File Formats


As the image editing softwares developed with the advent of computers and digital cameras, the various file formats developed and came into existence as well.   Leading image editors like Photoshop and capture one, support just about all the file formats for saving the final processed image.

Simple understanding about various available file formats can help you choose the most suitable one for saving an image.

All digital SLRs  support JPEG for sure as this format lets you squeeze more images onto memory cards that have limited amounts of space. A few (chiefly high-end) dSLRs also let you capture images in TIFF format, which is great at retaining detail but not so great at compressing photos to a reasonable size. All dSLRs have the option for saving images in a proprietary RAW format that supposedly preserves all the image detail and the camera settings and parameters that the sensor captures.

But that claim isn’t precisely true. The sensor data is processed quite thoroughly by algorithms that convert the image from analog to digital form. However, the resulting RAW data doesn’t have all the settings that you dialed into your camera (white balance, sharpening, color, and so forth) set in concrete. When you import a RAW file into your image editor, you can go ahead and use those settings, if you like, or — by using the RAW converter software that does the conversion — you can specify new parameters, instead. That’s where the “unprocessed” label gets hung on RAW files.

What!? Am I telling you that each digital camera vendor uses a different RAW format? If only it were that simple! As it turns out, some camera makers have created several different versions of their RAW format, each incompatible in some way with earlier versions, so rather than a dozen RAW variations, you have to deal with several dozen. Here are a few examples: 

 

The different RAW format for Canon dSLRs was CRW and now CR2.


Nikon has some slightly different variations of its format, including a trick it unveiled a few years ago of encrypting the white balance information of its newest cameras so that third-party RAW tools can’t interpret it. (After much consternation and reverse engineering by other vendors, Nikon ended up demystifying its encryption scheme.)

Other manufacturers might use one RAW format for their dSLRs and another for their high-end point-and-shoot models.

This mess RAW formats led to Adobe’s development of yet another RAW format, DNG (digital negative), which basically supports all the features of the rest of the RAW versions, as a sort of a standard. Adobe even provides a free Digital Negative Converter, if you want to change all your current RAW files to the new format. Pentax, for example, allows you to choose whether to save your images in the camera by using either Pentax’s proprietary RAW format or Adobe’s DNG.  The other leading camera manufacturers have continued to develop their own RAW formats.

Besides choosing the file format within the ones available on your camera, you can also choose the quality or size of these formats. These may be represented differently in different camera like Fine, Basic, Superfine, Good, Super good, and so on, Ideally shoot at the highest available quality as this step is irreversible. There may be a large RAW file or a smaller one, even thought it may have a lossless compression but still if the space is not a constrain shoot at the maximum size as you can always reduce it later on but not increase the size ever. Most of the cameras have RAW and jpegs and very few may have TIFF as well. 

while converting the images in the manufacturers or third party's RAW convertor, it is best to convert it to TIFF if you intend to work on these images in Photoshop or they are mean for some high end printing or editing. If these are general purpose shots, you may save them as JPEGS. The basic idea is reduce the size and quality only if its a copy for distribution or you do not ever need to revert back to the better quality.

Photoshop, just like most of the other Image editing softwares, gives you the option to save your images in a lot of different formats right there when you begin to save an image. Many of the names we are just unfamiliar with and are not aware as to what applications or purposes these formats may be required. A lot of these formats may be unheard of or the application unknown to us.

I’m sure each of the various file formats must have seemed like a good idea at the time. The ostensible reason for creating a particular format is that the software vendor wanted to add special features (such as the layers in the Photoshop PSD format) that weren’t possible in other formats. 

Some features are possible only in a particular file format. For example while saving the image in layers, you can do so only in PSD or TIFF but not in jpeg.

If you want to retain a transparent background as in case of cutouts or logos etc. and still want the file size to be smaller, then .png is the option instead of jpeg. 

Of course, in the earlier era of computing, another reason for creating a proprietary format was to tie the buyers to a particular application or software that relied on that particular format. In earlier times, softwares used in windows and Macintosh were simply un compatible until recent years. 

