Digital Pinhole Experiment

This past week I spent some time on a long overdue update to my website – www.forestrat.com. It’s nothing fancy. I’m no graphic artist so I keep things simple.

In the meantime I have also been experimenting with turning my digital SLR into a pinhole camera – Wikipedia.

In earlier posts I mentioned that it has been known for centuries that passing light through a small hole in one wall of a box will project an image on the opposite wall. This is known as the “camera obscura”. Photography was born from the desire to “fix” this image permanently without the need for someone to trace the image by hand.

A pinhole camera is basically just a box with a hole in one end and a light sensitive surface on the other side. It can be built out of all sorts of materials – shoe boxes, oatmeal boxes, tin cans, etc. as long as it can be made light tight. A gigantic one has even been made out of an entire abandoned air plane hangar – The OCRegister.

The tricky part is making a good pin hole. The hole needs to be very small when working at digitial camera body scale and it needs to be perfectly round without burrs. I searched the web for some guidance and ended up basically following the method described here – DIY Pinhole for dSLR.

I drilled a quarter inch hole in the center of an old camera body cap and used electrical tape to attach a piece of metal cut from a soda can with my pin hole in it. I made the hole using a pin saved from the packaging of a dress shirt.

I made several pin hole “lenses” trying to get the hole just right. I also tried using aluminum foil instead of the can metal. The foil was much easier to puncture and was much thinner, but it was also more delicate and took a steady hand to make the hole without tearing. I ended up preferring the foil once I got the hang of it. You can purchase laser cut pinholes from photo supply stores, but that takes away the DIY aspect of the whole deal.

Theoretically a pin hole lens will have a huge depth of field. Depth of field tells you where objects in a scene will be in focus. Setting your camera lens to f/2.8 will give a shallow depth of field which means that only those objects close to the same distance from the camera will be in focus. Nearer and farther objects will blur. As you reduce the aperture, depth of field increases. At f/22 (the limit for my regular lens) more objects front to back will be sharp. My pin hole should give me around f/168.

Although a pin hole lens will give you great depth of field, don’t expect razor sharp images. Producing a perfectly round smooth hole isn’t easy and deviations will cause interference. Also light does funny things when traveling through a very small hole causing diffraction patterns. The size of the hole depends on the distance between the lens and the film (the focal length). The short distance between lens and sensor on my camera requires a really small hole; something along the lines of .298mm or .012 inches. Images therefore tend to be soft. If I had a box with a much longer focal length, the hole could be larger and things would be sharper.

Exposure times in bright sunlight were on the order of five to ten seconds and required guessing since the exposure meter in the camera would not work under these conditions. The view finder was tough to use too since the scene was really dark - in bright light I could make out major landmarks, but in lower light conditions forget about it. Trial and error is the order of the day and digital makes this much easier. I would have ruined a lot of film otherwise.

The two waterfall images  show the difference between a conventional lens and a pin hole. The first image was made with my aluminum foil pin hole lens. The exposure time was ten seconds which produced the silky smooth water effect.

The second image is the same scene made with a conventional lens. Stopping my lens all the way down to f/22 still required a shutter speed of 1/1250 of a second thus freezing the water as it fell.

I like this pin hole image. On the other hand, I tried it on other things and was not as happy. Closer more detailed scenes were too blurry for my taste. Below is a test image I took of a deck post.

It is amazing that a shot this good can come from such a crude device, but the fuzzy feel just doesn’t work for me. I don’t mind misty images of lots of flowing water, but I tend to like the solid objects in my images to be nice and sharp. Picking the right scene is an important step in pin hole photography.

While messing around with pin holes, I ran across this little piece of equipment – the Loreo Lens in a Cap. It contains a fixed focus lens that fits on your camera sort of like a lens cap and offers f/5.6 all the way to f/64. It isn’t really a pin hole, but setting it to f/64 should be interesting.

It only cost fifteen bucks so I bought one. I’ve taken a few test shots, but nothing useful yet. I’ll give a full report once I have time to play with it under the right conditions.

MDW

Turning a Digital Image into a Photograph

When we left off last time we had made short work of over a hundred years of photographic history in a matter of minutes.

