Infra-Edd: infrared

Kolari Vision are a popular choice for IR conversions on many camera types. Their prices are reasonable and they have many wavelengths on offer. Recently they've added an option to have any of these internal filters coated with a special anti-reflective (AR) coating to reduce hot spots. When I heard about this I had to give one a try because a lot of native lenses for the Sony FE cameras (A7 series) suffer from hot spots and many of them quite badly. Normally there is no fix for the hot spot issue because it's due to the lens, but let's put it to the test to see if it's as good as they advertise...

Anti-Reflective coated external filters are nothing new, so it's been possible to use them on a full spectrum conversion for a while. Filters like the 093 MRC, from B+W (an 830nm IR filter) have this coating. You can spot these because instead of being an opaque (black) colour they reflect a blue/purple. The same is true of the Kolari internal filter (see below).

Full spectrum conversion (left) vs the AR coated 720nm conversion from Kolari (right)

The problem with these external filters is that they don't do anything for hot spots. I have tested this on several different types and there is no discernible difference at all. Because of this I was a little dubious as to the effectiveness using a similar trick on the internal filter replacement. Fortunately that concern was very short lived because this internal coating does indeed work. It doesn't completely remove the effect, but it does take it down by 1-2 stops in intensity. What I mean here is that; Let's say a hot spot normally starts to show up on a lens (using a normal internal conversion) at f/8, it will start closer to f/16 on the coated conversion, and that can make all the difference.

Results

Here are some samples, comparing a few different AF lens options for the Sony FE platform. All of these options are known to produce a hot spot to varying degrees. These will be compared between a standard (uncoated) 720nm filter and the Kolari Anti-Reflective Coating conversion. From left to right, these lenses are:

Sony FE 50mm f/1.8
Zeiss Batis 25mm f/2
Sigma 35mm f/1.4 Art (with MC-11 adapter)

Note: In all the below samples Kolari's coated version will be on the right.

Sony FE 50mm f/1.8

▲Uncoated Filter▲ - f/1.8 - ▲Kolari AR Coating▲

▲Uncoated Filter▲ - f/4 - ▲Kolari AR Coating▲

▲Uncoated Filter▲ - f/8- ▲Kolari AR Coating▲

▲Uncoated Filter▲ - f/22 - ▲Kolari AR Coating▲

The IR hot spot on the FE 50mm is not bad at all. It's not as clean as theSony/Zeiss 55mm f/1.8, but then not many lenses are. What little hot spot there is here on the smaller apertures is almost non-existent on Kolari's coated filter. Let's see how it does with a worse performer...

Simga 35mm f/1.4 Art

▲Uncoated Filter▲ - f/1.4 - ▲Kolari AR Coating▲

▲Uncoated Filter▲ - f/2 - ▲Kolari AR Coating▲

▲Uncoated Filter▲ - f/4 - ▲Kolari AR Coating▲

▲Uncoated Filter▲ - f/8 - ▲Kolari AR Coating▲

▲Uncoated Filter▲ - f/16 - ▲Kolari AR Coating▲

The difference here, between the standard and coated filter is much more noticeable. The difference at f/8 being the stand-out one for me. This lens really starts to get annoying at f/8 on a normal filter, whereas the coated version is considerably better.

Zeiss Batis 25mm f/2

▲Uncoated Filter▲ - f/2 - ▲Kolari AR Coating▲

▲Uncoated Filter▲ - f/4 - ▲Kolari AR Coating▲

▲Uncoated Filter▲ - f/8 - ▲Kolari AR Coating▲

▲Uncoated Filter▲ - f/22 - ▲Kolari AR Coating▲

Some lenses provide terrible results when stopped down and this is frustrating true of native wide Sony Lenses. Although the coatings clearly help, it won't be enough to save the day in these extreme cases. It'a worth noting that 720nm is also pretty forgiving. The hot spot will be intensified with the stronger wavelengths like 830nm or higher.

At 720nm the Batis lens is generally acceptable at f/4, when using Kolari's coated conversion. With a standard 720nm filter the chances of getting usable results on the same lens and settings are heavily against you, producing a large amount of failures. This is where the coated option shows it's true value in my opinion. Common middle apertures see improvements that often make the difference between a good image and a bad one.