Before long, most of the non-compatible formats fell into disuse (although they remain as shadowy wraiths in many Save As menus). Virtually all image editors support the Photoshop PSD format, plus JPEG (created to provide extra-small file sizes), and TIFF (the closest thing to a standard high-quality format that isn’t tied to one vendor). Image editors still have their own proprietary formats, but users of those programs are more likely to archive processed images as TIFF or PSD

There are file formats used only within the image editors and for applications outside the realm of digital cameras, such as Web pages or printing. These formats include GIF, PNG, PICT, PDF, and BMP.

When you’re trying to decide what format to shoot with, you need to look at only TIFF, JPEG, and RAW because digital cameras work with only those formats (other than some Pentax models that can save in DNG format). Each of these formats has its advantages and disadvantages, and that’s what you really need to know about to make the right selection. 


TIFF

The TIFF format originated in 1987 with a company called Aldus, which developed pioneering graphics and layout programs such as Freehand and PageMaker. Intended as a standard file format for images, TIFF (Tagged Image File Format) incorporates descriptors called tags, which you can use to provide parameters for any special features included in the file. Theoretically, an application could include any kind of information it liked in a TIFF file — such as layers, objects, special colour information, and selections and let any other application attempting to read that TIFF file know how to retrieve the special data.

In practice, the TIFF format’s versatility ends up making it possible to create “standard” files that not all the applications that have to work with them can read, which isn’t an advantage at all. TIFF files run the colour gamuts from RGB (red, green, blue), CMYK (cyan, magenta, yellow, black), and L*a*b colour models to grayscale and Black and white images. It supports both 24-bit and 48-bit (high dynamic range) colour depths, and it can be squeezed down without losing any image information by using optional Huffman encoding, LZW, or PackBits. (If you don’t know what these formats and compressions are,they aren’t important in everyday processing.) Adobe acquired Aldus in 1994, and today, Adobe offers options for saving Photoshop layers and selections right in a TIFF file as well besides PSD.

Keep in mind these two important TIFF characteristics : 

TIFF files are lossless. They don’t discard any of the image information. 

TIFF files are much larger than JPEG and RAW files. The larger size can increase the time it takes for your camera to store them on a memory card. Since RAW files write faster, this gives another reason to shoot in RAW in the camera instead of TIFF.

 Fewer dSLRs offer a TIFF option these days anyways except for few professional-level cameras especially from Nikon. 


JPEG

Virtually every dSLR currently on the market can create JPEG (Joint Photographic Experts Group) files. About 15 years ago, a consortium of the same name created this format. (The consortium originally consisted mostly of vendors such as Eastman Kodak Company, but an international standards body now oversees it.) The goal of devising the JPEG format was to create files that are significantly smaller than you can produce by using formats such as TIFF, which compresses files
somewhat without discarding image information, and to make those files readable by a wide variety of applications in a standard way. 

The first JPEG-capable applications reduced the time needed to transmit images by telecommunications links. The Internet wasn’t in wide use by the public at that time, it still is not in many parts of the world. So, newspaper photographers had to plug their unwieldy portable computers (laptops of that era needed several laps to support them) into devices called modems to beam their photographs back to the editorial office over telephone lines. JPEG can reduce files by a factor of 20 or more by throwing away some of your hard-won image data in a series of processes that are intended to reduce the size of the file by eliminating excess or redundant information.

JPEG compression first divides your image into luminance (brightness) values and chrominance (colour) information, on the theory that human eyes are less fussy about colour than they are about brightness. For example, If you see a stop sign that’s a slightly odd shade of red, you notice that colour less than if the same sign appeared darker or lighter than you expect.) The excess colour information or the variation in the colour information is discarded.

The process slices your image into cells, say 8 x 8 pixels on a side, and then the process looks at each of the 64 pixels in the resulting chunk individually. Using mathematical trickery called Discrete Cosine Transformation (DCT), the compression process discards pixels that have the same value as the pixels around them. (You don’t have to remember all these terms or even how it all is done as long as you are aware of the general characteristics of a JPEG file format.) Next, quantization occurs, during which pixels that are nearly the same colour are converted to a common hue, and the picture information that’s left is transformed into a series of numbers, which is more compact than the original information. (It’s a bit like writing 1500 rather than one thousand five hundred. Although the picture quality is reduced but a broader purpose is served.) If everything is done properly, the process compresses the image by 5 to 20 times or more, depending on what compression level you select when you choose to save the file. Ideally do not reduce the image quality while converting to JPEG as that further deteriorates the quality which is noticeable to the eye.

