# Expression And Time ? Pixel Anylyzer

**URL:** https://forum.highend3d.com/t/expression-and-time-pixel-anylyzer/9560
**Category:** Compositing
**Tags:** shake
**Created:** [October 18, 2006, 7:59am UTC](https://forum.highend3d.com/t/expression-and-time-pixel-anylyzer/9560 "2006-10-18T07:59:51Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![user\_deleted](https://forum.highend3d.com/letter_avatar_proxy/v4/letter/u/35a633/32.png) [@user\_deleted](https://forum.highend3d.com/u/user_deleted)
#### Post date: [October 18, 2006, 7:59am UTC](https://forum.highend3d.com/t/expression-and-time-pixel-anylyzer/9560/1 "2006-10-18T07:59:51Z")

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Hey Guys

This is what I am doing.

I have a fight scene which is taking place during a thunder storm.

My task is to comp further rain (particle or live action plate, does not matter) in to each shot to bring a level of consitance to the shots.

Now as I said above it is taking place during a thunder storm,, So I have used the "pixel anylyzer" to mapp the luminance values for when the lighting strikes,, I then apply this information via an expression (nothing special) to the "brightness" node.

one last note "the lighting flashs for only one frame for about 90% of flashes".

My question is, What sort of expression would I need to use if I wanted to add 1, 2, or even 3 frames of ease in and ease out either side of the lighting flash using the data from the "pixel anylyzer"

Regards  
sydway