We started out with the knowledge that passing light through a small hole will project an image. At first people just used a pencil or whatever to trace the projection in order to obtain a permanent image. From then until now we have been fooling around with different ways to fix the image.

We know that many different chemical reactions can be triggered by the energy in light. It is a short jump from there (except for the details) to capitalizing on the different reactive properties of exposed chemicals versus unexposed chemicals to create an image.

Now we come to digital photography. Speaking of it as “digital photography” makes it sound wildly different from traditional photographic methods, but it isn’t really all that different. We take the same energy that has been in light all along and instead of holding on to a chemical record of its presence (e.g. altered silver salts on a cellulose film) we just detect it and make a note of it on a chip with flipped magnetic bits.

Here is a link to an article that explains a bit about how digital sensors work. As with most articles on the subject, an explanation of how the photons are actually detected is avoided. I have yet to find a good article on it.

Drawing on my vague memories of quantum mechanics classes and what not while in college, a wildly simplified explanation of the deal is that when light falls on certain molecules, the energy in the light is transferred to the atoms and it gets their electrons all  jazzed up and they jump into higher energy states. When the electrons drop back down to their normal states, they release the energy as electricity which is used to record the light’s presence by flipping digital bits.

Again the devil is in the details, but we still have the same basic system – light falls on a sensitive surface and the energy causes a change which can be used to create an image based on the difference between exposed areas and unexposed areas.

So now we have a bunch of bits representing an image. What do we do now? Send ‘em to the printer of course so we can create a photograph. There are a lot of different printers out there that can be used. The most commonly used for photographs is the ink jet printer. Here tiny droplets of ink are sprayed onto paper. It works surprisingly well and a good printer matched with good paper can produce an excellent photograph.

But wait there’s more! Perhaps we would like to use a digital camera, but produce traditional chemical prints. Well we could buy a digital enlarger made by a company called De Vere. This is like a regular enlarger only instead of passing light through a negative, it takes a digital file and projects it onto photo-sensitive paper. I’d love to get my hands on one of these, but the price is in the tens of thousands range.

Another possibility is called a LightJet print. The digital image is fed into the machine like the digital enlarger, but instead of projecting the whole image onto stationary paper, lasers shoot little dots of light at a rotating piece of photo-sensitive paper until it has “painted” the entire image. Again the LightJet process is expensive. It isn’t something you can do in your basement.

How about something you can do yourself?

Well, you know, if we could turn the digital file into a physical negative, then we could use our regular old darkroom to make the prints. That is just what a guy named Dan Burkholder likes to do. He creates “digital negatives”.

An inkjet printer can print not only on paper, but on transparencies too. Soooo, we reverse our image using our photo editing software and print a negative on a transparent sheet – piece ‘o cake. Turns out that there are a few details to take care of, but luckily Dan has worked it all out for us and has written a book about it. Neat.

Once we have a digital negative, we can create any kind of print – carbon, palladium, bichromate, etc. We could use an enlarger, but since the inkjet printer can make us a really big negative, we can often just contact print. Hey, we can contact print and make the exposure using sunlight so that we don’t need the enlarger at all. We can even use our negative to print directly on plant leaves like Rosemary Horn does – no chemicals and no darkroom!

Some may ask why bother with all of this when you can just use a digital camera and print to printer. Wham bam. No muss. No fuss. It’s now, it’s hip, it’s what everybody is doing.

Well, because it is art. Art should be different, art should experiment, art should present things in different ways than the status quo. Just because something is quicker or easier or sharper or more colorful or whatever does not mean it is “better”.

Photography did not, as many people predicted, render painting obsolete. Painting is painting and photography is photography; they are not replacements of each other.

Neither are the various methods of “painting” replacements for each other. We should not stop using oils because there are watercolors. We should not stop using watercolors because there are pencils.

Just so each method of creating a photograph is not a replacement for another. An inkjet is not a replacement for a dye transfer nor for an albumen. They each have a certain look and feel and aura that a skilled artist can use to enhance an image.

We should not stop creating photographs, real live touch them with your hands hang them on the wall photographs, just because we use a digital sensor instead of a chemical one to record the image.

MDW