My wife does some photography on the side for a hobby. She uses Lightroom for most of her editing and she also uses the "Edit In Photoshop" option as well. I have no idea why she has to go to PS, but she does. When she does this her original file seems to get copied and exported to a HUGE TIFF file. These files are sometimes over 100MB each. Is there some way around Lightroom creating this intermediate file to link PS & Lightroom? She takes thousand of pictures and edits 100's of them. My fileserver is 1.5 TB, but it won't be much longer and I'll be out of space. Please help.
This is how things work when the Adobe "RAW Engines" don't match. Different versions of lightroom and photoshop have different internal engines, and when they match you should be able to seamlessly transfer the image back and forth.
When the engines are incompatible, it saves the in-memory version of the image to a tiff (in order to avoid losing data) and then loads it back in the other program.
You should be able to use the direct transfer by updating both Lightroom and Photoshop to the latest versions.
There is a little more information about this at digital-photography-school.com
You can change the file format passed back from Photoshop to Lightroom by changing Lightroom's settings.
Preferences -> External Editing
Here you can choose file format, bit depth and colour space.
You might be able to reduce the size of the resulting TIFF/PSD files by choosing 8 bit colour depth instead of 16 bit. If you want to use TIFF, select ZIP compression. It will make saving/opening the TIFF slightly slower but it is lossless compression and will save disk space without affecting your image quality.
Whenever you choose to Edit with Photoshop, and the ACR (Adobe Camera Raw) versions do not match, you have the option of "Render using Lightroom", or "Open Anyway". The first thing to try is to update both Lightroom and Photoshop, and get the latest version of ACR for both. Once they are in sync, Edit in Photoshop should happen seamlessly.
If for whatever reason you can not get synchronized versions of ACR for both applications, you still have a couple of options. The first option is to just "Open Anyway", which will simply open the RAW image in photoshop as-is. Quite often, differences in ACR engines are minor, and only apply to certain image formats. The ACR version check does not check or care if the differences in versions actually has any impact on the RAW format for your particular camera, it just shows the warning anyway.
If opening in Photoshop shows notable differences in appearance vs. Lightroom, then you might try manually selecting the RAW processing engine in Lightroom first. In Develop mode, under the Camera Calibration section, you can select the Process. You might try the 2003 process if you are using an older version of Photoshop, rather than the 2010 version. This will really only do you any good if your version of Photoshop/ACR is fairly old.
If all of these produce undesirable results, then your only real option is to "Render using Lightroom", which will take the current snapshot and generate a TIFF file from it.
Finally, you might try investing in a bluray burner. I have a 4Tb NetGear ReadyNAS NVX on my network where I back up all of my content, however it is generally not wise to use a NAS raid device as your sole backup. I regularly burn "archival" photos to 25Gb bluray discs, and store them in a dvd jacket with multiple pages. I also try to create and print an index card that goes with each disc that identifies the photo sets burned to them. The archival lifetime of bluray is more stable and generally longer-lived than a network backup device, however every few years it is a good idea to re-burn the content onto new discs to make ensure longevity.
She goes to Photoshop because some of the tools in there are not available in Lightroom; I do a lot of heavy lifting in PS that LR is not equipped to, but if I don't need to, I won't.
Try updating the RAW engine as chills42 suggested, but I have to say that in exchange for the convenience and power of editing in the digital age, we get the bugbear of increasing storage needs in return. Management of file sizes is also getting more important. One way to minimise file sizes would be to flatten the PSD/TIFF files instead of saving the layers. This is useful for images that she feels are "complete", ie there is no amount of work that can be done on it to improve the picture further.
The easiest way, however, is buy more storage space :)
I just recently encountered this myself. You don't need to do any of the above, simply, go to File>Preferences>Reset Warning dialog. When using edit in photoshop chose "open anyway" instead of "render using lightroom" Ta Da! :)