Because JPEG doesn’t keep all the image information, it’s referred to as a lossy format. Each time you load a JPEG image, make changes, and then save it again, you run the danger of losing a noticeable amount of information because the JPEG process occurs all over again — every time you save. The loss might be very slight at first, but it can accumulate,  a photograph looses sharpness after repeated savings in JPEG format. 

 

What’s cool about JPEG is that you can dial in the amount of compression you want, using a lot of compression to produce very small file sizes (with an attendant loss in quality) or very little compression to preserve quality at the cost of larger files. What’s not cool is that no one has come up with a standard way of referring to the amount of compression. Digital cameras tend to use discrete steps with names such as Superfine, Fine, Normal, Good, and Basic. Image editors might let you choose a continuous compression/quality range from, say, 0 to 15

or 0 to 20. (The Nigel Tufnel in you might wish that your editors offered an all-the-way-to-21 setting for when you need just that little bit of extra quality, but unfortunately, the designers of these applications apparently have never seen the movie This Is Spinal Tap.

 

instead, in-camera JPEG compression is a little like a box of chocolates: You never know what you’re going to get. 


RAW

RAW isn’t really a single file format. It’s the broad term applied to all the proprietary formats created by each digital camera vendor for its particular product line. Every RAW format is different, which means that in order to access a RAW file, you must have one of two types of programs:

  • Special software from your vendor designed especially for its RAW format

  • A third-party utility, such as Adobe Camera RAW (furnished with Photoshop and Photoshop Elements), that’s compatible with your particular camera’s RAW format

  • Not all utilities support all RAW formats (not even the Adobe DNG converter), so you might have somewhat limited choices for reading these files. Support for a particular version of RAW commonly lags behind the introduction of the camera that produces it for a few weeks or months, leaving you at the mercy of the camera vendor’s utilities until everyone else plays catch-up.

    You can consider RAW files your digital negatives because they haven’t been subjected to the usual manipulations that your camera settings mandate when the camera converts the raw image data to JPEG or TIFF. (See the section “Using RAW Files as Digital Negatives,” later in this chapter, for more details.) 


     

  • Choosing the most suitable File format

  1. So, your image-format choices boil down to TIFF, RAW, and JPEG (or, with some cameras, saving in RAW and JPEG simultaneously). Which do you select? Your decision might hinge on how you shoot and on what you plan to do with your files after you transfer them to your computer. Your available storage space might also figure into the equation.

    If you get good results most of the time by using your camera settings, don’t want to do a lot of processing in your image editor, and take a lot of pictures, you might opt for TIFF or JPEG. TIFF gets the nod if you want the best image quality (although, as I note in the section “Don’t get TIFFed,” earlier in this chapter, digital SLRs rarely offer TIFF as an option these days), but you might prefer JPEG if you’re on a trip and want to make your memory cards stretch as far as possible. You might find that RAW works best if you plan to do a lot of image tweaking. The following sections explore these options in a little more detail.

TIFF

If your camera has a TIFF option, here are some factors to consider: 

 

  • Highest quality: Use TIFF if you want the highest-quality image in a standard file format. This lossless format produces image files that are theoretically and practically better than even the least compressed JPEG image. The most common use for TIFF is for stock photography or advertising, where the client demands images taken as TIFF files. I think the clients are a bit behind the times, but those who write the checks make the rules.

  • Minimal post-processing: TIFF is theoretically a good choice when you’re generating large numbers of images for distribution and want to apply a minimum of post-processing. Perhaps you’re shooting a wedding or other event and don’t want to laboriously apply individualized set- tings to each photo with your image editor. If you carefully select your camera settings so that your TIFF files already have the exposure, colour balance, sharpness, and other attributes that you want to end up with, you can safely save your files in TIFF format and expect all or most of them to be good to go right out of the box. In practice, however, most photographers use JPEG in this situation because the camera can store the images on its flash memory more quickly.

