What to do if your highlights look clipped. FS700 in particular, but applies to many cameras.

One of the well documented issues or at least something that gives people problems is highlight clipping. This isn’t just an FS700 problem, but the AVCHD recordings from the FS100 and FS700 are particularly prone to getting clipped. You go out and shoot something and which looks great, but then when you get the footage into the edit suite it looks clipped and highlights look blown out, especially in any rendered clips or clips with effects applied. There are a couple of reasons for this. The first is that in the majority of setting the FS700 like most pro video cameras (EX, F3 etc included) records up to 109% (data bits 16 to 255). In the video world white is bit 235 (940 in 10 bit) or 100% and this is supposed to be your maximum with 104% typically allowed for broadcast. Anything above white is known as a superwhite. In the computer world white is bit 255. The second issue is that different edit applications handle white differently. Some will allow the full range of 0-109% without any clipping, some will clip anything above 100% and worst of all, some will do either depending on the codecany filters applied and other factors, so you often never really know where you stand. (See this article for more information on clipping and superwhites).

First, check to see if  your material is getting clipped!
The simplest way to check for clipping in the edit application is to apply a proc amp, gain or brightness filter to the original material and observe what happens as you reduce the brightness, the best filter to use if you have it is the proc amp filter as this reduces the input level of the clip. If the amount of clipping reduces when you reduce the brightness then you have a clipping problem. If the clipping remains the same and the image just gets darker then you are good. If you have a problem read on.

One way to avoid clipping is to shoot using a gamma or knee that will keep your signal levels to 100%. On the FS700 (and any EX camera or the F3) Cinegamma 2 is always “broadcast safe”. There is no significant loss of dynamic range by using this gamma, it has the same curve as Cinegamma 1, just only mapped to bits 16-235 to keep things out of clipping and legal. The other way would be to reduce the gamma gain or adjust the knee. As the FS700 does not have a gamma gain setting we must adjust the knee to ensure whites don’t go above 100%. You will find 3 example picture profiles for the NEX FS700 that keep the signal within broadcast safe in the forum here.

If you don’t want to do that, then you need to look at your edit application.

Premiere Pro: Apply the Fast Color Corrector filter to every clip with the Output White Level set to 235. This must be the top filter in the filter stack, so it’s effect takes place before any subsequent filters. On a Mac another option is to use 5DtoRGB to transcode your AVCHD material to ProRes. If you don’t do this and apply other effects to the clip many effects will hard clip the clip at 100% even many of the other color and level correction filters.

FCP7: Ensure you look in your sequence settings and open the Video Processing tab, and select process maximum white as superwhite. When set to “white” FCP is supposed to map superwhites (255) to broadcast white (235) during renders. This great if your producing for broadcast but not so good for online or content to be show on a computer as white will look slightly grey.

FCPX: Appears to handle superwhites correctly.

 

This entry was posted in Uncategorized. Bookmark the permalink.

5 Responses to What to do if your highlights look clipped. FS700 in particular, but applies to many cameras.

  1. This was very helpful. Much appreciated. I’ve been shooting for 40+ years, and used to edit A/B/C roll myself. I relied on my staff and freelancers for non-linear editing. I’m learning to use FCP7 now (don’t ask why 7).

    Thank you!

  2. Andy says:

    Wouldn’t it make sense to adjust settings in the camera as a priority so that information in the highlights can be maintained ? Otherwise, there may be little or no info. to recover in post.

    • alisterchapman says:

      I provided some links to picture profiles in the post that will keep your highlights below 100% and that is certainly one way to work. But the thing is that if you do allow the camera to go up to 109% then the information is there, or at least what you see on on the monitor when you shoot is there, it’s just understanding how to make sure you don’t then loose whats been recorded between 100 and 109%in post, because it’s there, just your NLE may not be showing it.

  3. Johannes says:

    Hi,

    i am from germany – so my english is very bad.

    Can you tell me how fix this problem with the a7s. Ive bought the camera for filming in clubs and that blue clipping problem makes me sick :/.

    Bye
    Johannes

    • alisterchapman says:

      Nothing much you can do about it and all cameras are effected badly by blue LED lights as the blue light is very intense.

Add Comment Register



Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>