when google indexes images what are they looking for? Myself and my competitors all use the same image for the products we sell but what would help get better ranking than them. Yes, there is the basics, alt, file name, page words relating to the image. But what stops Google from indexing the same image over and over? Do you need to save it at a different size? eg: competitor saves it at 200 X 200, I save it as 180 X 180. Therefore it is now a new image to them? Does google have image recognizing software so they don't double up on images? Seldom do you see the same image. They must have something that can scan the shades and contours and recognizes it is the same image just a different size. Any thoughts on this?
I had never seen photos replicating much, so to test it out i just searched on a brand/model of phone. Lots of the same pictures, presumably from affiliate stores. So no, I don't think there is a filter to stop identical pictures. However, lots of the ones I saw that looked the same had slightly different dimensions, so you could try tweaking the image by a pixel or two, to 'conceal' the fact it is not an original picture.
Yes, I think that would be best to save at a certain dimension rather than having the browser resize. Your chances of having the same image indexed are now increased.
I don't think images are irrelevant. for example: If you have a site about cars or wallpapers, you'll probably have an album with pictures, it will most likely be found with imagesearch as well.
Images make a majority of the sales for one of my sites. People can browse the item they want faster through Google images than they can by going from site to site hoping to find the exact item. If I want to buy a "purple hat with a feather" it is faster to look through purple hats in Google images than it is to luck out and find the exact special purple hat that you want. Irrelevant??? Tell that to my accountant. LOL.