Tiff files are extremely huge when exporting back to Lightroom

That TIFF files are huge is a perception that is sort of the reverse of the reality. An uncompressed TIFF represents the “true” size of an image, in that when you do the math…

[number of pixels * bits per pixel * number of channels * number of layers + masks, channels, and other data] equals

…the file size you typically get in a TIFF document. From any software, on any platform.

Instead of TIFF file being huge, what really happens is that source files are typically unusably small. For example, a raw file might only be 20MB. But you can’t use it, because a raw file is only one channel of unprocessed data, maybe 10 or 12 bits per pixel, and in some cameras that’s also compressed. To use it, you need to process the one raw channel into three color channels (RGB). Then you might want to edit it at 16 bits per channel. Already you have made the file quite a lot bigger: 3 channels at 16 bits each, instead of 1 channel at 10–12 bits.

Then you want to stack. That means unavoidably, you’re adding layers. If you have 5 stacked layers, of course your file just grew by another 5 times. Photoshop also stores a composite preview, so that the layered contents are visible in Lightroom and other applications; that adds one more layer. Did you also add any layer masks or additional channels? Each one of those also adds to to the pile of data, although the impact is less since those are grayscale only.

Those are the basics of how a file can balloon from a small raw or JPEG file to a large working TIFF or PSD file. You can make a TIFF file somewhat smaller by:

• Reducing bit depth from 16 bits per channel to 8 bits per channel
• Reducing the pixel dimensions
• Reducing the number of layers, or flattening it
• Applying compression

For TIFF files, Photoshop offers LZW and ZIP compression. I use ZIP because it’s smaller, but it takes a long time to save. To me this is not too bad because Photoshop does background saving, so I simply continue editing while it saves.

Which leads to the final thing. You decide what’s negotiable about how you need to work with your files. Do you require 16 bits per channel, preserving all original pixels losslessly (can’t use JPEG then), and preserving layers? If those are non-negotiable, then all you can do is apply a TIFF lossless compression option. And also, like many of us, budget for enough mass storage so that filling up a volume is not a concern. I use TIFF, and that means I’ll have an eye out for hard drive deals during the holiday sales that are coming up…