Vignetting

You may have noticed that there is significantly more vignetting on the normal filter. In some small part this may be due to the improved hot spot, but there is another big reason why this is happening. As well as the AR coating this conversion is also using a special 'thin' filter. This has the effect of greatly reducing vignetting on the Sony A7 due to the normal filter cluster having very thick glass on the filter. You can read more about that here. This service can be applied to normal Sony A7 series cameras as well as full spectrum or IR conversions. I'm so impressed by this that I want to have it done to all of my A7 cameras and I will if I can.

Summary

I don't really need to write much here as the pictures speak for themselves. Kolari's 'anti reflective' coating is doing a great job in my opinion. It's not going to fix any lenses hot spots entierly, but it will help and can make the difference of certain apertures being acceptable or not. I wouldn't necessarily suggest upgrading your current conversion for this, but that's totally up to you how much you're affected by this problem and that will depend on what lenses you're using. However, if you're thinking about getting a camera converted then I highly recommend going for this.

Future Tests

I will continue to post results comparing lenses on these two cameras. next up will be the Sony/Zeiss 35/2.8, this was another bad performer and could become not too bad with the Kolari camera. I want to do more testing on the Sony/Zeiss 55/1.8 because although that lens doesn't suffer from hot spot it did suffer from some issues with external filter, which I assume would be gone here. I'm also curious whether the thin filter on the Kolari conversion would adversely affect corner sharpness, so all those tests will be coming soon...

I've wanted to visit Switzerland for as long as I can remember. Last month I got to explore it pretty thoroughly for more than a week, by train. Since I've been back I don't think a day has passed without me thinking about some aspect of this journey, so it's safe to say that it left quite an impression. I took the full spectrum camera with various filters (ranging from colour to 830nm), so I have a bunch of IR photos to share here today. Actually this has been hard to edit down, so this will be a pretty photo heavy post. I want to post them all now and not write too much, but that doesn't seem right, so I will spend a little time on the words, to give a little story behind each batch.

So this was how it all began - We took the Thameslink to St. Pancras at around 6:30am. Here's a shot of the Eurostar, ready to depart for Paris. Ours was the newer model on the right, which apparently is capable of a higher top speed. It seemed more comfy than the old one we went to Paris on last time.

This trip spanned 8 days in total and involved travelling entirely on trains. In fact we would be on a train nearly every day (except one). We did this because we wanted to see as much of Switzerland as possible. Here's a list of the train changes we made for the whole trip:

Day 1: London - Paris - Geneva - Montreux
Day 2: Montreux - Lucerne - Bern
Day 3: -
Day 4: Bern - Brig - Visp - Zermatt
Day 5: Zermatt - St. Moritz
Day 6: St. Moritz - Tirano - Chur
Day 7: Chur - Zurich
Day 8: Zurich - Basel - Cologne - Brussels - London

Note: Each letter is a place we stayed over night

This involved three scenic trains - The Golden Pass, The Glacier Express and The Bernina Express. The above places don't count any intermediate stops during any of the train trips. The longest single train journey was the Glacier Express (green), which took around 8 hours.

The Eurostar was the only train that we had any significant delay on. It was due to being held before the tunnel (which is extremely common these days). This meant that we missed our connection in Paris by one minute and we then lost three hours of our exploring time in Montreux. A big shame because it would have been a thousand times nicer than a skanky Paris station! :(. Swiss trains were faultless throughout and although we didn't use them as much, so were the French and German trains.

Not too far into Switzerland we got some epic views of this impressive bit of engineering. This double decked road network curved around the mountain for several killiometers. I struggled to eliminate window reflections on most of the shots, but I'm glad I tried.

Montreux

Once here we were quite tired of being sat on trains for so long (and stuck in Paris), so we wandered around the station for a few minutes. Took some photos and worked out where our train would leave from the next day, before moving on to our hotel. At this point it was just starting to rain, but Montreux still looked amazingly pretty!

I took three different wavelength filters with me. Here's a list and roughly how much each got used:

590nm - 25%
720nm - 15%
830nm - 40%

I also took three lenses, but only used the Zeiss FE 55mm f/1.8 was used for infrared. I used the Canon FD 85mm f/1.2 for the last 20% of colour shots and unfortunately didn't touch the Sony FE 28mm lens once.

This was the fast train that we came from Geneva on (below). It was pretty fast and was the only Swiss train that tilts, which was pretty noticeable as we often couldn't see the horizon when curving around parts of Lake Geneva.

