This works fine if one only wants to convert four (4) images at a time. Converting 6-60? Fuggetaboutit. Any clues on how to do MORE than four at a time? Bear in mind, I'm an old codger and I need illustrated instructions (screen caps) of each step in the process. Thanks a million.
Mac mini (M4)
I suggest using Automator instead of Preview to batch convert images.
They key Automator action is called Photo > Change Type of Images. You can convert images to BMP, JPEG, JPEG2000, PNG, TIFF or HEIC.
I would suggest a workflow like this:
Note: the purpose of the Copy Finder Items action is to protect you from inadvertent conversion of your original files. It preserves your originals and changes the copies.
Once you have built the workflow (it's all drag-and-drop) you can run (test) it before saving it. It's that simple.
Here's what the workflow would look like in Automator. This one converts images to TIFF. The "Converted photos" folder is one I created to use for this workflow.
Convert what codec to what codec? Try Finder > ctrl-click images > Quick Actions > Convert Image > choose JPEG, PNG, HEIF.
Or use some app like GraphicConverter's batch.
Be aware that Preview.app batch convert has an old bug (still present in Sequoia 15.3.2) where it fails to batch convert (only the very first few images are really converted but the last images are not converted and just carry a wrong file suffix which might cause obscure problems later).
How to Batch Convert Images Using macOS Preview
