By: Gary Gray
Image Files. Which file type is best? Raw vs Jpeg (also known as jpg.) The debate continues. The answer of course is “it depends.”
When I first began using a digital camera 10 years ago, I initially used jpeg file format when I took photographs. After a year or so of a learning curve with the new digital technology, I switched to using RAW as my primary file format for my digital photos. Today, with the exception of the most casual of photography with my point & shoot cameras, I continue to use RAW format for all of my photography. I would never consider using jpeg as a file format for any “paid” work. When asked by people which format I use, I typically respond that I only shoot jpeg when I want my photographs to suck.
Fast forward to early 2013.
At a recent local camera club meeting, our club's guest speaker, a notable local wildlife photographer, indicated that he used jpeg file formats for most of his wildlife photography. I found this surprising, as virtually every other professional photographer I personally know, uses RAW as their primary image format.
He went on to explain that he shoots about 300,000 photographs a year, and that he felt the image quality from jpeg had improved over the years and was “good enough” for his type of work. I have to challenge this thought though, as an improved jpeg file format though approved (jpeg2000), it has not been adopted by any of the camera manufacturers and the original jpeg specification is what is being used today. He also explained that it allowed him to store a lot more shots on his camera chip and on his computer hard drive. This is fine, a photographer needs to rationalize what he is doing to achieve what he feels is correct for his business needs. I do the same thing, except I don't shoot jpeg images and my rationalizations are different.
I'll explain why I shoot RAW and why I do not recommend jpeg format for the serious photographer.
First and what I consider to be the primary reason for shooting RAW files is that the RAW image format is a far superior image file format for the purposes of image quality. In every regard. No exceptions. There is not a single technical or quality aspect of a jpeg file that produces a resulting image that is as good or better than a RAW file.
Second, editing of jpeg images is a destructive process. Editing of RAW files is a non-destructive process.
From my view of the road, I recommend that a photographer only shoot jpeg image file formats when the photographer is required to do so. If the photographer has a choice, he/she should choose not to use the jpeg format. Jpeg images are the lowest possible quality image files that can come out of your camera, and ultimately, no matter what you do, the image quality will never exceed that of the original file.
The sensor in your camera is what determines the original dynamic range, detail, color and potential tonal quality of the images your camera can produce. It is the electronics inside the camera that create the image files and the quality of those files are based on the mathematical algorithms used to produce those files.
I am going to attempt to explain this without a bunch of charts and 100% image crops. I'm not into pixel peeping and the technical and engineering details of photography, though important and sometimes interesting, are not what determines how good your photography is. Try to never lose sight of that fact.
So, the main differences of the two file formats are as follows.
Bit Depth: Jpeg is an 8 bit image format. RAW is currently a 12 or 14 bit image format, depending on the make and vintage of your camera. Simply, what this means is a jpeg image will contain at a maximum, 256 graduations of contrast and tonal rage. From the darkest black, to the whitest white, there will only be 256 steps of variation. Sounds like a lot doesn't it? Well, compare that to a 12 bit RAW file that has 4,096 graduations and a 14 bit file that contains 16,384 graduations of tonality.
Looking at this comparison in a chart will help explain how much image data is contained in each file format. Consider that half of the data in your image file is going to be found in the brightest stop of the scene. We're talking about pure white and 1 stop below pure white. Each stop below pure white will contain ½ the amount of preceding brighter image range. So, you can see that as the image brightness approaches black, you have very little image data being recorded in the file. Lets assume a digital camera with a total dynamic range of 8 stops. That's 8 stops of difference between the brightest white and darkest black, here's is how your image data will be quantitatively distributed by image brightness.
