Optics?

How did optics compare, used during WWII, bombsights, gun sights, sights on tanks, u-boats etc., etc...

How did they what, old boy?

That's a lot of different equipment types. Why don't you pick one category for comparison.

So many threads then!

Ok,

Let's start with.....optics on the tanks!

One of the best descriptions I have seen.
Tanks in World War 2 Forum ? View topic - British and US tank sights vs the Germans sights
Telescopic sights is something most people don't know a huge amount about or there are lots of myths about. One of the big ones I hear and is that allied sights were inferior in magnification to German ones. Allied optics for the most part were not inferior in magnification to German ones. Originally the British 2 pounder gun and associated tanks had a 1.9x magnified sight, which was somewhat inferior to the 2.4x magnified German sights on tanks, which may be the cause of this myth. However American and British tank sights (6 pounder, 75mm, 17 pounder etc) had a 3x magnified sight which was slightly superior in zoom to the 2.4x magnified German sight on more of their common tanks such as the Mark III and Mark IV.

Only certain German tanks had the fancy adjustable optics that had both a 2.5x magnified and 5x magnified option for the sight, mainly on the late production Tigers (originally had 2.4x) and Panthers, and probably other late war ones. The StuG Assault gun series had a 5x magnified direct fire sight it retained but it was not adjustable. However several allied tanks had high powered optics as well. The Sherman Firefly was equipped with a 6x magnified sight, but whether this was adjustable or had to replace the standard 3x magnified optic I am unsure of. The Shermans with the 76mm gun also had a 5x magnified optic while standard shermans had a 3x magnified optic.

So why the notion that German optics were better than allied ones? It has more to do with other factors besides the simple magnification. The 2.4x magnified German sight on Mark IIIs, Mark IVs, and early tigers had a wide 25 degree field of view. In comparison allied 3x magnified optics had only a 13 degree field of view. The adjustable German 2.5x and 5x optics also had an wide FOV compared to allied optics. The 2.5x sight had a 28 degree field of view, while the 5x optics were 14 degree FOV. In short German 5x optics had slightly better FOV than allied 3x, and German 2.4x and 2.5x optics had roughly double the FOV. The high powered 6x sight for the Firefly had a 9 degree field of view which is rather limited. The only allied optic that compared to german sights in magnification and FOV was the 5x optic put in the Sherman 76 series, which had a 13 degree FOV, similar to the 5x mag 14 degree FOV of the German adjustable optics. The StuG was something of an exception, with only an 8 degree FOV for its 5x mag optic, which means it was inferior in that respect to allied optics of similar or even better magnification. What this meant in practice is that German gunners had an easier time acquiring targets their commander assigned for them, as the larger field of view allowed them to see more than allied ones did.

Another advantage of the German optics was their design which created a 'Mili-radian' sight. If you have ever seen one you will see a lot of triangles, but there is a purpose. The triangles utilized a mils that, combined with some math skill taught to panzer crews and a rough idea of tanks size (not hard when your enemies has focused production of a few types of tanks exclusively), allowed the gunner to calculate a rough range of the tank without even having to take a ranging shot. This allowed German gunners to have a high chance of getting first shot hits, and combined with the high velocity guns and powerful guns they had access to from the middle of the war onwards on their tanks, this often meant a kill on the enemy tank before they could react. They were adjustable with a dial around the edges of the optics that let the gunner know what range was dialed in.

Its rather complex but if you are interested you can find a guide here http://www.75thguards.com/ww2online/dow ... _Guide.pdf

American optics were rather primitive in comparison, simply a line down the middle with crossing lines representing 400 yard intervals. They were totally nonadjustable and it must have been rather infuriating trying to land a second shot since the lay of the gun and sight would be thrown off with the recoil and with so many lines you could forget which of those many lines you had lined up on the enemy tank. I know from playing WWIIOL and using those optics that they are not particularly easy to use. British optics on their post 2 pounder armed tanks were similar to the American optics in that they had all the ranges listed in the sight, but it was adjustable so at least you didnt have the problem with the US optics. Whether the british put their own optics in the lend lease Shermans or not I do not know. Still allied tanks lacked this clever triangle system and would have had to rely more on ranging shots which put them at a disadvantage though modern american optics do have a triangle system though not the same design.

So in conclusion allied optics were not inferior to German optics because of magnification, for the most part they had similarly powered optics to the German ones, and standard allied tanks had a relatively adequate 3x zoom on them. However German optics were superior in field of view to similarly magnified allied optics, perhaps this is why the German optic industry had such a higher reputation than any other at the time. Also the German optic design allowed for panzer crews to estimate accurately the range of allied tanks without needed to fire a ranging shot, thus allowing for a higher percentage of first shot hits, and with the large amount of high powered guns they had as the war went on, often first shot kills.

