I've been using Photoshop CS4 with the camera raw plugin for many years without issue. I recently got a new computer with Yosemite and when I installed PsCS4 it no longer worked with RAW files (5D mkii). I just tried downloading the newest version of the camera raw plugin, but Photoshop doesn't seem to recognize it. What can I do?
The “latest version of camera raw” would be ACR 8.7.1 and that is only compatible with PS-CS6 or newer.
PS-CS4 would probably install with ACR 5.0 but the 5D Mark II needs at least ACR 5.2. The latest version of ACR you can install for PS-CS4 is ACR 5.7 which may be what you had on your old computer.
The usual way to update your Camera Raw plug-in would be to do PS / Help / Updates and let it check to see what is available, so try that.
I am not sure if that process still works, but you’re in luck because Adobe was still putting links to their installers on the website back in the CS4 era, so you should be able to download an installer and run it to get ACR 5.7 installed, from here:
It’s possible that something in the newest OS will prevent this installer from working, of course, but at least try.
You can check what version of the ACR plug-in you have installed by doing PS / About Plug-in / Camera Raw