I was trying to figure out how to make a “dream effect” with Cinelerra – you know this effect used by filmmakers to show that a character is dreaming or to give sort of beauty to a sequence – … so I shot a baby hummingbird (with my camcorder). Believe me or not; this effect is also called “instant sex” trick.
seems like I made an excessive use of the blur effect 😐
Open Cinelerra. Prepare your project (size, framerate, color model etc) in Settings -> Format according to the media you will use or the destination of your final work.
When done, load the video you want to modify twice on the timeline just like in the following screenshot:
The part of the video you want to modify must be loaded twice.
In the second track, insert a brightness/contrast effect and a blur one by dragging/dropping them from the resources window to the timeline.
We should insert them in this order: brightness/contrast effect on top of blur effect. Right click on the effect bar and move them top or down.
Click on the little magnifying glass 
to change the values of the effects.
For this how-to I chose these values:
– brightness: -0.0600 contrast: 1.800
– blur: 20
Add effects and deinterlace your video (if needed) with the deinterlace effect.
In the previous screenshot, as you can see, I deinterlaced my video (with the deinterlace effect).
If you use a progressive file format you can go directly to the forth step of this how-to.
Two links to understand what (de)interlacing is ==>100fps.com hardware.info (see the picture).
Cinelerra offers different deinterlace filters. The Bob & Weave one seems to be commonly used.
Now, Ladies and Gentlemen, the special ingredient:
For the first track, change the overlay mode to Addition and adjust the opacity to 50% for example.
That’s all Folks!
Change brightness/contrast, blur, opacity values to get the effect you want to make.
Go in the wild to shoot some birds… and don’t forget to warm your balance.
Note1: Bad new; overlay modes don’t seem to be keyframable :(.
Note2: I’m not sure if this is the better way to make this effect but I’m not unsatisfied of the result. If you have other methods I would like to test them.
Other how-tos playing with overlay mode:
– Vignetting-in-cinelerra from M4rci.
– Cinelerra: efecto lapiz from facilware.com
MakeFx 