I was reading the new Dart article about shooting and was wondering if anyone has seen a guide that explains how the different "revi" sights are marked...I've noticed that the Hurricane, BF109, KI-27, FW190, P-40, and Spitfire all have the same (more or less) markings (scale)...and that the A6M2,F4U-1D, J2M5,KI-43b,P-38L and YAK9 (most Russian) have another set of scale markings...

Ok...here's the thing. I have taken some screen shots and I have taken some rough measurements of gun sight rings and wingspans, and thats why I have some questions about what the rings, dashes, and hash marks on the various "in-game" gun sights actually measure...Historically the ring on the Spitfire gun sight held the FW190 at 100 meters but is that true for the "IL2 1946" Spitfire "ring"?

anyone?

This message has been edited. Last edited by: zardozid,

A simple way you could verify sight scales is to simply measure them on-screen with a ruler while zoomed all the way in. Of course, only the different types need be measured, and you could do this in less that half an hour.

If you want to be more precise, take screen shots and count pixels. But either way, make sure the sight is reasonably centered, because the gnomonic projection used does cause a small amount of scale distortion, even for the smallest FOVs.

I'm not sure about this, but the effective FOV (affects image scale) may differ by a small amount for the telescopic sights as carried by the Val, SBD, etc. That is, the equivalent FOV may not be quite 30 degrees.

quote:

Originally posted by Lurch1962:
A simple way you could verify sight scales is to simply measure them on-screen with a ruler while zoomed all the way in. Of course, only the different types need be measured, and you could do this in less that half an hour.

If you want to be more precise, take screen shots and count pixels. But either way, make sure the sight is reasonably centered, because the gnomonic projection used does cause a small amount of scale distortion, even for the smallest FOVs.

I'm not sure about this, but the effective FOV (affects image scale) may differ by a small amount for the telescopic sights as carried by the Val, SBD, etc. That is, the equivalent FOV may not be quite 30 degrees.

Ok...here's the thing. I have taken some screen shots and I have taken some rough measurements and thats why I have some questions about what the rings, dashes, and hash marks on the various "in-game" gun sights measure...Historically the ring on the Spitfire gun sight held the FW190 at 100 meters but is that true for the "IL2 1946" Spitfire "ring"?

Here is a screen shot I took of a FW190A4 as seen through the gun sight of a Spitfire VIII...At 100 meters the FW190's wingtips should touch the inside of the ring...but they do not.


According to "HardBall's Aircraft Viewer" the wingspan of the BF109G2 is 10.6 meters and the wingspan of the FW190A4 is 10.52...that makes the wingspan of the BF109G2 .08 of a meter larger then the FW190. And yet the BF109 appears to fill the "ring" of the of the "Spit" at 80 meters.


I have taken screen shots of most of the gun sights in "IL2 1946"...and all of the screen shots are at the same distance and all of them are centered "dead-a-head"...I have also measured the rings, dashes and hash marks of most of these gun sights, and for the most part they seem to be built from two different scales...what I mean is this: If you held the edge of a piece of paper along the middle line of one of the gun sights and marked off the rings, hash marks and dashes...you would find that the ring from one gun sight might be the same as a dash or dotted line from another gun sight. I marked off the ring/dashes of the BF109 and found that the Spitfire,KI-27,and P-40 (& probably a few others) all had rings & dashes, in common. I then measured out the rings and dashes of the A6M5 and found the same thing to be true of the F4U,P-38,and YAK9 (to name a few)...and yet the rings,dashes, and hash marks of one group doesn't line up against the rings/dashes of the other group...(are their two different "generic" wingspans that all "in-game" gun sights are built on??)


The last screen shot is of a Spitfire VIII (wingspan 9.8m) at 100 meters as seen through a BF109G2's "revi"...even though the Spitfire is not dead center of the "revi" it is clear that at 100 meters the wingtips reach beyond the ring of the gun sight...


I know that my screen shots are crude, and my conclusions are (somewhat) hasty, but I believe that they are adequate enough to conclude that the gun sights modeled in the game "may" not be "historically correct" models of the originals, and may in fact only represent a generic ruler (wingspans) to gauge your distance by...