  • Limited editing: TIFF is fine for images that you plan to manipulate in Photoshop to make improvements that don’t involve “unprocessed” RAW file attributes. For example, if you want to retouch portraits so that you can minimize facial flaws or composite several images into one, you really don’t need to work from RAW images. TIFF serves just as well.

  • Too slow for Action or Sports: TIFF might not be the best choice if you’re shooting sports or doing continuous shooting because your dSLR takes a long time to save such files to your memory card. Most digital SLRs store JPEG and even RAW files much more quickly than they do TIFFs.

  • Takes a lot of memory: TIFF is a poor choice if you have limited memory-card space. If you’re on vacation and have only a few 1GB cards to use between opportunities to offload your images, TIFF
    files fill up the available media with alarming speed. (Your camera’s best JPEG setting produces image quality that’s almost as good while consuming perhaps 10 percent of the storage space.) 


    JPEG

    1. JPEG is a highly popular alternative to TIFF (if your camera even offers TIFF as an option) and RAW. Some JPEG junkies use nothing else for their original photos. The format is compatible with virtually all applications, making it as much of a standard as TIFF and much more compatible than RAW formats. 

      Of course, JPEG has that nagging loss-of-quality issue. You have to decide for yourself how important that issue is to you. Ponder these points when considering JPEG: 

       

      Really minimises post-processing: Everything I say about TIFF as an option when large numbers of images are involved goes double for JPEG. Most of the wedding photographers  prefers to shoot and work with JPEG images, simply because they can’t afford to spend that much time post-processing hundreds of images or they are not even aware of the advantages of shooting in RAW.  some photographer prefer to  spend a little time before the shooting and take test pictures to adjust the white balance balance, sharpness, and exposure to suit the conditions. Then, they shoot away, knowing that most of their photos will require little or no post-processing. However, if you are the type who is concerned with fine adjusting your photography to every minute detail, then RAW or Jpeg+ RAW is the way to go.

      Gives you ready-made photos for Web display: JPEG is a good choice for display on Web pages, such as the one shown in Figure 8-4. Or, if you want to distribute pictures in digital albums on CDs, in online albums, or as prints no larger than 11 x 14 inches, the least-compressed JPEG option that your dSLR offers should produce files that can easily take care of these tasks. 

       

      Good-enough quality: If you do end up editing JPEG files, you probably find the quality good enough, as long as you remember to save your final ver- sion as a TIFF or Photoshop PSD file. Always save your JPEG files in one of those lossless formats after you make changes. By saving in one of those lossless formats, you avoid the quality loss that can result from repeatedly opening and editing JPEG files (just opening and closing such files, without making any changes, causes no quality loss). If you still need a JPEG file (say, for display on a Web page), create one and retain your new TIFF or PSD versions, in case the image requires more editing later on.

      More compatible with software: JPEG can be more compatible with some image-management/album-making software than other formats. The ancient application that I prefer (which predates the term digital asset management by about ten years) doesn’t handle RAW files at
      all, so I always catalog a JPEG version of the file that my camera produces at the same time as the RAW file. 

      Writes to memory faster: Your digital SLR probably can write JPEG files to your memory card faster than any other type of file. This speed might not matter if you’re taking only a couple pictures at a time; the photos first go into the camera’s high-speed memory buffer, which sucks up JPEG, TIFF, and RAW at similar speeds. However, writing these images to the memory card takes longer, and after the buffer fills, you can’t take any more photos until some shots make their way out of
      the camera’s internal memory onto the card. I’ve used dSLRs that
      are so fast at writing JPEG files to a high-speed 133X-300X (or faster) CompactFlash card that I can take sequence photos almost continuously for a dozen shots or more.

