Best Performance - ‘ET’ series sputter-coated filters:
Chroma’s Modified Magnetron sputter coatings (ET) achieve the highest transmission levels for interference filters, and produce the brightest images. Like ‘HQ’ filters, these filters also have a very steep transition from peak transmission to high OD to best exploit the spectral properties of commonly used fluorochromes. These hard-coatings offer the greatest hardness and durability, tolerance to high heat and humidity, and will last much longer than soft-coatings. Additionally, use of our ET filters assures image registration between filter sets in imaging systems which are otherwise in perfect register.
Better Performance - ‘HQ’ series soft-coated filters:
The coatings on our ‘HQ’ filters tend to have more layers than ‘D’ filters and result in filters with more abrupt, steeper transitions to high OD. This means that excitation and emission filters may be spaced closer together spectrally, more closely matching the excitation and emission spectra of the most common and useful fluorochromes which tend to have small Stokes shifts. The result is a brighter image and higher signal/noise than that obtained with ‘D’ filter sets.
Good Performance - ‘D’ series soft-coated filters:
These are Chroma’s most basic, bandpass interference filter coatings. Because these coatings have fewer layers than our other filter types, they tend to have blocking curves which are less steep. This means that the shift from transmission to high optical density (OD, or blocking) is not as abrupt or steep compared to our ‘HQ’ and ‘ET’ filters. The result is that the excitation and emission filters are spaced further apart from each other in “spectral space” in order to provide good blocking between excitation and emission wavelengths (high signal/noise).