Copyright Michael Karbo, Denmark, Europe.
Chapter 30. Best quality with RAW
RAW format is found in cameras, which are a little more advanced and it is meant for more advanced photographers. It supplies the camera’s absolutely best image quality but a little work with a computer is required if you want to get the best out of the format. For the demanding photograph, RAW format is brilliant to work with as it gives unconditionally the best image quality.
Maximum image quality
All cameras take photographs in RAW format. This is done quite automatically because the image sensor can only record “raw pixels”.
Normally the raw pixels are processed immediately in the camera’s image computer, which converts them into compressed JPEG files. But if you pack the raw pixels directly into an image file, without letting the image file touch them, then you have a RAW file.
RAW files are also called digital negatives, because they contain the completely untouched image data, which comes directly from the image sensor and which hasn’t been exposed to loss giving compression. RAW files contain the maximum number of image details and are, therefore, the best kind of files for storage of valuable recordings.
The disadvantage of RAW files is that they can’t without processing be displayed or printed out in a computer – they have to be processed in order to get a usable JPEG edition of a photograph.
RAW files are a bit more difficult to work with but they give brilliant results if you take your time to get to know them. The image quality will always be better than the JPEG files the camera makes itself.
When we work with RAW files, it means that the whole image formation with interpolation, white balance determination (colour temperature) and the general colour adjustments takes place in a computer instead of in the camera’s image computer. This is basically a completely new and very interesting method of producing images.
Figur 127. A large part of image formation is moved from the camera to a computer, when you work with the RAW format.
Recording in RAW
Unfortunately, not all cameras can make RAW files. Generally speaking, top models from the individual manufacturers can nearly always make RAW files, and the smartest of them can also store in both JPEG and RAW.
Figur 128. Selecting RAW format via the menu system. (Nikon D70)
Figur 129. Some of Canons cameras let you select storage in RAW format as soon as the image is taken – even though the camera is set to JPEG. This is really smart.
So RAW is a format you can choose to save your images in. But RAW files cannot stand alone; they cannot, for example, be printed out. They are intended for use as a digital negative, which is processed in a computer. After this, they can used to produce working copies in JPEG format, which can be used for printing out, etc.
The advantage is that you can use a computer to correct the photograph afterwards in a completely different way, when it is stored in RAW. It is here that we find the big advantages:
Both these functions are found in most RAW programs. On top of this the program Photoshop CS gives the possibility of high quality interpolation of the raw pixels so that the images’ resolution can be increased many times.
The colour temperature is normally selected in the camera in connection with the recording. Then the camera’s image computer processes the raw pixels based on a particular colour temperature in order to find the white balance.
But with RAW files we have a free choice of colour temperature after the recording. This ensures an optimal white balance – every time! You don’t have to worry about the white balance while the image is being taken – you can just nice and easily adjust it afterwards.
Figur 130. The colour temperature is corrected after the recording. Here, in Nikon’s advanced Capture Editor.
Even though you really try to find the best exposure values, images often become overexposed or underexposed.
Even a faint underexposure can be irritating, as the image has to be processed in a computer. Here, the RAW format also has advantages. You can easily correct the exposure with up to two diaphragms while retaining the image quality. It is unbelievable convincing and can save/improve masses of exposures.
Figur 131. PENTAX PHOTO Laboratory doesn’t have the most elegant user interface, but it does what it has to. The slider Sensitivity can compensate the exposure with up to three diaphragms. In this case, the image was underexposed with about 1 1/3EV, and was quickly corrected.
Normally the overexposed (burnt out) areas in a photograph will be ”lost”, when the image has been saved in a JPEG file.
After the image computer has processed the image’s data, the areas will have been converted into 100% white surfaces, with no image details at all. If the image had instead been saved in a RAW format, then there would probably have been some small nuances of very pale colour tones saved in these areas. These can be salvaged via the RAW format.
Programs for RAW
If we want to use RAW formats, then we have to have a program that can read RAW files. The problem being that every manufacturer has its own version of a RAW format.
