bmp's are not compressed, jpg's are. it's like wav vs mp3

bmp files must have more pixals per inch.

So what's the point nowadays to use uncompressed image files like bmp if jpg do the same job but in less space?

BMP files are bigger for two reasons, first BMP is an abbreviation of bitmap and every bit in the picture is mapped. Second JPGs are compressed using a lossy compression algorhythm, so some information is discarded. This is why you lose quality when you save a bmp as a jpg. In fact, every time you edit and save a jpg you lose more information, leading to a constant degradation in quality.

In theory, you do lose 'quality' using a JPEG file format over RAW or Bitmap. But if you find any quality problems in the .jpg I'm attaching to the this answer, you'll need to point them out to me... . .

1) "The BMP (bit mapped) format is used internally in the Microsoft Windows operating system to handle graphics images. These files are typically not compressed resulting in large files. The main advantage of BMP files is their wide acceptance, simplicity, and use in Windows programs. However, they may pose problems for users of other operating systems. Commonly, BMP files are used for Microsoft's Paint program. Since most BMP files are uncompressed, and BMP's RLE compression has serious limits, the large size of BMP files makes them unsuitable for file transfer. However, Bit Map images are suitable for background images and wallpapers. This is especially true for screen shots. In addition, images from scanners are usually stored in BMP files." 2) "The JPEG (Joint Photographic Experts Group) image files are a lossy format (in many causes). The DOS filename extension is JPG, although other operating systems may use JPEG. Nearly all digital cameras have the option to save images in JPEG format. The JPEG format supports 8-bit per color - red, green, and blue, for 24-bit total - and produces relatively small file sizes. Fortunately, the compression in most cases does not detract noticeably from the image. But JPEG files do suffer generational degradation when repeatedly edited and saved. Photographic images are best stored in a lossless non-JPEG format if they will be re-edited in future, or if the presence of small "artifacts" (blemishes), due to the nature of the JPEG compression algorithm (in the most of the compressing tools), is unacceptable. JPEG is also used as the image compression algorithm in many Adobe PDF files." 3) So bmp are bigger because they are typically not compressed, and JPEG are. The interesting in JPEG is that you get relatively small file sizes for a not - for the eyes - noticeable loss in quality. However, there *is* a loss of quality and this format is not suitable for further image processing, because the quality loss after quite a few processing will become noticeable. Used source: http://en.wikipedia.org/wiki/Image_file_formats Further information: http://en.wikipedia.org/wiki/Comparison_of_graphics_file_formats http://en.wikipedia.org/wiki/Graphics_file_format_summary

yes, you do lose quality with a jpg file (vs. bmp). however, unless you are planning to blow the picture up and view it on something besides a pc monitor, then the jpg/jpeg file will do the trick for less space.