[jase (Jason)]

There are many benefits that LRGB provides over conventional RGB. Possibly too many to list conclusively here, but here are a few;

• Reduction of total exposure time - through chrominance (RGB) binning
• Human eye does not detect great detail in colour information, thus using the luminance "greyscale" for detail makes obvious sense.
• Ability to separate and image process the luminance data from the chrominance data is a major advantage. I think many underestimate this.
  
• Typically, the luminance will pick up much greater detail in the target object as it's permitting a broader wavelength window.
• Provides improved flexibility - Luminance can also be combined with Hydrogen Alpha to bring out more details.

Of course, there are also problems with LRGB. Most commonly, problems occur when processing an LRGB image as the luminance data is much stronger than the RGB. This results in the typical "salmon pink" tones. Imagers avoid this as much as possible. You can get around it by blending channels and/or luminance layering.

Its worth acknowledging the founders of the LRGB Process - Kunihiko Okano and Robert Dalby. You can see some information of the process from Dr. Okano's web site - http://www.asahi-net.or.jp/~rt6k-okn/its98/lrgb.htm

"The basic premise of luminance layering is that by combining an unfiltered high resolution and high S/N greyscale image with the weaker color data we can in essense "buy back" the signal and detail lost in our filtered RGB exposures. The end result potentially should be a more aesthetically pleasing high contrast color image." - Rob Gendler

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Re: Your problem. Its sounds like your filters are not parfocal. Always use the Luminance filter instead of unfiltered for LRGB images. Unless of course you intend to refocus.