I believe this may warrant further clarification...what do you think? Are my preliminary (rough) conclusions close enough to warrant a more exact study...or is my methodology flawed? The FOV views stretch the gun sights into an oval shape, but as you toggle through the FOV's the relative size of the wingspan to gun sight remain the same through out...

quote:

Originally posted by zardozid:
Historically the ring on the Spitfire gun sight held the FW190 at 100 meters but is that true for the "IL2 1946" Spitfire "ring"?

It's 100 yards, not 100 meters!

100 yards = 91 meters

Look at your second screenshot, the Bf-109 is 80 meters away, thats slightly between 90 and 100 yards and it fits perfect into the ring.

Good info non the less! I never really knew that. Maybe I can put it to some use. I knew there was a scale, just never knew what it was. Thx.

I'm more interested in how you got on a close six of those aircraft without be noticed!

quote:

Originally posted by No41Sqn_Banks:

quote:

Originally posted by zardozid:
Historically the ring on the Spitfire gun sight held the FW190 at 100 meters but is that true for the "IL2 1946" Spitfire "ring"?

It's 100 yards, not 100 meters!

100 yards = 91 meters

Look at your second screenshot, the Bf-109 is 80 meters away, thats slightly between 90 and 100 yards and it fits perfect into the ring.

you are right...in RL the British sights where in yards not meters...But I thought that ALL "IL2 1946" sights where in meters, and not their native scale. Anyway...in the screen shot here the FW190A4 wingspan just fills the inside of the Hurricanes ring at 80 meters (I measured the wingspan as the fighter is not centered)...That equals 87.5 yards not 100.

Go to QM Builder and choose a Spit for you and
Bf 109 for the rest of your squad.

Thanks, I figured that out after I posted!

I don't have a screen shot to support this claim (I'm in a rush right now, but I will make one later) but the only airplane I have tested (so far) that fills the Hurricanes ring "wingtip to ring" at 100 meters is the Sturmovik with a wingspan of 14.6 meters (interesting...I wonder why?)

quote:

Originally posted by buzzsaw1939:
Thanks, I figured that out after I posted!

sorry...I would have answered but I thought you where joking.

quote:

The FOV views stretch the gun sights into an oval shape

That's why you measure the reticle when it's at screen-center. The gnomonic projection used by the game causes greater radial stretching than tangential, hence the oval shape when a circle is off-center.

I believe that only a few gun sight models had reticles dimensioned for specific enemy aircraft. The majority were given "generic" 100 mil diameter circles, which by "good fortune" happened to closely fit a fighter's wingspan at 100m.

Here's how to find a reticle's actual angular size:

1) Measure your screen's actual game window display width, DW.
2) Note the field of view used (recommend 30 degrees), FOV.
3) Measure the reticle's diameter or other width, RET.

For example, say you have:
DW = 400mm
FOV = 30 deg.
RET = 80mm

The reticle's angular diameter =

= 2 * ATN{(RET/2) / ([DW/2] / TAN[FOV/2])}
= 2 * ATN{(80/2) / ([400/2] / TAN[30/2])}
= 2 * ATN{(40) / ([200] / TAN[15])}
= 2 * ATN{(40) / (200 / 0.2679)}
= 2 * ATN{40 / 746.4}
= 2 * ATN{0.0536}
= 2 * 3.07 degrees
= 6.14 degrees

Another thing you could do for comparison purposes... assign screen shots their own layers in a paint program (e.g., Photoshop), and adjust one layer's opacity so that it can be seen through.

quote:

Originally posted by Lurch1962:

quote:

The FOV views stretch the gun sights into an oval shape

That's why you measure the reticle when it's at screen-center. The gnomonic projection used by the game causes greater radial stretching than tangential, hence the oval shape when a circle is off-center.

I believe that only a few gun sight models had reticles dimensioned for specific enemy aircraft. The majority were given "generic" 100 mil diameter circles, which by "good fortune" happened to closely fit a fighter's wingspan at 100m.

