For photograph restoration we prefer to use raster bitmap images, such as jpeg, png, bitmap and tiff. We scan all photographs as hi-resolution raster images, as we convert them into digital files. A raster bitmap image file format can save at 16, 24, and 32 bits-per-pixel. At the two highest levels, the pixels themselves can carry up to 16,777,216 different colors. Bitmaps images saved at 24 bits per pixel are great quality images, but of course the file size is triple that of an 8 bit image. Photo repair, photo enhancement, photo retouching, photo restoration and any other type of digital photo editing will require the use of raster bitmap images, as we want to make sure that we don't loose any of your photographs information when we work with it.

The following section is for those of you curious about different image types and why we like to use the ones we do to ensure that you recieve the highest quality image in the end. This informatin does not include Vector image types, which are used in print domminated industries. (Think brochures, and signs)

There are numerous Raster image formats such as the following:

JPEG Digital Image format - Joint Photographic Experts Group
JPG Digital Image format - (abbreviated is most commonly used ext.)
BMP Digital Image format - Microsoft Windows Bitmap
PNG Digital Image format - Portable Network Graphics
GIF Digital Image format - Graphics Interchange Format
TIFF Digital Image format - Tagged Image File Format
TGA Digital Image format - Targa; Truevision TGA

What Is A Bitmap?

A bitmap is a method of storing digital data that maps a visual image pixel, bit by bit. the pixels are mapped to specified dimensions to create an image. There are numerous bitmapped file formats, .bmp, .jpg, .png, tiff, .tga, .gif, .pcx, .pict, etc. All digital photos are bitmap images. This type of file produces the ´jaggies´ when examined closely. The line of pixels that create edges. Bitmap images are used by all computers. The desktop or screen information for all Windows machines uses .bmp files, while the Macintosh uses pict files.

Compression

Uncompressed bitmap images by nature produce large file sizes, however, various image compression solutions have been developed to reduce the file size of bitmap images. The same image saved in GIF or JPEG format uses less bytes to make up the file than that of a TIFF or BMP bitmap image file. How? Compression.

Image compression is used to reduce the amount of memory required to store an image. For example, an image that has a resolution of 800x600 and is in the RGB color space at 8 bits per color requires 900 kbytes of storage. If this image can be compressed at a compression ration of 20:1, the amount of storage required is only 45 kbytes. There are several methods of image compression, including iVEX, JPEG, MPEG, H.261, H.263, and Wavelet. "Compression" is a computer term that represents a variety of mathematical formats used to compress an image's byte size.

Bitmaps can be compressed to a point. The process is called "run-length encoding." Runs of pixels that are all the same color are all combined into one pixel. The longer the run of pixels, the more compression. Bitmaps with little detail or color variance will really compress. Those with a great deal of detail don't offer much in the way of compression. Bitmaps that use the run-length encoding can carry either the common ".bmp" extension or ".rle". Another difference between the two files is that the common Bitmap can accept 16 million different colors per pixel. Saving the same image in run-length encoding knocks the bits-per-pixel down to 8. That locks the level of color in at no more than 256. That's even more compression of bytes to boot.

JPEG Image Formats

JPEG is a compression algorithm developed by the Joint Photographic Experts Group. JPEG's big selling point is that its compression factor stores the image on the hard drive in less bytes than the image is when it actually displays. Bytes are lost at the expense of detail. The Web took to the format straightaway because not only did the image store in fewer bytes, it transferred in fewer bytes. Lossy compression achieves a significant file size reduction while providing very good image quality. Precise control over compression attributes such as image quality vs. file size, 8 bit grayscale or 24 bit RGB, etc., is very useful.

Progressive JPEG Image Format

A progressive JPEG fills in every other line as it loads, then returns to the top of the image to fill in the remainder.

PNG Image Format

The PNG format was designed to replace the dated GIF format, and to some extent, the TIFF format. It utilizes lossless compression, meaning no image data is lost when saving or viewing the image. It is a universal format that is recognized by the World Wide Web consortium, and supported by modern web browsers. The PNG format does not have any patent restrictions and can be read and written freely by software developers and webmasters alike. The PNG image format can store 32 bit image data and full 8 bit alpha channels, yet can be compressed much in the same manner as a Jpeg file.

What about GIF?

GIF images can only be saved as an 8-bit color mapped image, which means you are limited to 256 colors. Remember the GIF format was developed back when most PC's only had the capability of 256 colors. PNG can be saved not only as 8 bit, but also 24 bit and higher up to 64 bit! GIF images allow one out of the possible 256 colors to be fully transparent. As we discuss below, PNG has a much higher level of transparency support. Another benefit of PNG over GIF is typically the file size of a PNG is about 20% smaller then the same GIF image. Finally, as discussed in the PNG overview above, GIF has patent restrictions with it's use.

What about TIFF?

The TIFF image format has been around for a long time, and will likely be around for quite a while more. The TIFF format was the cross-platform image format by choice until PNG was introduced, and according to some still is. TIFF has been the most popular 24 bit image format for print collateral as, in addition to the bitmap image data, it can also store a numerous amount of various ancillary data, such as Photoshop layers, alpha channels, printing profiles, color profiles, etc. This tends to increase the file size some, but because print collateral require high resolution bitmap image files to produce satisfactory print quality, TIFF images are generally tote a very large file size regardless. Until PNG, was the only standard lossless compressed format. The standard 24 Bit PNG functionally is very similar in function to a LZW compressed TIFF. The TIFF format is able to store multiple images in one file. This is commonly used for FAX images. PNG's do not have this capability. The TIFF format remains to be popular, but there are few reasons to use it for photograph archival with the added benefits of PNG.

What about JPEG?

Unlike PNG, JPEG uses a lossy compression routine. Lossy compression means that the image loses quality and information each time it is saved. Because JPEG uses lossy compression, the file size is almost always smaller then a PNG, especially for photographic images. Care must be taken when working with JPEG images as each time a JPEG is re-saved, more and more compression artifacts are introduced. Since PNG uses lossless compression it's an ideal format ideal for archival purposes, and for editing before saving a final version as a JPEG. JPEG is the most common image format used on the web, and will continue to be. Most photographic have commonly been saved as JPEG as opposed to PNG for viewing on the web as the file size will be much smaller. However with the proliferation of broadband connections, the added functionality benefits of PNG images vs Jpeg images will see a trend usage of PNG images. As the bandwidth restricted dial-up connection gradually becomes obsolete and the broadband connection becomes the standard, the image and media files sizes used will be relaxed, almost certainly positioning the PNG to replace the Jpeg.

Anyone familiar with the Internet and custom web design recognizes the JPEG bitmap image as a household word. Graphic designers commonly use TIFF bitmap images for print collateral design. Custom web designers almost always use colorful Jpeg photos in their web pages. In a couple years PNG bitmap image format will have replaced the GIF bitmap image in custom web design, and graphic designers may retire Jpeg image format as well, considering the PNG bitmap image format offers so much more than the Jpeg bitmap image format.