Lima/Model Power heavyweight Coach

[Angus Shops]

I've read that car and locomotive builders often applied a temporary water based grey paint in preparation for builder's photos to eliminate the high contrast and loss of detail typical when photographing, for example, a shiny new black locomotive.
Geoff

[jmlaboda]

I've read that car and locomotive builders often applied a temporary water based grey paint in preparation for builder's photos to eliminate the high contrast and loss of detail typical when photographing, for example, a shiny new black locomotive.

I've seen a lot of Builder's photos and have never seen such being done.  Builders' were interested in the overall look of a car or locomotive, not the detail of it.

[jmlaboda]

Also not indicated in the drawings on the Keystone Crossing site

Ah... that's not the Keystone Crossing site.  Its Rob's PRR page...

[nickelplate759]

I've seen a lot of Builder's photos and have never seen such being done.  Builders' were interested in the overall look of a car or locomotive, not the detail of it.

Wikipedia claims that it was common practice in the UK.  https://en.wikipedia.org/wiki/Builder%27s_photo 
I'm pretty sure I've seen a few examples done in the US, but don't have any handy.

[ncbqguy]

I've seen a lot of Builder's photos and have never seen such being done.  Builders' were interested in the overall look of a car or locomotive, not the detail of it.

Jerry-
There are plenty of examples of temporary light color paint jobs being applied to a sample car representative of the lot of cars.   It was done to show up the construction details of the car, particularly the underframe and trucks which often were lost in shadow.  Lettering was sometimes reversed in black instead of white or lighter color for contrast. 
Freight cars were common; some steam locomotives got the treatment and less commonly passenger cars.
Charlie Vlk

[peteski]

Wikipedia claims that it was common practice in the UK.  https://en.wikipedia.org/wiki/Builder%27s_photo 
I'm pretty sure I've seen a few examples done in the US, but don't have any handy.

They also did that in Germany (Prussia and Bavaria). Model manufacturers even make models of steam locos in gray (photo) livery.