Here's how to find a reticle's actual angular size:

1) Measure your screen's actual game window display width, DW.
2) Note the field of view used (recommend 30 degrees), FOV.
3) Measure the reticle's diameter or other width, RET.

For example, say you have:
DW = 400mm
FOV = 30 deg.
RET = 80mm

The reticle's angular diameter =

= 2 * ATN{(RET/2) / ([DW/2] / TAN[FOV/2])}
= 2 * ATN{(80/2) / ([400/2] / TAN[30/2])}
= 2 * ATN{(40) / ([200] / TAN[15])}
= 2 * ATN{(40) / (200 / 0.2679)}
= 2 * ATN{40 / 746.4}
= 2 * ATN{0.0536}
= 2 * 3.07 degrees
= 6.14 degrees

Another thing you could do for comparison purposes... assign screen shots their own layers in a paint program (e.g., Photoshop), and adjust one layer's opacity so that it can be seen through.

I will give this a closer look later today when I have a chance...(thanks) the weird thing about the stretching is the sight is longer in the verticle not the horizontal...

Forgot to add the conversions between degrees and mils:

mils = TAN(degrees) * 1000

degrees = ATN(mils/1000)

TAN = tangent
ATN = arctangent

=======================

Your comment re. the orientation of the reticle's distortion is a bit puzzling. If your screen aspect ratio is correct (same scaling in both axes), the reticle when centered should be circular, and when off-center will always be oriented so that the long axis of the projected ellipse points toward screen center.

Is your monitor a CRT (video tube)? If so, and the centered reticle is stretched vertically, you should adjust one or both of your monitor's display dimensions, via the front panel buttons, to achieve a correct aspect ratio. (This usually needs to be done, sometimes periodically, for each of the resolution settings you use.)

Continuing on with my study of the "gun sight" system in "IL2 1946"...I took some screen shots of a "FW190A-4" through a "Hurricane" sight at 100 meters. The screen shots are three "FOV views" (close, middle and wide) of the "toggle FOV" command as chosen in the controls section of "hardware options" . As you can see the relative size of the FW190 (to the sight) doesn't change as the FOV changes...their-for we can assume that changing the FOV dose not distort the relative size of a fighter (to the sight markings) when calculating distance with a "reticle gun sight"...

All screen shots are centered, and un-touched...

close


middle


wide

You're obviously giving this some thought--way to go! By conducting your own "experiments" you'll understand the issue better.

In case you weren't aware, optical gun sight reticles do no change apparent size as your viewpoint moves closer or farther.

For example, if you're in a plane whose virtual pilot moves fore/aft a fairly large distance when switching between the "normal" and "peer-through-the-gunsight" seating positions, you'll notice that even though the sight housing/reflector plate does change size, the projected reticle always stays precisely the same size.

This is because the collimating lens projects an image that effectively appears to lie at infinity (or at the very least, at a MUCH greater distance than the sight itself.)

Some people mistakenly believe the reticle is actually projected ONTO the reflector plate. The reflector plate is there only to act as a re-directing window which superimposes the reticle onto the view outside the plane.

Another clue which reveals that the reticle is NOT projected onto the reflector... when the viewpoint moves perpendicular to the sight line (i.e., left/right or up/down, as when the pilot is bounced around), the reticle also moves in the same direction with respect to the sight. Move off-axis far enough, and the reticle is clipped, or even completely invisible.

Moreover, even while the reticle is "sliding" around the reflector because the pilot is moving around, the reticle remains stationary with respect to the outside world.

That's the reason optical sights exist. Unlike the old-fashioned ring-and-bead sight which requires the pilot to EXACTLY line up his eye with it, the optical sight negates the effects of parallax shift when the eye's position changes. The bigger the collimation lens/reflector plate, the more relaxed eye placement becomes. Definitely a good thing in a violently maneuvering plane!

--Lurch--

quote:

Originally posted by Lurch1962:
You're obviously giving this some thought--way to go! By conducting your own "experiments" you'll understand the issue better.

In case you weren't aware, optical gun sight reticles do no change apparent size as your viewpoint moves closer or farther.

