The hobbit, how is it possible that 48 FPS is better than 24 FPS

There is a huge difference in the feeling of the film based upon the Frames Per Second it was shot in.

There are a number of films that were shot using a digital camera, but at a higher 30FPS that were reviewed to have a "poor quality or feel" because the faster shutter rate gave it a television feeling.

Many professional digital camera now shoot at the slower 24FPS to capture that film feeling.

Many faster 30FPS digital cameras often produced a cleaner, sharper, wider range of color image that was perceived to be to different from traditional film stock. That the color space and feel of film could not be reproduced digitally. Much of this is true.

Today, many digital cameras now use all the same lens, hardware and mounts that older traditional film cameras used. The sensors are much more refined and adjusted to give a more natural color space. Post-processing has also greatly improved to reproduce many film stocks as a digital filter.

If you were speaking to someone who was not technical, but experienced in the film industry. He may have experienced producing films at 30FPS which were much sharper and cleaner then traditional 24FPS film stock. As a result. I can totally understand his perspective that 30FPS has a higher quality image.

The techniques to produce 30FPS and 24FPS films at one time was very different. Today, it's better to clarify that the difference is not frame rate, but film versus digital.

Additionally, frames per second can have a direct impact on the type of motion blur produced in an image. The higher the frame rate the less motion blur there is. Resulting in a cleaner sharper image for objects in motion.

Quoting Peter Jackson:

...it's like watching a movie where the flicker and the strobing and the motion blur what we've been used to seeing all of our lives -- I mean, all our lives in the cinema -- suddenly that just disappears. It goes. And you've got this incredibly vivid, realistic looking image.

And you've got sharpness because there's no motion blur, so everything is much sharper. And plus we're shooting with cameras that are 5K cameras, so they're super sharp.

Eliminating motion blur, even subtle motion blur we might not be consciously aware of, makes it appear sharper.

It also explains the "Made for TV look" some people are complaining about.

    ^[Source]

There are two key issues with higher frame rates. One is simply that more information can be transmitted at higher frame rates (if the recording was done at the higher rate: just showing the same frame twice as some TVs do doesn't really make much difference). The second is supposed to be that double rate overcomes a major limitation of 3D which is a loss of brightness on the projected image.

Other things being equal, more information should be good. But there is a problem with giving more information in a medium that is primarily about creating an illusion. Cinema maintains the illusion in many cases because of what it can hide from the audience. We don't shoot in outer space to get special effects in star Wars but join set-based action with imaginary images shot with models, computers, paintings and so on. The illusion relies on not being able to see the join. Dodgy models and make up don't matter if the image is transient or blurred. The trouble with higher frame rate recordings is that they show more and hide less making it harder to maintain the illusion and harder to hide the join between the real and the special-effect. They even make it harder to make make-up look real. So one issue with 48fps may be that it sometimes shatters the illusion: the image is better but the illusion is worse.

The other issue is more clear cut. The extra projected frames won't, if everything else is equal, make the screen brighter. The light source is the same but chopped up differently. In reality many 24fps movies are displayed with triple "exposures" of each 24fps frame now. Higher rates will probably compromise that a little but, even so, there isn't more light in total just because there are more frames.

Mark Kermode interviews a projectionist on his blog on this topic and after a humorous explanation of how things are projected gets a definitive no the the question of whether higher frame-rates solve the brightness problem in 3D.

Imagine a movie as a flipbook. Higher FPS = more pages in the flipbook. More pages doesn't affect the actual quality of each page, just the motion between the pages.