I recently acquired the Star Soft filter by Nisi. Designed specifically for astrophotography, what is the Star Soft filter? And could it help take your astrophotography to the next level?
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In Nisi’s own words, the Star Soft helps create a ‘dreamy nightscape with every shot’. That certainly sounds great, but what is it, what does it do, and does it work as expected? I decided to take the filter out on an astrophotography session and give it some tests. Make sure to read to the end, as there’s a special bonus featuring the Star Soft filter.
I was made aware of this whole concept by the KASE Starglow filter, made in collaboration with maybe astrophotography’s best known figure, Alyn Wallace. However, as far as I can see KASE have stopped making their Starglow filter, at least for the time being. Thus, after a little bit of searching for something similar, I discovered the Star Soft filter. As far as I can tell, it does pretty much the same thing.
Features of the Star Soft Filter
- Lens Grade Optical Glass
- Available in 100 x 150mm, or 150 x 170mm versions
- Water repellent coating on both sides
- Graduated filter with no effect being present on bottom third of the filter
After doing some digging on Nisi’s website, it seems the technical details of how the effect is achieved, i.e., what properties the glass has, are a closely guarded secret.
So, what does a ‘dreamy nightscape with every shot’ mean in practical terms? TheSTar Glow no intended use outside of astrophotography. The filter has the effect of accentuating the brighter stars in an image, whilst diminishing the effect of the dimmer, ‘background’ stars. The resulting effect is a ‘bloating’ of the most prominent stars in the sky. This in turn will lead to constellations (which are of course comprised from the brightest stars in the sky) popping out.
At the same time, the overall number of stars will be reduced, and the dimmest stars will become altogether invisible. But why would we want this? As astrophotographers, we got to great lengths to acquire the best camera equipment we can, as well as learn the techniques, to capture as many stars as possible.
Can There Be Too Many Stars in a Night Sky Photo?
I was simply thrilled at the sheer quantity of stars I was able to capture in my images when I began my journey as an astrophotographer. Potentially millions of stars might be present in a single image. Great, I thought. The more stars the better!
But as I progressed, and I suppose particularly when looking at the work of many world-class astrophotographers, I began to observe that these photographers often didn’t go for an emphasis on star quantity alone. As always, quality surpasses quantity. Particularly if you are looking to showcase constellations or the milky way in your images, too many stars may be a bad thing. The best way to illustrate this is with some photographs.
The first example is a milky way nightscape shot I took in west Cornwall, where I am based. The location is an obscure gully, known maybe only by rock climbers (which includes myself) and is called Ash Can Gully. It’s at Gwennap Head, a few miles south of Land’s End in the far west of Cornwall.
The gully has some great rock architecture, hewn out of the Cornish granite. It also lines up perfectly with the galactic core of the milky way on late summer. If we look closely, we can see just the sheer quantity of stars in the image. Try and count them! It would be nigh on impossible. Are there too many?
At the end of the day, it’s a matter of taste. The Star Soft filter is merely a tool you can use to achieve a certain effect. After reading this blog, you’ll be well-informed to decide whether you want to add it to your own astrophotography tool kit.
What Happened to the Constellations?
In the next example, we can see how a traditional, unfiltered approach to astrophotography can be very detrimental to the constellations that may be present in the sky you’re imaging. I took this image in the winter at the gorgeous beach of Gwynver in west Cornwall. The lights in the background are from the small village of Sennen Cove, situated just a mile from Land’s End.
So, here we have a winter milky way image. It also includes the winter circle, or winter hexagon asterism, and its associated constellations. Of course, the most distinctive and well-known of these is Orion, taking centre stage in this picture.
Alas, as a result of the fainter stars being so exposed, the bright stars and usually recognisable constellations are paling into insignificance. Yes, the brightest stars of the winter circle are still discernible, and anyone with a reasonable knowledge of the night sky will make out Orion, at least. But beyond that, the brighter stars and constellations are being lost in the multitude of stars present in the image.
This may be of particular interest for a winter night sky image. Due to the absence of the milky way core, and the relative faintness of the winter milky way, showcasing the various constellations that populate the winter sky can be a very productive way to spend those clear, crisp, winter nights. However, all that effort could be for nothing if your constellations fail to pop out of your final image.
The Problem with Milky Way Panoramas
This problem will only be exacerbated further if you are creating multi-panel panoramas of the night sky. Again, this is a good option when the galactic core is absent. Huge vistas with a relatively low-angled milky way arcing across make wonderful images.
