[damienf]

Rendering a product with a mask. Backdrop set invisible (hidden from camera).

At the end white background will be added in Photoshop.

How can one possibly change Maxwell's background from black to white to better help evaluating the render while Maxwell is working on it?

[feynman]

Just load a 1 x 1 pixel FFFFFF 8-bit PNG into the Background under IBL settings.

[seghier]

you can also use constant dome and than choose active sky in ibl background

[damienf]

What if my setup only make use of emitters, no IBL?

[seghier]

What if my setup only make use of emitters, no IBL?

use alpha channel

[damienf]

I already have an alpha channel (mask) set. This allows me to change the background color in Photoshop when the render is finished.

But what I'm looking for is a way to evaluate the render as it progresses with a white background instead of the default black.

I still want to render with the alpha channel so I'm not looking at simply adding a white background to my renders.

[seghier]

so use IBL and activate the background only (constant dome = white color ) than set the others to disabled

[RobMitchell]

A lot of people have requested for them to add the option of setting an alpha background colour, would be really helpful for the exact reasons dacct has listed here. There was a wish list topic about it at one point which I can't find right now, but I don't think it's in the pipeline sadly. Currently you're stuck with the black background if you preview a render with an alpha channel set.

One thing that could work, is if you disabled the alpha channel completely and put in an HDRI of the colour as the background. Then use the Custom Alpha channel option instead to create the alpha you need. I can't remember off the top of my head if this causes the background to go black or not, though. Worth a try!