WHY 9.7MB RAW file grows to 60MB?

[alx]

Using my Canon XTi RAW format I upload photos I took to my Mac iPhoto library. The photo files, 3888×2588 pixels, weight between 8-10.5MB.

For example, photo IMG_0138.CR2 weights 9.7MB. After cropping it within iPhoto to 3888×2187 (16x9) it shows for a short while a size of 2.6MB which turns to 0 (zero) after I release the mouse from the image.

When I drag the image file from iPhoto library to the Desktop, the file info shows some 60MB (sixty) in Tiff format!!!
IS IT POSSIBLE? HOW COME?

On the other hand, when I drag the above file as is (un-editted uncropped) to the Desktop, it turns to be a 2.6JPG JPG file. Weird (at least for me) !?

I'd appreciate your explanation if you are familiar with this issue.
Thanks in advance
Alex
israel

[i speak in math]

tiff is an lossless and often uncompressed file type. It is similar to a .zip file but for image data. You can use some compression methods on it, but its still lossless and huge. You can usually use 16bit as well, which easily doubles the file size. However, you get the best image quality possible for future use (printing, editing...)

jpeg is lossy and compressed. This means when you save the file as a jpeg, the file compresses the data and rounds colors a bit. You lose half the actual photo data in order to cram the data into a small 8bit file. This is okay if you save it once and don't edit it again. If you want to print, its okay as long as you save at the highest quality setting.

[OsmosisStudios]

Originally Posted by alx

Tiff format!!!

There's your problem. Unless youve got a printer that can easily handle higher bit rates and TIFF files, you're going to be considerably better served with jpgs.