      Takes less room on cards: You can fit a lot more JPEG files on a memory card of a particular size. A 2GB card can store about 600 photos snapped with a 6-megapixel camera if you use the typical JPEG Fine setting, nearly 1,200 photos at a representative medium-quality setting, and as many as 2,200 shots at the highest compression setting. Only

      360 RAW shots from the same camera might fill a 2GB card. My old 10-megapixel camera can fit 488 RAW images on an 8GB CompactFlash card, or more than 900 JPEG Fine images.

      I don’t usually recommend using card storage space as a criterion for choosing which file format to use. You can simply purchase enough memory cards, instead. However, in some situations (such as vacations), you have limited storage, and using the JPEG format (particularly the highest-quality setting) makes a good compromise. 


      JPEG + RAW

      Most digital SLRs include an option to save a pair of files every time a picture is taken: one as a JPEG file and a second in the RAW format. Many cameras, including modestly priced models from Nikon and Canon, let you select the 

      quality level for the JPEG version, so you choose between a high-quality JPEG and one that’s more compressed and lower in quality. Other cameras have a fixed JPEG quality level for the supplemental file; often, the version that has the highest compression ratio sets the quality level.

      Saving JPEG+RAW is a valuable capability. It lets you shoot JPEGs for cataloging, reviewing, and using in less-demanding applications (such as small prints, online auctions, and Web display), while retaining RAW versions as digital negatives in case you need to do more extensive tweaking. Generally, the image pairs share filenames (only the file extension is different), so it’s easy to match them up.

      The storage-card space penalty is fairly low. Even a 12-megapixel dSLR can save 198 RAW shots per 4GB card, and 132 JPEG Fine+RAW image pairs. It’s truly a case of getting the best of both worlds. I use this mode by default. 

MORE ABOUT RAW

Save in RAW format if you frequently need to fine-tune your images. RAW lets you make changes to settings that normally you apply in the camera, either to individual files or batches of them. For example, if you take a whole series of shots under a particular lighting setup and save them as RAW files, then later decide on a single group of settings to apply to all of them, you can do that quickly with one batch process. Also, you can manipulate individual photos to your heart’s content. 

People often describe RAW files as “unprocessed” image files that contain all the information captured by the sensor. 

The sensor catches photons in little analog buckets (setting aside the wave/particle duality of light, as well I should!). The data collected is manipulated by your cam- era’s digital signal processor, a special chip that converts the analog information into digital format. At the same time, the Bayer-filtered image data that mimics separate red-, green-, and blue-sensitive pixels is interpolated to create three different color channels of 12 to 16 bits each. That’s a lot of processing right there!

All that preprocessing can have a significant impact on the quality of your image, and that’s before your camera settings are applied. You can’t do a whole lot to RAW files to reverse the changes. But RAW does let you apply — after taking the photo — those settings that you normally make in the camera (such as white balance, sharpness improvements, coloUr saturation, and to an extent, exposure). If you used a too-slow shutter speed and you have a blurry photo, you can’t fix that. If you had a too-large f-stop and your photo doesn’t have adequate depth-of-field, you can’t fix that, either. You can apply a little sharpening, which might help somewhat in either case, but you have no way to undo serious errors that you made when you snapped the photo. 

RAW as Digital Negatives

The more you shoot, the more you realize that it’s always a good idea to have that (relatively) unprocessed image as a sort of digital negative that you can go back to at any time to work with anew. These files can be a treasure trove of images that may prove invaluable at a later time, whether or not you think so now. 


Salvage images from original RAW files

However adept you may be presently, your image-editing skills will improve. With an image saved in RAW format, you can salvage images that weren’t usable before you gained new capabilities. Pictures that you didn’t think you had any use for might turn out to be worthwhile with the passage of time.

You don’t always need to have the patience of Ansel Adams to take landscape photos. Sometimes, you do make errors and can correct the same later on. And its fine if this does not let you miss a precious moment.


Archiving RAW files

If you want to use RAW files as your digital negatives, you need to have a way to store them because they’re sure to eat up your hard drive space quickly. I have virtually every image I’ve shot in RAW archived on my computer’s hard drives, as well as on DVD. My archives include shots of my feet taken when I tested an electronic flash, semi-blank frames that are seriously underex- posed, and all manner of out-of-focus and poorly composed pictures. As my example in the preceding section shows, you never know when you might find some use for a garbage shot.

