Why use 25p over 30p in HD? at DVinfo.net

Go Back   DV Info Net > Sony XAVC / XDCAM / NXCAM / AVCHD / HDV / DV Camera Systems > Sony ENG / EFP Shoulder Mounts

Sony ENG / EFP Shoulder Mounts
Sony PDW-F800, PDW-700, PDW-850, PXW-X500 (XDCAM HD) and PMW-400, PMW-320 (XDCAM EX).


Reply
 
Thread Tools Search this Thread
Old February 18th, 2008, 07:02 AM   #1
Major Player
 
Join Date: Feb 2004
Location: Oxfordshire, UK
Posts: 425
Why use 25p over 30p in HD?

Just wondering what peoples thoughts are on using 30P or 60i as a standard for HD in the UK (if you're not going out to broadcast)?

Doesn't it make sense to use 30p/60i HD, given you get those extra frames and especially with undercranking? What am I missing?

Paul.
Paul Gale is offline   Reply With Quote
Old February 18th, 2008, 09:33 AM   #2
Major Player
 
Join Date: Jun 2006
Location: Savannah, GA
Posts: 456
What happens if you want to downconvert to SD PAL? Using a 25/50 framerate would work out much more easily for you.
Eric Darling is offline   Reply With Quote
Old February 18th, 2008, 10:38 AM   #3
Major Player
 
Join Date: Feb 2004
Location: Oxfordshire, UK
Posts: 425
Cheers - Yes I had considered that but most of my projects end up on the web or played back in HD from Powerpoint etc.

Just wondering if there's any other reasons I would stick to PAL?
Paul Gale is offline   Reply With Quote
Old February 18th, 2008, 10:44 AM   #4
Major Player
 
Join Date: Jun 2006
Location: Savannah, GA
Posts: 456
If you never expect your video to end up on a standard definition television, I don't expect the frame rate to matter much for anything beyond aesthetics.
Eric Darling is offline   Reply With Quote
Old February 18th, 2008, 05:11 PM   #5
Wrangler
 
Join Date: Oct 2003
Location: DFW area, TX
Posts: 6,108
Images: 1
Quote:
Originally Posted by Paul Gale View Post
Just wondering what peoples thoughts are on using 30P or 60i as a standard for HD in the UK (if you're not going out to broadcast)?

Doesn't it make sense to use 30p/60i HD, given you get those extra frames and especially with undercranking? What am I missing?

Paul.
You need to use 25P or 50i to sync to your power line frequency of 50hz. Under certain lights, the odd multiple of power frequency vs. frame rate will cause issues.

-gb-
Greg Boston is offline   Reply With Quote
Old February 19th, 2008, 03:42 AM   #6
Major Player
 
Join Date: Feb 2004
Location: Oxfordshire, UK
Posts: 425
Thanks Greg - I presume you're talking about flourescent lighting predominantly?
Paul Gale is offline   Reply With Quote
Old February 19th, 2008, 05:09 AM   #7
Trustee
 
Join Date: Dec 2003
Location: Malvern UK
Posts: 1,931
Presumably this would also apply to these new low energy bulbs that are becoming popular these days too.
Simon Wyndham is offline   Reply With Quote
Old February 19th, 2008, 05:40 AM   #8
Major Player
 
Join Date: Feb 2004
Location: Oxfordshire, UK
Posts: 425
I think this may certainly be the case with the cheaper (non integrated) CFL's as these do not have a high frequency ballast (I believe) - the expensive (or two part lamps) will have a ballast and will possibly(?) operate at higher frequencies.

Either way, they're orrible lamps! ;)
Paul Gale is offline   Reply With Quote
Old February 19th, 2008, 06:37 AM   #9
Wrangler
 
Join Date: Oct 2003
Location: DFW area, TX
Posts: 6,108
Images: 1
Quote:
Originally Posted by Paul Gale View Post
Thanks Greg - I presume you're talking about flourescent lighting predominantly?
Yes, but keep in mind that even a tungsten bulb is being energized/de-energized at 2x the line frequency. If your frame rate is an odd multiple of that, you could have some brightness/color fluctuation as your camera exposes each frame at a different point in the power line wave cycle.

