The IDAS HEUIB-II (H-a Enhanced UV IR Blocking) filter is designed for enhanced spectrum DSLR's and one-shot color CCD astronomical cameras.
Besides removing the IR and UV ends of the spectrum which are often out of focus in refractive optics, it isolates the common H-alpha line relative to the surrounding extreme red end of the spectrum, making it easy to bring out the faint H-alpha emission nebulosity of astronomical photos, yet retain the background color balance of broadband photos.
Some comparison shots taken with the enhanced Canon 6DH (standard Canon UV/IR blocking filter vs. HEUIB-II filter) show a clear difference both in background sky color balance and contrast of H-alpha nebulosity in the extremely faint object IC1396. Note the good background color balance as shown in the histograms of the individual color channels of the HEUIB-II filtered image. Click on images to view enlargements.
At left, a wide shot of the Milky Way clearly shows enhanced contrast of H-alpha regions. Click on the photo for enlargement.
The HEUIB-II filter also returns normal daylight color balance to spectrum-enhanced cameras as can be seen in this photo at right taken with normal DSLR auto-white-balance (AWB) enabled.