Hoya Red Intensifier Review: An Affordable Light Pollution Filter for Astrophotography

I don’t typically use filters for the type of astrophotography you see on Lonely Speck. Filtering for specific wavelengths of light is a common practice for astronomy and deep sky imaging. But most filters made specifically for astrophotography tend to be very specialized and very expensive. Luckily, there’s an option for those on a tight budget: the Hoya (Red) Intensifier (Red Enhancer RA54) Filter. In this short review, we test out the Hoya Intensifier while shooting the Milky Way from Trona Pinnacles, California.

Introduction

Before trying the Hoya Red Enhancer filter, I had never used a filter for astrophotography. Other than the SharpStar2 for achieving precise focus on the stars, I didn’t know of an immediate reason to use a filter while shooting basic night photography.

Many dedicated astronomy filters are made to filter out everything but a very narrow band of light, specifically for targeting certain parts of the spectrum, like infrared or Hydrogen Alpha. These narrow band filters are usually best reserved for shooting on a full-spectrum camera or dedicated astronomy sensor. Other more common photographic filters like a UV filter, polarizer or neutral density filters don’t really provide any tangible benefits for astrophotography.

The Hoya Red Intensifier (Red Enhancer RA54)

The Hoya Red Intensifier (Red Enhancer RA54) (also just called the plain “Intensifier”) is a special application filter that’s intended to enhance red and orange colors, particularly for autumn foliage.

The Hoya Red Enhancer is also known as a Didymium filter. It filters out the yellow-orange portion of the spectrum from about 575nm to 600nm. The original application for a Didymium filter is to protect the vision of glassworkers from the bright yellow-orange color of the hot sodium in the glass. As I originally learned from Nick at Noctilove, this type of glass should make a good light pollution filter.

Hoya RA54 Red Enhancer Intensifier Filter Transmission Curve
The Hoya RA54 Enhancer filters out yellow-orange light from about 575nm to 600nm (via hoyafilter.com)

 

The part of the spectrum that the Didymium filter removes is also the exact color of most sodium vapor lamps, one of the most common sources of light pollution. Many city and suburban street lamps and industrial lighting use these yellow-orange lights. They’re slowly being replaced with LEDs in major cities, but sodium lamps are still one of the most common types of outdoor lighting. Being able to filter out most of this type of light should provides a distinct benefit for astrophotography.

Hoya Intensifier Filter for Astrophotography

At first glance, the Hoya Red Intensifier filter looks like a pretty plain filter. It’s a relatively clear looking filter but with a very subtle colored tint. It can appear pink, cyan or bluish, depending on the light it’s viewed under.

As far as I can tell, it appears that this filter does not have any anti-reflective coating as reflections off the surface of the filter glass appear to have no colored tint. A lack of coatings shouldn’t really affect most astrophotography but photographers should be aware when using it in other situations; it may cause unwanted reflections, particularly when shooting with very bright light sources in the frame.

Other than that, there’s nothing else to say about the appearance of the filter. It’s a pretty standard looking thing and comes in most common filter thread sizes from 49mm to 77mm.

Testing the Hoya Red Enhancer for Astrophotography

To test the Hoya Intensifier, I traveled with my girlfriend to Trona Pinnacles, California. It’s one of my favorite spots for astrophotography and is the site of our upcoming Lonely Speck Meetup 2016. Trona Pinnacles is a relatively dark sky location but there are still a few distict light pollution sources in the area: Ridgecrest to the west, Trona to the north, and Barstow to the South. Each of these towns create a mild orange glow visible in astrophotos.

lonely-speck-meetup-2016-trona-pinnacles-4

Our test was made on a Sony a7S and two different lenses: the Voigtlander 21mm f/1.8 Ultron and the Sony Zeiss FE 55mm f/1.8 Sonnar T*. Each lens was fitted with a Hoya Red Intensifier for its respective filter size (58mm for the Voigtlander and 49mm for the Sony Zeiss).

