW as to make these images unsuitable for professional work. JPEG is different from RAW, that's for sure, and both have their advantages, but to consider JPEG files unsuitable for professional work is simply wrong.

First, some terms: RAW files are compressed files, but are “lossless” – that is, they lose no information in compression. Identical images shot with a six mega-pixel camera would yield a JPEG of about 3 megabytes (shot at highest JPEG settings), a RAW of about 6 mb, and a TIFF of 18 mb.

The myth of JPEG unsuitability arises because a JPEG image is a compressed image, and that in the process of compression, information is lost. It is also common belief that each time you open and close a JPEG file, it undergoes more compression, thus continuing to lose information.

While it is true that a JPEG file does lose some information in compression, the amount lost is so small that it is virtually indiscernible to the human eye. I’ve made giant prints from RAW and JPEG images to prove the point, and no one has yet been able to tell which was which. I’ve also sold many JPEG images to publications – some of which have run as a double-truck (two page spread) – and the editors had no qualms about the quality. National Geographic’s first all-digital photo story two years ago used nothing but JPEG images. So while theoretically, a RAW file is superior to a JPEG file most of the time, the question to ask is whether or not that extra information contained in the file is necessary for your intended results. In other words, if you can't see the difference in print, is shooting RAW really any advantage?

OK, so JPEG is fine, initially, but they’ll degrade over time, right, because each time you look at them and close them they get compressed again? No. It is NOT TRUE that opening and closing a JPEG file continues the loss. In fact, saving a JPEG image multiple times during a single Photoshop session introduces no addition compression.

To be sure of this, I contacted the programmers of Adobe Photoshop. What I learned is that when you use “SAVE AS” (renaming the file causes Save As) or Save/Close at the end of an editing session (over-writing the original), does it undergo another compression, and then, so very little as to be undetectable provided you save at Photoshop’s maximum JPEG setting of 12. Opening, examining, and then closing the file has absolutely no impact upon it, nor does using the SAVE option multiple times during a single editing session. So....when you SAVE, then close it (which also means you're over-writing the original, which I don't recommend so that you can return to it in the future) or SAVE AS (you edit the original, then give it a new name, requiring SAVE AS) does it undergo compression, but in both cases, it only goes through ONE MORE COMPRESSION. That's not enough to alter the image quality in any discernable way. Not at least to the human eye, or for the purpose of print.

To test this, I took an image and saved it 30 times during a single session – a number far greater than anyone would normally ever do. I then produced 100% crops of the two images and placed them side by side. I then emailed this composite image to several magazine photo editors, asking for their opinion and they all said the same thing – they could discern no loss of detail, or increased JPEG artifacts. To view this image yourself, click HERE.

I also tried “SAVE AS” multiple times. By the fifteenth time, image degradation was apparent. But judicial use of this method of saving (one or two times) results in no discernible loss.

Some claim that RAW is superior because it is your “digital negative.” Yes it is. But so is your original JPEG image. If you make any adjustments to a copy of it, and never re-save the original, you’ll always have an original to return to. And you can always save it as a TIFF file for editors who insist on this huge, disk-space robbing file format (they will never know the difference!). To insure the best quality when shooting JPEG images, make sure you shoot at your camera’s highest JPEG settings, turn-off in-camera processing, and if possible, set the color space to aRGB (Adobe RGB) if your final output is going to be for print (off-set printing, or even desk-top printing), since aRGB has a broader gamut of colors, which are similar to those used (CMYK) in off-set printing.

There’s one last myth about JPEG – that it doesn’t provide enough adjustment latitude for correction for our kind of work. Bunk. A JPEG file will give you a full F-stop above and below proper exposure for correction purposes. For our use as outdoor photographers whose work appears in magazines, JPEG is actually more forgiving than the slide film we shot for years, which has essentially zero latitude. When should you use RAW? Well, you can use it all the time, if that's your preference. It is very useful -- maybe even necessary -- if you’re shooting a concert or sports event indoors under funky lighting, so you can correct the white balance later. If you shoot just a handful of images a day, use RAW. And if you can't get within two stops of a proper exposure, by all means, shoot RAW.

One of my acquaintances who is a professional photographers' technical contact at Canon summed up the differences between RAW and JPEG in a useful, understandable manner. He suggested that photographers consider RAW to be the digital equivalent of print film, and JPEG to be the digital equivalent of transparency (slide) film. Print film has always allowed for great latitude in processing than slide film. I think this analogy is a good one. Magazine photographers have always shot slide film. We know how to get a decent exposure -- something even easier now with digital since you can look at the image in the review monitor, or examine the histogram, while on location. If the image is poorly exposed, you know it immediately, and can make the adjustments needed to get the subject right. There really is no reason to come away with a poorly exposed image these days.

JPEGs have advantages over the other file formats. Being a smaller file size, JPEG is better for action photography because your camera will not have to pause to write to disk as soon, and you’ll also get more shots per flash card. If you shoot many images in a day, your work flow will be easier and much, much faster with JPEG because, as anyone who has worked with RAW files knows -- even if they love RAW files -- these files require much more post-processing, which can be a time consuming venture. Finally, JPEG files take far less space on your hard drives, and you can fit many more on a CD or DVD for archiving, which is no small point for those of us who shoot thousands of images per year (I currently have over 60,000 images on file, spanning four hard drives!).

It is important that you preserve the integrity of your JPEG file. In addition to insuring that your retain the original file without over-writing it (make alterations to a copy), it is wise to turn off any in-camera processing, such as sharpening, contrast, and hue adjustments. Not only should you make these modifications in Photoshop, where you can do a more precise job, you want as "clean" a JPEG file as possible. Any processing done in-camera to a JPEG file can not be undone. Most dSLRs will allow you to turn off in-camera processing, although some point-and-shoot digital cameras will not.

There’s a time and place for RAW. It is a wonderful format for many photographers. That said, JPEG’s bad rap is undeserved, and it is time we disposed of the myths surrounding it.