Processing JPEG Image Data

If a JPEG image requires major corrections, we always convert it to TIFF format first. This helps to avoid the loss of image quality that is caused by the quantization that is part of the image saving process.* The resulting TIFF file is then our new master file that we use as the basis for subsequent corrections. We save the original JPEG files and don't touch them any more. We compress our TIFF files using LZW or ZIP because both algorithms produce smaller, lossless compressed files and are supported by all Adobe applications. This means you can embed 8-bit, 16-bit, and 32-bit color profiles,

* Quantization involves setting neighboring pixels to the same or similar color values in order to save disk space when compressing image files. The process unfortunately causes image quality loss and the formation of color blocks known as "JPEG artifacts".

> Viveza is described in section 7.16, page 282 and most of the other programs and plug-ins mentioned here in chapters 8 and 12. Multishot techniques and software are described in chapter 9.

you can access and process layers and channels, and you add EXIF, IPTC, and XMP metadata to your files. LZW compression produces slightly larger files than ZIP, but it is compatible with more third-party applications.

If we are working on TIFF data (from a scan, for example), we compress the file using ZIP or LZW and embed the appropriate color profile if it has not already been assigned.

We then apply all necessary correction steps for RAW files as described above and in chapter 4, using either your RAW editor or Photoshop.

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