The next morning, after a nice breakfast in the hotel, we wandered around the edge of the lake for an hour or so before going back to the station to catch the first of our scenic trains. It was still drizzling a bit and very cloudy, but you could still get a hint of how epic this location was:

The Golden Pass (Scenic Train)

This was train that would take us on the first leg (of three). It was very spacious and not that busy, so we had plenty of room for moving around to take photos. It goes on the rack very soon after leaving Montreux because it climbs very steeply. Within 25-30 mins it was in the snow, even at this time of year (May 1st).

I quickly switched from the 830nm filter to the 590nm so that I could get some colour separation and show off the snow. With b&w IR I was worried you wouldn't see it because it would have been white grass next to white snow.

The lovely wife. Using the Sony A7 mkII, Sigma 35mm f/1.4 Art lens, with MC-11 adapter. I like the way that the metal parts on the camera pick up the infrared colour. She was having some trouble with the focusing speed in these conditions. Unfortunately the Sigma combo is really no quicker than a Canon lens on this camera.

Zweisimmen

This was our first stop on the Bernina Express. This route has three sections, so two stops. This is mainly for the change in train gauge, although I think they will simplify this at some point by having trains that can dynamically change (impressive). Unfortunately it means that you have to pay for reservations three times as well and the amount doesn't seem to be much less. The reservations are not that expensive, but this is on top of the Swiss travel pass, which was about 363 Swiss Francs each for 8 days. If you compare that to commuting costs into London it doesn't seem that bad and don't get me started on the quality and reliability comparisons between the two o.0.

Luzerne

We stayed at for about 3 hours until moving on to Bern. We used this time for a dinner break and a mini photo walk. Still raining...

Bern

This was the only day that we didn't go on any trains. We were lucky enough to stay in an old flat just to the left of this cathedral, which my wife found on Air BnB. It was so nice to stay in a real apartment after the rather average hotel in Montreux, the night before! This is where the sun started to come out, so I switched back to pure IR (830nm) for a bit.

Walking up to the Rossen Garden, in Bern. A beautiful place to look over the old city. The higher we go the more the sun came out too.

Friendly ducks.

Leaving Bern on day four was hard. We were having such a relaxing time and knew that it was non-stop from this point forward. What we didn't know however, was that it was all up-hill from here. Not only did we get physically a lot higher up after this point, but everything kept getting better and better and that's not to say that Montreux or Bern were bad in any way.

Once again I switched to the colour IR filter (590nm) so that the snow areas would be more noticeable. Looking down into these valleys was simply breathtaking. The most difficult thing was taking photos here. We know that we were getting a lot of window reflections and motion blur, so we probably wouldn't want to keep many or any of the shots we felt compelled to take. We often said to each other that we should probably give up and just take in the views. Looking back on the more successful photos I'm kind of glad we didn't.

Brig

Stopping at Brig to change trains, towards Zermatt, although we also had to change at Visp. Although Brig has about 10 platforms inside a building there were four platforms outside in the street and these were the one's we needed. This was looking away from Visp, towards St. Moritz.

This image was looking in the direction we were headed.

This was the train from Visp to Zermatt. A super impressive run up the mountain takes you nearly up to the Matterhorn. This was quite a climb, so again the train used a rack to pull up to just over 1600m.

After a few shots using the pure IR filter out of the window I realised that the camera was really struggling with shutter speed at base ISO. When I realised that I could pull the window down to take photos I realised what the problem was - the windows actually block IR (not just darken).

Zermatt

Zermatt may be mountain to mountain hotels, shops & bars, but you'll never care about its cheesy side when you see the Matterhorn from the bridge on Kirchstrasse.

I still can't believe this was the view from our hotel room balcony. I got up around 5:30 and stuck my head out of the door to see what the Matterhorn looked like, but it was covered in clouds. About 10 minutes later it looked like this 0.o

After breakfast at the hotel, we made our way to the train station, passing the bridge view again. We were so lucky to get a super clean sky, so I took a panorama with the 55mm lens. This was about 10-12 shots, maybe equivalent to about 20mm.

The Glacier Express - As good as the hype!

It seems a shame to backtrack on a trip like this, but there are no other train routes out of Zermatt (and no roads at all). There are certainly worse places to see twice :P. The next few images are from just passed Brig, so at this point it was all new to us.

These great views were thanks to our carriage being the last one in the train. The door that would have connected through to another carriage was just a big sheet of glass so it was really easy to get nice clean photos. It was a bit disconcerting pulling up the hill here as it felt like I could have fallen out on to the tracks at times being so steep. You can see the rack in the middle of the track here.