This first article will be rather short, but I have to split the whole “against bright light” into several parts.
What are starbursts?
Starbursts, also known as sun stars, star effects or sun flares, are the result of diffraction on the small aperture opening causing a point source of light to adapt a specific shape (See this article on b&h photo for more information.).
Of course, this effect also occurs with street lights and the like, as you can see in this example:
How can you get this effect?
Anyone who has ever read a lens review on lenstip and co. will have stumbled upon the term “diffraction”. It’s commonly used with the resolution of a lens dropping after a certain aperture value. As I mentioned above, the diffraction is caused by the light being “bent” at the aperture blades which causes a fine details to appear smudged. But this also causes the starburst effect.
You often need a small aperture (f/13 and smaller), a bright point source of light and that’s about it.
This link also provides some useful tips.
What role does the shape of the aperture play?
The more aperture blades you have, the more spikes the star will show. However, if the aperture consists of an uneven number of blades, you get even more (twice the number of blades) spikes in your stars.
- a 6-bladed aperture will cause stars with 6 spikes
- a 7-bladed aperture will cause 14 spikes
- an aperture with 8 blades will cause 8 spikes
Keep in mind, that rounded aperture blades are great for Bokeh highlights and smooth background blur, but they won’t allow for beautiful starbursts.
How did I compare my lenses?
I set up a black background with my Jansjö LED lamp from IKEA in front of it.
The lamp was placed in the upper right border area to be able to also have a glimpse at the lenses handling of flaring when stopped down.
All lenses were shot at f/16.
You can quickly judge the number of aperture blades on most lenses. The handling of starbursts is yet another reason for me not to like the dreaded 6-bladed apertures.
A quick explanation:
the coloured blobs (or hexagons, octagons, etc.) are caused by internal reflections. These are being kept in check with advanced lens coatings and usually multi-coated lenses handle that issue much better.
The lower the contrast (the less black the background appears) the more the lens flares. This is caused by the glass itself.
Notice the supremely beautiful starburst created by the 9-bladed aperture in the Nikkor 50mm f/1.2 Ai-s, but also the 14-pointed stars from the Nikkor 50mm f/1.4 Ai and the Yongnuo, both handling the flares pretty well.
The Helios has 8 aperture blades, but there seems to be something wrong. Looking at the stars from the Pancolar and the Takumar – both with 8-bladed apertures too – the Helios seems a little “off”. On the other hand, the massive flares created by reflections of the aperture show that the aperture is perfectly shaped as an octagon. The reflections also show the poor quality of the coatings.
The Olympus seems to have a problem with the aperture blades. In my overview article I already mentioned that the lens has no aperture stops anymore, because a ball bearing got lost with a previous owner (I suppose). He obviously also messed up the aperture blades of the lens. It also shows how poor the coating is, because the flaring is even worse than with the Helios.
The Takumar handles flaring pretty well, better even than the Zeiss Planar T* 50mm f/1.4. The Pancolar and the Tessar both show a weird texturized glowing pattern of flare. I haven’t been able to identify the cause for that yet.
From the 6-bladed lenses, the Color-Ultron looks best in my opinion. Very clean and contrasty, despite the slight halo around the stars center. The Rikenon fares quite well regarding flares, but it suffers from several bright reflections of the aperture (single-coated again). The Planar isn’t quite capable of the same clean star shape as the Color-Ultron, but it is superior to the two Fujinon lenses.
It can be clearly seen how the EBC coatings helped against the nasty internal reflections, but both Fujinon lenses aren’t that great compared to the rest of the field.
The Tessar only has 5 aperture blades, which is terrible in regards to OOF highlights, but it beats both the 6-bladed and 8-bladed apertures, because it causes stars with 10 spikes. Unfortunately, the coatings are so poor that the star almost vanishes among all the flaring.
The Yongnuo shows that the modern coatings are superior to all the hyped stuff from the past, at least in this test.
Keep in mind that you won’t get that much flaring if you have a light source that is further away/less intense or partially covered (works especially well with the sun).
Here’s an example with the Helios 44 and the sun partially covered by tree branches (with basically no flares at all).
If someone has an explanation for the weird flaring pattern on the Pancolar, I would be really happy to hear it.