Blank DVDs and external hard drives are so inexpensive these days that you have no excuse for not saving all your digital negatives. (Just don’t forget to copy them to whatever format replaces the current formats in ten, or five, or two years.) When you use most operating systems, you just need to archive files by dragging and dropping them to the DVD drive or external hard drive. Or use a backup program to perform the task automatically. 


RAW convertors or Image editing softwares

Remember, to work with RAW files, you need an application that can read them. A variety of RAW converters are at your disposal. Your camera’s vendor provides some of these converters, and as you might expect, those converters work only with the RAW files for that line of camera. Unless you own several different digital cameras from different manufacturers that can produce RAW files, these proprietary converters might be all you need — or you can check out third-party RAW applications, if you prefer. The following sections introduce some of the more popular proprietary and third-party applications. 

Nikon capture NX2

Nikon offers the eponymous Nikon Capture NX, an extra-cost  program that handles both older and the latest versions of RAW files that Nikon cameras create. Besides offering control over settings that you could have made in the camera, this utility provides some interesting additional capabilities. For example, it can de fish images taken with Nikon fish-eye lenses, producing undistorted photos that have straight lines where straight lines ought to be. If you have Nikon Capture NX, you can get super-wide-angle photos from your trusty fish-eye lens.

Nikon Capture NX, has a separate lightness/chroma/hue palette for modifying these image attributes directly, along with post-shot noise-reduction features and vignette control to remove (or add) darkening/ lightening to the corners of photos. You may also find handy an image-dust-off feature that compares your shots with a dust reference photo and removes spots caused by dust on the sensor. 


Digital Photo Professional

Canon provides the EOS Utility and Digital Photo Professional software utilities, which allow you to view and convert RAW images that you took with Canon cameras, as well as control the camera remotely. The EOS Utility is a bare-bones program; most dedicated Canon shooters prefer Digital Photo Professional.

Digital Photo Professional offers much higher-speed processing of RAW images than was available with the late (not lamented), sluggardly File Viewer Utility formerly offered for Canon cameras (Digital Photo Professional is as much as six times faster than the File Viewer Utility). Canon says this utility rivals third-party stand-alone and plug-in RAW converters in speed and features. The program supports both Canon’s original CRW format and the newer CR2 RAW format, along with TIFF and JPEG.

You can save settings that include multiple adjustments and apply them to other images, and use the clever comparison mode to compare your original and edited versions of an image, either side by side or within a single split image. The utility allows easy adjustment of color channels, tone curves, exposure compensation, white balance, dynamic range, brightness, contrast, color saturation, ICC Profile embedding, and assignment of monitor profiles. A new feature gives you the option to continue editing images while batches of previously adjusted RAW files are rendered and saved in the background. 


Third Party Aplications

Lightroom

Capture one Pro

Irfan view

Adobe camera raw

 

At this time, the most popular and widely used third-party RAW converter is probably Lightroom and more professionally Capture one pro followed by Adobe Camera Raw (known commonly as ACR), which is supplied with Photoshop Elements 7.0 and Photoshop CS4. It works with a long list of RAW formats from vendors including Canon, Nikon, Sony, Fuji, Olympus, Pentax, and Sigma. It does most of the general-purpose RAW conversion tasks that the vendors’ own utilities handle, and it has the advantage of working transparently with a lot of different RAW formats, plus Adobe’s DNG format.

Of the others, Irfan View, a Windows freeware program that you can down- load at www.irfanview.com, is at the low end of the price scale. It can read many common RAW photo formats. It’s a quick way to view RAW files (just drag and drop to the IrfanView window) and make fast changes to the unprocessed file. You can crop, rotate, or correct your image, and do some cool things such as swapping the colors around (red for blue, blue for green, and so forth) to create false color pictures.

Phase One’s C1 Pro is the gorilla at the high end of the price scale, and this premium Windows/Macintosh program for professionals
does everything, does it well, and does it quickly. Phase One has taken pity on us mere mortals and also provides several budget “lite” versions that have limited feature sets and more affordable prices.