Here is a simple bokeh test you can do now to know if your lens has good bokeh wide open. This is good to know, especially if you are into buying old lenses or simply if you want to see how your bokeh looks. I usually do this to know if the aperture blades are sitting properly where they should be and if they are, I know my bokeh will be ‘perfect’ when I shoot wide open.
For example, if you bought a lens like this
Nikon 50mm f1.4 ais
or like this
Helios 44M 58mm f2
you may want to try this test!
All you really need is a point of light (my iPhone) and a camera with the lens you’d like to test. Here’s a photo of my setup.
Set your lens to its widest aperture e.g. Here I used an Auto Rikenon 55mm 1.4 lens set to f1.4 and turned either all the way to infinity or all the way to its closest focus distance. It doesn’t matter once you have it as out of focus as possible. Point your lens straight towards the light source and you can underexposure the photo if you’d like just to see the ball better.
Here is the shot I got from this setup
NOW
Here I’ll give an example of a Nikon 50mm f1.4 ais that looked great on the outside but had a slight distortion in the bokeh at f1.4 because the aperture blades were not fully going all the way to f1.4, the blades were slightly visible in the circle where they should be fully retracted at f1.4. I hope my explanation wasn’t too confusing.
See if you can spot the difference!
Here is the first image. Look at the bokeh circle carefully and now compare to the second image
Here is the second image
At first, you may not see the difference but look closely and you will notice the first image bokeh ball is slightly distorted, that is, it is not a perfect circle. The second image however is perfect!
To fix this is a bit complex and I would not explain it here because your lens will look like this…
and the aperture block isn’t even disassembled yet!
Hopefully you wont have to do this :)
When you have a perfect bokeh circle, you can now be confident your out of focus areas will be very smooth.
Nikon Nikkor 105mm ƒ/2.5 ais @ 105mm, ƒ/2.8, 1/500s, ISO 125
By the way, if your bokeh is not smooth and is bubbly or swirly in the out of focus areas, these characteristics are by design.
Hope this will help in understanding your photography adventure a bit more!!
Do what you love and love what you do :)
Thank you for reading!