Sodium vapor lamps, which are used in street lights, cause much of the light pollution produced by cities. These lamps emit yellowish light with a wavelength around 589nm. Didymium is particularly good at blocking this wavelength and finds its way into many light pollution filters, including the Hoya Intensifier (also known as the Hoya Red Enhancer). Here are a few test results showing what the Hoya Intensifier can do to help reduce the effect of light pollution in your astro images.
The Canon EF 35mm F/1.4L USM lens (first generation) has been around since 1998, but is still highly acclaimed for its overall image quality despite its age. This lens was my first prime with L glass and is probably my most used. Here are some star quality tests I shot with it using a Canon EOS 6D body and a Hoya Intensifier to mitigate the effects of light pollution where I live.
The following mosaics were made from 100% crops using light frames shot at ISO1600 from a red zone. Exposure times started at 4 seconds at F/1.4 and doubled with each successive aperture stop, all the way through F/5.6. A Hoya Intensifier LPS filter was used to reduce the effects of light pollution, as well as some very light curves work in post. Use the gallery below to cycle through light frames gathered at different apertures (click to view full-sized images). Coma and Chromatic Aberration remain strong at apertures wider than F/2.8, then all but disappears at F/2.8 and narrower. Some is still present in the extreme FF corners, but slight cropping of images is enough to get rid of it.
Vignetting is fairly strong wide open on a full-frame sensor, but improves dramatically by F/2.0 and is mostly gone by F/4.0. APS-C users will see great vignetting performance from F/2.0 and narrower.
There seems to be a sweet spot at F/2.8 for this lens, as far as astrophotography is concerned. Vignetting is well-controlled, as well as Comatic and Chromatic Aberration. It’s a great focal length for stitching wide landscape shots. It’s also possible to shoot deeper stacks with this lens, but you’ll need wide-open skies; plan to deal with gradients in post, as this lens covers a lot of sky!