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View Full Version : An innaccuracy with telescopic sights?



Lurch1962
06-17-2008, 01:09 AM
Leitmotiv's comments in another thread regarding the "new" way to use the telescopic sights via the 6dof support in that "entity-which-must-not-be-discussed" reminded me...

In IL-2, when the pilot's eye is up against a telescopic sight the view is magnified to the equivalent of the narrowest 30 degree wide FOV. This is, I presume, to closely simulate a 3X magnification, given that most of one's flying is done at the 90 degree FOV setting. But when the viewpoint is in the "normal" seated position, the small part of the scene still visible through the sight's eyepiece is shown at the *same* scale as the rest of the view.

This is incorrect.

Whether your eye is close to or distant from a telescope's eyepiece, the view through it will always be of the same magnification. The only difference is in the size of the visible field of view through the instrument. As you move your eye farther from the eyepiece, the visible field shrinks markedly, but the magnification remains the same. If you have a binocular handy you can verify this for yourself.

So let's say for the sake of argument that the sight's magnification is indeed 3X, as was the case for the SBD, at least. As seen from the "leaning back" seated position, the small piece of the scenery seen through the sight should also have a magnification of 3X. This means, to first approximation, that at the FOV setting of 90 degrees, the small part of the view seen through the sight should be zoomed in by a factor of 3, or roughly the equivalent of the image scale for the 30 degree FOV. And if the FOV is set to 30 degrees, the sight's view should also be zoomed in by a factor of 3 with respect to that, resulting in an equivalent FOV of 10 degrees.

But as it is, when sitting back from the sight, as one varies the FOV setting, the scene in the eyepiece is always at the same magnification as the general view. This would be the true situation for a unit-magnification (1X, if you wish) sight.

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So, Leit, I'd be curious as to how your "new" ( http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif ) implementation handles the sight picture. Does it still render the incorrect "1X" magnification with respect to the non-sight view? If so, then I guess you get the 3X effect by simply zooming in the FOV to 30 degrees, as is normal for other sight types.

If you could provide a picture or two, if there are differences graphically?