That's why I said in my first post that the most people don't know that some TVs labeled as 4K don't give you a 4k image in full size, because of the TV size, it's a marketing strategy. 4K means 2160p, that is the double than 1080p. So, if I have a 1080p TV of 37", which gives me full 1080p definition, a 4K TV should be the double at least, 74".
Look, I have a 47" 4K curve Samsung TV. I observed there both sample images that I shared, the 4k one and the 1440p one, and I tell you both images look perfectly defined. There's no significant diferences, because none of the images lacks definition, both are completely nitid. I can watch 1440p with almos full definition in my 4k TV because the TV isn't that big. But, in a 75" 4K TV the 1440p will lose significant definition, and the 4K image will not lose anything, then you can perceive significant differences.
Something else, besides the resolution and definition, there's HDR, which is relative to colours. Something that my 4K TV has. I put it in this way, I perceive more differences between a 4k HDR image and a 4K image, than a 4k image and a 1440p image. The thing is that not all 4K movies or videos have HDR. But when you watch something in HDR the experience is marvellous, the image is richer in colour tones, the three dimensionality increases, the image has more depth. That's the principal quality of my 4K TV, but HDR (high dynamic range) has nothing to do with resolution or definition, it's about colours, lights and shadows.
I understand that you
F4iunyl3x are trying to upscale 720p to 4k, and you certainly increased the definition. But I'm being honest here, you didn't reach the definition of a 4K nor a 1440p in the first images you showed us, so you shouldn't call them 4K nor 1440p images, I think that you don't even reach the definition of a 1080p in none of those first images, despite of the resolutions they have. If you give us an image that hasn't the 1080p definition and sell us as a 4k image, it's like you were cheating. I understand that it could be very difficult, but you shoud go step by step, based in the first images that you shared, you are far away of achieving a 4k image. That's why I compared your upscaled images to those standard 4k images I found in the web. I used my 1080p TV and not the 4K one for that, because is the TV that I have connected to the PC, but it doesn't matter really.
Edit: In my previous post I didn't notice that the forum didn't allow me to upload the sample image in 4K, the original resolution is 5000x2160, and was converted automatically to a lower resolution. It seems that you can't surpass 3840 here. But still I did the test with the original images and there are not significant differences between the 1440p image and the 4K image in a 47" 4K TV.