Photos was supported on Yosemite, OS X 10.10 onwards.
Perhaps you can consider downloading iPhoto instead?
If it's a Mid 2011 iMac, it officially supports OS 10.13.x High Sierra. Photos comes with the OS.
Download High Sierra from the App Store and build a USB installer before a clean installation. Don't forget to trim the SSD.
Cant seem to find High Sierra from App Store.
I'm upgrading it to El Capitan now 1st. Thats my only option.
What do you mean by trim the SSD?
Use this link: https://support.apple.com/macos/high-sierraCant seem to find High Sierra from App Store.
I'm upgrading it to El Capitan now 1st. Thats my only option.
What do you mean by trim the SSD?
Use this link: https://support.apple.com/macos/high-sierra
Scroll down to the Download section where there is a link which will bring you direct to the High Sierra page in the Mac App Store.
Just to share, i managed to get my 2011' iMac running with a clean High Sierra install. Struggled initially because the High Sierra OS link in official Mac store does not download the full app image.
Anyway, this is the steps i took.
1. Considering High Sierra is the latest OS that the 2011 iMac can support.
2. In order to find the full High Sierra install file, i had to download a patcher tool (available here in http://dosdude1.com/highsierra/)
3. With the patcher tool, i downloaded the 5.6Gb full High Sierra installation file.
4. Following instructions in https://support.apple.com/en-sg/HT201372 to create a USB installer
*can ignore the OS download link due to above reasons
Conclusion
1. Its easy to install SSD & clean OS to "refresh" a flailing old iMac.
2. Boot up time 20secs (not sure if my 16Gb DDR3 helped)
Sometimes I wonder if there's any "commercial" hackintosh.