AG Photo luxury
raw format
Introduction
As I explained in the second part of the chapter dedicated to the sensor, it transforms light into an electrical signal; for each pixel, the sensor collects information regarding the intensity of the monochromatic light and, thanks for the CFA filter, also information relative to the wavelength of only three fundamental colors of the RGB system. The data collected at this point are crude and not yet translated into a proper image. This data can take two different roads depending on the settings chosen on the camera and the format in which the image will be saved.
If we choose to save it in the Raw format, the data is saved as described, on the memory card.
If we instead choose the Jpg format, the processor carriers out a demosaicing by using an algorithm that determines the two missing chromatic components for every pixel, obtaining them from the pixels nearby thanks to interpolation. Afterwards, it applies the white balance that was selected in the settings, any possible filters, color styles, contrast, saturation and other elements. In the end it compresses the file, saving it in the Jpg format (figure 01).
The Raw format, then, consists of raw data that still has not had filters, white balance or other parameters applied. If we look at the Raw image as it is seen by the sensor, we would see a mosaic of monochromatic squares and each of them would assume a gradation of only three colors: red, blue or green.
In practice, we never see the photo in this way on the display of the camera or on our computer, because the Raw data is shown to us after the demosaicing has been done in “real time”. Therefore, we can say that this conversion takes place “on the go” in order to display the image on the screen.
01 Difference between Raw and Jpg.
The CMOS sensor with CFA transforms the light signal into an amplified digital and electric one
Lens
Memory card
The image processor reconstructs the colors with the demosaicing algorithm, applies the white balance, contrast, saturation and whatever filters that were chosen and then compresses the file, saving it in Jpg format on the memory card
Image processor
The Raw data provided by the sensor is saved in a Raw file on the memory card
Memory card
Raw file characteristics
Now we explore some of the details so that we can better understand what the Raw files characteristics are.
From figure 01, we can easily infer that not only is this Raw file uncompressed (in other words, it maintains all the original image data), but it is not subjected to any added white balance, contrast, saturation, filters or demosaicing. All of this means that the original file can be modified many times (by saving it as a separate file); in this way, we do not lose the original data from the original file. The demosaicing, in fact, depends on the algorithm that it uses. If ones camera is not of a high level and uses an unrefined algorithm, shooting in Raw, we can make use of the same calculation on the computer (simply saving the Raw file in Jpg) by utilizing the processor (of the computer) which is more powerful and can then easily use the algorithm better set for this task (obviously, on high gamma reflex cameras the algorithm is a high quality one). The demosaicing, in fact, is not reversible (once the file is saved), because, for each pixel, it interpolated 67% of the information about the color from the adjacent pixel.
Another important aspect is that in the Raw file we can always enhance it on the computer later since the white balance has not been applied and thus we can save the file many times (without saving over the original Raw file). If on the reflex digital camera we choose the Jpg format, we can always modify later but starting from those settings already applied to the file at the moment the shot was taken and not the native data that we have available when we save the file in a Raw format. This does not allow us to make unlimited attempts at modifications of Jpg’s because with each file save we lose some of the original data. Applying the white balance on a Raw file allows us to manipulate the image exactly as we saw it at the moment the shot was taken. The reason for this is because often the Raw file manipulated on the computer can provide us with better results than the limited settings offered from the menu of even the most advanced digital camera. In the end, it is always possible to save the file as a Jpg. For more important photos, it is always better to conserve the original in the Raw file format (so that we can always go back to it later without losing any of the original data).
The same things said for the white balance, we can say for all the filters, the saturation, as well as the contrast that we want to apply to the photograph.
Therefore, if we make a mistake with these settings, saving the file in Raw format makes it possible for us to modify the photos later on without any loss of information: just as if the subject was standing in front us when the shot was taken. With the Jpg file, it is possible to correct our mistakes, but it depends on the level of compression applied. There will be a loss that will affect the quality.
The only thing that we cannot get wrong is the exposure because we cannot fix it later. This is because if we over- or underexpose the photo, the white and dark zones derived from the incorrect exposure will wipe out details of the image in those zones, and it would be impossible to recover them.
