This gotcha also rears its ugly head if you want to use two RAW-capable Photos extensions. In this situation, which Photos extension should you use first? RAW Power has strong RAW editing controls, based on the same engine that Photos uses. DxO has high-quality lens correction. I believe it’s best to start with RAW Power to access its RAW-only editing sliders, and then use DxO OpticsPro, because DxO’s lens correction works on both RAWs and JPEGs.
But the article also says extensions only receive a JPG file from Photos even when the original master is RAW, and that the extension does not even know the original is RAW. If so, how can extensions like RAW Power or DxO use any RAW editing tools? If only Photos has access to the RAW file then only Photos can develop and edit in RAW, no?
The extension can only produce JPEGs for storage in the library (per Apple’s specification). If working on a JPEG is okay, then you can use another extension that has local adjustments / Photos for healing, or export the JPEG to the other app.
In addition, the extension has the ability to export TIFFs through the export button at the bottom of the interface. That image could be edited in another app and then imported back into Photos. That would maximize quality but is a few more steps.
If an image is unedited (by Photos or any extension), then Photos sends the original image to the extension (a RAW). However, once the image has been edited by Photos or another extension, then extensions are passed a JPEG, and they have no way to locate or use the original RAW image.