If I understand correctly, OBAs turn UV light into bluish visible light, which causes paper with them in to look brighter when exposed to UV light. Substances that make the paper whiter by making it reflect more white visible light, such as baryta or titanium dioxide, don't do the uv trick. The problem with OBAs, other than a slight blue shift, is that they'll eventually stop performing their trick, which'll cause the paper to appear yellower.
On Sun, Nov 3, 2013 at 11:25 AM, Jon Zax <lotus@...> wrote:
I find something in these terminologies confusing.
Isn't a Baryta layer in a photo paper there to whiten the substrate,
so doesn't that make Baryta an OBA ?
J.Z.