I am somewhat hesitant to reply to this post, but if I don't, I'm afraid you may get advice that will send into the forest destroying hundreds of trees.
In the early spring (Mid February-mid April, depending on latitude) Scarlet Kings can be found under the bark of dead pine trees and stumps. HOWEVER, it is not necessary, nor is it herpetologically ethical to peel the bark off the tree to find them.
If you can gently pull the bark a few centimeters away from the tree and peek under it you can usually see them. If you do this correctly, you won't remove the bark from the tree. If you see one, I guess you will have to pull the bark back further to catch it, but don't go just stripping bark off hundreds of pine trees because you will destroy the habitat for SKs and many other creatures. If you can't pull the bark gently back like that and you can't see under it otherwise, there aren't SKs there anyway. You almost never find them under tight bark.
That said, it may be too late in the year for this to be very productive. They can be found by roadhunting forested areas on warm summer nights. You can also find them under trash in openings in forested areas.
You say you are only looking to photograph and I take you at your word. I will say to others who are reading this post that Scarlet Kings (in spite of their attractiveness) do NOT make good captives. They are high strung, escape artists, and generally insist on skinks for meals unless they are really large specimens.
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Chris Harrison