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A:  Most Semrock filters have a preferred orientation.  Filters that are mounted in a metal ring are marked with an arrow that points in the preferred direction of light propagation. Unmounted filters designed for use at normal incidence are marked with a carat ("^") pointing in the preferred direction of light propagation. Note that the multiphoton emission filters can be used in any orientation, so there is no marking on these filters.

Our standard dichroic beamsplitters are marked on the coated side, typically with a small linear scribe or a corner chamfer.  When viewing the filter, the coated side is facing you when the mark is in the lower right-hand corner.

A:  While filters have traditionally been manufactured using soft-coating technology, Semrock pioneered the introduction of hard-coated filters to the biotech market. Soft-coated filters are made by an evaporative deposition process and the resulting porous nature of the soft thin films means the coatings must be sealed between two glass substrates or with a "semi-hard" protective coating to limit environmental degradation. The coating thickness is limited by the deposition process associated with these materials, limiting filter performance.  As a result, extended blocking is often provided by absorbing glass and/or metal-dielectric attenuation, rather than pure dielectric reflection, causing a lower overall transmission and problems with optical and thermal damage to the filters.

Semrock offers exclusively hard-coated filters manufactured with ion-beam sputtering technology. The coating is deposited directly onto the substrate, with no epoxy required. The simple all-glass structure and hard dielectric glass coatings (as hard as the glass on which they are coated!) mean they are virtually impervious to humidity-induced shifting and can be cleaned and handled like any standard glass optic.  All Semrock filters are coated on a single glass substrate, so there is never any adhesive in the optical path to autofluoresce, scatter light, or degrade with environmental or optical stress.

A:  Pixel shift results when a filter in an imaging path has a wedge that alters the angle of a beam of transmitted light, thus causing a shift of the image detected on a high-resolution CCD camera.  When two or more images of the same object (from two or more different filter sets that cause pixel shift) are overlaid, the images will not be registered to identical pixels on the CCD camera. Hence, images produced by different fluorophores will not be accurately correlated or combined.  Semrock offers the "zero pixel shift" option for only $99 on all of the highest-performance BrightLine filter sets, including those for FISH and Qdots.