Target size relationship

[Frommy]

Originally Posted by OpaNL

18 m = 40 cm face
30 / 50 m = 80 cm face
70 / 90 m = 122 cm face

Opa

Also 25m indoor = 60cm

[!!!]

Thanks for all the answers think I have just about got my head round this one.

Originally Posted by OpaNL

BTW: Nice bug, what do you have on the other end of the lines?

Opa

I fly Ozone Razors, think I was on the 5.5M the day that photo was taken.

[geoffretired]

Ben, I was using geometry of similar triangles but I have a suspicion that they give close approximations rather than exact answers. I don't remember the reasoning too well, but I think it's to do with the angle at the eye made by the target at different distances. When the target is a long way off, the distances and angles go hand in hand. When the distances are reduced, the angles are not such a close match to the relative sides of the triangles.
It's the tangent of the angles at the eye, I think. 1 degree has a tangent very very close to half that of 2 degrees. Tan 20 is not half of tan 40, however. The closer the targets are, the worse the error is between my rough working and the real answers.

[nelly]

I dont know if this is what you ment but here goes

the equivalent of a 122 face at 100 yads is
80 face at 65.34 yards
60 face at 49.00 yards
40 face at 32.67 yards

Ive got the same equivalents for 80,60,50 and 40 if you need them

[King Custard]

Someone please tell me i have it all wrong: but if I really want to make 6 gold ends at 100 yards ( the gold being 10 ins across) am i not trying to make 2inch groups at 20yds, 3inch@30yds and so on?

I have 16 meters at home to shoot at a layered foam boss so I just resize a jpg. file target face in 'word' until the gold is 1&1/2 ins across and then I can count line cutters. Must be nearly right cos it's still damn hard to make inch and half groups at 15/16 m

[Quadratus]

Yep - you're not wrong.

The ratio of the diameters is exactly the same as the ratio of the distances:

90m = 18m x 5,
therefore equivalent of a 122 cm face shot at 18m = 122/5
= 24.4 cm.

I sometimes shoot equivalent faces indoors, just to help avoid 'outdoor shock'. You know, that feeling when you see that tiny target about 5 miles away after a long winter of indoor luxury. Fun, so long as you realise that it won't tell you very much about how well you are shooting in reality.

[ThePinkOne]

Useful for getting the feel of sight pictures though.

I got my CorelDraw wound up and running and made a set of scale faces- both for home and for taking to club. Although the 60cm face at 20yd is like the 50yd target and the 40cm face at 20yd is like the 60yd so I only did 80 and 100yd scales equivalents in the end.

P.

[n.rijkebusch]

Originally Posted by nelly

I dont know if this is what you ment but here goes

the equivalent of a 122 face at 100 yads is
80 face at 65.34 yards
60 face at 49.00 yards
40 face at 32.67 yards

Ive got the same equivalents for 80,60,50 and 40 if you need them

Hi. Can you please let us have the equivalents (80 face) for distances 20, 30, 40, 50 and 60.
Thanks

[nelly]

Hope the photo of drawings helps. Obviously these are mathematical equivalents and take no account of the effects of wind over real distances.

[n.rijkebusch]

Hi. Thanks for all of your replies to my question. The diagram from Nelly is very helpful and makes sense to my maths. The formula that I have come up with for a 80 face equivalent to a 122 face is: Distance divided by 3 times 2 ( 2/3 ) So equivalent to 122 face at 40 yards would be 26 yards on a 80 face. This formula is only for a 80 face and is approx. distance, give or take a foot.
Thanks again.