8 bit image 12 bit image 14 bit image
Brightest stop 128 bits 2,048 bits 8,192 bits
2nd stop less bright 64 bits 1,024 bits 4,096 bits
3rd stop less bright 32 bits 512 bits 2,048 bits
4th stop less bright 16 bits 256 bits 1,024 bits
5th stop less bright 8 bits 128 bits 512 bits
6th stop less bright 4 bits 64 bits 256 bits
7th stop less bright 2 bits 32 bits 128 bits
8th stop less bright 1 bit 16 bits 64 bits
What may occur to you as you look at this chart is the fact that a jpeg image format is not going to hold shadow details very well. A 12 bit raw file can contain 6 times the image data in the shadows that a jpeg image can contain. As a result of a lower precision and bit depth of the jpeg file, one serious side effect is posterization. Posterization is a visible artifact that results in images with distinct transitions between similar tonalities in the image. It's generally considered undesirable.
Posterization as defined by Wikipedia.
“Posterization of an image entails conversion of a continuous gradation of tone to several regions of fewer tones, with abrupt changes from one tone to another. This was originally done with photographic processes to create posters. It can now be done photographically or with digital image processing, and may be deliberate or may be an unintended artifact of color quantization.”
Post-processing/Editing: The post-processing limitations of the image file is what I consider to be the major flaw of the jpeg format. A photographic analogy would be to think of the RAW file as a digital negative and the jpeg image as a drugstore print. The negative (RAW file) is going to contain the highest possible amount of image information, the print is going to be manipulated by a photographic reproduction process to generate a viewable image.
RAW files have a much larger possible range of post processing adjustment with tonality, color, hue, white-balance, contrast, sharpness and exposure. It is because of this significantly better range of adjustability, one can create a final image or print that is visually far superior to that of an out of camera jpeg file. With a camera created jpeg image, you're stuck with what you have for the most part. Some post processing can be done with a jpeg image, but not nearly to the extent of the RAW file. In some instances, a RAW file can be fixed whereas the identically shot jpeg image may not be fixable. A good example would be on images that have very bright highlights. Over exposed highlights can be recovered from a RAW image, up to 2 full stops worth. With a jpeg image, you' may get an additional ½ stop of highlight recovery at best. Also, the details in the shadow areas of your images will suffer far more with jpeg files than they will with RAW files. You can pull out another 1-2 stops of shadow detail in post processing using RAW files that you will simply never see using a jpeg image. In addition, RAW files inherently have a greater dynamic range to begin with.
The other major limitation of the jpeg image relates to it being a “lossy” file format. Since image data is discarded to create a jpeg file, you can see a visual difference in a jpeg file and a RAW file when it comes to fine detail and transitions of tonality and contrast. Take the identical scene and examine them closely, you'll find that a properly processed RAW file is going to be sharper, clearer, crisper and more dynamically colorful than an identical jpeg file.
Think about it. A RAW file is going to be 3-4 times the size of the jpeg file. What happens to all that data when you create a jpeg file? It's thrown away. That smaller file size is a result of discarding image information during the compression process. RAW files aren't compressed, therefore, no data is lost.
The drawback of the RAW file, if it is a drawback, is that you have to learn how to properly post-process a RAW file to get that result. Straight out of the camera, an unprecessed RAW file will not have the same "Pop" to it that you see with a jpeg image. The reason for that is simple, the file hasn't been processed. It's akin to having a chunk of meat and learning to cook it. If you can't cook, the jpeg file is the fast food of photographic image files. A good cook can make a better meal themselves by doing their own processing of the image, but it takes longer and requires more knowledge.
The improvement in image fidelity using the RAW format is going to make itself apparent with large prints and in applications where maintaining fine detail is very important, such as in medical or precision photography environments.
Image Data/File Size: As I've already mentioned, the jpeg file format utilizes “lossy compression.” When the image file is created, some of the image data is tossed out in a process called down-sampling in an effort to reduce the size of the file while still maintaining a large amount of visual accuracy in the image. Once that data is gone though, it can never be retrieved. The net result is that image detail across the image will suffer, as there is simply less data image detail stored in the image file.
Most RAW file formats will contain the full amount of the data that was captured by the camera's sensor. RAW files are not compressed to reduce file size. Note however, that there are some RAW file formats that reduce the size of the RAW file, typically called “small RAW or S-RAW” and these types of images are not a topic of this discussion. The S-RAW file will still have better detail and post-processing possibilities than a similarly size jpeg image though.
