Optical Filters FAQs

Here we have provided comprehensive lists of commonly asked questions regarding our optical filters and related applications. This information is designed to support your inquiries, but if you don’t find the answers you are looking for we encourage you to contact us for further assistance.

Please use the sort buttons in the left navigation to navigate between questions and answers that are specific to Fluidics, Cameras, Microfluidics, our Webstore, and Engineering Partnership.


What is pixel shift?

Pixel shift results when a filter in an imaging path (the emitter and/or dichroic beamsplitter in a fluorescence microscope) deviates the light rays to cause a shift of the image detected on a high-resolution CCD camera.  This shift becomes problematic when two or more images of the same object are acquired using different filter sets and then overlaid in order to simultaneously view fluorescence from multiple fluorophores.   Images produced by different fluorophores (and different filter sets) will not be accurately correlated or combined because each image is shifted by a different amount according to the wedge angles found in each filter set.  To eliminate pixel shift, BrightLine ZEROTM filter sets are manufactured and tested to exacting tolerances to ensure accurate image registration when combining multiple images.

The BrightLine ZERO™ option guarantees that the worst-case image shift when interchanging Semrock ZERO sets will be less than ± 1 pixel, measured relative to the mean image position for a large sample of filter sets.

epifluorescence geometry schematic

This schematic of a typical epifluorescence geometry (as in a standard microscope) shows how filter wedge causes pixel shift.

composite image from conventional filter versus BrightLine ZERO filter set image

Composite images produced from conventional filter sets (above left), which typically have signifcant pixel shift, are distorted, whereas BrightLine ZERO pixel shift filter sets (above right) yield precise multi-color images.