Pinhole Results

In my last couple of posts I described making and shooting with a pinhole attachment for my 35mm Pentax P30t SLR. Well, the scans are now back from the lab and I’m very pleased with them. They were shot on Fujifilm Superia Xtra 400.

As suspected, the 0.7mm pinhole was far too big, and the results are super-blurry:

See how contemptuous Spike is of this image. Or maybe that’s just Resting Cat Face.

The 0.125mm hole produced much better results, as you can see below. My f/stop calculations (f/365) seem to have been pretty close to the mark, although, as is often the case with film, the occasions where I gave it an extra stop of exposure produced even richer images. Exposure times for these varied between 2 and 16 seconds. Click to see them at higher resolution.

I love the ethereal, haunting quality of all these pictures, which recalls the fragility of Victorian photographs. It’s given me several ideas for new photography projects…

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Pinhole Results

Adventures with a Pinhole

Last week I discussed making a pinhole for my Pentax 35mm SLR. Since then I’ve made a second pinhole and shot a roll of Fujifilm Superia X-tra 400 with them. Although I haven’t had the film processed yet, so the quality of the images is still a mystery, I’ve found shooting with a pinhole to be a really useful exercise.

My Pentax P30T fitted with a 0.125mm pinhole attachment

 

A Smaller Pinhole

Soon after my previous post, I went out into the back garden and took ten exposures of the pond and the neighbour’s cat with the 0.7mm pinhole. By that point I had decided that the hole was almost certainly too big. As I noted last week, Mr Pinhole gives an optimal diameter of 0.284mm for my camera. Besides that, the (incredibly dark) images in my viewfinder were very blurry, a sign that the hole needed to be smaller.

Scans of my two pinholes

So I peeled the piece of black wrap with the 0.7mm pinhole off my drilled body cap and replaced it with another hole measuring about 0.125mm. I had actually made this smaller hole first but rejected it because absolutely nothing was visible through the viewfinder, except for a bit of a blur in the centre. But now I came to accept that I would have to shoot blind if I wanted my images to be anything approaching sharp.

The 0.125mm(ish) pinhole magnified in Photoshop

I had made the 0.125mm hole by tapping the black wrap with only the very tip of the needle, rather than pushing it fully through. Prior to taping it into the body cap, I scanned it at high resolution and measured it using Photoshop. This revealed that it’s a very irregular shape, which probably means the images will still be pretty soft. Unfortunately I couldn’t see a way of getting it any more circular; sanding didn’t seem to help.

Again I found the f-stop of the pinhole by dividing the flange focal distance (45.65mm) by the hole diameter, the result being about f/365. My incident-light meter only goes up to f/90, so I needed to figure out how many stops away from f/365 that is. I’m used to working in the f/1.4-f/22 range, so I wasn’t familiar with how the stop series progresses above f/90. Turns out that you can just multiply by 1.4 to roughly find the next stop up, so after f/90 it’s 128, then 180, then 256, then 358, pretty close to my f/365 pinhole. So whatever reading my meter gave me for f/90, I knew that I would need to add 4 stops of exposure, i.e. multiply the shutter interval by 16. (Stops are a base 2 logarithmic scale. See my article on f-stops, T-stops and ND filters for more info.)

 

The Freedom of Pinhole Shooting

I’ve just spent a pleasant hour or so in the garden shooting the remaining 26 exposures on my roll with the new 0.125mm pinhole. Regardless of how the photos come out, I found it a fun and fascinating exercise.

Knowing that the images would be soft made me concentrate on colour and form far more than I normally would. Not being able to frame using the viewfinder forced me to visualise the composition mentally. And as someone who finds traditional SLRs very tricky to focus, it was incredibly freeing not to have to worry about that, not to have to squint through the viewfinder at all, but just plonk the camera down where it looked right and squeeze the shutter.

Of course, before squeezing the shutter I needed to take incident-light readings, because the TTL (through the lens) meter was doing nothing but flash “underexposed” at me. Being able to rely solely on an incident meter to judge exposure is a very useful skill for a DP, so this was great practice. I’ve been reading a lot about Ansel Adams and the Zone System lately, and although this requires a spot reflectance meter to be implemented properly, I tried to follow Adams’ philosophy, visualising how I wanted the subject’s tones to correspond to the eventual print tones. (Expect an article about the Zone System in the not-too-distant future!)

