Huge Tiff files when Exporting

[nancyd3031]

I have 3000 jpg files, most under 20MB. I'm importing and cataloging them by batches in Lightroom, then exporting them as Tiffs. Some are just fine at 30 to 70 MB, but as this project goes on I'm now getting batches that are exceeding 217MB.  Why are these images growing so large?  All I'm doing is adding keywords and other metadata, I'm not doing any other enhancements. The amount of metadata added is pretty uniform as well.

[JP Hess]

TIF files by nature are much larger, especially if you are exporting them as 16-bit TIF files. You can export them as 8-bit TIF files and significantly decrease their size by comparison. You might also consider using one of the compression algorithms.

[nancyd3031]

I do understand that TIFs are by nature much larger, however these images seem to grow with every batch.  The early batches exported around 70-119MB, now they are exporting at 217MB and higher, but the original files aren't any larger than the early ones.  I wasn't sure if it was a cache or something in Lightroom that needed to be cleared

[Brad_Polt-Jones]

Have you defined an export preset that you can use to maintain consistency each time you export the original JPEG's. Check to make sure the image size settings are consistent for the exported TIF. The metadata you've added will have little effect on the final size of a TIF.

There is no need to use the 16-bit option if the original files are JPEG, as they are only 8-bit.

[johnrellis]

If you've enabled TIFF compression in the export settings, the amount of (lossless) compression depends highly on the image.  Those with less detail compress significantly smaller.

If you upload to Dropbox (or similar) two sample JPEGs, one with a smaller exported TIFF and one with a larger exported TIFF, along with the settings used in the Export window, and post the sharing link here, it will be pretty quick to figure out what's the cause.