Yes 100%, Photon does have a HUGE impact on image SEO. You will actually have a hard time getting the images served by photon indexed into Google at all, even if the original image url is provided in a sitemap.xml feed.
Not a single image hosted by the photon wordpress cdn is indexed in the google database.
No Google does not recognise the images as coming from your site. If you take a look at a photon hosted image url. You can see your domain has become the subdirectory of the photon root directory, as /wp-content/ is to your site.
A great way for wordpress to manage their photon cnd index but shows 0 association to your site in Googles eyes. You may as well say that image is photon's property in Googles eyes.
You may wonder why Google is not indexing your original images since they are listed in your sitemap.xml. "Example image"
Google obviously have a close look to see if resources listed in the sitemap.xml are associated with the resources listed on the rendered web pages. Google would not see any of the original images your sitemap.xml file lists, on the visible web pages. Due to the image urls on the visible pages changing to photon cdn urls.
Cannot blame Google for not indexing resources that it thinks visitors don't actually see on the visible pages. Since this appears like a deceptive tactic to get mass images indexed into google, I'm surprised Google isnt penalising sites for this.
Obviously this is not what webmasters using photon are trying to do but its easy to see how Google would be mistaken by this.
I can think of one possible solution to this issue and it would allow images to still be indexed into Google and continued use of the Jetpack Photon feature.
Instead of Photon changing the image URLs on a page in both the src="" and href="" attributes, it should only change the src="" attribute while leaving the href="" attribute as the original image URL.
That gives Google the visible page/sitemap.xml reference association to allow them be indexed and also get the page load time benefits from having the photon cdn version of the images load and displayed.
Don't get me wrong, I think Photon feature is great but there are a few downsides to using it.