The limitations on L*a*b colors & is there a workaround?

Question

I am working on a piece that will be printed on a 7 color printer with a very, very large gamut. I was planning on taking advantage of all that but just discovered that Adobe limits the L*a*b colors to those with a or b +127 to -128. The printer I'll be using is capable of doing more. Two questions:
why this limiation?
is there any way around it?

Answer 1

My guess would be the printer LAB space is not the same as the image LAB space and going beyond the application's LAB space creates bizarre color shifts.  It could also be a type of threshold within the application to keep color within a colorspace' range.  Typically, printer gamut is smaller than image gamut.  This discussion could get very textbook fast, so I'll try to constrain it to where you can get a handle on it, OK?  Eventhough the printer uses 7 cartridges, there are some colors it cannot match.  When inkjets first came onto the scene, the were limited to CMYK.  Most highlight densities 1 - 5% were non-printable and simply got blown-out.  On the other end of the spectrum, shadow densities of 89 - 99% were non-printable and simply filled-in.  This was due to an inherent low printer resolution of 300 to 600 dpi.  As part of a solution, printer manufacturers used more cartridges like Lc and Lm ( light cyan, light magenta ) to help image highlight and shadow areas.  At the same time, additional carts and finer printer head technologies allowed for photographic printing.  Suddenly, photographers could abandon their darkroom facilities.  More recently, some printer manufacturers added Matte Black and Gray carts for greater Black + White photographic flexibility.  These added carts increased the printer's gamut where skin tones and blue skies became manageable.
So, the print gamut has become wider, but still remains short of transmissive color ( monitor ) simply because it is reflective color ( ink on paper ).  My recommendation would be to work in LAB to get the results you are looking for and then convert a copy of the file to an RGB colorspace suitable for photographic printing.  If you are printing in a graphic arts scenario, convert an additional copy from RGB to CMYK in the most appropriate profile.  Illustrator does not use a LAB document color space.  It's either RGB or CMYK.  Why?  Printer drivers ( and/or RIP ) convert either RGB or CMYK into LAB to interpret the color and print the file.  LAB is part of the printer's language.  LAB is a conversion process from color space into print driver language.  There really are no LAB color limitations involved.  What you perceive as a limitation could actually be the parameters where printers can interpret accurately the color info coming in.  Therefore, the end result is accurate representation of printer capable color.  The entrie print process is a huge math equation full of constraints to keep things manageable.  Should software engineers become so irresponsible as to eliminate those constraints, there would be print anarchy with artists making color demands that would be impossible to reproduce no matter how many color catridges the inkjet has.  See my point?  The entire process, creation to print, is a discipline.