We are used to the fact that, for example, a JPEG file always works in the same way, regardless of where the camera comes from. It’s not like that with RAW files. They are specially produced for the individual cameras and the manufacturers are still developing the format, so they can differ from model to model. This makes it difficult for the programs, which use the files.
A camera, which can record in a RAW format, is usually supplied with some sort of RAW software. There are exceptions; Nikon only supplies RAW in a few of its cameras, and you have to buy special software if you want to use the format. This doesn’t seem to be especially user-friendly.
On the contrary, Canon, Minolta and Pentax all supply software with those of their cameras, which support the RAW, format.
Minolta’s RAW program works very well. It is not at the level of Photoshops plug-in, but the two most important functions, adjusting colour temperatures and compensation for exposure, function excellently: (1) The colour temperature is adjusted here. (2) Here the exposure can be compensated with up to plus/minus two diaphragm values.
These two adjustment options are absolutely crucial! However, the best software of them all is ”Adobe Photoshop Camera Raw plug-in”, which is supplied with the program Photoshop CS.
Figur 132. If you aren’t satisfied with Minolta’s own RAW program, then you find other very advanced Photoshop plug-ins on the Internet, which extend options for processing the raw image data.
Different file types
RAW files contain uncompressed data, which has come directly from the image sensor. In many cameras, this format is also called CCDRAW in the menu system. But when it comes to the image files themselves, the individual cameras all have their own names:
Figur 133. The file type names are all names for RAW formats.
Canon’s CRW files are the most widespread; this means that, a lot of programs can read them: i.e. image browsers like FotoAlbum and ACDSee show CRW files. But if you want one program, which can handle all of the versions of RAW images, then you should invest in Photoshop CS.
Photoshop Camera Raw plug-in
Photoshop is a big, expensive and extremely comprehensive program. It can almost do everything, you need to do within image processing.
In 2003 Adobe introduced their Camera Raw plug-in, which received a sensational reception. An American photographer wrote, that Adobes Raw plug-in was ”the biggest invention since the pixel”! Not exactly small words, but there is no doubt that this program can almost revolutionize the processing of photographs in a computer.
Photoshop Camera Raw plug-in is continuously being developed so that it can handle RAW files from the new cameras, which come on the market. The updates can be fetched free of charge from Adobe’s website.
Figur 134. Adobe continuously updates its RAW software so that it can process images from the new camera models. Here is an update from spring 2004.
The maximum image data
The advantage of Photoshop Camera Raw plug-in is, that it really can get the most out of all the aspects of the RAW files’ quality.
What happens is, the camera’s image sensor takes a number of image details, which disappear when the camera’s image computer makes JPEG files. Some of the details disappear because the images are compressed.
Other details disappear because the JPEG format only works with 8-bit colours, where there are only 256 tones of every colour. All cameras take images with several tones. Even the absolutely cheapest models operated with a 10-bit colour depth and better cameras can register colour tones with both 12 and 14 bits accuracy.
This raw image data can have thousands of different colour nuances within each primary colour. When they are packed into a JPEG format, necessary details disappear, when there is only room for 256 nuances for every colour. You can’t always see this “simplification” of the image material. But if you take exposures, where you want the image material to be perfect, then you have to use RAW files.
In Photoshop Camera Raw plug-in there are ample opportunities for adjusting the colour temperature, exposure, colour tone balance and much more. All of it takes place in a special window, which is opened in Photoshop itself.
The idea is that you can take care of as much of the processing as possible in this window, where the program works with the raw pixels in full bit depth.
During this, you can see the alterations in a big preview window. They can also be seen in the histogram, which is shown for each primary colour. Here is, for example, a histogram for a pale underexposed image:
By compensating with +1,05 EV, the image gets a better exposure. You can see this by pulling the slider Exposure, while watching the effect on the histogram:
Figur 135. The interface Photoshop Camera Raw plug-in is very easy to use and there are lots of options for adjusting.
