Dec 28, 2012

Shutter speeds, apertures and Warnerke sensitometer values

In my previous blog I mentioned that I did not have the means to measure shutter speeds. Since then I experimented with a fast rotating disc. I put a little bulb on the rim of the disc and one in the center. The rotating light on the edge of the disc is projected on a ground glass in the back of the camera. When I snap the shutter of the old camera, I take a photo of the image on the ground glass with my digital reflex. The degrees of the arc of light on the ground glass is measured and when the rotations of the disc per second are known, I can calculate the speed of the shutter.

My testlab to measure shutter speeds.
To photograph the ground glass I set my camera to 3400 ISO, f/2.8 and 6 seconds exposure. During the exposure the room is dark, so the image on the ground glass can be seen and photographed. With much lower ISO settings the image could not be photographed.

To "calibrate" the speed of the disc I photographed it with my digital camera set on 1/10, 1/20 and so on. Calculations showed how fast the disc had spinned. Also I filmed the rotating disc and viewed it in slow motion, counting the turns per second.

I am still trying to find out the film speed of the early films. There are some original film boxes with the text "30 sensitometer", but I do not know which scale was used. Maybe it is the Warnerke scale, but even if it is, I cannot compare the Warnerke scale to a ASA/ISO or DIN scale. Even a conversion to a Scheiner or H&D scale would be useful, as long as I know which version of these scales are used. There are US, UK and German versions of these scales.
My own conclusion based on shutter speeds and standard aperture settings is that film speed around 1900 was about 25 ISO. 

What else did I do? Well, I bought two nice photographs to go with my cameras. The first one is a scene made with a No. 4A Folding Pocket Kodak. Yes, it says Folding on the back of the card. It must be a mistake of the printer, because the 4A was called Folding Kodak. It was and is way to large for any Pocket.
The second photo is a beautiful shot of an early aeroplane. It was made with a No. 3A Special Kodak. I do have that camera model, but I display the photo with my much more interesting Military version of the No. 3A Autographic Kodak Special. Only 100 of these cameras were made in 1916 for the US Signal Corps. 

Dec 9, 2012

Of apertures and a 1893 world fair album

You know Le Corbusier? If not: he's one of the most important architects of the 20th century. That's short enough, isn't it? And if you want to know more, just Google.
What about him? I have been asked by the author of a book on Le Corbusier to say some sensible things about the first camera that our famous architect bought. Guess what brand it was! Some questions related to the apertures of Kodak box cameras from the 1900 period. I have a nice library of photo-history books and journals, but in it I could not find what the apertures on these cameras are. So I had to go back to the basics, meaning that I had to measure the diameter of the stops and the focal length of the cameras. Of course you all know that you can calculate the aperture value with the simple formula a=f/d, where a is aperture value, f is focus and d is diameter of the opening. To make a long story short, here's what I found:

My measuring tool is a simple caliper, nothing digital, no laserbeam. So give or take a millimeter in the focal length and + or - 0,2 in the diameter of the stop. The results stay much the same.
The largest stop on these cameras is about f/15, very close to the value we are used to: f/16.
The smallest stop is about f/30, also very close to the better known f/32.
There is one stop in between and it wouldn't be foolish to expect that this was f/22 or f/21. But it is not. The middle stop is f/18, about halfway between f/15 and f/21. Rather confusing if you are used to the standard range where every stop is equal to half the light passing through the lens. That made combining shutter speeds (1/30 - 1/60 - 1/125 - 1/250 etc) and apertures simple in the days not so long ago, when your camera was not a computer.

But in the days of the No. 2 Bull's-Eye or No. 2 Falcon, the stops on these cameras were not used to combine with shutter speeds for artistic effect. They were meant to accomodate to light conditions. Standard condition was bright sunny weather. Everything else was some sort of a problem. Let's see what the No. 2 Flexo instruction booklet say about this. (They all say the same.)

The largest stop f/15 is for all ordinary work in sunny conditions.
The middle stop of f/18 lets in slightly less light in very bright conditions.
The smallest stop f/30 is for Time exposures only, out doors or in doors.

There is some more info in the booklet that confirms the calculation of the middle stop as being f/18 and the smallest as being f/30.
When the middle stop was used, one had to add one half of the exposure time. That is equal to one half stop.
With the smallest stop f/30 one had to give four times the exposure time. This is equal to two stops. Example:
f/15 with 2 seconds
f/21 with 4 seconds
f/30 with 8 seconds

Apart from the question about the apertures, there was a question about film speed in the early 20th century. There was not a global system to indicate the speed in those days, but several methods. Kodak used a very indistinct system with descriptions like "slow" of "fast" films. Quite a difference compared to our ISO system or the ASA and DIN system of my youth.

