Whether you have conducted a google image search or a stock photography agency search, the owner of the copyright and photographer can be found in seconds. Stock photography agencies highlight the photographer or designer of all images on the website.
When you search on a stock photography agency website and click on a photo or image, the main page of the photo will show you available image sizes, download instructions, prices and the photographer or artist that created the image. It is possible to click through to the entire portfolio of a designer or artist and review all of their work if you choose to purchase more or review for similar images. It is not uncommon to like the work of a photographer and continue to purchase their images through the stock photography agency site.
If you have found a stock photo through a google search, the website where you can purchase the image will be a link associated with the image. You can click through to the stock photography agency website, sign up for a membership and pay for the image directly on the stock photography agency website.
In some cases you read a blog and find an image that you like on that site. If this is the case you can email the blog owner and request where the photo can be purchased if the photo is not credited on the blog. (though it should be) If the blog owner cannot let you know where they purchased it, attempt to find the image on a stock photography agency website using keywords that match what the image represents. The more keywords you use, the greater the chance you have in finding it. Do not use the image from the blog or website in which you found it. This is a breach of copyright laws. It is best to find another image and buy the rights than it is to use the photo as you found it on the internet.
It is much easier to credit where you bought the image directly on digital media so a visitor can find the image and buy it. Crediting the stock photography agency where you purchased the photo, and the artist or photographer who created the image is a nice thing to do and relieves you of any questions about the image.