The quick answer
A Smart Object is a special layer that keeps the picture it came from. This helps when you resize it or try another picture in the same place.
It does not fix errors in the AI picture. Check the result itself too.
In this article
Keep these in mind
- Keep the original source content available.
- Use a mask to control what appears.
- Save a layered working file.
When a Smart Object helps
Imagine trying several backgrounds in one poster. You want to swap the picture without placing it from scratch each time. A Smart Object can help.
An embedded Smart Object keeps its picture inside the Photoshop file. A linked one uses a separate file. Keep that separate file available.
Read more: Smart Objects: overview and benefits
Add the picture
Use File > Place Embedded to add a picture as a Smart Object. For a layer already in the file, use Layer > Smart Objects > Convert to Smart Object.
Keep the original photo on another layer. Resize or move the new picture to fit. The saved source helps with later changes. It cannot add real detail that was missing.
Read more: Adobe: Create embedded Smart Objects
Hide parts with a mask
A mask hides parts of a layer. Use one to keep only the useful part. For example, show a new background but keep the real product above it.
After moving or resizing the picture, check the mask again. It may no longer line up. The Smart Object keeps the source; the mask controls what you see.
Swap the picture
Use Replace Contents to choose another picture for the Smart Object. Photoshop keeps its size, angle and position. Check the fit, especially if the new file has different dimensions.
Keep a copy of the old result if someone may want it back. Do not lose an approved version while trying a new one.
Read more: Replace the contents of a Smart Object
Save a file someone else can use
Give the layers clear names and keep the original. Explain what you changed. If the file uses linked Smart Objects, include their picture files when you hand it over.
Open the saved file to check it. JPEG and PNG copies are useful for sharing, but they do not keep your separate Photoshop layers.
Sources & further reading
Product features can change. Check the linked documentation for the version and service you use.