# Integrating sphere as a uniform backlight

**URL:** <https://forums.negativelabpro.com/t/integrating-sphere-as-a-uniform-backlight/6302>\
**Category:** Digital Camera Scanning\
**Created:** [June 10, 2023, 7:40pm UTC](https://forums.negativelabpro.com/t/integrating-sphere-as-a-uniform-backlight/6302 "2023-06-10T19:40:26Z")\
**Posts on this page:** 1\
**Showing post:** 9

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**Author:** ![nicnilov](https://yyz1.discourse-cdn.com/flex029/user_avatar/forums.negativelabpro.com/nicnilov/32/324_2.png) [@nicnilov](https://forums.negativelabpro.com/u/nicnilov)\
**Post date:** [June 14, 2023, 9:46pm UTC](https://forums.negativelabpro.com/t/integrating-sphere-as-a-uniform-backlight/6302/9 "2023-06-14T21:46:41Z")

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Great stuff!

> [@damien](#):
>
> One frequent problem I have is that colors that should be deep red appear purple instead. Other color shifts I noticed are light brown to dark brown, pink to red, red to orange, etc.

One possible reason for this would be the after-effect of neutralizing the orange mask. The mask participates in the color formation _ **proportionally to the exposure** _. If we remove the orange component equally throughout the image (which is what we are doing either by individual RGB channels power or by subtracting cyan in Photoshop), we end up with the residual effect of the film dyes crosstalk, which the mask was supposed to compensate. The color deviation then should be more noticeable in the (positive) highlights areas than in the shadows.

Did you try to [calibrate](https://forums.negativelabpro.com/t/color-management-custom-profiles-at-capture-slides/5161/11)?

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