Aperture Shape & Custom Bokeh blur

Have you ever looked at the out-of-focus areas in an image and wondered why all objects and more notably objects like a lights blur in a round shape?  Playing with my Camera Obscura got me thinking about aperture shape and Bokeh blur.  I think it is important to know that the out-of-focus parts of an image actually acquire the shape of the aperture. This got me thinking about creating a custom aperture shape. As I don’t fancy opening a lens up, its possible to mound an aperture modification to the front of a lens much like a filter, just so long as the new aperture is smaller than the original aperture in the lens(if not the shape is clipped by the old aperture). The only real problem is that once the new aperture is mounted, the original aperture becomes obsolete, so control over the aperture is lost. It’s also important to remember the max aperture will be stopped down a few (depending on the size of your shape) as this is now your new aperture. This becomes annoying as this whole project is about creating Depth of Field and out of focus areas.

So where to start?

I wanted to start simple, so just used some card that I cut to the size of my Cokin filters. This way I was able to mount them easily. In the center for each card, I cut my new aperture shapes and then could just slide them into my Cokin Filter Holder.

Bokeh Filter and Standard Bokeh Shape

Let’s Take Some Shots

I found that my 50mm f/1.8 was the best choice of lens and simply whacked it out-of-focus and took some photos of some old Christmas lights.

What I Found

1.       The more out-of-focus an image is, the larger the shape shows. This allows you to control the size, but only when none of your image needs to be focused. Obviously ,when shooting with part of your image in-focus, depth of field controls/limits this

2.       Using a Cokin filter holder is a good way to mount the aperture filters

3.       As the filter becomes your new aperture exposure and DoF will be affected

4.       It’s worthwhile to make nice filters once and keep them in your bag

While searching online I also came across some pre made “creative aperture kits” like this one below. I Have not had a chance to try them yet but defiantly worth a look.
Lensbaby Creative Aperture Kit

AlexAndrews

Camera Obscura

I guess there is only one place to really start my blog on photography… Yes the Camera Obscura. Don’t you find it odd that the modern camera uses the same basic principles as technology invented around 2500 years ago? I know the Camera Obscura has no real commercial uses today but I think we can all learn something from creating one for ourselves and for the little geek that is inside all photographers, it’s pretty awesome too.  

 My Background With Camera Obscura

I think my first really experience of a Camera Obscura was during the 1999 total solar eclipse where we used them to protect our eyes as we could look at a projection of the sun. It’s odd that I would remember the little pinhole Cameras we used as I was only about 8 years old. However for some reason it stuck and I locked this knowledge away. The next time I really thought about the idea of a Camera Obscura was with my Dad. I guess my Dad will come up a lot in this blog as I have to put my creative and experimental attitude to life down to his influence not forgetting why I can get so OCD about my projects. My Dad is the kind of Dad who seems to be able to make anything and as I grew up there where very few weekends went by were we were not making something.  Despite me being the only one to really push photography my Dad seems to love playing with optics and equipment like that. I guess working as a surveyor meant he is always using cool kit too. He has also made his own telescope that sadly, being at Uni, I have not had a chance to play on the latest generation of. Anyway back to the point… One day he decided to convert our living room into a large Camera Obscura and the results were quite cool.

My Attempt With Camera Obscura

My Camera Obscura setup and results

So that leads us to now and I was in town looking at some boot sale style deal and found a box camera that uses a fixed focus but a small aperture to create an in focus image. This triggered my memory and I began to think about creating pinhole cameras and try a camera Obscura again. In my dad's’attempt we came across a few problems one being that my living room at home was a pain is the ass to make light proof, the other being that it would have been nice to have a way to quickly adjust the aperture to test how it changes the image. The light leaks for my attempt were no problem as a search in the attic uncovered a huge piece of cardboard that would cover my window in one go and then a min with some gaffa tape and job done. For the aperture adjust problem I found a solution that I was frankly quite proud of. I borrowed a lens from a photo enlarger and unscrewed all the glass. This left me with nothing but a fully manual aperture ring. I cut a hole in my card and screwed this into place.  The 3 images show my setup and results. I don’t really need to go into much detail about the science behind this as there is loads online about how it works but I hope that some of you will give it a go.

AlexAndrews