File Formats in Digital Photography

 

There are numerous file formats available and which one you are going to use depends largely on what you're going to do with the file. So which file format should you choose?

 

 

 

 

Usually you can choose between the uncompressed (RAW, DNG, TIFF) and compressed file formats (JPEG).

 

 

 

 

RAW is an unprocessed format. This is the original unprocessed image that the camera captures with the sensor. Use this format if you are going to edit images afterwards and you want to set the specific image parameters manually (like white balance, contrast, sharpness, etc).

 

Different manufacturers provide their own version of raw format (it is not standardized): Nikon (.nef), Canon (.crw, cr2), Kodak (.kdc, .dcr), Minolta (.mrw), Pentax (.ptx, .pef), Sony (.arw, .srf), Panasonic (.raw), and so on (read below about .dng format). Note that some raw files are nothing more but tiff files and could also apply some camera processing to the image.

 

I always shoot in this format.

 

 

 

 

DNG stands for digital negative format and was created by Adobe in an attempt to standardize raw formats. Some newer cameras already have it as an option, so I highly recommend using it if available (instead of raw).

 

 

 

 

JPEG stands for Joint Photographic Experts Group; pronounced »jay peg«. It is the most commonly used format when you are concerned about the use of space and you do not want to edit images afterwards.

 

It is really a data-compression technique: the file size can be reduced to as little as 10% of the original. There are usually different quality levels available, depending on the amount of compression used (the quality of  the image and its size change parallel): usually named High, Fine, Normal, Basic.

 

If you choose to save the image directly in the jpeg format, the image is applied with not only compression, but also contrast, sharpness, white balance, saturation etc. (depending on the settings of the camera)! If your camera doesn’t have the option to shoot in raw (and if you don’t want to edit the images manually after shooting), I recommend you choose the tiff format or the best jpeg option your camera allows you.

 

 

 

 

TIFF stands for Tagged Image File Format. It is a format that uses compression, but it doesn't necessarily loose information while compressing (like jpeg does): it has different compression levels, from lossless (it is compressed with no loss of data), to lossy. Just like with jpeg, camera applies some of the settings to the image prior to saving.

 

In the last years it has been replaced with the raw format, which is smaller and retains more information.

 

 

 

Comparison:  the difference between RAW, JPEG and TIFF file formats

This simple diagram presents it simply: there is a difference in what happens AFTER the image has been captured with the camera sensor:

 

 

Camera parameters are applied according to the settings set in the camera.

 

 

 

RAW	JPEG
you are going to edit some of the captured images	you know you won't want (or bother) to edit images afterwards
you want to have as much information available as you can for more control and better editing at a later time	you're only interested in capturing the images, browsing them, uploading them on the web or printing them as fast as you can
	you need the camera to work fast - process and save images fast on the memory card (e.g. events, kids playing, sports..)
	you want to save as many images on the memory card as you can (you are limited with the size of the memory card)

 

 

You must take into consideration that you can always reduce the amount of information in the image (resize, reduce resolution), while increasing it is impossible (you could "make up" pixels, but the quality is not the same).

 

My recommendation is that, if you know you won't bother to edit images afterwards and you just use your camera for shoot-show (as most people do) either on the web, tv or print, use JPEG. It's good enough.

 

If you know that you would like to edit specific image later on, you can always switch to raw temporarily. And of course, for those of us who always like to be in control, RAW is the best answer.

 

 

 

When editing images in programs such as Photoshop, it is always best to use the native file format. 

 

Avoid using any format that compresses images in any way (like jpeg) because every time you are going to save that file it is going to do another compression again and again, consequently ending up with much lower quality image (if you still prefer to use .jpeg, always make sure you are working on a copy of the original).

 

 

 

PSD or Photoshop Document is a native format of Adobe Photoshop program. It supports layers, colour management, 48-bit colour.. When editing image in Photoshop always save it in the .psd format so you can come back and change the edits you’ve made.

 

 

 

PSB is a Photoshop Large Document Format. It is used when saving documents larger than 300,000 x 300,000 pixels in Photoshop. It can only be opened by Photoshop CS or later.

 

 

 

DNG stands for digital negative. I highly recommend converting any raw images into this format for archival and other purposes.

 

Most companies that make digital cameras have their own raw format, so to be sure you will be able to open your images in few years time, it is best to use an open format, which dng is. You can convert the images inside programs (eg. Adobe Photoshop Lightroom) or with free Adobe DNG converter found on Adobe website (it is available for both Windows and Mac).

 

 

 

If you don't have any of those formats above  available, use tiff. It can store levels and selections (alpha channels), supports different compressions.. The images can be stored as black&white, grayscale, in 24-bit, 48-bit, RGB, Lab, CMYK. It is supported by most applications.

 

 

 

 

To save an image in a different file format just open the image in an image-editing program and choose file/save as. Then in the save as dialog-box choose a different file format (usually in a drop-down menu).

 

 

 

Depending where you want to print. Usually you can just use jpeg (best quality of course), for more advanced printing, I would recommend using PDF format.

 

 

 

PDF stands for Portable Document Format and was developed by Adobe and is originally a native file format of Acrobat. It is based on PostScript. It has many advantages: embed fonts, accurately color-manged, supports 16-bits, preserves original layout, can be used on all platforms, is supported by many programs..

 

You can print documents in high resolution and at the same time have a small file size. But do not use this format for editing images!

 

 

 

 

 

JPEG (Joint Photographic Experts Group) is the favourite format to use for the images on the web or for sending images via email. The quality loss is minimum (but still depends on the compression!!!). The file size is bigger the more contrasting the lines in the image are.

 

 

 

GIF stands for graphic interchange format. Only use it (conditionally!!!) when transforming images into grayscale.

 

 

 

Use it when you want to send PSD images to people who don't have Adobe Photoshop installed on their computers or when you want to add security to a document. Do not use this format for editing photos!

 

 

 

 

GIF stands for graphic interchange format. This is a format for graphics where you have large areas of even colour (WHILE images have smooth tone transitions!!!). It is mostly used on the Web because of some of its useful features: transparency, animation, progressive display when downloading. It can handle only 256 colours. It is used mostly for animation, logos, charts, dialog boxes, line art..

 

 

 

 

It has extensions like .jp2, .jpx, .jpc.

 

Not all applications support it (Photoshop does) and is not supported with web browsers (so you cannot use it on the internet). It allows you to download the lower-resolution image first and let you decide whether you want to see the image in its original quality. It also allows you to choose parts of the image that are important to you, consequently using less compression on those parts.

 

 

 

 

This is a native format for Macintosh graphics. It supports both bitmap and vector graphics. It is being replaced by .pdf.

 

 

 

 

BMP stands for Windows Bitmap Format. It is a standard bitmap file format developed by Microsoft.

 

 

 

 

PNG stands for Portable Network Graphics and was designed to replace GIF.