No. 2 Falcon, one of the cameras that was used to
calculate the aperture range of early Kodaks.
Do you remember the old Sunny 16 rule? I quote from wikipedia: The basic rule is, "On a sunny day set aperture to f/16 and shutter speed to the [reciprocal of the] ISO film speed [or ISO setting] for a subject in direct sunlight." For example: On a sunny day and with ISO 100 film / setting in the camera, one sets the aperture to f/16 and the shutter speed to 1/100 or 1/125 second (on some cameras 1/125 second is the available setting nearest to 1/100 second).
Knowing that the largest stop in the early Kodak boxes is f/16, one can calculate the speed of the film if one knows the speed of the shutter. I have not the means to measure the shutter speed, but my guess would be between 1/25 and 1/60 of a second. Following the Sunny 16 rule, this would mean that the speed of the film woud be around 25 to 60 ISO.
If I follow the instructions in the booklet and give 20 seconds exposure with f/15 in door on a cloudy dull day (like today), I can calculate that the speed must be around 40 ISO. We will leave it to that for now.

Something quite different is the photo album I stumbled upon while browsing through eBay. It is a Columbian Exposition album, dated 1893, with cabinet and CDV portraits and tintypes. I assume it was sold at the world fair as a souvenir. I have no idea of its value or rarity, but I would want it because of its beauty. Be quick if you want it. Only 14 hours to go, no bids yet, starting price is $ 150.

Dec 1, 2012

Continental Zenith camera

They all come along, some sooner, some later, but eventually all those rare camera models cross your path. Last month I noticed a 9x12 cm Zenith Kodak box on eBay. I had known for a long time that the model existed. Brian Coe mentioned it in his book Kodak cameras, the first hundred years. According to Coe 1000 were made in 1899, but I had never seen one before or heard of one. And now a Paris dealer had one for sale. When the auction ended I had been the only bidder.

So now I am the happy new owner of a very rare camera (that almost no one cares tuppence about). It completed my series of Eureka and Zenith Kodaks. This is a range of cheap box cameras that were made during a short period, ranging from 1898 until 1900. Apart from the extremely simple No. 2 Eureka Junior, all could accomodate plate holders and roll film holders. The Junior only took a single metal plate holder.
The Eureka name was already in use in Europe, so (t)here some models were sold under the Zenith name. The No. 3 Zenith came in two versions: one for the UK market and one for the continental (metric) market. This last one was called 9 x 12 cm Zenith.
There are 6 different models (and some variations within the models):

From left to right:
From the 1899 RPS catalog.
  • No. 4 Zenith
  • No. 4 Eureka
  • No. 2 Eureka Junior
  • No. 2 Eureka
  • 9 x 12 cm Zenith (see it on my website)
  • No. 3 Zenith
Apart from the two lines in the Coe book, I knew nothing about the 9x12 cm Zenith. That was a good reason to dive into the deep web to hunt for some more info. I tried the digital repositories I know, like the Hathi trust, Internet Archive, Gallica and even Google Books. What I did find were some tiny remarks about the No. 3 Zenith, but not one single word about the 9 x12 cm Zenith. There must be an ad around somewhere in all those online journals, magazines and newspapers of 1899 and 1900, but I did not find it.
The best find was a small piece in a Royal Photographic Society exhibition catalog of 1899, describing the No. 3 Zenith.

Le Pascal
What else is going on?

Most interesting was the auction of a Japy & Cie "Le Pascal" box on eBay. This small simple looking camera of the late 1890's is described as the first motor drive camera. When loading the camera the roll of film is wound onto a drum. At the same time a spring is tensioned. The mechanism advances the film after a pic has been taken. On one roll there were 12 exposures of 40 x 55 mm.
The one on eBay sold for € 335, which is about US$ 435.

Tisdell Detective camera
Another fine item is a 4 x 5 inch Tisdell Detective camera from the 1890's. Only 1 day to go, 14 bids at the moment, price now $ 520.

The last item I mention is a negative with an Autographic remark on it. There must be many of these around, but I do not see them often. If you would like to have one, here's your chance. 4 days to go, no bids yet, starting price $ 5.
Autographic negative