 

D.I.Y. pinhole Camera

On Tuesday night I went along to a meeting of Cambridge Darkroom, the local camera club. By coincidence, this month’s subject was pinhole cameras. Using online plans, Rich Etteridge had made up kits for us to construct our own complete pinhole cameras in groups. I teamed up with a philosophy student called Tim, and we glued a contraption together in the finest Blue Peter style. The actual pinholes were made in metal squares cut from Foster’s cans, which are apparently something Rich has in abundance.

DIY pinhole camera

I have to be honest though: I’m quite scared of trying to use it. Look at those dowels. Can I really see any outcome of attempting to load this camera other than a heap of fogged film on the floor? No. I think I’ll stick with my actual professionally-made camera body for now. If the pinhole photos I took with that come out alright, then maaaaaaybe I’ll consider lowering the tech level further and trying out my Blue Peter camera. Either way, big thanks to Rich for taking all that time to produce the kits and talk us through the construction.

Watch this space to find out how my pinhole images come out.

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Adventures with a Pinhole

Making a Pinhole Attachment for an SLR

Last autumn, after a few years away from it, I got back into 35mm stills photography. I’ve been reading a lot of books about photography: the art of it, the science and the history too. I’ve even taken a darkroom course to learn how to process and print my own black and white photos.

Shooting stills in my spare time gives me more opportunities to develop my eye for composition, my exposure-judging skills and my appreciation of natural light. Beyond that, I’ve discovered interesting parallels between electronic and photochemical imaging which enhance my understanding of both.

For example, I used to think of changing the ISO on a digital camera as analogous to loading a different film stock into a traditional camera. However, I’ve come to realise it’s more like changing the development time – it’s an after-the-fact adjustment to an already-captured (latent) image. There’s more detail on this analogy in my ISO article at Red Shark News.

The importance of rating an entire roll of film at the same exposure index, as it must all be developed for the same length of time, also has resonance in the digital world. Maintaining a consistency of exposure (or the same LUT) throughout a scene or sequence is important in digital filmmaking because it makes the dailies more watchable and reduces the amount of micro-correction which the colourist has to do down the line.

Anyway, this is all a roundabout way of explaining why I decided to make a pinhole attachment for my SLR this week. It’s partly curiosity, partly to increase my understanding of image-making from first principles.

The pinhole camera is the simplest image-making device possible. Because light rays travel in straight lines, when they pass through a very small hole they emerge from the opposite side in exactly the same arrangement, only upside-down, and thus form an image on a flat surface on the other side. Make that flat surface a sheet of film or a digital sensor and you can capture this image.

 

How to make a pinhole attachment

I used Experimental Filmmaking: Break the Machine by Kathryn Ramey as my guide, but it’s really pretty straightforward.

You will need:

  • an extra body cap for your camera,
  • a drill,
  • a small piece of smooth, non-crumpled black wrap, or kitchen foil painted black,
  • scissors,
  • gaffer tape (of course), and
  • a needle or pin.

Instructions:

  1. Drill a hole in the centre of the body cap. The size of the hole is unimportant.
  2. Use the pin or needle to pierce a hole in the black wrap, at least a couple of centimetres from the edge.
  3. Cut out a rough circle of the black wrap, with the pinhole in the middle. This circle needs to fit on the inside of the body cap, with the pinhole in the centre of the drilled hole.
  4. Use the gaffer tape to fix the black wrap tightly to the inside of the body cap.
  5. Fit the body cap to your camera.

The smaller the pinhole is, the sharper the image will be, but the darker too. The first pinhole I made was about 0.1-0.2mm in diameter, but when I fitted it to my camera and looked through the viewfinder I could hardly make anything out at all. So I made a second one, this time pushing the pin properly through the black wrap, rather than just pricking it with the tip. (Minds out of the gutter, please.) The new hole was about 0.7mm but still produced an incredibly dark image in the viewfinder.

 

Exposing a pinhole image

If you’re using a digital camera, you can of course judge your exposure off the live-view screen. Things are a little more complicated if, like me, you’re shooting on film.

