Can someone please explain why 25p is important (and other questions)

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clicktor

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OK I clearly need to do some reading. I think I am out of my depth with regard to video specs. Can someone help me understand stuff? I think the only way is to just list them all as questions. Sorry.

1: What is the difference between 24p and 24fps?

2: What actually does 24p mean?

3: Is 24p better than 50fps or 60fps?

4: If a video cam shoots at 1080i and 60fps, is 24p better than that?

5: Why do people crave 25p support in cameras like the Panasonic GH2 when it does 24p? Why can you not convert to 25p? I get NTSC is 24p and PAL is 25p, but why does it matter when you can convert? Is it hassle?

6: Should I be looking for a camera that does 24p, 25p, 30fps, 50fps, 60fps, 1080i, 1080p ? It's all very confusing to me.

7: I read of people saying things like "if you use the right shutter speed you can avoid such lighting artifacts when using 24p". What does that mean?

8: What is the difference between rolling shutter and global shutter?

9: What is the significance of a CMOS sensor vs CCD vs whatever else types of sensor in video cams or DSLRs that shoot video?


I kind of get stills stuff, but video is new to me really with regard to specs. I've always just "made do" with my video, but I think I need to start understanding it more.
 
  1. 24p means 24 progressive frames. 24fps means 24 frames per second. Film is shot at 24fps, PAL is 25fps and NTSC is 29.97fps
  2. 24 progressive frames
  3. Depends on the application, as a videographer that is for you to decide.
  4. Again, depends on the application and requirements of the task at hand.
  5. If you are in a PAL country (is europe) then 25fps is the tv standard that is used so 25fps is prefered. The difference in negligible IMO. BTW, see above, NTSC is 29.97fps not 24fps. 24fps is used for film (ie film stock)
  6. Depends on what you want from the camera?
  7. No idea
  8. Google jello effect
  9. See above.

Also recommend you read up on the different between progressive and interlaced video. All the information you want/need is out there, either google for a quick answer or ask & someone will answer when they have time.
 
3. Higher frame rates allow you to stretch a timeline. If you output a 50fps or 60fps video at 24p you will get a nice slow motion effect

4. 24p looks nicer than 60fps but 60 will give advantages (as noted in my last answer).
 
24 frames per second with a 1/48 shutter speed is the standard format that film is recorded in. This gives the footage a certain appearance with motion blur characteristics that people have become used to and associate with cinematic film even if they don't realise it. Alot of film makers stick to this format to try and ensure their footage has a similar 'film' feeling to it.

The problem with 24 fps is that it is a relatively low framerate so you need to be careful with things like speed of panning or high speed motion. Film directors work around this because they have always had to and they know what they can or cannot shoot.

60 fps obviously has much less movement inbetween each frame so it is much better for recording action stuff with fast panning movements. It also allows you to shoot with a faster shutter speed without getting gittery motion.
 
The real answer to your question is go to 50p, then you get the best of both worlds... :)

Hardly anyone uses 25p, its too problematic, 50i is by far and away the most common. Although don't mention the "film effect" filters that some editors use that drop alternate frames, drives me nuts, sooo many visual illiterates...but can't say more :)

...The great thing about standards, particularly for HD, is everyone can have their own :lol:
 
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flossie said:
The real answer to your question is go to 50p, then you get the best of both worlds... :)

Hardly anyone uses 25p, its too problematic, 50i is by far and away the most common. Although don't mention the "film effect" filters that some editors use that drop alternate frames, drives me nuts, sooo many visual illiterates...but can't say more :)

...The great thing about standards, particularly for HD, is everyone can have their own :lol:
Click to expand...

I have a vid cam that I was under the impression shoots at "full HD". it actually shoots at 1920 x 1080i @ 60fps. I personally find the footage looks ace on my HD TV, but can I assume that 1080p would like twice as good in that it draws each frame in full rather than half at a time like with 1080i interlacing? I would assume it would look "better" but in what way would it? :)
 
clicktor said:
I have a vid cam that I was under the impression shoots at "full HD". it actually shoots at 1920 x 1080i @ 60fps. I personally find the footage looks ace on my HD TV, but can I assume that 1080p would like twice as good in that it draws each frame in full rather than half at a time like with 1080i interlacing? I would assume it would look "better" but in what way would it? :)
Click to expand...

You probably assume wrong as most wouldn't notice. You would however see the difference in the fps. 24p looks very movie like.
 
Old TV used 50i or 60i in the states for a simple reason and it's to do with the frequency on the mains.

In the uk we use 50hz so we can use the cycle on the mains as a conveniate "clock". Which is why we used 50fps as opposed to 60fps in the US. Interlaced means that the picture is drawn using altenernate lines (lines 1,3,5,7,9 etc then 2,4,6,8,10) progressive. Although the frame rate is doubled it's only drawing half the image.

Strange things can happen (depending on the media) with interlaced video from memory. Especially if you convert it between formats. Seeing as most screens now (especially HD) can draw the entire screen at fast rates most of it has edged towards the progressive route.
 
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clicktor said:
I have a vid cam that I was under the impression shoots at "full HD". it actually shoots at 1920 x 1080i @ 60fps. I personally find the footage looks ace on my HD TV, but can I assume that 1080p would like twice as good in that it draws each frame in full rather than half at a time like with 1080i interlacing? I would assume it would look "better" but in what way would it? :)
Click to expand...

as I said... there's a multitude of HD standards (even more than SD standards, which is insane for a format that was intended to be used globally..).

"Full HD" is just a marketting catch-phrase to indicate that a device has 1080 lines instead of 720, but just like with still cameras, the resolution doesn't tell you the quality of the picture, its just a headline number!

As for 60p instead of 50/60i, I'm not even sure if any consumer camera can do that, certainly only the top end displays can show it - and even in studios the vastly increased infrastructure requirements to go to 50p instead of 50i are such that its a rareity at present even for originating material (and there's still tons of upscaleing of SD being done behind the scenes anyway...).

If you want the simplest example of why higher frame rates are good - consider somone running (e.g. a footballer). If you show it at 25fps, they look like a cartoon - leg forward/back/forward/back. At 50fps, you get smoother movement backwards and forwards...Unless you apply a dodgy film effect filter to your 50fps source though... The difference between Interlaced and Progressive is not so obvious as the eye is quite good at blending horizontal lines together, and on anything less than a huge display the individual lines are not discernable...
 
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