Hello Nicola
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First I opened the photo in Photoshop. Then I added a new transparent layer. Then I painted it all black. (yes, black ! )
Then there was no image at all
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I changed the Opacity to Overlay and miracle: I could see the photo again as if nothing was on it.
Then I went to Filter / Render / Lens flare and I choose the light which was the best, or looked like the best to me and adjusting more or less in the final position.
Oh boy I am having a colored image. I don't want that.
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OK No prob. Convert to black and white.
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Bang. There it is in black and white.
Then with V key I fine tuned the spot to where I really wanted.
Export to jpg etc etc
Not the perfect way. Not probably the best blending mode but... so what ? It works, right ?
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I forgot to say that at the beginning I cloned the tree.