Do you use layered Tifs?

Started Jan 30, 2013 | Discussions thread
Redcrown
Senior MemberPosts: 1,251
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Re: Do you use layered Tifs?
In reply to Antlab, Jan 30, 2013

I don't know PSP, this is about Photoshop. Maybe too much detail for some, so skip to the bottom for the bottom line.

Choosing a format for saving image files involves a trade off between 4 variables:

1. Speed of saving and reloading the files.
2. Size of the saved files.
3. Compatibility of the saved files with other programs.
4. Preserved quality of the image.

We have 3 basic choices - jpeg, tif, or psd. Ignore jpeg for this discussion, since jpeg can't preserve quality (it's lossy), and can't save layered files.

With tif and psd, there are several other varaibles. With tif you have 3 compression variables (none, LZW, and ZIP.

With psd you have 2 options. Under Edit/Preferences/File Handling there is an option called "Maximize PSD File Compatibility", which you can turn on or off. What does that mean? If PSD compatibility is "on", then a full sized jpeg is embedded in the file. If the file is layered, the jpeg will be a flattened version of the layers.

When Photoshop saves a tif file, it always embeds a full sized jpeg, regardless of bit-depth, layers, or compression. There is no option. The embedded jpegs increase file size and save/load times. Any other program that tries to read the file will use that embedded jpeg.

In addition, there are 2 long-term bugs to consider. Bug #1 is in the LZW compression option of the tif format. LZW compression works well on 8-bit files, but on 16-bit files the LZW compression actually makes a file that is LARGER than if no compression was used. Zip compression works well on both 8-bit and 16-bit, but zip is slower than LZW.

Bug #2 is in the PSD compatibility option. If you turn PSD compatibility off (to hopefully make smaller files), you get the embedded jpeg anyway on FLAT files. Only if the file is layered will the no compatibility (no embedded) jpeg option be honored. If you want the smallest possible psd file, flatten it and then add a blank layer before saving.

Bottom Lines:

The biggest and slowest option is to save layered, 16-bit files in the psd format with compatibility on. Files will be huge and slow.

The fastest save and load times come with tif no-compression.

The smallest 16-bit file sizes come with psd layered no compatibility. The smallest 8-bit file sizes come with tif lzw or zip compression. Tif+zip is slightly smaller than tif+lzw.

The best compromize between size and speed is to use tif with no compression on 16-bit files and tif with lzw on 8-bit files.

There is no compatibility issue because the embedded jpeg is not included in the zip or lzw compression. Therefore other programs can read that embedded jpeg, even if they don't support zip of lzw.

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