What exactly is an impression in Google Webmaster Tools search queries with the image filter turned on?

[EcommerceSite]

Is it when someone does an image search? Or does it count a regular search that has images in it?

On an image search does the picture actually have to be viewed on the screen or can it be below in the infinite scroll?

[Martijn_Scheijbeler]

It's when someone does an image search and I don't think it's counting as a regular search as that would be counted within web.

I don't have a definitive answer on your second question but my guess is that it wouldn't be that somebody explicitly should view the image itself.

[Cyrus-Shepard]

Although my best guess tends to agree with Martijn, I'm not absolutely sure. I searched Google Webmaster Forums but couldn't find a definite answer. It might be worth posting there to see if a representative from Google could lay the question to rest: https://productforums.google.com/forum/#!forum/webmasters

That said, I believe image search impressions are only counting regular image search (not images that appear in regular results) and do not count impressions below the fold that haven't rendered (because that could go on for a very long time and result in 1000s of impressions that never happened.

[EcommerceSite]

I will ask in the forums to see what they say. This particular site has a great web presence and really good impressions. The image impressions are almost triple the search impressions which really took me off guard.

[EcommerceSite]

That is what I thought but our numbers are so off that it didn't make sense. This site has a great web presence with high impressions and image impressions are much higher. Personally I use web search much more then image search and I imagine most other people do as well.