According to Adobe (Camera Raw plug-in | Supported cameras) the Canon 70D wasn't supported until Camera Raw version 8.2.
Unfortunately, Camera Raw 8.x only works with CS6 and CC, not CS5.
If you want to carry on using CS5, you can download Adobe's DNG Converter 9.0 for free, and create DNG copies of your CR2 files, which you can then open in CS5.
Download it from here:
[Please note that DNG Converter works on folders and not on individual files.]
[You will first need to adjust its compatibility preferences for Camera Raw 6.6 and later.]
Many thanks for the prompt reply. Obviously I am disappointed to learn that my version of Photoshop won't be able to open RAW files from my camera but I will look into this DNG system, which is all new to me. I presume that I would be able to make adjustments in CS5 to a DNG image in much the same way as I would be able to adjust a RAW image if my camera had been supported.
seville servant wrote:
I presume that I would be able to make adjustments in CS5 to a DNG image in much the same way as I would be able to adjust a RAW image if my camera had been supported.
Precisely. Once you create DNG copies of your 70D raw files, you can open them in CS5, make any changes/edits, and then save the changes with the DNG, just like any other raw file. The main difference is that the DNG format stores your settings internally and not in a separate 'sidecar'/XMP file. You can still clear any settings and go back to the original, if you desire.