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Fairly new to blender nodes. How can I keep the alpha part of a 2d image texture, without having a principled BDSF changing the lighting/brightness of the original image? This is what I want, but without the brightness effectsenter image description here

This is the original, without alpha. I want the colors to look like this, straight from the original source, but with an alpha background. enter image description here

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  • $\begingroup$ The easiest way is to connect the image's Color to the Emission socket instead of the Base Color socket, then make sure the Base Color socket is pure black. $\endgroup$
    – scurest
    Jan 27 at 2:36

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You want to connect it like this:

AlphaConnect

You can connect your image as an (unshaded) input into a mix shader, with a Transparent BSDF in the other slot. Use the image's alpha output as a mix factor.

Also, for best color accuracy, make sure your view transform is set to "standard" (instead of default "filmic").

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  • $\begingroup$ This makes me wonder if the IAP_SHADELESS group node provided with Images As Planes is doing anything different than this. It currently contains 11 nodes, doing a bunch of Light Path calculations. If it is functionally identical, that's hilarious! $\endgroup$
    – Mentalist
    Jan 27 at 17:30
  • $\begingroup$ @Mentalist This is the same as using an emission node, which will glow (emit light onto nearby objects) in Cycles. The IAP_SHADELESS node is designed to prevent that. $\endgroup$
    – scurest
    Jan 28 at 19:47
  • $\begingroup$ @scurest I see, good to know! When setting up shadeless materials myself I usually just add a Light Path node and plug its Is Camera Ray output socket into an Emission node's Strength input socket. (Of course I also add a Mix Shader with a Transparent BSDF if there's an alpha channel.) Do you know if there's any case when using IAP_SHADELESS gives a noticeable advantage over the simple camera ray method? $\endgroup$
    – Mentalist
    Jan 31 at 3:00
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    $\begingroup$ @Mentalist That won't glow, but it will appears pure black when reflected in a mirror. IAP_SHADELESS will reflect properly. Judging by the names of the nodes in the group, it also does something for refractions and shadows, but I don't understand the whole thing. $\endgroup$
    – scurest
    Jan 31 at 3:51
  • $\begingroup$ @scurest Thank you for that important info regarding shadeless reflections! $\endgroup$
    – Mentalist
    Jan 31 at 5:03
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Just plugin the image directly in the material output as you did in your last screenshot.

If this doesn't help, please provide blend file. Don't forget before upload to do File-> external data -> pack resources.

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