But due to this greatly enhanced field of view, the bright stars and constellations will become smaller, and thus harder and harder to make pop out in your image.
The following image is a 24-panel panorama (3 rows, each of 8 images). It shows off the winter milky way arcing across Drift Reservoir, which lies just outside of Penzance in west Cornwall. Taken on a rare windless night (very rare for Cornwall!), I always try and shoot over water if I can on such a night, as who doesn’t find the effect of stars and nebulosity reflected in water?
Hopefully this image serves to illustrate my point. As the field of view is increased, those constellations and asterisms, so obvious to the naked eye, become all but impossible make out. Orion is just about discernible, but as for others, such as Cassiopeia, Taurus, or Auriga, to pick a few at random…well, there’s no chance.
Testing The Nisi Star Soft Filter
So, having made a case for why we might want a tool such as the Nisi Star Soft filter in our camera bag, does it actually do what it claims to do?
I headed out on a clear night in January to find out. It must be said at this point, that the last six months have been truly dreadful for astrophotography in Cornwall, with only a few clear night in that whole time. It seems that the problem hasn’t been limited to Cornwall. The general mood in groups across social media suggests that much of the northern hemisphere has been unreasonably cloudy throughout this time. Let’s hope that spring brings with it a well-deserved run of clear skies.
Right, to business. I set off to run some tests with the Star Soft filter. The plan was to take some shots both without and then with the Star Soft filter. I would use the same camera settings for each shot. Afterwards, in post, I would then apply identical edits to them in Lightroom. Hopefully with this approach, I would be able to make as good a comparison as possible.
I decided to head to a well-known beauty spot, and one of Cornwall’s oldest tourist attractions, the Crowns Mine Engine Houses at Botallack in west Cornwall. These iconic buildings have drawn visitors from far and wide due to their unlikely position, right at the cliff’s edge, and only just above the sea. Indeed, these things take a hammering during winter storms. But they’re still standing strong, after hundreds of years.
They have been photographed to death, but my plan was to shoot from behind the engine houses. Due to its precarious access, they are seldom seen from this angle. Moreover, shooting from this direction meant that Orion and the winter circle would be perfectly in frame. The perfect test for the Star Soft filter.
My Astrophotography Camera Gear
All of the following shots were taken with my Sony A7iii. Despite being released back in 2018, it still remains an incredibly capable camera for its price point. I would highly recommend it for photography in general, but it seems that Sony gear handles itself very well for landscape astrophotography.
Two minor grumbles for me are: Firstly, the lack of a flip-screen does irk me on a regular basis. Secondly, in my experience, the autofocus doesn’t work too well with fast-moving subjects, therefore I wouldn’t recommend this camera for wildlife or sports photography. Apart from that, it really does everything I want.
The lens I used for this experiment was my trusty landscape astrophotography workhorse. That is the Sony 14mm f1.8 GM lens. This lens is a low-light beast. Obviously, with its ultra-wide focal length, you can fit stacks of sky in your image, and whether you’re using it at night or in good, daylit conditions, I find the lens to be impeccably sharp.
However, read on to find something I discovered with this lens only after using it wit the Star Soft filter.
Star Soft Filter Test 1
First off, I wanted to take a simple, single image for the most bare-bones comparison possible. I took some test shots with an ISO of 20000 so I could quickly find a foreground composition in the dark, and then began shooting. The settings I used were fairly typical for astrophotography. I stopped down only a little, to f2.2, and set the ISO to 1600.
I have no tolerance whatsoever for star trailing, so my standard shutter length for untracked Astro shots is 8 seconds. The performance of the Sony 14mm f1.8 GM lens adequately compensates for this relatively short exposure time.
After taking a shot without the Star Soft filter, it was a simply procedure to install the filter and press the shutter to take another shot. So, part one of the experiment was completed as simply as that.
Here are the images. The first image was taken without the Star Soft Filter; the second image was taken with the Star Soft filter.
I’m sure you can see, the difference between the two images is striking.
Analysis With and Without the Star Soft Filter
Image 1: Probably due to atmospheric conditions on the night, Orion is particularly faint. The Orion Nebula shows up quite well, but even Orion’s belt is only just visible. If my intention was to showcase Orion in this image, this would not have made the cut.
