Tip Understand What Your Camera Is Saying

Unfortunately, camera manufacturers have never agreed to any standard for resolution and compression terms, which can lead to confusion. Some cameras put JPEG compression settings under a menu heading called "Quality," while other cameras put resolution and compression settings under the same heading. As we discussed in Chapter 2, resolution does not determine quality so much as it does the quantity of data. On the other hand, as Figure 5-1 demonstrates, compression level relates directly to image quality. If the options under "Quality" are listed in numbers, such as 1024 x 768 or 3MP, then it is a resolution setting.

Figure 5-1: The photo on the left is an original JPEG photo of an antique urn. But when it was opened and saved several times, using high JPEG compression settings, details became indistinct, with noticeable pixelization and blurring. This is a severe example of what can happen when too much compression is applied to a JPEG image. Most digital cameras will not compress JPEGs to such a great degree, and the visual effect of light compression may be imperceptible to most people.

Figure 5-1: The photo on the left is an original JPEG photo of an antique urn. But when it was opened and saved several times, using high JPEG compression settings, details became indistinct, with noticeable pixelization and blurring. This is a severe example of what can happen when too much compression is applied to a JPEG image. Most digital cameras will not compress JPEGs to such a great degree, and the visual effect of light compression may be imperceptible to most people.

One problem with JPEG compression is that it is cumulative. The initial capture in the camera throws away some data when it saves the picture as JPEG. Then, when you open the file in your photo-editing program and resave it as JPEG, it will rearrange and throw out a bit more data. Open and save it again, and you'll lose a tiny bit more image integrity. So, you'll want to be very conservative about the amount and frequency of compression you allow.

Our advice is to never overwrite your original file with edited versions. Instead, archive the original, and save edited versions under new names. Incidentally, when you archive JPEGs to a CD or DVD, they're permanent and will not change or degrade whenever you open them.

If image quality is paramount to you, you will want to do as most professional photographers do—avoid JPEG capture, because of the destructive, degrading nature of its compression. And if you do capture images in JPEG, save them as TIFFs when you download them to your computer.

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