P: TIFF compression settings have no effect when Lightroom sends image to Photoshop for editing

"However, that is not 100% correctly "enforced" by the preferences dialog." This part of the bug has been fixed in in Lr 6.9 or 6.8 as I remember.

"Me, too!!" This sort of thing is commonly called a "Misfeature" and needs to be fixed.

As documented in the LR help for the external editing settings, LZW compression is not possible for 16 bit TIFF files. However, that is not 100% correctly "enforced" by the preferences dialog.What is correctly handled: When switching from 8 bit to 16 bit, an entry "LZW" is removed from the "compression" drop-down menu and if "LZW" was previously selected, it is replaced by "None".What is not correctly handled: If the preferences dialog is opened with bit depth already set to 16, the "compression" drop-down menu still contains the entry "LZW", and it is selectable. However, when "LZW" is selected then, and the preferences dialog is closed using "OK", the compression setting saved is actually "None", which is also visible the next time the preferences dialog is opened.Not a big deal, but one can accidentally use "LZW" for 16 Bit and end up with no compression at all - without any indication that "LZW" was not a valid choice.Applies for both "Edit in PS" and "Additional external editor". LR 4.3 64 Bit, Win 7.

+1 This is ridiculous, and the only reason this hasn't been fixed is that the majority of PS/LR users don't know anything about computers, haven't bothered to check the file sizes and don't know it's an issue.  This has been a KNOWN ISSUE for 5 YEARS. Fix your broken software Adobe. 
...Or should I send you the bill for all my extra hard drives?

LR CC 2015.8 on Windows 7....it's a mystery why LR TIFF ZIP is significantly smaller than PS TIFF ZIP....it's not due to metadata differences as far as I can see!

Just chiming in on this one. Every picture I work and save with ctrl - s takes 1 GB of both main drive and backup. I am too lazy to Save As, select compression and then re import into Lightroom. Still, 100 edited photos is 100 GB of disk space. It could be a third if this worked.

It's now 2016 and the bug is still there. Worst part is that most people, are unaware of the issue and waste hdd space by having uncompressed files.

 How far is your office exactly??? 

I am also wondering about this, the compression option is still not working with current versions of Lightroom and Photoshop CC. Any news?

Just a follow-up: how are plans to deal with this progressing???

Thanks again, Chris. It would be great to have this functionality (as great as it was when I was using 'incompatible' versions of LR and PS! - maybe I should just cancel my CC subscription 😉 ).