Tiff file size is excessive

Hi Roger 🙂

Your screenshot gives it away: the pixels are identical in both files (same dimensions, 8-bit RGB), so the extra ~70 MB is not image data — it is accumulated metadata inherited from the master PSD, exactly as you suspected. When a file has been copied/placed from many other documents over the years, Photoshop keeps an ever-growing XMP history list (photoshop:DocumentAncestors) in the metadata. You can confirm it under File > File Info > Raw Data — that list will be enormous.

Two ways to fix it:

1. Quick way (what you already found): save the flattened TIFF from the new, clean document — it starts with fresh metadata, which is why it drops to 4.3 MB.

2. Clean the master PSD itself: work on a duplicate of it, then run this little script via File > Scripts > Browse (save it as a plain-text .jsx file first). It deletes only that ancestor list, nothing in the image:

if (ExternalObject.AdobeXMPScript == undefined) ExternalObject.AdobeXMPScript = new ExternalObject("lib:AdobeXMPScript");

var xmp = new XMPMeta(activeDocument.xmpMetadata.rawData);

xmp.deleteProperty(XMPConst.NS_PHOTOSHOP, "DocumentAncestors");

activeDocument.xmpMetadata.rawData = xmp.serialize();

Then Save As the TIFF again (8-bit, LZW) and check the size — it should come back down to a few MB. Doing it on a duplicate first lets you compare before replacing your master.

Hope that tames it!

Your paste-into-a-new-document test confirms it is metadata rather than image data. When you save the TIFF, open the TIFF Options dialog and make sure Save Image Pyramid is turned off, then re-save. Also worth checking File > File Info on the master PSD to see what metadata has attached itself, and look at Preferences > File Handling to see whether Maximize PSD Compatibility got switched back on. One of those is almost certainly where the extra 70MB is coming from.