For emission targets, considerably — a narrow band can make a nebula reachable from a suburban garden. For broadband targets it costs signal, and the calculation is about processing rather than about seeing more.
The arithmetic is different from visual use, which is why the same filter can be a bargain for one and a waste for the other.
What narrow bands buy a sensor
A sensor integrates, so it can afford to throw away most of the light if what remains has far better contrast. Under a bright sky, that trade is often decisive: an emission nebula becomes photographable from a garden where it was hopeless before.
What they cost
Exposure time, and colour. A single narrow band produces a monochrome image; colour comes from combining several, which multiplies the time again.
Where a broadband filter fits
Between the two. It suppresses a gradient without removing most of the signal, and it makes a stack far easier to process. For colour cameras under suburban skies this is often the most useful single accessory.
What no filter does
Help a galaxy or a star cluster. They shine across the spectrum, and anything that narrows the band removes them along with the sky.
If this page and the manufacturer’s own documentation disagree, follow the documentation. Every aperture, focal length, payload rating, field, eye relief, transmission figure and thread size on this page comes from the maker’s own published figures, with the unit as printed and the source named. None of it is measured here, and no figure is converted into another convention, because a converted number is a different number. And for any filter: the name is not the bandpass. Two filters sold under the same three letters can pass windows of very different width, and the figure that decides what a filter does is the transmission at the emission lines together with the width of the window. This page reports the band and the percentage where a maker publishes them, and says they are missing when they are not.
The questions that keep arriving
Are visual and photographic filters the same?
Sometimes physically, but the choice differs. A band narrow enough to be superb on a sensor can leave nothing visible at the eyepiece, because the eye cannot integrate.
What does a filter do to exposure time?
Lengthens it, in proportion to what it removes. The gain is contrast rather than speed, and a narrow band trades a great deal of exposure for a great deal of background suppression.
Last reviewed 17 September 2026