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Thread: Need help for SFX

  1. #1

    Default Need help for SFX

    The explosion effect at 03:15 in my latest video doesn't look as real as I would like. I already played around with color grading and have a light mask but the result is not what I was aiming for.
    The quality is more than fine for this video but I would like to improve for others. Is there something obvious I did wrong?

  2. #2


    As I'm sure you know I'm not an SFX expert but that has never stopped me on giving advice is the past.

    The first thing that I observed was the explosion didn't start from within the container, for me it should have been more of a mushroom cloud starting inside the container and working it's way up. The other big "out point" was the lack of effect of all the other things on screen. An explosion is a bright light, what would that look like on the other objects ? Would it cause shadows ? etc... Take a look at some "Hollywood Explosions" and see what is happening right across the screen.

    Hope that helps get you started.

  3. #3


    Too much fire, too much smoke around the edges. That's not what it's going to look like for real.

    The fire would be unlikely to cause any smoke or black edges in this scenario (they tend to appear many meters away from the source) and would also create additional lighting effects on the background and the arm. It's can't be treated in isolation.

    Alsol flames tend to be coloured based on the combustable materials. That looks like a petrol/oil fire. If you look at the fire from (say) butane it's blue.

    Making explosions like this is really hard, especially if you're using stock fire designed for larger sets.

  4. #4


    I think I get your points. Actually I tried grading the color and added light masks for inside the container and the surrounding but probably I should just have pushed it harder.

  5. #5


    Out of interest, here are images from XXXRay's exploding bottle, my own burning garden table; and an exploding building from the 007 movie (Skyfall).
    XXXRay's fire only appears to be coming from the gap in front of the hand.
    Although my table fire looks fake; I removed any black edges; and used some keying make some tones semi transparent.
    Would XXXRay's clip look realistic if the brightness of the scene changed; giving the effect of a camera's auto exposure mode?
    Attached Images Attached Images

  6. #6


    Nice comparison.

    How could I get rid of the black edges btw.? Just reducing the contrast and making it a bit brighter?

  7. #7


    You could try keying out the black.

    Also, try adding more transparency. A small explosion of that size wouldn't be so dense.

    Play with the colours. Does it really have to be orange?

    Play with expanding it really quickly so it starts small (the size of the container opening) then get's bigger to fill the screen but disappears very quickly (along with transparency).

    The explosion you're using looks intense. Would a 'pop' from your bottle be quite so intense? It's more likely to be a funnel shape and blowing upwards from a tiny source (the neck), isn't it?

  8. #8
    Join Date
    Feb 2006
    Surrey, UK
    Blog Entries


    Try different compositing modes - Add or Overlay might work better.

  9. #9
    Join Date
    Feb 2012
    Helsinki, Finland


    Midnight Blues comment about the explosion not sitting in the scene might be biggest thing here. If the bottom of the explosion would be keyed out it could look more like it's coming from inside the container. Right now it seems a bit glued on as it doesn't seem to respect the container.

    One simply fix would be to speed up the explosion footage a bit. The way it expands looks like the scale is not right, combustion of that size would be over pretty soon. People's eyes are quick to notice things like that even if they're unable to point out just what is wrong. They will have time to notice the explosion even if it's faster, but they'll also have less time to spot the unsavory details.

    Other thing would be to make your explosion light up the scene a bit more (momentarily). Sudden fiery explosion (as it is now) propably wouldn't sit so nicely in scene if it was real, but would cause some grievance to your camera. If you're using AE you could try LightBurst (or was it Lightray?) and key it out to last only for the duration of the explosion.

  10. #10


    Very useful tips. Thanks a lot.


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