Meters & Feet?

[stephen_w.]

My "50" mm DR as actually 51.9mm

[mskovacs]

<i>This may also explain the 39mm x 26 tpi thread of the screw-mount Leica.</i>

<p>Since there are 25.4mm in an inch, it is more likely that it corresponds to 1 thread per mm or 10 threads per cm. In Canada, I'm young enough to have been educated in metric but its always been necessary to know both systems IMO. What drives me nuts is the difference between American and British units, e.g. the gallon.

[andy_piper2]

"The metric system never really caught on in the USA, excepting of course, the nine millimeter bullet."

 

...and, of course, 35mm film. Have you EVER heard it called "inch-and-a-half" film?

[icuneko]

Since this is a photography forum, let us not forget "light years." Try measuring one of those using 5 feet per two paces when tipsy. You could end up in a black hole.

[summitar]

186,000 miles per second. It's not only a good idea...it's the law!

[michael_spencer3]

Mike Kovacs wrote: "What drives me nuts is the difference between American and British units, e.g. the gallon".

 

A long time ago a "gallon" was not very specific. It was used in the same vague manner that a "glass" of something is used nowadays. For example, if you go to a restaurant and ask for a glass of water and a glass of tomato juice you will probably not be surprised if the former is a larger glass than the latter. Anyway, before 1824 or so gallons had the same non-specificity although there were semi-standard sizes for various liquids beer and wine among them (both different quantities).

 

In 1824 or so they had an international conference to settle on various measures. The French got their metric system adopted as an international standard, the British got the Prime Meridian at Greenwich. The British proposed the Imperial Gallon (277 cubic inches) at the same time, but the US was still smarting from having the White House burned down, so it balked at that one and adopted the traditional US wine Gallon (of 231 cubic inches) as it's standard rather than the Imperial gallon. At the time, probably no one cared and no one worried about the future impact of the US economy on all types of international commerce.

 

For easy conversion remember that the British pint=20oz and the US pint=16oz. Both systems have 2 pints=1 quart; 4 quarts=1 gal. So the Imperal Gallon=160oz and the US gallon=128oz.

 

Barrels have a similar history. They typically vary according to the fluids they are carrying (beer, oil, spirits, wine), although there are some standards e.g. a barrel of oil is probably standard the world over. If you really like trivia, try to figure out how many "gallons" are contained in a "barrel".

 

Mike Spencer

[stephen_w.]

"Simple" answer: 42 gal/BBL.

[kelly_flanigan1]

Barrels vary all over the place; so no real simple answer at all. Beer maybe 31.5 gallons; or 42 gallons; or 31 gallons or ??. But then Hogsheads tend to be 63 gallons. Ok the student needs to convert Tuns to gallons; for ale and wine :) Rain barrels come in all sorts of sizes; with barrel usually between 50 to 65 gallons. <BR><BR>The crafty State Liquor laws define the barrel for liquors sometimes different liquors; depending on the state. Taxes on Fermented liquors can be 31 gallons; other liquids at 31.5 gallons; oil at 42 gallons. Proof spirts can be 40 gallons for a barrel. In rain and cistern work the 36 gallon barrel is used sometimes. Beer in Washington, Iowa, Michigan, Missouri, Ohio, Utah, Arizona, Texas and Oregon are taxed with the 31 gallon barrel. Nebraska defines a half barrel as 15.5 gallon; in their Liquor laws. <BR><BR>Arkansas uses the 32 gallon barrel for beer tax. <BR><BR>I think Ohio was once a 31.5 gallon state.<BR><BR>In bourbon; the barrel maybe 53 gallons. After being store the wood absorbs a few gallons.<BR><BR>There are a mess of variants for the barrel; that vary with location and contents.<BR><br>OK enough of this Firkin around and alot of hot Ullage

[Jeffrey L.T. von Glück]

An interesting thread, and there can be disasterous consequences when working carelessly with both systems. NASA generally measures altitude and distances in feet or international nautical miles (6,076.1 ft or 1,852 metres), velocity as feet per second or miles per hour or knots, which is the custom in civil aviation, and most other measurements in metric.<p>A few years back NASA had one of their Mars probes crash land on the planet. It was later discovered that someone inputted navigational data in one system rather than the other. The result was a multimillion-dollar pile of junk on the surface of Mars.

[kelly_flanigan1]

In the USA a nickel; ie 5 cents; 1/20 dollar coin weighs 5.00 grams. Currency; USA bills weigh 1 gram each. 1 million 1 dollar bills weighs 1000,000 grams; ie 1000Kg; one metric ton. The million dollars in 20 dollar bills weighs only 50 Kg.

[huw_finney]

The US standardised its yard on the (French) metre in the late 1900's to save the cost of their own standard, we (the British) did this as 25.4mm/inch (precisly) in 1959 so we could build Concorde.

[huw_finney]

er 1800's, 19th century.

[mskovacs]

Huw a yard is 3 feet not 1 meter.

