Optical Filters FAQs

Here we have provided comprehensive lists of commonly asked questions regarding our Semrock 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 Optical Imaging Systems, Fluidics, Cameras, Microfluidics, our Webstore, and Engineering Partnership.


What is pixel shift, and how does the Semrock ZERO option help?

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 monochrome digital camera. This shift becomes problematic when two or more images of the same object are acquired using different filter sets and then overlaid 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 depending on the wedge angles found in each filter set. To eliminate pixel shift, BrightLine ZERO and Avant ZERO filter sets are manufactured and tested to exacting tolerances to ensure accurate image registration when combining multiple images.

The BrightLine ZERO and Avant ZERO options guarantee 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, and assuming an 8 μm square pixel.

epifluorescence geometry schematic

The above schematic of a typical epifluorescence 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 significant pixel shift, are distorted, whereas in this example the BrightLine ZERO pixel shift filter set (above right) yields precisely registered multi-color images.


Technical Note: Pixel Shift in Fluorescence Microscopy

White Paper: Physics of Pixel Shift