In theory the TTL (through the lens) light meter should give me just as reliable a reading as it would with a lens. The problem is that, even with the shutter set to 1 second, and ISO 400 Fujifilm Super X-tra loaded, the meter tells me I’m underexposed. Admittedly the weather has been overcast since I made the pinhole yesterday, so I may get a useful reading when the sun decides to come out again.

Failing that, I can use my handheld incident-light meter to determine the exposure…. once I’ve worked out what the f-stop of my pinhole is.

As I described in my article on aperture settings, the definition of an f-stop is: the ratio of the focal length to the aperture diameter. We’re all used to using lenses that have a clearly defined and marked focal length, but what is the focal length in a pinhole system?

The definition of focal length is the distance between the point where the light rays focus (i.e. converge to a point) and the image plane. So the focal length of a pinhole camera is very simply the distance from the pinhole itself to the film or digital sensor. Since my pinhole is more or less level with the top of the lens mount, the focal length is going to be approximately equal to the camera’s flange focal distance (defined as the distance between the lens mount and the image plane). According to Wikipedia, the flange focal distance for a Pentax K-mount camera is 45.46mm.

So the f-stop of my 0.7mm pinhole is f/64, because 45.64 ÷ 0.7 ≈ 64. Conveniently, f/64 is the highest stop my light meter will handle.

The website Mr Pinhole has a calculator to help you figure this sort of stuff out, and it even tells you the optimal pinhole diameter for your focal length. Apparently this is 0.284mm in my case, so my images are likely to be quite soft.

Anyway, when the sun comes out I’ll take some pictures and let you know how I get on!

Making a Pinhole Attachment for an SLR

“Barry Lyndon”: The Full Story of the Famous f/0.7 Lenses

After seeing Barry Lyndon (1975) on the big screen this week, I felt compelled to write a blog post about its cinematography. But what aspect of the cinematography? The painterly look? The many zooms? The use of natural light?

What I knew for certain is that I should definitely not write about the entirely candlelit scenes lensed on f/0.7 Nasa glass, because everyone knows that story. However, reading the vintage American Cinematographer article and some other material, I found the details surrounding this groundbreaking use of high-speed lenses so interesting that I decided to do it anyway.

 

The Vision

Barry Lyndon is the 18th century tale of a low-born Irishman who strives – through various misadventures, and ups and downs of fortune – to become a gentleman. The key visual influence of director Stanley Kubrick and DP John Alcott, BSC were the great painters of the story’s era, such as Vermeer.

Next week’s post will look at this painterly influence in Barry Lyndon more closely, but for now the important thing is the use of candlelight on those classical canvases, and Kubrick’s desire to replicate that look. According to lens expert Ed DiGuilio, who was tasked with adapting the f/0.7 glass for Lyndon, Kubrick “wanted to preserve the natural patina and feeling of these old castles at night as they actually were”.

Typically in movies, a candle in frame may motivate the lighting, but most of the illumination on the actors actually comes from an orange-gelled lamp just out of frame. Kubrick wasn’t interested in shooting Lyndon that way. He wanted all the light in those night interior scenes to genuinely come from the candles themselves.

 

The Problem

How much light does a candle shed? Conveniently, there is a unit of illumination called the foot-candle. One foot-candle is the amount of light received from a standard candle one foot away. Without going into the detail of what a “standard” candle is, it is enough for our purposes to say that the scene below has a key light of about three foot-candles…

… because there are three candles, about a foot away from the actor’s face. (The level of your key light, and consequently where you set your aperture, is almost always measured at your subject’s face, as that is usually the focus of the shot and the most important thing to get correctly exposed. This is why we DPs are always waving light meters in actors’ faces.)

If we look at an exposure table, such as this one, we can see that a three foot-candle key can be correctly exposed with an aperture of T1.4 and an EI (exposure index) of 800. Today that would be no problem, with many digital cameras having a native EI of 800, and the availability of fast lenses like Zeiss Master Primes and Super Speeds.

In the mid-seventies however, long before the advent of digital cameras, things were not so simple. Kubrick and Alcott had little choice but to shoot on Eastman Kodak 100T 5254. Those first three digits denote the film stock’s exposure index: 100. Alcott pushed the stock (brought the brightness up during processing) one stop, re-rating it to an EI of 200. But it still needed four times more light, or two stops more light than our modern-day Alexa or Red. (Check out my post on f-stops and T-stops if you’re getting lost.)