Having said this, it should be pointed out that Raw files occupy more memory, and they are not easy to manage when generated from a sensor of at least 10Mp. Therefore, it is difficult to send it over email, save it (many photos in this format require a very large hard drive). Even looking at it on the computer would take up a good deal of time due to the fact that there is a lot of data that needs to be processed.
The visualization of the Raw files
The Raw file cannot be viewed by all computers like Jpg images because many operating systems do not have a program installed that is able to demosaic the file in order to display the image. In order to see this type of file, there are two possibilities: the first is to install professional software that we would use for post-production or simply as a file viewer that is able to display Raw image files: examples of this that I could cite are Photoshop, Camera Raw (a photoshop plug-in) and all the software from the manufacturers that make reflex digital cameras such as Canon, Nikon and Sony. But there are also many others. The second possibility is to use a Mac computer because the Mac OSX contains all of the Raw file drivers that current exist for reflex digital cameras (and they are continually adding others).
Also, I should add that a Raw file is not displayed the same way on all computers as Jpg files are. The reason for this is simple to understand: it is because each program uses a different algorithm for demosaicing as well as applying properties of each file in a different way. Therefore, while a Jpg file shot with a reflex camera of a certain brand is the same on all computers regardless of the type of software used, the Raw file type can change notably from software to software. Often, in order to best visualize a Raw file, it is important to use the software provided by the camera’s manufacturer (the same camera that you used to take the shot, ideally) or use a Mac computer. In this way, you are certain to view the file as it should be seen with the correct colors. Otherwise, the colors could be misconstrued or, in some cases, dulled or flat.
Proprietary and compressed Raw file format
Although there was much to say about this format, it is not finished here. In fact, there also exist proprietary Raw file formats. In practice, it can happen that one maker of a digital camera has its own type of Raw file that really assumes another name. This is the case with Nikon whose Raw file format takes the Nef file name (Nikon Electronic Format). As I have been able to understand, the Nef file, besides being a Raw file format, also contains three previews of the image in Jpg in order to be able to view the image on the screen more quickly.
Even owning reflex cameras of the same manufacturer show some differences in how Raw files are visualized, because Raw files can change from sensor to sensor. In any case, we have assumed up until now that the Raw format is native and uncompressed. It is always true except for some exceptions. For example, some of Nikon’s Nef files are compressed even minimally so that no information is lost. This is done to allow us to benefit from the advantages of more easily managing these types of files without any loss of quality.
Jpg format
Up until now, we have looked at the Raw format that is the file type that gives this chapter its name. In this same chapter, it is also important to know the Jpg format (the most utilized in the world) so that you can properly understand the differences between the two and always know which of the two to use before a shot. Since the Jpg is a compressed format, please refer to the dedicated chapter on this topic for a more detailed explanation. The Jpg format, as already explained sufficiently by figure 01, is compressed and already demosaicked and complete with all the settings from the camera’s menu. In practice, it is “packaged” and ready to be seen on any computer around the world (old and new ones). Its principal advantage is really in its practicality and greater versatility as well as the small amount of memory it occupies. In order to understand the difference in memory we are talking about, a Jpg file, assuming that is has an average compression, would occupy a quantity of 5 to 10 times less than its Raw file equivalent.
Choosing the level of Jpg compression
The Jpg file is compressed, but when we use post-production software or reflex digital cameras, we always have the possibility to choose the level of file compression. As always, with software like Photoshop, the chosen level of compression is more ample than that offered by the digital camera. Usually in the menu dedicated to the image quality in the camera itself, besides the possibility of choosing the size of the image (in megapixel) we can also find 3 or 4 Jpg compression settings that can be: high, medium, low or fine, which is usually the lowest level of compression that causes only a minor loss in quality.
In order to better understand what happens with excessive compression, I will show you an example in figures 02 and 03. Here we find in the first photograph a minimal compression of high quality while in the second we see the same photograph but with a compression that compromises the beauty of the photo. Between the two figures, the difference in the compression level is deliberately elevated to easily show how to recognize the loss of quality caused by the elevated compression. Once that we learn to recognize the damage, we can try to avoid it when circumstances make it possible.
