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Tips for Better Pictures

Today's e-tip:

Understanding Image File Formats
(JPEG, RAW, TIFF, etc.)

Understanding Image File Formats
When you take a picture with your digital camera, the image is saved in a format that the camera defaults to, or one that you have selected in the camera's menu system.

If you edit your images on a computer (highly recommended!), you have a choice of many other image file types. These include:
  • JPG (pronounced J-PEG)
  • NEF
  • CRW (or CR2)
  • GIF (pronounced JIF)
  • BMP
  • TIFF
  • EPS
  • PSD
  • DNG
  • PNG
  • etc., etc.
Image File Formats
This is only a partial list, but includes most of the common file types.

This eTip explains the differences between the files and the most common uses for each. We'll start with the most common and then work our way thru the less common file types.

JPEG (or just JPG)
JPEG files are the most common image files. Most, if not all, digital cameras provide JPEG images by default. JPEG is popular because the images are relatively small, with decent quality.

The "JPEG" standard was created by the "Joint Photographic Experts Group" in 1992. It defines how an image is compressed and decompressed. Compression makes images smaller to store in a file, thus its popularity. But, JPEG is a "Lossy" compression method. This means that the compression lowers the quality of an image. It lowers the quality in 2 ways:
  • Some of the data in the image is destroyed during the compressoin, causing loss of detail and introduced "artifacts"; and
  • Images are usually reduced to 8 bits - thus drastically reducing the number of colors in the image.
When compressiong a JPEG image, there is a choice of how much compression you want. Most digital cameras offer you 3 levels of compression, usually displayed with words such as "Fine", "Normal" and "Basic".

You can see how the loss occurs with these images.

Click the image below to see a larger image which will show the compression loss
JPEG Compression

The images below are from Wikipedia, showing the extreme degradation
between the least and most JPEG compression.
ImageQualitySize (bytes)Compression ratioComment
JPEG example Highest quality (Q = 100)83,2612.6:1Extremely minor artifacts
JPEG example Lowest quality (Q = 1)1,523144:1Extreme loss of color and detail; the leaves are nearly unrecognizable

RAW to JPEG conversion
No digital camera takes JPEG images initially. They take what's called a RAW image. The RAW image has all of the data that the camera's sensor captured, but, it needs "processing" to make it look good. If you don't choose what kind of image you want from your camera, it defaults to an automatic "processing" to convert the image to a JPEG. This processing makes assumptions about how the image should look - sometimes it gets it right; sometimes not. But, the result is a much smaller file than the RAW file, as about 90% of the data is destroyed during the "processing", and the image is then compressed.

If you choose to have your camera provide you with the RAW image, you will need to do the "processing" on a computer, but the result will be a much better image. Once processed on a computer with Photoshop, Elements, Lightroom, etc., you can then convert to a low-compression JPEG image to reduce its size, without a lot of "loss".

Since JPEG files are relatively small, they are best used on web pages, email, etc. They are best used with digital camera images; they do NOT do well with text or other subject matter. JPEG files can be good for print when high resolutions and low compression is used.

Because JPEG image files are small, they take less room to store on your device. They also are more suited to emailing. But, if the camera is producing the JPEG image, you are relying on your camera to decide how your image should look, which is the reason many people are unhappy with the images they get from their cameras.

When JPEG images are saved and re-saved, more "loss" is introduced. For this reason, they shouldn't be saved and resaved multiple times.

RAW files
RAW image files are created by digital camera sensors. Unless you specifically tell your camera you want the RAW file, it is generally discarded once the JPEG file is created. You "Ask" for the RAW file thru your camera's menu system or with a button/dial combination on your camera. Not all cameras offer this option, but most do.

RAW files require some post-processing, in a program like Photoshop, Elements, Lightroom, etc. These files are much larger than JPEG files, as they aren't compressed. Some cameras allow the RAW files to be compressed without loss. This is a very good option, as no quality is lost.

RAW files are "proprietary" to the camera - Nikon has their own formats; Canon theirs, etc. And, the format is constantly changing with each new camera. Adobe has a "plugin" for their programs that is contantly being updated for the new formats.

RAW files can be very large, so this could be construed as a disadvantage, but because no data is lost, no quality is lost. RAW files can yield much better images than JPEGS that have been processed by the camera, thus it is the choice for most advanced photographers.