For example, if you're in a plane whose virtual pilot moves fore/aft a fairly large distance when switching between the "normal" and "peer-through-the-gunsight" seating positions, you'll notice that even though the sight housing/reflector plate does change size, the projected reticle always stays precisely the same size.

This is because the collimating lens projects an image that effectively appears to lie at infinity (or at the very least, at a MUCH greater distance than the sight itself.)

Some people mistakenly believe the reticle is actually projected ONTO the reflector plate. The reflector plate is there only to act as a re-directing window which superimposes the reticle onto the view outside the plane.

Another clue which reveals that the reticle is NOT projected onto the reflector... when the viewpoint moves perpendicular to the sight line (i.e., left/right or up/down, as when the pilot is bounced around), the reticle also moves in the same direction with respect to the sight. Move off-axis far enough, and the reticle is clipped, or even completely invisible.

Moreover, even while the reticle is "sliding" around the reflector because the pilot is moving around, the reticle remains stationary with respect to the outside world.

That's the reason optical sights exist. Unlike the old-fashioned ring-and-bead sight which requires the pilot to EXACTLY line up his eye with it, the optical sight negates the effects of parallax shift when the eye's position changes. The bigger the collimation lens/reflector plate, the more relaxed eye placement becomes. Definitely a good thing in a violently maneuvering plane!

--Lurch--

thanks for the info...

I have been a little slow with my research (as time permits)...

I figure that with the importance convergence makes (with .50cal fighters) and all the tutorials on judging range with the reticle sight I should clarify (for myself) what scale (distance) the circles/hash marks, and lines represent...

(and) why their seems to be two different scales used for modeling the sights...(whats up with that?)

quote:

Originally posted by Lurch1962:

That's why you measure the reticle when it's at screen-center. The gnomonic projection used by the game causes greater radial stretching than tangential, hence the oval shape when a circle is off-center.

I believe that only a few gun sight models had reticles dimensioned for specific enemy aircraft. The majority were given "generic" 100 mil diameter circles, which by "good fortune" happened to closely fit a fighter's wingspan at 100m.

Here's how to find a reticle's actual angular size:

1) Measure your screen's actual game window display width, DW.
2) Note the field of view used (recommend 30 degrees), FOV.
3) Measure the reticle's diameter or other width, RET.

For example, say you have:
DW = 400mm
FOV = 30 deg.
RET = 80mm

The reticle's angular diameter =

= 2 * ATN{(RET/2) / ([DW/2] / TAN[FOV/2])}
= 2 * ATN{(80/2) / ([400/2] / TAN[30/2])}
= 2 * ATN{(40) / ([200] / TAN[15])}
= 2 * ATN{(40) / (200 / 0.2679)}
= 2 * ATN{40 / 746.4}
= 2 * ATN{0.0536}
= 2 * 3.07 degrees
= 6.14 degrees

Another thing you could do for comparison purposes... assign screen shots their own layers in a paint program (e.g., Photoshop), and adjust one layer's opacity so that it can be seen through.

Lurch,

can you help me with 2 questions on this topic ?

first, the formulae you give above for calculating the gunsight reticle's actual angular size, includes amongst its variables a value for the screen FoV setting and a measurement of the reticles measured diameter on the monitor/screen. since the FoV setting is an "angle value" already, extracting the angular size of the gunsight seems a logical process.

but is there a way you can calculate the diameter that a real gunsight reticle would have been in a real aircraft cockpit in ww2, as it was seen by the pilot when displayed on the gunsight glass of a real gunsight in front of him ?

if that is possible with your knowledge of optics and geometry, i'd be most interested in knowing how to calculate this. lets presume that a real reticle as seen in the Spitfire and Hurricane MK-II gunsight was 110mills diameter (those were the early british gunsights during ww2) , and a german A Revi 16B Reticle was 100mill diameter (as used in the late model 109's), do you know of a way to calculate what the displayed diameter of that reticle would be as measured by the pilot directly on the reticle glass of the gunsight ? we know that the pilots head was more or less an arms length from his instruments and gunsight, so we could choose the distance value to be between 60 cm and 1.00 meters as an example. since we know the viewing distance and the mill size of the reticle diameter, how can we calculate the exact measurement of this reticle diameter in cm ?



secondly, i always thought that the diameter of the reticle luminated circle stayed the same when the pilot would lean forward or backwards in a real aircraft. and i noticed you earlier made a statement in this thread that indicated the same ....

quote:

Originally posted by Lurch1962:
In case you weren't aware, optical gun sight reticles do no change apparent size as your viewpoint moves closer or farther.

