This article answers the following questions:
What does Raw format mean? What does JPEG format mean? What are the common Image formats in digital photography? What are the differences between Raw and JPEG? What is the recommended image format in professional digital photography? What is meant by “banding effect”?
Before you press the shutter release button you need to have made a decision regarding the format your images are going to be saved in. The two common image formats in digital photography are Raw and JPEG. In this article, with clear examples, I will outline what a photographer needs to know about these two formats.
JPEG stands for “Joint Photographic Experts Group”, a group that set the standards for JPEG in 1992. The format itself relies on a lossy compression technique, in which some data will be removed / or disregarded, in order to create a smaller and ready for use images. As a result a JPEG contains a narrower tonal range and limited number of colours on its colour palette.
Raw is not an abbreviations. It refers to the fact that image consists of the complete original data without any or with minimum processing. As a result a Raw image contains a wider tonal range and a tremendous number of colours on its colour palette.
Comparison between Raw and JPEG
JPEG is smaller in size
JPEG is a lossy compressed format. As a result JPEGs are substantially smaller in size when compared to Raw images. The image size, either Raw or JPEG is also related to the size and resolution of the camera sensor. The higher the resolution, the larger the image size. Hence, the absolute size of a JPEG image is meaningful when compared to the size of the Raw image made by the same camera. In addition, your camera is able to generate JPEGs with different level of compression. Increasing the compression level, reduces the image size. Different sizes of JPEG might be indicated as “Large, Medium, and Small” or “Fine, Norm, and Basic” on your camera. Data depicted in Table 1 comes from an experiment in which four images where made from a single scene, using the same camera / lens, and camera setting. The only variable here is the image format. In practice a smaller image size allows you to save far more images on your device / memory card, which is an advantage in smartphone and point-and-shoot photography.
Table 1. Image size in relation to the image format. All images are made with a NIKON D850, a full frame DSLR.
JPEG is a processed and a ready for use image format
As soon as you make the photo, camera’s software will process the data to create an image, which is not only smaller in size, but also it has gone through some postprocessing. This automated postprocessing includes colour correction, increasing contrast and sharpness. In contrast, Raw is an unprocessed image format. It should be read in a Raw convertor, edited and saved in a required format. e.g. JPEG for online sharing, TIFF for print etc. This is why Raw image is similar to the ingredients of a meal, and JPEG to the cooked meal made from the same ingredients.
Figure 1. How an unprocessed Raw image may look, on a computer screen, in comparison to a JPEG is really dependent on the photographed scene. The two images on the first row look quite similar. They depict a scene predominantly made of mid-tones. For a high dynamic range scene, -images on the second row-, the results would be different. For instance, notice a yellow-greenish colour cast in JPEG.
When it comes to the image quality JPEG is no match for Raw
Raw images are superior to JPEG in regard to the following parameters.
1- Raw images have a much wider dynamic range
The two images on the second row in figure 2, are made right after the sunrise, when a massive amount of light illuminates the scene from the left side. The only difference between these two images is the image format. By turning on the “highlight clipping” on the histogram, the overexposed parts of the images will turn into red. For the Raw image the amount of overexposed area is much smaller in comparison to the JPEG. This is because a Raw image has a much wider dynamic range / tonal range. The other two images on the first row are made late in the afternoon. Camera is pointed towards north and a soft light illuminates the scene from the left. The scene is predominantly consists of mid-tones. Hence, dynamic range does not form a problem for the JPEG here.
Figure 2. This is another example that scenes with high dynamic range are more problematic for JPEG format.
2- Raw image gives you total freedom in the post-processing
Because JPEG is a processed image format, some changes have already been made in the image and some tones and colours are lost. This is not the case for Raw images. As a result you have far more options in the post processing to change the images according to your liking. A clear example manifests itself in correcting the colours using the white balance setting. For a Raw image you do not need to be worried about the white balance setting at the time of shooting, since you can change it easily in the post processing. While shooting in JPEG requires attention to the white balance at the time of shooting.
It is still possible to improve the look of a JPEG in the post-processing. But the freedom you have is much limited. In particular when you are dealing with a high dynamic range scene. Notice for instance a phenomenon called “banding effect” on the top right corner of the JPEG in the second row in figure 3. In this area the level of luminosity is changing very fast. However, because JPEG has a limited tonal range it can not create a seamless change from one tone to another one as you see in the Raw image.
Figure 3. In this example some identical and exclusively global adjustments have been done to all images. These adjustments affect: Exposure, Contrast, clarity and vibrance, but exclude white balance correction. Again a mid-tone scene forms less problem for JPEG. While a high dynamic range will become a major problem. Notice the emphasised yellow-greenish colour cast, as well as a banding effect on the top right corner of the JPEG on the second row.
JPEG is the standard format for some built-in camera functions
Some of the camera’s built-in functions, for instance HDR, and focus-stacking, may only work with JPEG. If this is not your preferred format, you need to be aware of that. You can always make such images without the use of the built-in functions.
JPEG and Raw are the most common image formats in digital photography. Both are absolutely necessary for their own intended use. In smartphone and point and shoot photography, JPEG is without doubt the preferred format. Since it allows you to save much more images on your device or memory card. In addition, the smaller size of JPEG might be also an advantage for some professional photographers who need to shoot in barst mode, which creates huge amount of data in a short time.
Raw, in general, is absolutely the preferred format in professional photography. This relates to the quality concerns as well as freedom in the postprocessing. Even if you wish to minimally edit your images, it is still recommended to shoot in Raw.
I hope this was useful, should you have any comment or question, please feel free to send me an email.
Triangle Photo Academy