Here's an example of a JPEG processed by the camera (left) and the same image taken as a RAW file processed on a computer (right).
RAW Post Processing

GIF files
GIF files (pronounced JIF - purposely pronounced like the American peanut butter brand!) were created by Compuserv in 1987. The acronym stands for "Graphics Interchange Format". GIF files are compressed using a "lossless" compression method, so quality isn't lost. Like JPEG images, they are 8-bit images, meaning that they can only support a minimum number of colors - but unlike JPEGS, they can only support a "palette" of only 256 colors. Also unlike JPEGS, they have the ability to support animations and transparency. Because of this palette limitation, GIF files are best for graphics - not scenic or people images.

You've undoubedly seen many GIF animations such as this:
Animated GIF

GIF files also support "transparency" - such as this:

The bottom image is a transparent GIF where the background was deleted and made "transparent".
We made the page background gray so you could see how the background shows thru.

Transparent GIF

The ability to support animations and transparency, make them ideal for use on web pages. You need a software that is capable of creating animated GIFs. There are a number of websites that can convert images to animated GIFS and some post-processing software (such as Adobe Photoshop) can do it as well.

GIF files are best used for graphics - not digital camera images. Although you can create some nifty animations with images:

Animated GIF

PNG files

PNG files were created in 1996 as an improvement to GIF files. PNG stands for "Portable Network Graphics" and supports significantly more colors than GIF files do. PNG files also support transparency, however they do not support animation. PNG also compresses files with NO loss, producing a relatively small, high quality image. PNG files support only the RGB palette; there for isn't a good choice when using images for print publication, which often requires a CMYK palette.

PNG files best used for viewing on a web page. They are a good replacement for GIF files.

PNG files can be quite small and offer a decent color range.

BMP files
BMP files were created around 1995. The acronym stands for "Bitmap", as the BMP file was an early bitmap format file. The BMP file is a relatively simple image file, but images can be quite large compared to JPG, PNG, GIF and other formats. It generally is only used with Windows.

BMP files are used on Windows OS. It is an older format, and isn't used much anymore.

There aren't a lot of advantages to using BMP files.

PSD files
PSD files were created by Adobe in 1990 as a format that could be used between Windows and Mac system. It was developed for use with Adobe Photoshop so that images created on one platform (Windows or Mac) could be used on the other. It is a very extensible format - supporting RGB, CMYK, LAB, spot color and duotone color models. It can also support text, vector, raster, 3D, video and animated graphics. It also supports multiple "layers". It is currently used in Photoshop, Lightroom, Photoshop Elements, and other Adobe products. It is also licensed to other vendors. 

If you are editing your images, chances are you can save images to the PSD format.

PSD files can be used when editing your images and you want to save them in an intermediate format for re-editing. They are not good for emailing, as the person receiving the file will need to have software that can view the PSD - plus, PSD files tend to be quite large, so they aren't a good choice for email.

PDF files can be quite large, they take a lot of storage space. They are loss-less, so are ideal for storage when you plan to re-edit a file. It is ideal when sharing files between Windows and MAC operating systems.

TIFF files
TIFF (or TIF) files were created in 1986 by Aldus corp for use in desktop scanning and was updated by Adobe in 1994. The acronym stands for "Tag Image Format File", and works well for grayscale & high color-depth color images. TIFF files also be compressed without loss. TIFF files can be quite large, even when compressed. They are ideal for using when you plan on editing a file multiple times as the files can be re-saved without loss. TIFF files can contain much more data than JPEG files, and are thus a higher-quality alternative. They can be stored with 16-bit color (large # of colors) or 8-bit color (similar to JPEG). They do not contain as much data, however, as RAW files.

Best used as an intermediate format when editing files multiple times or when you want to send a file for print-publication. If your camera supports saving as TIFF, it's a better alternative than JPEG as it can store very high-quality images.

Because TIFF files are quite large, they take more storage space than JPEGs, but they are higher quality than JPEGs.

DNG files
DNG files were created by Adobe in 2004. It is based on TIFF files but stores a lot of informational data (metadata) in the file as well. This data can be data directly from the camera sensor, such as the data in a RAW file. Since RAW files by Nikon and Canon are "proprietary", Adobe designed DNG to be an open-standard replacement for these RAW files. When a RAW file is edited in an Adobe product, it can be exported to a DNG file. This DNG file will be very large, as it actually embeds the RAW file within it. The DNG file format never really became popular.

Not recommended.

The biggest disadvantage is that these files aren't very well supported.

In Summary...
Each file format has it's place. Digital cameras generally support JPEG and RAW formats. When you edit these on a computer, you can save them to other formats. Which one you choose detemines the file size, quality and color.

If you choose to have your digital camera save the RAW images, you will have to edit them on a computer and then select a format to save them in. Editing a RAW image and saving as a JPEG will result in a MUCH better image than having the camera do this for you.

File Comparison

Happy shooting!

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