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That is a trade-off that the end user has to decide. Compression reduces size which saves space on a disk (including within a document) and cuts time while sending and doing backups. You have to look at how the photo will be viewed and decide how much distortion of the image is noticeable and how much you are willing to go out of the way to keep the quality at a certain level. That will determine how many and what size memory cards to buy, what size hard drive to install, how fast a processor you need and so on. Whether you're comparing different size JPEG's, or raw versus JPEG, the answer is in the application and the eye of the viewer. That boils down to how large the picture will be displayed and how far away the observer is. Just remember that once the image information is altered by compression, making the file large again can't bring it back. You cant generate a good 16x20 portrait from a 2x2 passport photo. But you don't want to insert several 5 MB images into a Powerpoint document. That makes the file unmanageable. And you may not want to send a very large file to your printer if the output on paper will be a wallet print. But just because you may compress a file to make a page load faster doesn't mean you need to over-write the original. Drive space is relatively cheap.
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Do digital photos from disc lose quality each time you print?
A JPEG image loses quality when it is opened and resaved due the compression algorithms. The more an image is opened and resaved, the more the quality can degrade. An image on a disc will not lose quality unless you resave it on a CD-RW. Opening an image to print will not affect the quality.
How does the quality of a sound or image file relate to its file size?
Smaller the size, more information is lost due to compression and therefore the quality gets lost. Smart compression techniques like mp3 or jpeg are using assumptions about the intended use of the image/sound to minimize compression losses in the relevant domain.
How resolution and colour depth affect file size and image quality?
Changing the image resolution will affect the file size of the image and the quality of the image. Image resolution is measure in DPI, which is Dots Per Inch, this means that if you increase the resolution then the DPI will increase and the quality of the image will get better as a result as there are more pixels that make up the image, so the image will be more distinct and sharper. When the image resolution is increased the image has more pixels, this is the exact opposite to the compression techniques, this means that the file will get a lot bigger as the number of pixels increases. Decreasing the resolution, however, will make the image quality lower but will reduce the file size.
How do you convert from pixel to kilobyte?
There is no straightforward conversion. An image that has (for example) 800 x 600 pixels needs to represent that many picture points. Without data compression, each picture element needs about three bytes (depending on the color depth); however, formats such as JPEG do use data compression, more precisely, lossy data compression - and the factor by which data is reduced with data compressed varies, depending on the image quality. That is, in lossy data compression, more compression means less quality.
During JPEG compression some data was discarded. Why it does not affect the overall quality of an image?
It does but not in a way that is visible to the eye as it's a reasonbly . What format is the original in? Formats such as GIF are high-compression "lossy" formats so the compression is more obvious. If you do small scale editing you'll notice the quality dropout as the image will appear blurred and then just pixels at a higher zoom. Then it's a headache.
What is the purpose of a PSD file?
PSD is Photoshop's proprietary format that can store information in multiple layers. It's useful when you have edited/are editing an image in separate layers and want to return at a later time to make changes to one or more of those layers. PSDs also do not use compression, so you won't loose image quality from saving your file; this is ideal for editing and if you want to save out your image in multiple file formats with different resolution and compression settings, while preserving the original image quality within the psd.
What is the relation between compression and enhancement of an image?
In general, the more you compress the less you enhance.
Why lossy compression is used for JPEG image?
The JPEG format was specifically designed to minimize the size of the file beyond what other formats were able to do at that time (for example BMP RLE or GIF LZW). In order to achieve it, it was decided to accept minor degradation of the image quality - with other words the compression is lossy. For more details about how the JPEG format compares to other image formats, please see the related question.
Is it important to consider the resolution of an image in adobe photoshop?
Yes it is, depend of what You want to do with image. IF You want to print then resolution is very important, if You gonna post image on web site more important are pixel dimensions because on web images will be displayed with 72 ppi regardless of original image resolution.
What jpg compression level from 1 to 12 to choose in photoshop edited photos with red eyes removed when having taken full quality and resolution photos with IXUS 500?
I now use this rule for any kind of photos: use either Windows Photo Gallery to correct red-eyes or Gimp and when saving on Gimp, I save the picture with optimization and with a level of quality in the quality bar such as the size of the new file is lower than the size of the original file but, with this limitation, being the highest possible size. the higher the number the better the image quality will be, but also will result in a larger file. the lower, worse quality and smaller files. JPG is compression and anytime you use it you will lose information in the image. The more times you save in JPG, the worse the image quality gets. To save an image with no degredation, save in TIF or PSD format.
JPG and Tif file formats should be used for?
JPG is optimized for photographs and similar continuous tone images that contain many, many colors. It can achieve astounding compression ratios even while maintaining very high image quality. GIF compression is unkind to such images. JPG works by analyzing images and discarding kinds of information that the eye is least likely to notice. It stores information as 24 bit color. Important: the degree of compression of JPG is adjustable. At moderate compression levels of photographic images, it is very difficult for the eye to discern any difference from the original, even at extreme magnification. Compression factors of more than 20 are often quite acceptable. Better graphics programs, such as Paint Shop Pro and Photoshop, allow you to view the image quality and file size as a function of compression level, so that you can conveniently choose the balance between quality and file size.TIFF is, in principle, a very flexible format that can be lossless or lossy. The details of the image storage algorithm are included as part of the file. In practice, TIFF is used almost exclusively as a lossless image storage format that uses no compression at all. Most graphics programs that use TIFF do not compression. Consequently, file sizes are quite big. (Sometimes a lossless compression algorithm called LZW is used, but it is not universally supported.)
What is the advantage of jpeg?
JPEG images (jpeg, jpg) use compression formats to reduce the data file size for digital images. While this causes a loss of image quality, it enables images to be more efficiently stored and transmitted.
