Exported tiffs are double the file size of original imported tiffs despite only applying minor edits

[Connor35497834mj7m]

Hi all,

I want to import tiffs into lightroom classic, apply very minor edits (minor crops and minor straightening) and then export the images again as tiffs. Currently when I try this, the exported tiffs are over twice the file size as the originals and the bit depth increases from 8 to 24. I'm quite new to image editing and I don't understand why this is happening/if there's a way to keep the file size pretty much the same as the original? I've attached images showing the details of my imported image (17.2MB) vs the exported image after using the straightening tool (49.1MB) and my export settings in lightroom. Any explanation would be appreciated!

[JohanElzenga · Accepted solution]

Are these B&W photos? It looks like the original TIFF was greyscale (8 bits), but Lightroom Classic does not support greyscale. So after editing and exporting an edited copy, those copies are now 24 bits color images (even if the photo is still B&W, which simply means all three color channels are identical). 

[Connor35497834mj7m]

Ahh yes, the originals are B&W (captured on a microfilm scanner) so that sounds like the root of the issue, thank you so much! Is there a program you'd recommend that supports greyscale but is as easy for making mass crops/straightening as lightroom is? I'm working with between 400-800 photos at a time for reference. 

[JohanElzenga]

Your export settings show that you do not compress the exported TIFFs. Try LZW compression. That is lossless and may make the TIFFs as small as the original ones.