Im very confused about all this hz business and what not, when watching freeview HD my tv says its running at 50hz, when i swap to PS3 its 60hz, then when i watch a blu ray, its 24hz

is this due to the PS3 that the Blu Ray is at 24hz? or are all Blu Rays recorded at 24hz? im trying to get to the bottom of a picture quality issue where it seems grainy, not sure if this may have an effect?!

I suspect you mean fps (frames per second) not hz (which is properly spelt Hz).

Movies are filmed at 24 frames per second, and so Blu-ray discs tend to be 24fps also.

It shouldn't be causing a grainy image. It should look better than the picture you get from Freeview HD.

sorry being lazy with my capitals!

this is a link to the PS3 info on 24Hz, doesnt say anything about frame rate?

http://au.playstation.com/ps3/suppor...I%29-settings/

The author of that article is ignorant.

Hertz is a frequency measurement denoting cycles per second, so in a progressively encoded video output context Hertz (Hz) and frames per second (FPS) are the same thing.

As said, the vast majority of movies are filmed at 24Hz as this is the speed at which the human eye sees images (it's actually very slightly below 24Hz but it gets rounded to 24 for ease of use).

However, the screen panels in HDTV's don't refresh at this speed. They typically use refresh rates of 50Hz, 100Hz or 200Hz, so a re-sampling step has to take place before the video signal is sent to the panel.

For a high quality TV's (especially high quality 1080p TV's) you are best off making the PS3 output movies at 24Hz and letting the TV process the signal in the best way it can, but for lower quality TV's and non 1080p native HDTV's it can be better to have the PS3 re-sample the signal and then have it sent to the TV.

Conventionally you would denote the field rate of an interlaced source in Hz but refer to frame rates in fps.

So UK broadcast TV is 50 fields per second, hence 50Hz but 25 frames per second. The US use 60 Hz and 30 frames per second.

Blu-ray is 24 frames per second. If it were interlaced then it would be 48 fields per second or 48Hz

Film is 24 frames per second. Previous methods to make this 50hz were ugly....and inferior...that is why bluray has this feature. Not sure why you are worried, modern displays and even film projectors project a frame multiple times, it isn't really 24hz, it is 24 frames. The tv has to has a refresh that is divisible by 24 that is all. 50 is not divisible by 24!

Grain is part of the picture, the no grain you get from low resolution transfers is blur vision.

Actually, to get to 25fps from 24fps film is really easy - the film is sped up by 4%. (Hence running times on 25fps DVDs are shorter than the same films on a 30fps DVD).

However, it's the 3:2 pulldown that is ugly, and that's the conversion from 24fps to 30fps for those format TV's, and unfortunately for blu-ray, if you don't have a 24p TV set, it's the 30fps version you'll see, with all the inherent problems caused by the 3:2 pulldown.

You just made that up!

(or quoted someone else who did). Either way, it's meaningless and false.

Cheers,
David.

I imagine it was simply the slowest speed they could get away with

Well, okay, it is a bit more complicated than that. It's about creating the right amount of motion blur for movement to seem natural to the eye.

If 24fps was perfect then why is James Cameron and Peter Jackson shooting their new films in 48fps. To quote Peter Jackson:

They are using a much wider shutter angle of 270 degrees on The Hobbit (180 degrees is typically used), which gives a different feel to the images and Jackson has gone up to 48 FPS to counteract the motion blur deficit that occurs.

The Hobbit will only be shown at 48 FPS in a select small number of cinemas. Most theatrical releases and all consumer releases will be resampled to 24 FPS.

http://the-hobbitmovie.com/peter-jac...or-the-hobbit/

And even then they show the same frame 2 or sometimes 3 times to reduce flicker. A film actually shown at 24 frames per second would look awful.

How much motion blur does reality have then, if your eye tracks the moving object? (hint: the answer is none - which is only possible on film with very slow moving objects, very fast frame rates, or making the camera track the moving object too).

FWIW 24fps was chosen to allow the sound track to reproduce speech intelligibly when sound was first introduced (because the sound track was/is printed optically onto the film; slower = lower quality). In the days of silent film, 16-20fps was considered acceptable to reproduce movement.

Cheers,
David.