Two of the most important things are missing in that article.
1) In 1938 the Zeiss company pioneered a manufacturing technique that coated gunsight lenses with argon gas. This resulted in much clear lenses and that only lost about 4% light per lens. As the war began the Germans could manufacture gunsights with up to six lenses that either got a higher magnification for the same field of view or greater field of view for the same magnification than other countries.

2) During the war their optical glass was improved by the addition of 'Lanthanum' that further improved the clarity and light transmission.
One of the crucial materials the German sent to Japan was this optical glass.

Mobius, methinks you mispoke - one cannot "coat a gunsight lens with Argon" Argon is an inert gas and as such cannot be "coated" but one could extract the air between lenses in the tube and replace it with Argon thus removing water vapor, oxygen, carbon dioxide, sulfur dioxide, etc. The inert gas woud also prevent any moldsfrom growing within the tube

Interesting.

mikewint said:

Mobius, methinks you mispoke - one cannot "coat a gunsight lens with Argon" Argon is an inert gas and as such cannot be "coated" but one could extract the air between lenses in the tube and replace it with Argon thus removing water vapor, oxygen, carbon dioxide, sulfur dioxide, etc. The inert gas woud also prevent any moldsfrom growing within the tube

Click to expand...

I beg to differ.
AVS Thin Films History

During the evaporation, the material is heated to a high temperature in a crucible so that it evaporates. These vapors spread in the high vacuum straight out and condense on all cooler spots of the apparatus. High vacuum is essential so that compact films develop (hard and abrasion resistant films). If the base on which the vapors condense is shiny and smooth, thin films develop that are also shiny, i.e., target reflective).
During the cathodic sputtering, an argon gas is ignited through glow discharge.
Through bombardment with Argon ions, the material (of which the film is supposed to be made) gets sputtered. The great advantage of this method is, that it is a cold procedure, where the film material doesn't have to be heated.
Newer procedures could be interpreted as a combination of both processes: Through an activating process, the vapor gets partially ionized to increase the chemical capacity for reaction. In so called ion plating, the condensation takes place under a bombardment through ions (argon and evaporation material) which add energetic particles to the process.

Click to expand...

I can't tell if Argon is the end coating material or just a carrier of the actual coating molecule Cryolite (Na 3 Al F 6, sodium hexafluoroaluminate). Though from that article it looks like it just enables the coating and then dissipates.

There are 6 inert gases starting with Helium through Radon which is radioactive though chemically inert the large atomic radius of Krypton and Xenon make it possible to remove/add electron (high temps/pressures/catylic agents) and form stable compounds. In recent years Argon has been forced to ract with Fluorine but the compound Argon Fluorohydride is unstable above -233C. None of this would have been possible in WWII Germany but the chemically inert Argon was used (as it still is) as a "carrier" in electrospray ionization which allows the deposition of ultra-thin coatings. For example Argon is preferred for the sputter coating of specimens for scanning electron microscopy. If you read your quote carefully: Argon (ions) gas is being used to carry "the material of which the film is supposed to be made" for the sputter deposition of an ultra-thin film. The thiness of the film is important because light "bends" refracts as it enters and leaves different materials (bent pencil in a glass of water). Each color bends at a different angle thus lenses produce color halos (chromatic abberation). These color halos can be lessened by multi-element lenses and special coatings. Collectively these bring the various colors to essentially the same focus. It is also important to eliminate, as much as possible, reflection. Ordinary window glass reflects as well as transmits light. The reflected light is un-noticeable in the daylight but becomes quite apparent at night.

OK, thanks for clearing that up. I couldn't tell by that article if Argon was used as a carrier of the coating material or was etching the glass.

Argon is inert chemically and reacts with nothing including Fluorine (except under VERY special conditions) Glasses and even ceramics instantly burst into flame in Fluorine.
If you really mean "etch" that is done with Hydrofluoric acid. Under electron bombardment Argon can be forced to accept an extra electron forming an ion which will electrostatically attract and hold a metal. Thus Argon is carrying a metal atom. The entire system is unstable and when it breaks down the metal is deposited on the target surface, in effect, one atom at a time.

Mobius is referring to "Sputtering", which is a process that employs gases, including Argon.

It's used in several industries, such as optic coating. Basically, it's a momentum-transfer process where ionized Argon gas is accelerated towards a negatively biased target and the ions dislodge (sputter) particles from the target to deposit on the substrate.