Test shots were made in pairs: One set of shots was made with the filter removed and another identical set was made with the filter installed. The camera was set with identical settings for each set of shots. All photos were made with daylight white balance, manual exposure and manual focus. Let’s take a look at a first test shot:

Before:

DSC00733

After:DSC00732

This first test shot was made on the Voigtlander 21mm f/1.8 Ultron wide angle lens. The partially illuminated moon was still visible so the sky was naturally blue. As you can see, the filter noticably reduces the yellow glow created by the sodium vapor lamps of the mineral mining plant in Trona, California. The sky is darker and deeper blue and less hazy with the filter installed. Overall contrast is increased and you can see that the scene is slightly darker, likely since a portion of the ambient light spilling on the landscape is from the light pollution of Trona.

So far so good. The results were immediately noticeable, the filter seems to be doing its job of filtering out some light pollution.

Let’s take a look at another test image, this time of the Milky Way Galactic center, made after I had waited for the moon to set below the horizon.

Before:
DSC00969-Edit
After:DSC00939-Edit

This second test shot above was made with the Sony Zeiss FE 55mm f/1.8 Sonnar T*. Each image was made with the camera set to daylight white balance and by stacking 30 exposures to reduce noise. Images are normalized for brightness but post processing is otherwise identical between test images.

And below is a comparison of completely unedited images (exported straight from RAW) that should give you a good idea of the difference the Hoya Red Intensifier can make:

Before:hoya-intensifier-light-pollution-filter-before-after-2
After:
hoya-intensifier-light-pollution-filter-before-after-1

If you’d like to see these as straight-out-of-camera RAW files, check out the download link to a zip of 3 before and after pairs of shots shot using the Hoya Red Intensifier. The files included in the .zip below are unedited and exported directly to DNG.

Want to see some RAW before/after files?
Download a .zip of RAW files (65.9MB)

The advantages of the filter become a lot more apparent when shooting the galactic center. The Hoya Red Intensifier seems to have almost completely neutralized the yellow/amber hues caused by the distant town of Barstow. The image with the filter installed shows more variety in color, especially when it comes to the blue, red and orange nebula of Rho Ophiuchi around the star Antares. The photo without the filter still looks acceptable but editing the shot to include a good balance of color would be a lot more difficult to achieve due to the orange tint. Overall, the filter really seems to have made a positive difference in the results and I’m super happy with how pronounced the faint colors are when they aren’t drowned out by light pollution.

What about in heavily light-polluted areas?

In the comments below, Anthony Roggio asks: “Any shots with this filter in a heavily light-polluted setting? Somewhere near a major city maybe?”

I shot the following sample of the constellation Orion in Simi Valley California, near Los Angeles. It’s a pretty heavily light polluted area and the photos from the location initially had a lot of amber tint to them.

Before:
hoya-intensifier-suburban-light-pollution-before
After:
hoya-intensifier-suburban-light-pollution-after

The light pollution filter seems to have completely neutralized the amber tint. I still think that the light from Los Angeles was too intense to really start to get some of the faintest nebula detail from the constellation Orion, but it’s neat to see how the filter removes the amber glow.

More Samples Made with the Hoya Red Intensifier Filter

I continued to shoot for the rest of the night with the Red Intensifier filter installed. Overall I’m very happy with how much staturation is apparent across the sky. Nebula are colorful, airglow (the green glow) is saturated and the bright light pollution on the horizon seemed greatly diminished from what I am typically familiar with at Trona Pinnacles. Here are a few more examples made with the filter installed:

DSC00898-Edit-2

DSC00752-Edit

LrMobile1604-2016-123660041766444983

LrMobile1604-2016-122360088312715984

Conclusions and Verdict

The results of using the Hoya Red Intensifier on the night sky is subtle but tangible. I very much prefer the results with the filter installed. I never thought I’d find myself thinking a filter as being essential for astrophotography but I think I’m going to keep using one on all my lenses. It’s cheap, it reduces light pollution, it works. Highly Recommended!

