Why am I getting a "frame" in my picture when I made my own shaped bokeh?

Question

I have tried to play with the shaped bokeh trick, by following the instruction at DIY - Create Your Own Bokeh.

I am using a M4/3 camera with its kit lens, which is 14-42mm f3.5-f5.6.

I shot at 14mm f3.5, thus the shape I created had dimension less than 4mm (14/3.5). However, I don't get the effect for the light sources. Also, the pictures I took all have the shaped frame, which means let say the hole has a shape of star, my image would be all black but having a small star 'window' in the centre, and it is where my camera sees.

What did I do wrong please? Is it just not possible to play with this effect using the kit lens?

Answer 1

At 14mm your field of view is too wide. You are looking at the shaped frame you have made rather than just through it. Most lenses that people use are 50mm and above, and a wide aperture of 2.8 or bigger. Whilst the long end of your zoom might not get the frame of your DIY kit in shot, the f stop won't be fast enough to create the bokeh effect you want.

This was previously asked here so take a look at what people said.

Also I just found this site which shows you how to calculate what sizes you'd need for your cut shapes etc with what focal lengths and apertures

And to answer your last question, you may get some amount of shaped bokeh if you experiment enough, but with such a 'slow' lens you are not going to get the kind of images given as examples in your link.

Answer 2

In fact custom bokeh will work only if the shape is close enough of the optical center of your lens. (Ideally you should replace your diaphragm.)

Therefore this works very well with prime lenses but you will get trouble with zoom lenses which have complicated optical formula.

I have tested it on a 4/3 camera with a 50mm. See http://www.flickr.com/photos/floquif/4189953390/in/photostream for an example.