Quality Settings and File Formats
The reason this is confusing is that the Quality settings have nothing to do with resolution. The pixel dimensions remain the same because they reflect the total number of pixels being recorded by the camera - in width and height. The total should be roughly equivalent to a million pixels per megapixel. (An exception is that the lowest quality settings on the camera may drop to a lower pixel dimension, but it is better not to use these anyway.)
My camera is a 4 megapixel camera. The pixel dimensions in the viewfinder read 2288 x 1712 which equal 3,917,056 - pretty darn close to four million. This remains the same no matter which quality level I choose.
Where the difference in Quality comes in is in how the camera saves the image - what file format is used, and how much compression is allowed.
What are File Formats?
Graphic (picture) files have always been huge. I’m not talking about inches here, but rather, the space a file takes up on your hard drive or memory card. (I usually call it “weight”). A heavy file is a problem not only because it takes up a lot of room on storage media, but also because it takes a lot of time to transfer (upload/download) - from camera to computer, from computer to web etc.
Way back in the computer dark ages, it became obvious that some compression of these files was going to be necessary if they were going to be usable, and especially if we were going to be throwing them around on the internet. So compression file formats were created.
TIFF The TIFF file format was created when the internet was still just a gleam in somebody’s eye. It was intended primarily for scanning. TIFF is a non-lossy format, meaning that it compresses the file without throwing away information - therefore the result is still a pretty fat file - and a high quality one. Good for use on the computer for scans and prints and source files, but not good for the web. Produces a high quality, but very heavy digital photo file.
JPEG (jay-peg) stands for Joint Photographic Experts Group and you can tell by its name that it is primarily intended for photographs. It is the most widely used file format on digital cameras and the internet - everywhere that photographic images have to be moved around quickly. JPEG is a lossy compression format, meaning that in order to condense the file, it throws out pixels. The number of pixels thrown out is controlled by what level of compression you choose - via the Quality settings on your camera. Obviously, the smaller the file, the more pixels you will part with.
So, on your digital camera, when you choose Super High Quality (SHQ), you are asking the camera to retain most of the image info and save your pictures as relatively heavy files. When you choose High Quality (HQ), you are allowing more pixels to leave in the interest of smaller files, so you can get more of them on your memory card before having to empty it. This is a judgement call and balancing act on your part. Do you want fewer, better pictures, or to be able to fit more pictures on your card?
My camera also has a TIFF choice at the high end for saving a best possible image (with this camera anyway), and a couple of standard settings at the low end which are best forgotten.
The number of pictures that will fit on your memory card will vary greatly according to the setting you choose. This is why some people (me, for example) often choose to shoot at only HQ to get enough photos on a card. On my camera, the HQ mode produces beautiful quality that I can’t argue with anyway. Your camera may be different, but here is how my quality settings translate to picture capacity on the 128 MG memory card I have in my camera.
TIFF = 11 shots
SHQ = 46 shots
HQ = 130 shots
SQ1 = 398 at only 1280 x 960 pixels
SQ2 - 1326 at only 640 x480 pixels
Other File Formats
RAW
The reason that most digital cameras have so many automated settings, and that decent digital pictures can even be shot by chimpanzees with learning disabilities, is that the camera is doing a lot of the picture taking. I swear some cameras could go out on a shoot without me and bring home a nice set of images. And I’m waiting for one that will allow me to tag along and learn a few things!
Anyway, a RAW file is recorded without any adjustments by the camera. It is just the raw image information. If you are a professional, this may be desirable because you can do all the adjusting in the computer - as long as you own the necessary RAW processing software. This is very, very complicated stuff and not for the faint hearted. And, you need huge memory cards because there is no compression applied to these files either.
PNG
Stands for Portable Network Graphics. This is a relatively new one - not yet widely used, but coming along - and some digital cameras do save files in the PNG (ping) format.
PNG is a lossless compression so it throws away no information as it compresses the file. There are other benefits like the ability to zoom in to see a close-up on the web - and the ability to adjust the brightness. A PNG file also carries gamma (color) information that other formats don’t. So, its time will surely come - probably as soon as all browser software can display PNG files and all image software programs can open and save them.