Back to Photoshop
When you have finished with the adjustments, then it is time to close down the special RAW program. Closing the window does this and the image’s data is transferred to Photoshop.
Before doing this, you can select a 16-bit colour depth, if you want to continue working with colour adjustment in Photoshop. You select the depth 16 bits/Channel:
This means that Photoshop gives every pixel’s 16 bit data to each of the three primary colours (channels). We achieve by this a colour depth of 48 bits altogether in contrast to the 24 bits, which are used for JPEG images.
The advantage of a 16 bit colour depth is that all the image details from the raw pixels are transferred to Photoshop. Here you can continue to adjust the image, work with filters and layers, etc. – all this in an environment, where all the image’s colour tone nuances stay intact.
Every time you make a corresponding adjustment in a JPEG image, you risk losing image details. Every time you process the image’s data it will relentlessly cost details. But when Photoshop works with 16 bit colours, there are many more nuances to “take from”, and the loss, therefore, has no practical importance.
Photoshop Camera Raw plug-in has one very interesting option, which isn’t to be found in the other RAW programs. You can, you see, ask the program to resample the image in a very high resolution.
You don’t normally get very much out of artificially increasing an image’s resolution. It will only mean that a program interpolates lots of pixels that don’t contain authentic image details.
But by using the image’s raw pixels as a basis, Adobe has succeeded in making an interpolation, which works. You can simply enlarge the image’s resolution radically without it looking muddy or pixilated.
It seems almost like a miracle when a six million megapixels large RAW image can be blown up to a resolution of 24 MP – in a good quality. You can do it with this program:
A resolution of 24 megapixels with 16 bits colour depth is altogether the best image material that can be taken out of a RAW file from a 6 MP camera.
Figur 136. The interface to Adobe’s great RAW program, which can, unfortunately, only be used in connection with Photoshop CS.
Storing a working copy
When the image processing is complete, a copy of the result has to be saved. Here are several options.
You can choose to save a working copy in JPEG; this is the quickest and the easiest, as it doesn’t take very much space. The disadvantage is that you can’t continue working with the JPEG version without reducing the image quality. This doesn’t have much importance normally if you have saved the RAW file as a ”digital negative”.
If you want to have an uncompressed working copy of the image, then you should choose a TIFF format. This is a bit map format, which can be used with either 8 or 16 bit depth per colour channel and without compression. The problem is that it gives massively big image files.
Figur 137. The file size is very different from the one format to another. The size of RAW files varies too from the one camera brand to another.
There is also a difference in how effectively the individual camera brands use a RAW format. Some cameras compress the raw data with a loss free compression, which circa halves the size of the file. This is a big advantage because storing on a RAM card takes time proportionally with the size of the file.
Figur 138. W files fill up a lot on a RAM card, but it is worth it for the quality.
It can take many seconds to save a RAW file with Sonys zoomcamera F828, whereas it only takes a fraction of a second with Fujilfilms model S7000. There is also a big difference between how effectively the individual companies make use of a RAW format.
Some cameras like Nikon D70 and Sony DSC-F828 can be set to save both in JPEG and RAW files. This is smart, because then every exposure will have both a digital negative and a usable working copy – at the same time. This is probably a function we will see in more and more cameras when photographers open their eyes up to the possibilities of the RAW format.
A lot of cameras give you the option of saving images in the uncompressed TIFF format. This can only be recommended if you, for some reason or another, don’t have access to using a RAW format. TIFF files are enormously big so a RAM card will be quickly filled up. Furthermore the storage is often with only 8 bit per colour channel; and, therefore, the quality will be worse than in a RAW file.
A TIFF format is completely superfluous, if you have RAW files; they don’t take up nearly so much room and still contain all the image details.
Figur 139. Always use RAW instead of TIFF
The camera’s opticsIn this section we are going to look at subjects like sharpness and depth of field, which are strongly bound to the construction of the lens. We will also look closer at wide and tele lenses.