720pn vs. 1080i

A

arzhang

New member
Going to shoot a short film on the P2 in a few days - had a quick question on 720pn vs. 1080i. I'd prefer better resolution all things being equal.... but I guess all things aren't equal!

My question is about two issues - post and strobing.

(1) Post production - At my school, I can edit either on Avid or FCP (flexible b/c I'll download the MXF files which I think either program can use) - given that, is 1080i a potential nightmare or is it "pretty solid but just a bit more time-consuming"? If 1080i is almost as easy in post as 720pn, I'd go 1080i. But if there are lots of potential problems and/or headaches, it won't be worth it for me to go 1080i. The school should have a new Mac based workstation for FCP and Avid (installing it now, don't have the specs).

(2) Strobing - How bad is the strobing effect of 720pn? My footage may have some fast motion, but not a huge amount (say 30% of my film has actors gesticulating quickly in argument scenes, but no car chases or sports scenes, etc..). Does the image break-up (according to the average non-DP viewer)? Would the average non-DP viewer in the audience find it annoying in 720pn and say "wow, video stinks compared to 16mm, look at those wierd artifacts, it looks like a scratched DVD is playing"?

I hope to project the film in HD (for the film festivals I'm lucky enough to get into!) in addition to make DVD's. I would not finish on film no matter what because of cost.

To give you a sense of what I consider a "good image quality": If I had an image quality that was comparable to Super 16, I would be happy (I know that's really touchy feely).

"Bad image" quality: For instance, I don't like the DVX-100 for wide shots because I think they break up and look bad when projected. If I shot with the DVX100 (almost did) would have changed my shooting style because I think those DVX-100 wides look pretty cruddy when projected.

I don't have time to test (unfortunatly) so this is a fuzzy type of inquiry, apologies for that.

Any advice much appreciated!
 
I shoot everything in 720pn --both for the space savings on the P2 cards, and for the variable frame rates. I have encountered no quality issues.

I highly recommend Barry Green's HVX Book if you are looking for ways to minimize strobing.
 
thx for the tip

thx for the tip

I don't mean to cut into his book sales at all (honestly, i know what it's like to try and sell your work!) - but I'm shooting in a few days and am a little worried I wouldn't get it in time.

are there 1 or 2 main, easy culprits to watch out for?

btw, I'm the tech-stupid director, my DP is Varicam experienced, but probably too booked to read it also before the shoot!

Thanks - quite good to know about your experiences!
 
If your DP is a Varicam guy then let him know the detail will be greatly less in the HVX 200 and if he's a fan of heavier saturations, again the HVX doesn't really hold up (though at least the latter can be worked on in post).

Other than that just toss the HVX manual at him. The menu system is Panasonic, so a Varicam guy should find his way around. Warn him though that the menu buttons on the HVX are in a really bad orientation, so that could be a bit of a headache for him. It won't prevent him from doing what he needs to do, but its no in a very logical orientation.

As for 720pn versus 1080i, I don't think you'll be in any kind of hell shooting 1080i, especially if you have no film out aspirations. The big difference there is really shooting time on your card/hard drive/whatever. The only other reason I'd avoid the 1080i is if you need any effects work done. Then you'll want a progressive shot. Though, do some reading around the net, I've had quite a few people quote to me that 720 uprezed in post to 1080 holds up great. Haven't done that myself so can't give you my own personal experience on that front though.

cheers.
 
A few strobing rule of thumbs: If you are panning, make sure it is slow enough so that it takes about 7 seconds for still to pass from one side to the other.

Also if you are panning, and you follow a subject that moves at the same pace as you, the audience will watch the subject, (which isn't strobing) and not notice the strobing background.
 
I don't have the chart in front of me but it's way more than 7 seconds . . . maybe someone else can help me with that?
 
If your DP is a varicam guy then he SHOULD fully understand strobing and how to minimise. But the basics are:

1/ pan time. For a wide scene of the top of my head its about 23 seconds. But it can vary based on distance so you may need to test the pan based on what your shooting to have it where its acceptable to you.
2/ If its a close quarters pan you can minimise how people percieve it by either using a slower shutter speed say 1/48th (you will get more motion blur), also pan on subjects if you stay fixed on a subject people will be drawn to it in the frame.
 
panning - to prevent strobing it depends on the focal length (zoom) and can range from 10 secs to more then 90 secs for 90 degrees - but if you have a subject in the center of the frame and pan with it you will reduce the APPARANT strobing.

720 has nothing to do with strobing - it is 24 frames that make it occur and that is true in 24p, 24pn or 1080i with pulldown for 24 frames.

Your varicam guy will know all about this
 
First off, you actually get 1080p even though it's encoded to a 60i signal you are still getting a progressive image.

Now, 1080p on the HVX200 is going to give you about 10-20% more resolution than 720p. Indistinguishible on an SD DVD and not hugely different when projected.

720p will give you 2.5 times more record time and the ability to do undercranking and over-cranking (variable frame rates just like film).

In Avid, 720p is a bit easier to edit since it can use the native 24pN resolution where as you won't be able to extract the progressive frames and work in a 24p timeline when doing 1080i and will be stuck working in a 60i timeline (not a big deal since you still get 24p frames but a bit annoying nevertheless).

The strobing simply comes from having 24 pure frames. There is no compression in between HVX frames so the motion should be identical to film.

As far as comparisons to S16, I'd say the HVX200 is very comparible to Super 16mm. I've seen a few side by side tests and they are so close it's quite amazing (with the HVX200 looking better in some respects and the S16 looking better in others). I don't think the HVX200 can hold a candle to 35mm (since 1080p performance isn't really all that hot) but it holds up fine compared to Super 16 (except for lattitude).
 
dregenthal said:
kuzco- great reference, but does it have anything to do with slow pans to reduce strobing?
Click to expand...
arzhang said:
Going to shoot a short film on the P2 in a few days - had a quick question on 720pn vs. 1080i.
Click to expand...
Just a short answer to arzhang, as he wrote "1080i". That's all. Nothing to do with pans and strobing, in deed.
 
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