I've done this for awhile now, (using underscores as "spaces") but am told it doesn't carry any weight? Don't know if it used to though. My page names, page image (if applicable,) and image alt text would use the same keyword phrase. I'd even try to incorporate a keyword phrase into the subdirectory name, if there was one.
2. naming of pages to contain keywords
Question: How does the Google image search determine relevance? Is it by the text on the page where the image resides, the file name, alt text or a combination of all 3?
Just out of curiousity, I searched for an image on my site that has a rather unique name using Google's image search and quotation marks. The results were rather interesting. There were only 4:
2 results were from my site and I used the method shown above for page names and image file names. I used underscores. I also have a text link to the other page on each page. (see 4th result)
The 3rd result was the exact same file name but they used hypens. The exact phrase I searched for was not shown in the text portion of the page, the image alt text OR the source code. (Interesting!)
The 4th result was named " j-879.jpg" and totally irrelevant to the phrase I searched for. But, there was a text link on the page with the exact phrase searched for. This was the only instance of the exact phrase within the text or source code.
Does this mean anything? I think it just might. Anyone have any insite, comments or similar/different results?