Apart from Orion, only the heads of Gemini, Castor and Pollux, really seem to be standing out. No other stars or constellations are standing out from the background seas of stars.
Image 2: To my eye, this reveals a much more pleasing balance in the amount and size of stars in the image. Orion is now very obvious, and I’m sure a lay person would have no problem identifying him. I don’t know if it’s just me, but I daresay the faint arm of the milky way next to Orion is vaguely more discernible too?
Winter Milky Way
In all the photos I took that night, the milky way barely comes through. This is probably a result of atmospheric conditions, and I guess it wasn’t as clear as it maybe looked to the naked eye.
What’s also very noticeable is the much richer colour in the stars. In the first image, all the stars come across as white, more or less. In the second image, it’s much clearly to see the whole range of star colours, from white, yellow, and orange, all the way to beautiful blue.
Finally, the Star Soft filter revealed something about my Sony 14mm lens that I’d never noticed before. Due to the accentuated size of the brighter stars, it’s very apparent that the stars towards the edge of the frame are suffering from quite sever star distortion.
Up until this point, I had always thought my ultra-wide lens performed very well in this respect, even wide open at f1.8. With unfiltered, and therefore smaller stars, I had never really noticed this phenomenon.
This is certainly something to be aware of when using this filter. But there should hopefully be a simple solution. Most schools of thought would encourage the stopping down of the lens a little to combat this effect. So, next time I use the filter, I’ll stop down to f2.8 and see what results that brings.
Don’t Forget A Filter Holder
Note that, the filter does require the use of a filter holder, and no round, screen-in versions of the Star Soft filter are available. Unfortunately, the Sony 14mm f1.8 doesn’t take a screen-in filter adapter, so a bespoke filter holder is needed for this lens. Luckily Nisi come to the rescue once again, with a filter designed specifically for the Sony 14mm f1.8 GM.
For all of my other lenses, I use the Nisi V5 Pro filter holder kit. The Nisi V6 and V7 filter holder systems have now superseded the V5. Make you get a kit that comes with the stepper rings. That way, one filter holder should work with all of your lenses (apart from awkward models like the Sony 14mm f1.8 GM!)
Star Soft Filter Test 2
Normal practice in astrophotography is to take multiple images and stack them in post-processing to reduce the inevitable noise that arises from shooting at the higher ISOs needed when shooting at night.
I was curious to see, what effect, if any, the Star Soft filter would have on a stacked image. Maybe it would have none, and as the single images that comprise the stack will be the same as in the first test, it would only be in post that these effects would potentially become apparent.
Therefore, with the same things as before, I set my Sony A7iii’s built-in intervalometer to take 20 shots, with the filter removed. I’d then add the filter and take another bracket of 20 shots. As a final step, I’d put the lens cap on and take 6 dark frames, which is usually sufficient for a wide-angle landscape Astro shot.
For stacking, I use Sequator. Sequator is a free software that does everything you need it to do for a landscape astrophotography shot. It’s very easy to use, and there is a tonne of useful tutorials on YouTube to help you get up and running with it. In addition, it’s fast. Similar processes in Adobe Photoshop take significantly longer to perform.
As well as using it to reduce noise in your sky images, I also frequently use it to clean up my separate foreground shots. As long as you select the sky, a requirement of the software, it will clean up your stacked foreground shots. Don’t forget to take some foregrounds darks as well!
Results of the Second Star Soft Filter Test
Here are the stacked images with, once again, the unfiltered image on the left, and the filtered image on the right.
It has to be said, that there is no discernible difference in terms of filter effect between the single and unstacked image. This is not at all surprising. But if you don’t try, you’ll never know, right? However, as ever, the stacked image is superior due to its reduced noise levels.
Star Soft Filter with a Star Tracker?
It’s going to have to wait until another night to perform another crucial test. That test is how to Star Soft filter performs when used with a star tracker. I’m particularly excited to try this once the galactic core starts to make a re-appearance. At the time of writing, this is about now, so once the waxing moon has passed, that’s what I’ll be doing.
The photos from the test above indicate that the use of the filter not only increases the brighter stars, but possibly nebulosity too. This will obviously be fantastic for shots of the milky way core, but another experiment will be on some telephoto astrophotography too. For example, what results would one get shooting the Orion nebula with the Star Soft filter?
Only an unusual number of clear nights in Cornwall give me the chance to find out!
