Easy Bokeh Highlight Shapes

Bokeh is a term for the quality of out-of-focus light in a photograph. One interesting effect is that points or small areas of light that aren't in focus take on the shape of the aperture they pass through on the way to the film (or digital sensor). This instructable will show you how to easily make the highlights into interesting shapes.

Camera lenses control the amount of light that passes through them by making a hole (the "aperture") larger or smaller. They usually do that by moving a set of metal blades (check out this trippy animated gif ). You can count the number of blades for many lenses by looking at the shape that a point of light becomes when it's out of focus. My 50mm lens produces a 7-sided figure (a heptagon).

What if we want something more interesting than a heptagon? It would be tricky to change the shape of the aperture inside the lens, but it's easy to make the light pass through another aperture as well...

Step 1 Materials

All you'll need is:
- A sheet of paper. You should get more pronounced effects if this is opaque, but I just used thin paper that's black on one side and white on the other. A friend had good results with a sheet of aluminum foil.
- Cutting tools. I used scissors to cut the outside shape and a knife to cut the inside shape
- A screw-in filter (semi-optional)
- A camera with a "fast" (large maximum aperture) lens and a screw-thread for a filter

I found I had pretty good results with my lens aperture set to f/4 or larger (that is, closer to f/1). It may work better with telephoto lenses. Please comment if you find particularly good (or bad) effects with various lens settings.

Comments

[Closer]

Check out this site for dozens of "gobos" (shapes like the star and teardrop apparently are called "gobos") I have wondered about printing masks on transparancies based on these patterns. I have some old filters to take the old filter out of and put the new "filter" in based on these patterns but I have not gotten around to it yet. http://www.leefilters.com/lighting/products/gobos/

[trifle]

very nice tut, i like that you linked to the history of the term, that was the question in my head all this time :)

i'm gonna try this tomorrow, i hope it works with my camera

thanks for the tut!

[~teknoarsonist~]

"My God, its full of stars" -epic quote! i give you props for that one!
Thanks for the explanation! it was very helpful! i gotta make me one of these :)

[incorrigible packrat]

Neat. On a non-photographic but optically similar note: If you're incredibly myopic like me, you can have minutes of fun staring at point sources of light (status leds on computer stuff, for example) without your glasses on. I might just be some particular form of mutant, but I can watch the junk floating around in the aqueous humour of my eyeballs. Just one of the multitude of advantages I can lord over those with perfect vision.

[jaysbob]

you sure your retinas just haven't detached? neato trick though. when I first saw the pictures I thought it was those shaped glitter confetti things you can buy in craft stores and the like.

[incorrigible packrat]

I dunno. My eyes have maintained the same superb level of visual acuity for about 15 years now. Without glasses, I can focus on objects a whole six inches away from my face!

[gschoppe]

I've seen the same effect... on odd days, I swear I can catch a glimpse of bacteria on the actual lens of my eye... oh yeah, I thought it was insane too, but I've seen them occasionally since I was about 6 (that I can remember), and it was only when I was 10 that I saw images of unstained bacteria and recognized them.

[incorrigible packrat]

Yeah, I first noticed them around that age. Kept asking my sister what those things in the sky were... I think most of the "floaters" are dead blood vessel cells from the retina, and similar ocular garbage. I suppose there could be bacteria as well. I had a bacterial eye infection a couple of years ago. A fun mix of intense pain and extreme sensitivity to light. It didn't hurt quite as much as one time when I put in contacts, that had been disinfected with a hydrogen peroxide solution, that I had forgotten to neutralize. That only hurt for a few minutes, but each moment hurt like 57 varieties of Hell.

[iamthemargerineman]

ah. finally. an answer to my most unanswerable question.

[incorrigible packrat]

Which question? "What's the stuff floating in my eyes?" or, "How much does it hurt to get hydrogen peroxide in my eyes?", or something else entirely?

[iamthemargerineman]

the eye floaties.

[darkmuskrat]

OOOO shiny 8)

[iamthemargerineman]

SO BRILLIANT!

[wompastompa]

"it's full of stars!" Nice reference to 2001, which was an amazing series! have you read rendezvous with rama yet?

[gschoppe]

I saw this trick on DIYPhotography.net a while ago, and have gotten some pretty awesome photos with it. However, I do want to note that Bokeh is a term referring to the overall quality and characteristics of a lens or shots unfocused areas... this is technically a form of vignetting, where the borders are outside the area of the sensor for areas that are reasonably in focus.

[aneel]

Aha. I see the effect you're talking about. Because the shaped screen blocks some of the light reaching the sensor, it can cast a shadow, causing shaped vignetting. You can minimize this effect by opening the aperture of the lens wider. I've made some crude figures to show what's going on. In the first, the lens aperture is small. Light passing through the top point of the star screen is prevented from hitting the top portion of the sensor. In the second, the lens aperture is large enough that light passing through the top point of the star screen can illuminate the entire sensor. And some example photos (please excuse the poor quality, they were for science, not art). All use the same star screen. They are at f/16, f/8, f/4, and f/2. In the f/16 shot, there's a distinctly star-shaped vignette. In the f/8, it's less obvious what the shape is. As the aperture opens wider, the shadow falls on less of the image.

[aneel]

I was going to further argue that vignetting and shaped bokeh highlights are different phenomena, both of which happen to be caused by putting a screen in front of the lens.

But then I realized that the shaped highlights could be said to be caused by vignetting of the of the circle of confusion of the highlight, which is an interesting way to think about it.

[aneel]

Yes, the shape of highlights is only one aspect of bokeh. Some other important aspects are:
- the pattern of light intensity and its tendency to form hard or soft edges (see Fig 1-3 here)
- the tendency of the blur to solidify or double lines (see Fig 6 here)
- the tendency to create chromatic aberration (see the second set of figures here).

I'm not sure what you mean about this being a form of vignetting. Vignetting is light falloff towards the edge of the photo. Your (very nice!) photo with the colored leaves demonstrates vignetting. The corners are dark, and the light falls off quickly outside a circular area towards the middle of the frame. However, the bright orange leaf-shaped highlight in the center is not vignetted at all.

None of my example shots demonstrate significant vignetting.

[GorillazMiko]

Wow! Smart idea! I might do like the Instructables Robot silhouette, that would be pretty sweet, nice job!