[huw_finney]

I know, it was standardised on, not made equal to i.e. 0.9144m = 1yd

[neil_parker]

B/W shooting always made me feel schizo; I would buy a 100ft roll of bulk 35mm film,

shoot it in my 35mm camera w/ a 105mm lens, load it into a metal tank and add 16 ozs of

developer, then finally print it with a 50mm enlarging lens on 8"x10" paper.

[al_kaplan1]

Does anybody know how the British got to calling 6.5"x8.5" cameras "full plate" and 3.25"x4.25" cameras "quarter plate"? Was it based on a standard window pane size or something back in the days of coating your own plates? And how did the industry ever decide to standardize the outside dimension of both 4x5 inch and 9x12 cm (about 3 1/2"x4 3/4") film holders so they'd both fit either your Speed Graphic or your Linhof?

[kelly_flanigan1]

Aerial Plotting glass Plates from Kodak were 9.5x9.5 inches; or 7.5x7.5 inches. <BR><BR>In Kodak Spectroscopic Plates; a mess of sizes was used. 1x3 inches; 2x10 inches; 3.25x4.25 inches; 4x10 inches; 5x7 inches; 8x10 inches;<BR> 6.5x9 cm; 9x12 cm; 16x16 cm. <BR><BR>These are 0.040 thick plates; that are?/were special order; about 3 months for delivery. In Astronomy; the 103a series was popular; a slow speed film that didnt poop out with a hours exposure

[kelly_flanigan1]

The Kodak glass plates for Scientific usage are of a very special glass; of a known controlled very low expansion rate. In Astronomy; a micrometer rig/lighttable rig is used to measure a stars position on the glass plate

[kelly_flanigan1]

The single exposure back for my Mamyia C3 TLR holds a glass plate about 2.5x3.5 inches. One removes the cut film holder insert. With cut sheets; the holder/insert is used; for 2 1/4 x 3 1/4 inch cut sheets. The single exposure back kit has a different back; and three film holders; each with a dark slide. Since of course the image is only a 6x6cm format; there is a good margin for fingers to hold the films during loading or development :)

[rico_tudor]

<<American cars switched over to metric some time ago...>>

 

Say that when shopping for tires!

[huw_finney]

Try tyres!

[jonathan_reynolds]

<< On a related topic, an English banker recently explained to me the advantage of Britain's pre-1970s duodecimal money system (12 pence to the shilling) over our American decimal system (10 cents to the dime).

Having 12 rather than 10 as the money base allows equal division in a greater number of different ways, as 12 is evenly divisible by 2, 3, 4 and 6, while 10 is evenly divisible only by 2 and 5 (discounting the trivial case of division by 1 and 12 or 10, respectively). >>

 

Unfortunately, by the 1970s it was meaningless to divide a shilling more than once, because the resulting fragments bought nothing. There were twenty shillings in a pound (not so handy for division), hence accounting took place with 3 different bases (10, 20 and 12). OK, a modern computer can handle that (though they still weren't very advanced in 1971), but it required the entry of 3 numbers instead of just one. It was just silly.

 

On the other hand, working in fractions is handy for carpentry, where you often need to divide lengths, and I find the old feet and inches handy. For instance, if you need to divide 5/8 by two, you just read off 5/16. (The people who invented the A-series of paper sizes should really have thought this out: look at the official dimensions of A4, only 4 divisions down the series: 210 x 297 mm!) For rough work, it's handy that feet and inches (and ells and cubits) can be measured off your own body.

[dan flanders]

JONATHAN: Actually the Roman Legions had a slightly shorter mile which the English copied but enlarged a bit. As it stands today a 'pace' (1/1000 mile) is obviously 5.28' or 23.36". In any event it makes a good barroom bet if you don't win too many in a row. The famous Swiss/French architect, LeCorbusier, claimed that his apprentices who had been trained in the English measurements had a better understanding of scale and proportion than those trained in metrics, attributing it to the English system having been derived from human proportions versus the totally abstract metric system.

[jonathan_reynolds]

Harry, I thought I knew that the Romans only counted their left feet, so that they counted fewer paces than we do? Was that simply rubbish?

[dan flanders]

Apparently the Romans counted their cadence the way most armies do, each time the left foot hit the ground, and called it a pace. Unfortunately we moderns have become quite loose and many confuse the pace with the step. A pace is two steps and there are a thousand to a mile. By todays standards it isn't very precise, but for the Romans it enabled them to conquer much of the known environs of Europe and parts of Africa and the Near East. The mile was simple to divide binarily and then again by half, and then again resulting in a Furlong (furrow long, 660', ten chains). Then measure out a field one chain wide (66') and you have an acre, the amount of land that can be plowed with a yoke of oxen in one work day (custom was to rest the oxen four hours in the afternoon while the plowman took a siesta or went about other business). The yard was derived from the fathom which was supposedly the width of a Viking's embrace (6') and was divided into two ells or four spans. Those proportions were easy for the common man to comprehend and employ in everyday life and there was no need for anything more precise until the advent of the industrial revolution when manufactures required more precision.