Hoya Red Intensifier Pros:

  • Greatly reduces the effect of light pollution, neutralizes yellow tinge from Sodium lamps
  • Affordable
  • Available in most common filter thread sizes (49mm-77mm)

Hoya Red Intensifier Cons:

  • Does not appear to have any anti-reflective coating
  • No square version available for filter systems
  • Reduces some light transmission

Hoya Red Intensifier Verdict:
Highly Recommended! (4.8/5)

Lonely Speck PureNight

We saw some of the shortcomings of the Hoya Intensifier and the requests by many photographers for a square version of the filter so we decided to make our own light pollution filter called the PureNight. PureNight is stronger in filtration than an intensifier, multi-coated for better anti-reflective properties and is now available in square 85mm, 100mm and 150mm sizes.

Lonely Speck PureNight Light Pollution Reduction Filter

 

Links:

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Thanks so much for being a part of our astrophotography adventure.

-Ian

103 Replies to “Hoya Red Intensifier Review: An Affordable Light Pollution Filter for Astrophotography”

  1. I have been using the 77mm Hoya red enhancer on my Nikon 20mm/1.8 for a month now over in the UK, in my back garden which has a yellow street light nearby. It works really well! The manufacture of didymium filters does seem to have declined since computer-based image processing has become so easy, but I find it really useful to kill the yellow fuzz at the initial stage. They are not sold directly in the UK – the Hoya distributor does not import them – but you can get them from the US.

    I have been struggling to find larger didymium sizes. The Tiffen 95mm seems to have been discontinued and I have been trying to source the Tiffen 4inx4in square to use with the Cokin Z system – I am not sure if one is on the way right now. Singh-Ray have literally just sent me one of their enhancers to try – their web site wording suggests it works slightly differently from the Hoya, but some e-mails confirm it does suppress the yellow, so I am giving it a go on a trial. They also make some low-profile ones that might mitigate possible vignetting on UWA lenses. They do a range of larger round and square sizes, at (for a serious price!)

    http://www.singh-ray.com/shop/lighter-brighter-lb-color-intensifier/

    Anyway, they do a 95mm that will fit on my current 200-500 Nikon, the Zeiss 15/2.8 and the interesting forthcoming IRIX 14/2.4 – I’d be interested to know if other astros have had luck with the Singh-Ray version. They do a range of sizes – it’s a shame the bigger ones are so expensive.

    As far as I know the “LPS” filters use a totally different mechanism which does not work on UWA, but the didymium recipe seems fine, as per Ian’s photos. My Sinbh-Ray is due next week so I will be trying it on the next cloud/moon free night after.

  2. Is the use of this filter at all redundant considering that Lightroom can make adjustments to mimic these same effects? Is it worth it get better looking photos right out of the camera? Thanks!

    1. I think that it’s still very helpful to use the filter, particularly because it seems so specifically targeted towards removing the most problematic colors, something that’s not very easily done in post without affecting other parts of the image. Getting the image as good as possible in camera will usually always yield better final results.

  3. Hi Ian and thanks for the review. I would like to buy this filter, but I’m a bit confused as to which one I should actually get, as there are red, blue, green and other variants of the intensifier. I guess I should get the blue one, but the one that looks pink in the photos is the red one, so I’m not really sure. Can you please clarify?

    1. Interesting… so the red intensifier will filter out the yellows, if I understand correctly.

    2. Alright, I had some Amazon gift certificates to spend, so I ordered a 67mm one for my Samyang 12mm. Bring on those night skies!

    3. Yes, the red intensifier actually filters out the yellowish orange part of the spectrum.

  4. Absolutely wonderful. I’ve learnt a lot from you in terms of best lenses to use for astrophotography, post processing methods and now this! I commend your attitude towards sharing valuable information with others and people hardly do that these days to the level that you do. You are indeed a great man. Thank you!

  5. ian,

    does this work for UWA lenses? what’s d difference between this filter n the LPS filter. it’s a known fact that the LPS filter don’t work well on lenses <35mm.

    1. Yes it seems to work just fine on the 21mm which is considered “super wide”. I think it would work fine on shorter lenses as long as the lens has a filter thread.

  6. Ian,
    Any shots with this filter in a heavily light-polluted setting? Somewhere near a majoy city maybe?
    -Anthony

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