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!