Microscope filters explained

If you’ve ever wished your image was clearer or that the colours were more vibrant and natural, filters might be just the thing for you.

By letting you filter out certain colours, light angles or wavelengths, microscope filters can significantly improve the quality of your final image. They are used for both observation and photo microscopy.

This article will give you a quick look at how filters work and some of the more popular options.

Whether you’re a hobbyist or a working professional, microscope filters have something to offer.

What can filters do for you?

There are many different kinds of filter, each with its own specific purpose.

The simplest filters can help you fine-tune your colour balance and correct for lens errors such as spherical aberration.

Other filter options can reduce light intensity or block certain light angles, letting you use contrast boosting techniques such as darkfield, oblique and Rheinberg illumination.

More advanced filters can even selectively block light wavelengths or a specific range of wavelengths, protecting your image from infrared or UV light, or enhancing your fluorescence microscopy

Installing a filter

Installing a filter is usually easy. Many microscopes even come with a filter holder ready to go.

You simply place your filter in the holder or above the illuminator. Some microscopes might require you to slot the filter into the illuminator box, but it’s uncommon.

Even if your microscope doesn’t natively support filters, there are many resources for DIY installations and home-made filter options, so you won’t need to break the bank with a new microscope to get started.

Types of filter

Here are some examples of the more common microscope filters and their uses.

Yellow filters

Yellow filters are often used to adjust the colour of halogen and tungsten illumination, bringing the light back to a whiter, more natural colour. Yellow filters are also able to boost contrast and to compensate for spherical aberration, as well as sometimes helping to identify structural defects in metals.

Green filters

Green filters are primarily used to correct for spherical aberration in achromatic objective lenses. They can also improve the quality of phase contrast images.

Daylight blue filters

Daylight blue filters are generally just used for colour correction. They can bring a yellow light back to a more neutral white, as well as improve resolution.

Red filters

Red filters are particularly good at reducing the amount of ‘background noise’ in an image, bringing shape outlines and edges into sharper focus. They can be used to help with measurements and occasionally identification.

Neutral density filters

Neutral density filters are used to uniformly reduce the amount of light that gets through by a specific percentage. The light isn’t altered, nor is the range of wavelengths impaired. The light intensity is simply lowered.

These filters are available in a variety of light reduction ratios. They are often used in photomicrography for exposure control and lighting adjustments.