TEST – Kenko Night Focus
TEST - Kenko Night Focus
Test Kenko Night Focus
For the last three months, I have been able to test the brand new Kenko Night Focus. This equipment has been specifically created to help astrophotographers focus on the night sky, for nightscapes as well as for deepsky images.
It comes in one size, 82mm but can be easily mounted on lots of lenses using the proper adapter. I have been using it with no difficulties on my Tokina Opera 50mm 1.4 which has a 72mm screw size on the front of the lens.
To reach its purpose, this filter is using a technology called « Bahtinov mask« , which was invented in the early 2000s by russian astronomer Pavel Bahtinov, but intended for telescopes in the first place.
That being said, the teams at Kenko had to find a way to use this technology on a filter and managed to print its patterns on the glass in a way that allows light transmission but still generates three stripes astrophotographers will use to focus.
Even if the technology behind this filter is quite advanced, the result is an equipment that is very easy to use. You would not need any in-depth knowledge to be able to precisely focus on the sky with it.
Let’s now test Kenko Night Focus and check on what this filter can do for us, astrophotographers.
Test Kenko Night focus : on the field
To get the best out of this filter, the manufacturer recommends to use a lens between 18 and 75mm, 24-70mm being particularly good. For my part, I have tried it either on my Tokina Opera 50mm 1.4 and on a 24-70mm. Both happened to work out perfectly.
Moreover, you should wait until astronomical twilight so your view of the stars would be ideal. An app like Stellarium can be of great help to program your night photography sessions and optimize the results.
Even though I always recommend to get away from light pollution sources such as cities, you can make your first tests right next to your door. Even in difficult conditions, I have found the filter to be very effective. Actually, I think it is even when the conditions are the hardest that it helps the most (light pollution, slight veil, etc.).
Also, it can be used to focus on the stars, but I found it pretty effective on any light source, from the Moon to the light of my smart telescope (see the carousel below) or even cities.
Using the Kenko Night Focus is an easy four steps method :
- 1) First, put the filter on the lens, without screwing to hard to it, because you will have to take it off later.
- 2) Find a bright star using the live-view of your camera and center it
- 3) Turn the filter until three concentric stripes appear on the star. Then you are focused correctly
- 4) Take the filter off and be careful not to touch the focus ring at any time or you would have to go back to step 3.
- The first time, you might be struggling a little to get that perfect focus but within few tries, you will easily get a sharp image.
It might seem a bit binding at first to be putting on and off a filter just to focus, but trust me, the quality improvement you get from using it is worth it. Now that I have been using it for a few months, I don’t even think about it anymore. It has become an automatism.
Test Kenko Night Focus
Right above, you can see the pattern printed on the filter. This is how the fitler generates these stripes you will use to get a precise focusing.
Conclusion
I think this filter is a perfect addition for any type of night shooter. From astrophotographers to cityscapes photographers, it will prove very useful to get a perfect focus on what really matters in your image. The fourth picture in the carousel below is an image I took using Kenko Night Focus to properly focus on the smart telescope, which is pretty hard when the night is really dark. I found it helpful in situations where you work in dark conditions, even if it is not related to astrophotography at all.
I have used it to get pictures of stars (obviously) and Northern Lights and when I got used to it, I felt like I was actually gaining time using it to focus instead of using the live-view the classic way. Also, the error margin gets really tiny with it as the stripes that appear on the bright subject you use to focus are pretty clear : you either are focused or you are not. There is no space for misinterpretation.
I would solely recommend to be careful if you are using other filters. You can put the Night Focus on another filter but I would not recommend it, as you might unscrew the other one as well while taking it off. I personally use the Hoya Starscape a lot and I prefer to put it on my lens after I have focused and taken Night Focus off.
But of course, as the filter has been given to me for free by the brand, you might wonder wether my opinion is influenced in order to drive you to their products, and you are right to question this point. Nowadays, lots of partnerships rely on testers getting free equipment and trading it for good reviews. In some domains (sports equipment for example), it is not rare for the brand to send to the journalist the exact text they expect her/him to publish in the magazine.
So, where does my partnership with Kenko stands here ? Well, I am glad to say that we are not working this way. Even though the brand obviously appreciate good reviews, they do not ask me for anything in particular (apart from pictures of the filter and taken with it, which seems pretty fair) and most certainly don’t try to influence my reviews. I have a partnership with Kenko because I like the equipment they provide. There are brands I would not work with, even if they gave my thousand of euros worth of equipment.
PROS
Adapts to several type of lenses
Possibility to use an adapter for lenses with front smaller than 82mm
Helps focus on any bright subject at night, not only stars
CONS
You have to keep in mind to take the filter off before shooting
Be careful not to unscrew both when another filter is on the lens too
Test Kenko Night Focus
These four images below have been taken using Kenko Night Focus for focusing on either the stars (pictures 1 and 2), Venus (picture 3) or the light of the smart telescope (picture 4). The first three pictures are a 100% crop of the original image, which shows the accuracy of the focusing and the sharpness of the planets and stars. I did not see any difference or experienced difficulties focusing at 24mm, 50mm or 70mm.
