As some may already be aware, I recently bought an old 19th century tailboard plate camera from Asha. In the sale thread, I mentioned that I plan to use it, and that means that it needs to be checked over and any issues addressed. As expected, given that it is already a working camera, the issues I found are minor and straightforward to take care of. In this thread, I'll describe what I found, and what I did, as well as add comments about the camera as I find things out.
The first thing I looked at was the tripod mounting. The thread for this was neither 1/4" or 3/8". I measured the diameter of the bolt that came with the camera, and got a smidge under 7.8mm, which is very close to 5/16", and a thread pitch gauge told me that the pitch was 18 tpi (threads per inch). A check online for some Whitworth thread specs confirmed that it was 5/16 BSW, so a die and some taps were duly ordered.
When they arrived, I made a new screw that would fit into a Manfrotto 410PL quick release plate. Here's the new screw, surrounded by the two modern screws that came with the plate, and the bolt that came with the camera...
It's made from hexagonal profile brass bar, mostly on a lathe.
Fits the plate nicely...
I milled a little slot in it so that I can tighten it up with the screwdriver on my Swiss army knife...
It all seems to tighten up nicely and sits well on the tripod.
That gave me a chance to focus on distant objects through the window and get a handle on the focal length of the lens and see what the apertures are in reality.
The focal length looks to be 8", or 203.2mm if you don't speak groats and cubits. The diameters of the openings in the aperture wheel were then measured. Here's the list of diameters with the engraved numbers on the wheel...
11 - 14
16 - 10.1
22 - 6.6
32 - 4.8
44 - 3.56
When the areas are calculated and compared to each other, the stops aren't quite double/half, but are pretty close. From the '11', the ratios of the subsequent areas are 1.9x, 2.3x, 1.9x and 1.8x. What's more relevant is the calculation of focal length divided by diameter to get the actual f-numbers...
11 - 15
16 - 20
22 - 31
32 - 42
44 - 57
In practical terms, the real f-stops in modern-speak are: 16, 22, 32, 45, 64. So, to set an f-stop, I just go up one from the number on the aperture wheel. In spite of being f/16 at max aperture, the image on the ground glass was surprisingly bright - easy enough to focus in a darkened room looking outside, with no dark cloth.
More to come...
The first thing I looked at was the tripod mounting. The thread for this was neither 1/4" or 3/8". I measured the diameter of the bolt that came with the camera, and got a smidge under 7.8mm, which is very close to 5/16", and a thread pitch gauge told me that the pitch was 18 tpi (threads per inch). A check online for some Whitworth thread specs confirmed that it was 5/16 BSW, so a die and some taps were duly ordered.
When they arrived, I made a new screw that would fit into a Manfrotto 410PL quick release plate. Here's the new screw, surrounded by the two modern screws that came with the plate, and the bolt that came with the camera...
It's made from hexagonal profile brass bar, mostly on a lathe.
Fits the plate nicely...
I milled a little slot in it so that I can tighten it up with the screwdriver on my Swiss army knife...
It all seems to tighten up nicely and sits well on the tripod.
That gave me a chance to focus on distant objects through the window and get a handle on the focal length of the lens and see what the apertures are in reality.
The focal length looks to be 8", or 203.2mm if you don't speak groats and cubits. The diameters of the openings in the aperture wheel were then measured. Here's the list of diameters with the engraved numbers on the wheel...
11 - 14
16 - 10.1
22 - 6.6
32 - 4.8
44 - 3.56
When the areas are calculated and compared to each other, the stops aren't quite double/half, but are pretty close. From the '11', the ratios of the subsequent areas are 1.9x, 2.3x, 1.9x and 1.8x. What's more relevant is the calculation of focal length divided by diameter to get the actual f-numbers...
11 - 15
16 - 20
22 - 31
32 - 42
44 - 57
In practical terms, the real f-stops in modern-speak are: 16, 22, 32, 45, 64. So, to set an f-stop, I just go up one from the number on the aperture wheel. In spite of being f/16 at max aperture, the image on the ground glass was surprisingly bright - easy enough to focus in a darkened room looking outside, with no dark cloth.
More to come...