720 or 1080?, tell us what & why

[Eric Pascarelli]

Many optical flow algorithms have a tough time with "occlusion" where one object crosses over another. This is because they attempt to track the movement of pixels and get confused when a pixel disappears.

They also have difficulty with repeating patterns, such as a complex wallpaper, and more random phenomena like rustling trees, fire, splashing water.

The system in FCP/Motion is based on the one in Shake, which is not so robust, but does well in general circumstances. I have used it with success if slowdown is not so severe or if the subject matter is simple. Otherwise it can be used for interesting warp effects!

Though I've never tried the system in AE, I am told that it is based on the Foundry's algorithms. These are much more robust and useful than Shake's. The Foundry (from the UK) is an amazing company with some great image processing technology and I think we will hear more from them in the prosumer area soon. If these algorithms become common in NLE's we'll have a lot more options for convincingly speed changing footage.

[Thomas Smet]

sure 720p may have a little less detail but it isn't as large as some would like you to think. People laways talk about 2 times more pixels but really that is all garbage. Sure it is more detailed but only slightly.

720p 24p has the advantage of using 2.5 times less frames then 720p 60p. So you will end up with much better compression. 35mbits/s is used no matter what format you shoot in. 1080p 24p would need over 60 mbits/s to equal the level of compression as 720p 24p.

720p also gives you more creative options in terms of framerates and slow motion. 1080p cannot do any slow motion at all. 1080i could but you are taking a massive quality hit and massive processing time involved.

720p 60p is much easier to encode then 1080i 60i. Mpeg2 handles progressive encoding much better then interlaced encoding. So even if you shoot 60p you should still see much less compression artifacts then you would with 1080i.

If you are shooting for a client that wants 1080i then shoot 1080i.
If you are shooting for a client that wants 720p then shoot 720p.

If you are shooting for yourself then you have to weigh the quality tradeoffs.

1080i will give you more image and compression artifacts but with that a little bit more crispness and extra detail.
720p will give you very few if any artifacts, smooth motion and a clean image but with slightly less detail.

There is no such thing as one is better then the other. They both offer tradeoffs in terms of quality and creative options.

[Ray Bell]

They have a demo of some nice slow mo work done with twixter here....

http://www.revisionfx.com/products/twixtor/gallery/

[Craig Seeman]

In Apple, both Motion and Compressor have Optical Flow ability. I haven't tested yet. I did use the one with Boris Continuum Complete and I too got strange warping. It has to do with how it's trying to predict motion to create new frames I believe. The issue has to do with the motion as one "object" passes another.

Originally Posted by Simon Wyndham

To be honest I've not had much success with these post production slow motion software in the past. I always find that they create strange warping effects if you try to go too slow.