"No Field", "Lower Field First" and &quo

[wai2]

What is it?

What is the difference between them?

Appreciated if someone could elaborate on this, as I'm a newbie to video editing.... Thanks in advance....

[Ken Berry]

Putting it simply, as you know, normal 'old fashioned' television transmits in lines, but the technology used meant that it was not transmitted as Line 1 followed by line 2 followed by line 3 and so on. Rather it was transmitted as line 1, line 3, line 5 etc (i.e. one half of the picture), followed by line 2, line 4, line 6 etc (the other half of the picture). But of course all of this is done so quickly that the eye 'sees' a solid, moving picture.

In this example, the lines with odd numbers are in effect the Upper Field, and the even numbers are the Lower Field. And to our eye, it does not really matter whether the Upper Field is all transmitted first, followed by the Lower Field, or the other way around as long as they are transmitted the way they were filmed.

Digital video cameras in effect work the same way, and either film using one or the other field order. Hard disk and mini DVD cameras, for instance, just about all use Upper Field First, while mini DV cameras are LFF. OK?

Now the only problem which comes is when you either change the original field order, or mix them up in the same project. If, for example, you have captured Upper Field First video, but then use project settings of LFF. In that case, the original 1-3-5-7-...etc UFF is forced to play back 2-4-6-8-... then 1-3-5-7.... Again all this happens very quickly, but the eye perceives that something is wrong, and the result is that we see jagged lines along edges that are supposed to be smooth, and what seems like jerky motion in fast moving or panning shots.

Hence, the importance of getting the field order correct and consistent throughout a project.

Frame Based is just that and applies to still photos. A still photo is a still photo or a single, solid frame. It is not filmed as a series of lines and projected as a series of alternating lines. We see it as a single frame. However, it can also be converted in a video project to become either LFF or UFF. That is why we say that with a slideshow, you can normally use Frame Based throughout the project properties, but you can also make one using either LFF or UFF and include still photos in a moving video, and they will take on the characteristics of either LFF or UFF.

Now, with this idea of a photo being a single frame kept in mind, new technology in digital and HD televisions has taken the idea one step further and applies it to moving film/video/live broadcasts. It is called Progressive Scan. In essence, the lines are projected in sequence 1-2-3-4-5-... and it is done so super fast that our eye perceives a single, whole image at once. This makes the image we see crisper or more clear, and thus raises the quality -- which is why digital, and high definition (high because they use more lines) TVs seem so much better than the old fashioned ones.

Progressive scan TVs also have converters in them so they can happily detect and play back videos which started life as either LFF or UFF standard video.

Hope you understood all this -- and apologies to the experts for the simplistic way I have presented it all!

[Clevo]

You did well Ken.

[wai2]

Thanks Ken, your detail elaboration is appreciated.