I don't understand why you're persisting with this. What is it you are trying to ascertain? the demo was rendered at 4k? The source material of the 15MP photograph is a blurry photo of an upscaled render. 4k is 2x2 times 1080p. There's not a single pixel in that image, either your 15 MP photo or my 720p closeup, that isn't blurred less than a 2 pixel Gaussian. There's no evidence that the detail is more than 1080p, and there cannot be any evidence as such because the resolving power of the higher resolution images is no better than a 1080p screenshot (or even SD screenshot in the case of Gubbi's test). Whatever detail you are seeing is in the model and the textures, and not in the rendering resolution or the projection.