Another reason to get excited about the use of the Star Soft filter with an equatorial mount is hopefully an increase in the effect we’ve already seen. That is the much greater development of star colours. The main reason for using a tracker is to get ricker detail and colour in your astrophotography shots. Therefore, with increased exposure times, and a corresponding reduction in ISO, I’m sure the colour-development of the stars captured will be amazing.
The Crown Mines and Orion
As well as doing the experiments described above, I also wanted to get a final image form the night that I could share. Throughout the test, Orion was in the frame, but compositionally not in the best place.
Situating Orion in the top right of the frame would be the prefect counter to the two engine houses in the foreground. And, of course, I’d want a bit more than total blackness for the foreground.
Happily, I only had to wait a relatively short time before Orion would track across the sky and be in the perfect position for my desired composition. My foreground shots came next. I took total of 4 shots at approximately 200 seconds each, as well as one dark frame to assist with the stacking that would come in post-processing.
I simply whiled away the remaining time before Orion was in position, enjoying the peace and quiet of this location at night. (Isn’t that one of the best things about astrophotography?) I was also playing around on the Stellarium app on my phone, increasing my knowledge of the night sky all the while.
Then it was simply a case of another 20 lights, with the Star Soft filter. And, of course, and another 6 darks, before heading home.
360° Astro Panorama with the Northern Lights, Milky Way!?!?
Stop the press! Before finishing this blog I got the chance to take the Star Soft filter out for another very special night sky photography event. At the end of February 2023, strong geomagnetic storms resulted in intense displays of the aurorae across the world. The northern and southern lights put on magnificent shows in the polar regions. This activity extended much farther south than usual. Places such as northern France and Colorado, USA produced stunning photos of the aurorae.
Cornwall too, also got to witness this rare event. It was in 2015 that southern England last witnessed the northern lights. As luck would have it, Cornwall got a rare (for this winter) break in the clouds for the nights that the geomagnetic storms occurred. Also at this time, the galactic core of the milky way had just started to reappear in the early morning sky.
I had a dilemma. Whilst likely to occur, a strong showing of the northern lights at 50°N was far from certain. Did I want to spend the night putting my eggs all in one basket and face north in the hope of catching the aurora? Or did I want to face south and get a guaranteed image of the galactic core, yet miss an extremely rare event?
Was there any way I could do both? Indeed, was there a way to capture both the northern lights and the milky way in the same image?
The answer, of course, was to shoot a panorama. I have done many astrophotography panoramas before. However, they typically still only took in half of the sky. Usually enough to capture an entire milky way arch. This was not a time to be shrinking violet. On the contrary, this was a time to think big. Thus I decided to embark on a epic 360° spherical panorama.
The location I chose was one that would simply maximise the amount of sky in the image. A hilltop with panoramic views of west Cornwall was the order of the night. The hill I chose was Chapel Carn Brea, a prominent hill in wet Cornwall, just a few miles from Land’s End and Sennen, the village where I grew up.
I’ll save the lengthy process that goes into both capturing the images and editing them for another blog. But what’s relevant is that I used the Star Soft filter for all of the sky shots that comprised the image. I removed the filter for the foreground shots, as the Star Soft effect is not desirable fore the non-sky sections of your images.
Here is the image. Make sure you open it in full screen and use the 360° viewer to scan around and see the night sky in full. The green glow across the northern side of the sky is the aurora. And counter-balancing the northern lights on the other side of the sky is a full milky way arch, complete with the galactic core just above the horizon.
Would I Recommend the Nisi Star Soft Filter?
Definitely! The Star Soft filter gave very impressive results. I think the filter ‘tames’ the image and does exactly what it claims to. As mentioned above, I’m looking forward to using it in a variety of applications going forward. However, I think I’ll try where possible to take shots with and without the filter. You never know when a good ‘old-fashioned’ star fest may be just what the doctor ordered!
The Star Soft filter is a graduated filter, and one third of the filter has no effect whatsoever. As the Star Soft effect will affect your foreground, this does give you the option to place the filter so the effect begins at the horizon line.
There are some obvious problems with this. Firstly, looking at the filter, it’s not obvious, even in daylight, where the effect stops and starts. Good luck arranging that in the dark! Secondly, unless you have a perfectly straight horizon, this will be some kind of compromise. For me, I always take separate foreground shots, so I don’t anticipate having to deal with these issues.
If you’d like to grab yourself a Star Soft filter, go here.