In this article we are testing the STC Astro Multispectra Clip Filter.
What exactly is this filter and what does it do?
The filter as with all clip filters from STC, fits inside the camera body in front of the mirror. Focusing is performed manually and in Live View mode, there is a focus shift from the norm so auto focus does not work so well.
Constructed with an ultra thin stainess black coated frame and filter glass being German Schott glass with a special ultra layer multi coating. The multi coating layer removes some specific parts of the light spectrum. To be precise it is designed to filter out light pollution caused by sodium vapour lighting, the purpose being to produce cleaner nightscapes, in turn making stars appear clearer.
Looking through the filter a blue hue can be seen
Chart provided with STC Astro Multispectra filter shows which part of the spectrum is blocked.
For the purpose of this test we used a Nikon D800 fitted with a Sigma 15-30mm lens for the main images and a Nikkor 24-85mm lens for the images of the pier. Camera and lens were mounted on a medium weight carbon fibre tripod and the camera triggered by a wireless remote trigger.
Meter was set to aperture priority, Daylight colour balance and with an aperture of f8, exposures were made in NEF mode and converted to Jpeg in Adobe Camera Raw.
We had two main questions to answer whilst performing our test. These being. How effective is the filter and does it affect overall sharpness?
In the first test we tested for blocking of sodium vapour lighting, having found a site with a mixture of street, signpost and general lighting, we made two exposures one without the filter and one with.
Without filter
With STC Astro Multispectra filter
A second pair of images of an early moon rise were taken using the same method as previous.
Looking at the data on the chart in ACR, it shows exactly how the colour of the image is changed by the Astro Multispectra filter.
Without filter
With filter
The third image is multi layer image taken with the Astro Multispectra filter in place.
Having tried and tested several other STC Clip filters, as expected there was no loss of sharpness when using the filter. See samples below.
Without filter
With filter
Full area of image
When viewed at full size the number of stars that can be seen is amazing
Conclusion
STC make several different Astro filters. If photographing nightscapes are of interest to you, this is the filter to have. If however your primary interest is the night sky, there is a specific filter made for that which blocks a much larger part of the colour spectrum.
Because of the way the Astro Multispectra filter works some adjustment to exposure may be required and as previously mentioned the camera must be in Live View mode and focused manually.
We were impressed with the effectiveness and quality of the STC Astro Multispectra filter.
The images were sharp and even across the frame.
Can we recommend this filter? Absolutely!
By C