HOYA Ra54 Red Enhancer (Intensifier) filter
For some photographers, filters are not required for astrophotography or night photography in general. This is in general partially true, but with the exception of Light Pollution Filters.
Light pollution filters were well known for astronomers and deep sky astrophotographers for quite some time now. Night sky enthusiasts started using them back in the 80s when they realised that they could gain more contrast and detail for the faint deep sky objects when using them in front of their telescopes. Their issue though was that they were very expensive and a little difficult to find.
In our days, where the biggest percentage of our planet is heavily light polluted with lights of every kind, Light Pollution Filters is a must-have for night (sky) photographers as the most us lives near big cities.
As for the filters, there are plenty of choices in the market, with the cost ranging between a logical amount of euros and reaching nearly the cost.. of a lens..or even more !
The HOYA Ra54 is made from a rare earth element called Didymium and it is ideal for landscape photography because it primarly enhances red, orange and brown colors, giving them more contrast and saturation while not altering other colors of the spectrum.
It can also filter out the yellow and orange part of the spectrum from 575nm to 600nm, the colors of sodium vapor lamps which are mainly used in big cities, making it an excellent light pollution filter.
It looks like a common clear uv style filter, only having a faint purple tint and it comes in ranges from 49mm to 82mm.
Testing HOYA Ra54 Red Enhancer on the field
All my tests were made with the following gear.
Cameras : Nikon D850, Nikon D800, Sony A7R2, Sony A7s
Lenses : Tokina 17-35mm F4, Tokina 24-70mm F2.8, Tokina Firin 20mm F2, Nikon 20mm f/1.8, Sony 28mm f/2, Sigma 35mm f/1.4 Art and Nikon 180mm f/2.8 (only for deep sky).
The lenses specified above had the HOYA Ra54 filter attached.
The images are mainly straight out of camera raw files converted to jpeg, with no editing, except from the first test which I deliberately auto edited them to show you the difference in exposure.
My first test was made directly from my house. In the street below and of course in the nearby island of Paros, there are sodium vapor lamps with a strong yellowish glow so it was the most obvious thing to do as a test.
The first two images are straight out of camera.
(Nikon D850, Sigma 35mm F1.4 Art, 1.6s exp, ISO 3200, Natural Auto WB)
The image on the left is without filter while the image on the right is with the filter on.
As you can see there is a clear difference even without edits.
I auto edited the two images in Adobe Camera Raw which suggested for the first image (no filter) a +1.10 exposure, +25 contrast and -21 blacks. The white balance temperature at 5100k and the tint at -7. No other editing was made. No noise reduction or sharpening, no lens profile loaded.
Again the same procedure for the second image (with the filter). This time Adobe Camera Raw suggested a further increase in the exposure to +1.60. Everything else remained the same as the first image.
This is the comparison of the final edited result.
Again in the left the no filter image and in the right the image with the filter.
It is clear that there is a difference, where the sky in the second image is way more blue than the first one.
One minor issue I discovered was some unwanted flaring/ghosting that can be seen sometimes, especially when the lens is directly facing any lights, probably because the filter does not seem have any anti-reflective coating so beware of that when shooting.
But lets see how it performs in clear dark skies, far away from big light pollution.
As you can clearly see in the last image, there is again some unwanted flaring in the center near the galactic core, which I assume it was created by the intense light of the Syrp Genie which was directly in front of the lens. In my opinion it’s not something to worry about as it can be removed easily in most cases or even prevent it before capturing the image.
From my tests I measured that the filter also reduces a little more than a half a stop of light transmission (0.60 – 0.75 stop), something that also was confirmed when auto editing the first images, so be sure to manually focus before attaching it in the lens (live view and/or focus peaking) because the decrease in the exposure will make it harder to focus when the filter is on, and also remember before using it that you should alter your final exposure a bit, either in shooting or in post. I always prefer to capture the image I want as best as possible and do only minor editing in my final image. So I suggest that you should alter your exposure, if possible of course, when shooting. It is an insignificant loss as todays cameras are capable of producing great quality raw files that helps equalise the exposure flawlessly, so even if you can’t increase your exposure or you simply prefer the in-post method, you will still get a great result.
One other thing to keep in mind is that the filter works better under dark skies although it can be used in light polluted areas. Just don’t expect to capture the Milky Way Galaxy or the Orion Nebula from a city just by attaching the filter on your lens.
My conlusion is that this is an excellent filter, in a very affordable price compared to other options, with an immidiate effect in your night sky images ! I strongly suggest it !
PS – My award winning film “Keep Looking Up”, a night sky themed time-lapse film, was filmed entirely with the HOYA RA54 Red Enhancer filter with amazing results !
You can watch it here : https://vimeo.com/247373542
More photos taken with the filter