The followig article is a guest post by Murok Marci
The following lenses will be shown
Porst Color Reflex PK 50mm f1,2
This question splits up the photographic community in several groups. Overall you can say that bokeh is the not sharp area of a photo. For some photographers “good” bokeh is when the unsharp area is smooth and calm. Others love it when the bokeh is swirly (Helios 50mm f2) or bubbly (Meyer Optik Görlitz Trioplan 50).
Bokeh is created when light sources are out of the focus area of the lens. These light sources dont create a sharp spot on the sensor plane. They create a blurry spot shaped like the blur circle of the lens.
As you can see in this illustration the light from source A creates a huge spot because its in the out of focus area. Source C has the same phenomenom. Only light source B creates a sharp spot on the sensor.
If you open the aperture of your lens as wide as you can, the sharp area gets smaller and its easier to get bokeh in the background.
The shape of the bokeh is dependent to the shape of the lenses aperture. Lenses with a huge number of aperture blades like the Meyer Optik Görlitz Trioplan 50 create almost round bokeh bubbles.
Lenses with five blades in the aperture create a pentagonal like bokeh.
Thank you Ian Chattam for the example.
A different bokeh effect is the swirly bokeh of the Helios 44-M4 lens. It swirls the out of focus area around the center of the image.
In the end you cant say what bokeh is the best or perfect. It depends on what you want to create and what you personally like. Beauty is in the eye of the beholder.
Today I took some test shots to compare the Zeiss Flektogon 20mm f2.8 and the Zeiss Flektogon 20mm f4.
Both of these old vintage lenses have the m42 mount and can be adapted to every modern camera (Sony, Canon, Nikon, Pentax, Fuji etc.). The M42 mount is the best to adapt.
The design of both lenses is almost indestructible. They are completely made from metal and glas.
When it comes to the price, the f4 version (160€ at ebay.de) is about 100€ cheaper than the f2.8 version.
When you compare the optical quality of the lenses, you soon realise that the Carl Zeiss Flektogon f2.8 is the better lens.
click the image to enlarge it
The Flektogon f2.8 is sharper even wide open at f2,8 compared to the f4 version at f4.
This better sharpness continues through all apertures.
The vignetting is almost the same when you compare f2.8 with f4. But when you stop down the f2.8 version to f4 its almsot gone.
The sharpness in the corners and with subjects far away, the Flektogon 20mm f2.8 is better wide open compared to the f4 version. From f8 there are no significant differences between the both. At f16 the f4 version is almost a little bit sharper.
click the image to enlarge it
Last but not least a comaprison of the “star” both lenses create.
Its hard to tell which of these two lenses is the better one. In my opinion the Carl Zeiss Flektogon f4 is a really good lens for landscape and architecture photography for all Sony, Nikon, Canon, Fuji, Panasonioc (and all others) photographers. When you use a tripod and can stop it down to aperture 8 or 16 there is almost no difference to the f2.8 verison.
Because the f2.8 version is way way better wide open, i recommend this version for astro photography.
As this is my first “lens review” I would kindly ask you to leave a comment how you liked it. I’d love to read some lines of wishes, criticism and suggestions.
Daniel