Introduction
The camera
How it is made a Reflex camera
Photographic lenses
Equipment and accessories
Take a picture:
Buyer’s guide
02 Photo in Jpg format with a low compression.
03 Photo in Jpg format with a high compression and significant loss of quality (one can see clearly the curves becoming gradated, almost resembling “steps” or “stairs” instead of the straight, clean line.
Jpg, Raw and Jpg+Raw: which to use?
Now we have arrived at the question that afflicts many people who become interested in a high level of digital photography for the first time.
Once the differences between the two formats are understood, I would advise the use of one format over the other based on common sense, the circumstances where you find yourself as well as any objectives we have set.
As I touched on before, on the majority of reflex cameras, we have the possibility of choosing to save the file in: Jpg (with various levels of quality), Raw (or Nef), or a combination of Jpg and Raw (Jpg + Raw).
The first two cases have been extensively discussed: the third case is nothing more than a double saving so that you can have the Raw file but also have the ability to open the file as a Jpg in order to quickly share it (two files for every shot).
The first things to ask ourselves are: what type of photographer am I? What kind of situation do I find myself shooting in? What kind of equipment do I have at my disposal?
In order to respond to this question, whose response is subjective, I will use my good sense and accumulated experience that I have gained through numerous trips and various other situations. With current technology, once a Raw file is saved as a high quality Jpg, one does not note many differences between the two. There isn’t any real difference.
Therefore, I advise saving the Raw file in a situation where the subject is very important and where we cannot allow any room for error: for example, a wedding, a rare animal spotted after waiting a long time. In this case, we often do not have time to select the right settings, and we cannot repeat with ease the shot if at all. In these cases, I strongly advise taking a burst of shots and saving them as Raw files. In this way, once we are calmly in front of our computer, it will be possible to correct errors and work in post-production making many modifications to the images without any loss of quality and always making use of the original data. The only thing that we cannot correct is an image that is out of focus or one where the exposure is not correct (both produce a loss of information that cannot be subsequently recovered).
We should keep in mind that since the RAW file takes up more memory, and the Jpg + Raw even more, we have to equip ourselves with a lot of memory if we want to use this format.
For all other situations where this kind of shot taking is not necessary, it is not useful to shoot in Raw format to get the best quality. This simply isn’t true, and, above all, the difference would be, at most, in the colors and not in the details. Many people fall into this trap, because they do not know the Raw format, and they think that it is the best way to make full use of their digital camera. In order to use the camera to the best of your ability, you do not need to do this: you only need to learn and study.
Therefore, I personally, after many attempts, much practice, and several tests, shoot 70 percent of the time in Jpg, especially on long trips when I need to optimize the memory and do not want to always be modifying images when I get home. In fact, I often shoot in Jpg: I make use of Raw only for certain situations. My advice is this: if you possess a reflex camera (this indicates a certain desire to shoot photos at a good level) to use the Jpg settings always set to the maximum quality. You will always be able to, later on, to increase the compression of the photos by making a copy of the original if, for example, you want to share it on internet sites or through email. The choice is always between Raw and Jpg in the end. Lower quality Jpg photos can be come notably useless if shot with too low a quality. Once you return from a trip that you might not be able to take again for many years if at all, you will regret the loss of detail to your photos.
Jpg in post-production
The title of this paragraph is almost provocative but useful in explaining the last concept of this chapter.
As noted before, in the majority of cases, if we have learned a good technique with the exposure and focus and if we do not find ourselves in an important situation, such as a wedding, we can calmly shoot in Jpg. This is because, with current technology, if we do not set white balance levels that are extreme, we can modify them later with Photoshop using the Jpg file. You will be surprised by the level of quality that we can arrive at.
Obviously, if we have to make substantial modifications, it is not the same thing as using the Raw file. However, if the Jpg is a high quality image, we can also make many changes to this type of file. For example, the HDR images seen in this book, have been done by using Jpg files.