The image file sizes will be dramatically different between a identically sized full resolution final jpeg and RAW images. The RAW files will be between 2-6 times larger and require much more storage space on your hard drive and in the camera's memory chip. For an example, using my Canon EOS 7D as a reference, I can expect to store 38 images per gigabyte of storage memory, whereas I can store about 133 full resolution jpg files per gigabyte. That's 3.5 times more images on a memory card using a jpeg file format. Being able to store substantially more images in the same amount of digital storage space can be a major consideration in favor of jpeg file formats. The smaller jpeg files can also be transmitted more quickly over data connections such as ftp or modems, or even when loading from the camera to the computer, thus reducing the amount of time spent waiting for images to be moved electronically from one location to another. A lot of newspapers and printing services use jpeg file formats as their standard because of the efficiency of faster transmission rates and lower storage costs per image as they are willing to sacrifice image reproduction quality for speed and efficiency. For applications such as newspapers and print media, the amount of quality loss from RAW to the actual print CMYK and offset printing process is very high to begin with, so whatever quality is lost in converting RAW images to jpeg file formats for offset printing is insignificant from a technical standpoint as other factors have a much greater impact on final print quality.
Another consideration in favor of using a jpeg file format over a RAW file format in your camera is the camera's ability to shoot continuous bursts of shots. Using my Canon EOS 7D as an example, loaded with a high speed UDMA memory card, I can expect to get about 22 continuous photographs at about 8 photos per second. That gives me at best, 2.75 seconds of continuous shooting at full resolution using RAW.
When I switch to jpeg file format, and everything else being identical, I can rationally assume that I'll be able to take up to 60 photographs at 8 frames per second, allowing me to shoot continuously for up to 7 or 8 seconds. Your camera, assuming it is not a Canon 7D, will of course have a different result, but the same general buffering constraints and continuous shooting performance issues will apply. So, a sports photographer taking photographs of an action sequence at a sporting contest may very well be better off shooting jpeg file format as he can capture much more of the action sequence in a single burst and he can store many more photographs using the same amount of camera flash memory. That same sports photographer can also transmit his images to his publication faster because the file sizes are smaller. Or he can download those images to his computer more quickly.
Lastly, another consideration is how the final images are going to be used. If your photographs are primarily going to be displayed on the internet, jpeg file formats are probably all you'll ever need. In 2013, the standard file format for photos displayed on the internet is jpeg. Higher resolution images are simply not going to do you any good. I would say though, that just because you are going to show your images on the internet, that alone is not enough criteria to justify always shooting jpeg, as by shooting RAW format, you'll always be able to convert to a jpeg image and you can do a much better job of making a jpeg image using your computer than your camera can, if you have even basic editing skills and suitable photo editing software.
The bottom line though is that there are some advantages to shooting jpeg images, depending on your speed requirements for work-flow, final intended usage of your images, digital file storage limitations and file transfer requirements. From my view of the road, the advantages of the jpeg file format don't out-weigh the disadvantages of the loss of image quality. Even as a wedding or event photographer, I don't find that the RAW file format is slowing me down to any measurable or problematic amount. I can take 2000-3000 photos at a wedding and the minuscule increase in download time doesn't really affect my work-flow. If I were shooting 4 weddings a week, that speed may be an issue. Also, I look at file storage as a requirement of the business, so I've invested in large hard drives in my computer and for file backup storage. I shoot 50,000 or more photographs every year and keep about 35,000 of those images. File storage space is a consideration, but keeping my files weeded down to only those images I feel are ultimately worth saving is the key to managing storage space. One terabyte external hard drives are cheap and getting cheaper each year. I'd rather have the negative and the ability to edit the final images than save a few bucks on disk storage. Plus, if you're shooting jpeg files, you're still going to run into the storage issues, just not as quickly. So, it generally comes down to speed, efficiency and budget vs image quality. You decide if your budget and or time is more important than your quality.
As for me, I've decided. I'm a professional photographer and artist. The quality of my final product is more important than everything else.
(original publication date: January, 2013)
Raw vs JPG