-gb-
Greg Boston is offline   Reply With Quote
Old February 19th, 2008, 06:43 AM   #10
Major Player
 
Join Date: Feb 2004
Location: Oxfordshire, UK
Posts: 425
Sure - but tungsten is going to react much less compared to flourescent isn't it?
Paul Gale is offline   Reply With Quote
Old February 19th, 2008, 04:40 PM   #11
Regular Crew
 
Join Date: Dec 2007
Location: Rotterdam (Netherlands)
Posts: 60
Hi Guys,

These are interesting thoughts on the AC current frequencies of light but I wonder: I used the shutter in 70 or 85 Hz regularly to shoot CRT computerscreens in the past and it never occured to me that that change of shutterspeed led to weird effects with lamps.

What should you see in the VF with different AC freq.?
__________________
XDcamHD F330, 2" VF, Fujinon 13x3,3. 550D, MagicLantern, CS5.5
www.picturethis.tv
Eelco Romeijn is offline   Reply With Quote
Old February 19th, 2008, 11:33 PM   #12
Wrangler
 
Join Date: Oct 2003
Location: DFW area, TX
Posts: 6,108
Images: 1
Quote:
Originally Posted by Paul Gale View Post
Sure - but tungsten is going to react much less compared to flourescent isn't it?
Standard fluorescents will be more of a problem for sure, unless they have high frequency ballasts. Not likely in the average office scenario though.

-gb-
Greg Boston is offline   Reply With Quote
Old February 20th, 2008, 02:32 AM   #13
Inner Circle
 
Join Date: Dec 2005
Location: Bracknell, Berkshire, UK
Posts: 4,957
You'll also have problems with many industrial lights such as sodium and halide discharge lamps. The types of high bay lighting in many factories and warehouses runs at 50hz.

I use 25p. Most of my web clips run at 25p to save bandwidth (compared to 30p). 25P is slightly less compressed than 30p, although I cant see a difference at 35MB (I can at 25Mb).
__________________
Alister Chapman, Film-Maker/Stormchaser http://www.xdcam-user.com/alisters-blog/ My XDCAM site and blog. http://www.hurricane-rig.com
Alister Chapman is offline   Reply With Quote
Old February 20th, 2008, 02:45 AM   #14
Major Player
 
Join Date: Feb 2004
Location: Oxfordshire, UK
Posts: 425
Changing the subject completely - Do you always use 25P regardless? - I'm used to doing everything at 50i in the old SD days with my 570 and de-interlacing at final compression stage. Always had excellent results with pans and zoons etc.

I'm still not sure I like the motion effects with 25P - seems a backward step to me! I don't go for the cinema look either very often. I do like a smooth and seemless result :)

I guess the biggest benefit of editting progressive (for me) is for graphics and titles etc - they never do too well when de-interlaced. I used to often run a progressive project and import the filmed interlaced footage into it and set it to de-interlace. I also have regular jobs where I composite a chroma-keyed presenter onto motion graphic or computer screen capture background and mix between them with various other effects. These types of project are ideal for progressive footage of course.
Paul Gale is offline   Reply With Quote
Old February 20th, 2008, 02:52 AM   #15
Trustee
 
Join Date: Aug 2006
Location: London UK
Posts: 1,939
Quote:
Originally Posted by Greg Boston View Post
Standard fluorescents will be more of a problem for sure, unless they have high frequency ballasts. Not likely in the average office scenario though.

-gb-
how does 24p deal with these issues as opposed to 30p?
__________________
Philip Bloom
Cinematographer, Director, Filmmaker www.philipbloom.net
Phil Bloom is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > Sony XAVC / XDCAM / NXCAM / AVCHD / HDV / DV Camera Systems > Sony ENG / EFP Shoulder Mounts

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 03:47 AM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network