For example, if you're in a plane whose virtual pilot moves fore/aft a fairly large distance when switching between the "normal" and "peer-through-the-gunsight" seating positions, you'll notice that even though the sight housing/reflector plate does change size, the projected reticle always stays precisely the same size.

This is because the collimating lens projects an image that effectively appears to lie at infinity (or at the very least, at a MUCH greater distance than the sight itself.)

Some people mistakenly believe the reticle is actually projected ONTO the reflector plate. The reflector plate is there only to act as a re-directing window which superimposes the reticle onto the view outside the plane.

Another clue which reveals that the reticle is NOT projected onto the reflector... when the viewpoint moves perpendicular to the sight line (i.e., left/right or up/down, as when the pilot is bounced around), the reticle also moves in the same direction with respect to the sight. Move off-axis far enough, and the reticle is clipped, or even completely invisible.

Moreover, even while the reticle is "sliding" around the reflector because the pilot is moving around, the reticle remains stationary with respect to the outside world.

that makes perfect sense to me, because the gunsight reticle represent a fixed value of "mill size" (depending on the brand/type of gunsight), and the distant object it measures (say a 109 at 300 meters) remains unchanged when the pilot leans forward or backwards. the pilots head movement might be about 40 or 50 cm, but for a distance of 300 meters that is negligible, so when the pilot leans forward/backwards the reticle indeed should stay the same in my opinion.

this is a nice diagram to illustrate one of these gunsights.


now the confusing part is that when i asked the owner of one of these working gunsights to report what he observed when it was switched on, and he would lean closer or further away from it, he reported that the luminated circle did change size ! when he moved his head back it became larger, and similarly when leaning towards the gunsight the luminated reticle would get smaller.

i could understand that when the pilot leans forward towards the gunsight, that the gunsight itself now takes up a larger part of his field of view (so appears larger to him, but its actual physical measurements remaining the same), and if the reticle circle represents a fixed "100 mill" then this circle will seem to be smaller in relation to the gunsight glass it is displayed on (but the size the 100 mill is equivalent to should have remained unchanged)

yet the person who played around with the working gunsight reports the reticle changes approximately 1 cm in size, depending if it held closer or further away from the viewer. he made those size comparisons by keeping a ruler placed against the gunsight glass.

what is your take on this ? the gunsight had an improvised light source, not the normal lightbulb (he used a flashlight at its base instead), but that shouldnt have produced such radically different observations. interestingly, when the observer looked through the gunsight and the reticle circle was aimed at a distant object, the small scenery section it "framed" remianed unchanged when the observer leaned forward/backwards. that seems logical, so the sight was working correctly. but why would the reticle size seem to change by 1 cm when the observer leaned forward/backward ?

The flaw in the gun sight owner's methodology was placing the ruler on the glass! That's completely invalid. Of course he will get the results he got. For example, as you pointed out, when the pilot moves in closer the reflector plate appears to get larger, while the reticle stays the same size. Your correspondent was only noting the same thing with his ruler, but neglected to note the reticle's size with respect to something *much* farther away than the reflector plate.

As you very clearly already understand, the reticle size must be compared to a *distant* object. The collimating lens ensures that the reticle will appear to lie essentially at infinity. And this means that as seen from *any* distance, the reticle's angular size will remain fixed.

If one were to step back quite far from the gun sight, the reflector plate will appear to shrink to the point where the full reticle pattern will not be seen, but instead only a portion of it. Even so, in this case the reticle will still present the same 100 (or 110) mil circle.

I forgot to add... the gun sight illustration has the optical path ray tracing completely wrong. And as a result it can very easily lead to an incorrect understanding or just how they really work.