Today’s Question: How would using ZIP compression rather than “None” [in the External Editing settings for Preferences in Lightroom] affect opening the resulting photo once it is sent back to Lightroom or Photoshop?
Tim’s Quick Answer: TIFF image files with ZIP compression are supported by a variety of software applications, including Photoshop and Lightroom. As a result, there is not a significant issue with using the ZIP compression option for images you are managing in a workflow that includes Lightroom and Photoshop. The only potential issue would be the risk of other software applications not supporting TIFF images with ZIP compression. In general you won’t find this to be a problem.
More Detail: In the External Editing section of the Preferences dialog in Lightroom you can specify the file type and other settings to be used when sending a photo to another application, such as Photoshop or various plug-ins.
In the past there had been issues with a lack of support for TIFF images with compression applied, especially with the LZW compression option. These issues have largely been resolved, with most imaging applications supporting both ZIP and LZW compression for TIFF images.
As a result, I generally don’t hesitate to apply compression to TIFF images. I typically employ the LZW option rather than ZIP, but both of these options provide lossless compression and are widely supported. In other words, either option will typically be perfectly fine, and will result in smaller file sizes compared to the “None” option.
Frankly, the bigger issue here relates to the potential to create layered images in Photoshop. When you create layers in Photoshop the resulting image cannot be opened with layers intact using other software applications, because the features in question are specific to Photoshop. But again, in the context of a workflow employing Lightroom and Photoshop, this isn’t a significant concern.