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View Full Version : 25p native over 25i: "real world" advantages?



emory
07-20-2010, 01:45 AM
I finally mustered up the courage to hack my GH-1. Everything went smoothly, and I just made my long-overdue donation to the cause.

With the "C" settings, FHD looks noticeably sharper than SH (before the hack, I couldn't tell much of a difference).

But this brings up a problem: in FHD mode with "25p native" checked, my GH-1 displays "write error" and locks up even with a fast Sandisk Extreme 30 MB/s card -- but only on a tripod with little or no subject movement. This could be an issue for interviews, etc.

So here's my question:

50i is just a 25p file in a "wrapper," correct? And in PAL, 50i does not require pull down, correct?

So, in "real world" situations like editing in, say, Sony Vegas Pro, will 50i files be rendered to MPEG-2 (DVDs) or AVI or even to Blue Ray discs with the same quality as 25p files?

In other words: in PAL-land, is there any real advantage to enabling 25p native?

Thanks for your input.

crunchy
07-20-2010, 02:15 AM
25i is just a 25p file in a "wrapper," correct? And in PAL, 25i does not require pull down, correct?

In fact, yes. In your editing program you should just mark the file as progressive instead of interlaced (for example, in Canopus Neo 2 right click the file and under properties select progressive).
By the way, you probably mean 50i instead of 25i?


So, in "real world" situations like editing in, say, Sony Vegas Pro, will 25i files be rendered to MPEG-2 (DVDs) or AVI or even to Blue Ray discs with the same quality as 25p files?

There are some differences due to coding. Namely, interlaced frame is coded as two fields and progressive one is coded as a whole frame. There are some differences. Try to take a shot where you have "deeply red" subject on a black background and observe edges of "deeply red" subject when applying 25p and 50i settings. You'll see that 25p settings gives better results. You might explain it like that: 4:2:0 coding means that colour resolution is reduced. If you are coding fields instead of a frame, it results in even worse vertical colour resolution. At least I think so.

emory
07-21-2010, 05:05 AM
Thanks for your reply, Crunchy. I tried your "deeply red" test and found 25p better -- if only marginally.

Overall, 25p native looks so good, I'm going to try and live with the occasional write error. Even shooting static greenery on a tripod, I can normally record at least 10 seconds before the camera locks up -- and ten seconds is more than enough for an establishing shot.