I probably should have addressed this subject sooner. Which format should you use with your digital camera? This information is not going to be technical. It is important that you understand the difference between the formats. It will be up to you to choose the format that works best for you. Depending on your particular camera, you will have some or all of the following choices:

Jpeg (Joint Photographic Experts Group) : A specially compressed file in bitmapped format. The file size of a JPG file is much smaller than similar pictures in other formats .On my D100 in the highest quality setting, a jpeg file is 3 mb in size. JPEG is &lossy,& meaning that the decompressed image isn't quite the same as the one you started with.

Tiff - Tagged Image File Format : a file format for exchanging bitmapped and grayscale images among applications. This format produces a file with my Nikon D100 of approximately 17 mb. Files with the .TIFF extension are usually created by scanners or image processing programs. These bitmapped files come in a number of different classes. There are many different varieties of TIFF.

Raw - The image file created by a camera using Raw Format contains data prior to all of the processing for White Balance, Contrast, Sharpness, Color Saturation, etc. This gives the photographer the most control and flexibility in handling these images, since these variables can be changed even after a photo has been taken: they can all be modified in the conversion process itself. In this way, images can be individually customized to a very high degree, different versions of the same image can be created and compared, etc. Raw file size with my Nikon D100 is 9 mb.

Which Format is Best?
There is no correct answer for this. There are formats that I do not use.

Tiff : I do not use tiff because of the large file size (17 mb). It takes too long for the camera to write the file to the compact flash card. It also allows less images on the card.

Raw (compressed) : The write time from the camera to the compact flash card is very long with this format (see table below).

Jpeg : This is a format that I don't use but it may be the right format for you. Jpeg produces the smallest file and more photos will fit on a compact flash card. I don't use it because it compresses the data too much and information is lost in the compression. Depending on what you do with your photos, this may not be an issue. If you use jpeg, please read the following paragraph:

When you open a jpeg file and make changes to it and then save it as a jpeg, you will degrade the original image. I recommend that if you intend to make changes to a jpeg, that you save it as a tiff file. The tiff file will be much larger than the jpeg but you will not lose data and you can reopen the tiff and make changes without losing additional data. You can open a jpeg file and look at or print it and then close it without losing any data . You only lose data when you make changes to a jpeg and then save it as a jpeg.

Raw : This is my format of choice. I can open the raw image in Nikon Editor or Adobe Raw Converter and change the white balance, contrast, exposure, color balance, etc. I then save the image as a tiff file. I keep the original raw file. It's like having a digital original negative. I will always have the original file to use.

The table below shows D100 Write Times to a compact flash card. All rates are based on a single frame in the highest quality for each format. They were complied using a fresh battery in the camera and a Lexar 512 mb 24x compact flash card:

It is clear from the write times shown above that raw-compressed and tiff take a long time to write compared to the other formats. The jpeg files are all in the same range and the raw-uncompressed file takes about twice the time as the best jpeg format yet the raw file is three times the size. In most underwater situations, a wait time of 5.50 seconds is inconsequential.