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IMO, the ALT tags need to be related to the image and H1 and H2 titles on the specific page or blog post.
For instance, if you're making a blog post for a family session but hoping to get better rankings for "XYZ Wedding Photographer" it's not going to help if you set the ALT tags for that post with "XYZ Wedding Photographer". You're better off setting the ALT tags to something like "Family photography at XYZ location (or venue)". These keywords should be similar to the H1 and H2 title keywords on the post or page. Google is smart, very smart; it knows the difference between keyword stuffing and meaningful content.