Negative layers in gerbers and pcb fabs

[varesa]

I am designing a 4 layer pcb in Altium which has a ground plane. Altium seems to want to make it a negative layer, which carries on with the exported gerbers (checked with gerbv). With a quick googling it seems that Altium itself atleast tries to detect negative plane layers if you try to import gerbers, so there is some difference.

If I send the gerbers off to a PCB fab, do I have to manually invert that layer to get a "non-negative" one, or will they somehow know at the fab that it is in fact a negative layer?

[toohec]

If you use the Gerber RS-274X format (and perhaps even the prior version), the positive and negative layer information is imbedded in the file format and will not require you to invert the negative plane layers.  The fab house should be accustomed to working with negative plane layers, however, it's best to specify on your fabrication drawing/notes details about the layers types to prevent any possible confusion.

[Psi]

Open your 'ready to send' gerbers in a different gerber viewing program and see if they all make sense before sending.

[varesa]

Okay, I might just send them as is and specify it in the comments to avoid any problems.

I did try them in two gerber viewers: Altiums internal one and Gerbv, both showed the negative (voids) by default. To see the copper, I had to manually enable "negative"-mode