If we’re losing two stops on the EI, we need to gain two stops on the aperture to compensate. And two stops up from T1.4 is T0.7. You may notice that T0.7 isn’t on that table I linked to. This is because a lens with such a large relative aperture pretty much doesn’t exist.

Pretty much…

 

The Solution

Kubrick obsessively researched the problem. He eventually discovered that Nasa had commissioned Carl Zeiss to build ten Planar 50mm f/0.7 stills lenses in the sixties, which were used to take photos of the dark side of the moon. (I was unable to find out the T-stop of these lenses, but I’ll assume it was close enough to T0.7 for it to make little difference to my calculations above.) The developments leading to these lenses stretched back through Nazi military applications during WW2 all the way to the late Victorian era, when the double-Gauss cell at the core of the lenses was first invented.

Anyway, Kubrick promptly bought three of the Zeiss Planars. He liked to own equipment himself, rather than hire it in, and to this end he had also purchased at least one Mitchell BNC camera. As befits Kubrick’s perfectionism, these were perhaps the world’s most precisely engineered cameras, previously used for special effects work.

This is where Ed DiGuilio comes in: “[Kubrick] called one day to ask me if I thought I could fit a Zeiss lens he had procured… to his BNC.” It wasn’t simply a case of the f/0.7 glass having the wrong mount. The rear element was so large and needed to be so close to the film plane that DiGuilio had to extensively modify the camera, literally cutting parts out of it.

Ed DiGuilio (left), President of Cinema Products Corporation, working on adapting a zoom lens for Kubrick’s Mitchell BNC

Once this was done, extensive testing ensued. The focus scale (distances marked on the barrel) had to be calibrated from scratch, and indeed the focus ring was re-engineered to allow the precision focusing that the lens’ tiny depth of field would require. Whereas the focus ring on a stills lens will turn about 90° to go from infinity to close focus, and the ring on a cine lens might turn 270°, the rings on these unique Planars now turned a whopping 720° – two whole revolutions!

50mm is a very useful lens length for close-ups, but Kubrick understandably wanted a wider option as well. Accordingly, DiGuilio located an adapter designed to adjust the throw of cinema projector lenses. Mounted onto one of the 50s, it gave an effective focal length of 36.5mm with only very minor light loss. A 24mm version was also tested, but Kubrick disliked the amount of distortion in its images, and rejected it.

 

The Execution

The colour brown and the trousers of Doug Milsone, Barry Lyndon‘s focus puller, cannot have been strangers to each other. Imagine trying to hold focus on this dolly-back at f/0.7!

By my calculations (which were difficult, because most depth of field tables/calculators don’t go to f/0.7!) an MCU on Kubrick’s 50mm Planar with the subject at 2.5m (8.2ft) and the iris wide open would have had a depth of field of about 43mm (1.7″). To get this same depth of field at f2.8, a popular working stop for cinematographers today, the subject would have to be just 1m (3.3ft) from the sensor plane, which would be a biggish close-up. And remember that focus monitors, peaking and Cine Tape did not exist in the seventies.

To give Milsone a fighting chance, a unique system of focus assist was developed. While the main camera shot an actor from the front, a CCTV camera captured them in profile. This profile image was piped to a monitor, over which a grid was placed. This grid was marked off with distances so that Milsone could see how much the actor had moved by, far more accurately than judging it by eye from beside the lens.

Another problem thrown up by the low-light cinematography was with the viewfinder. Interestingly, the Mitchell BNC was a non-reflex camera, meaning that it didn’t have a mirror on the shutter, reflecting the image to the viewfinder when the shutter was closed. Instead, the camera body racked over to one side to allow the viewfinder to get an image during line-ups and rehearsals, and when it was actually rolling the operator got their images from a side viewfinder with its own lens – just like in a disposable 35mm stills camera. The original prism-based viewfinder on Kubrick’s Mitchell BNC suffered from far too much light loss for a candlelit image to be visible through it, so it was replaced with a mirror-based viewfinder adapted from a Technicolor camera.

The shots resulting from all of these technical challenges are quite soft to the modern eye, but I think that only adds to their beauty. Barry Lyndon captured the exquisite fragility of candelight, and 42 years on the images are still unique and captivating.

“Barry Lyndon”: The Full Story of the Famous f/0.7 Lenses