Optics

Target shooting glasses

From my discussion thread: http://slingshotforu...ooting-glasses/


I have made some target shooting adjustable iris safety glasses.

Such devices are sometimes used for target shooting disciplines that require iron sights because they offer several advantages:

• Superior depth of field
  
  • Both the fork tip and your target will be in sharp focus at the same time
    
  • Your eye will not have to find focus
    
  • Superior focus with or without spectacles
• Lower lighting levels
  
  • Less eye strain in bright light
    
  • Your iris sphincter and dilator muscles have less work to do
    
  • Your ciliary muscles around the lens have less work to do
• No cross-dominance issues
  
  • Only one eye can see
    
  • If like me, your left eye is ordinarily dominant and draw the pouch under your right eye, it will avoid parallax
    
  • No need to squint

These glasses look all gucci, but they cost me all of $10 in parts and the prohect was done in 20 minutes. You could make a passable non-adjustable in five minutes from a $3 pair of safety specs, a small drill and some black spray paint. A better, though still non-adjustable, version would use a bit of soft drink can with a pin-hole drilled in it to make a better, thinner, aperture plate.

They are functionally similar to Knobloch shooting glasses with an adjustable iris and left eye blinder, except for the additional benefits of:

• Eye protection
  
• Greater range of iris adjustment
  
• More complete black out
  
• All matt-black internal surfaces to cut reflection from the face

Drawbacks:

• Restricted vision
  
• Loss of binocular vision and depth perception
  
• Reduced light transmission
  
• A bit Borg-tastic; other shooters will likely take the mick

But don't knock it till you've tried it. It makes a huge difference in vision.


Fully Stopped Down to 0.7mm for Daylight Shooting




Partly Stopped Down to 2.5mm for Indoor Shooting




Fully Open




Specifications:

• 2mm polycarbonate safety glasses
  
• 10 blade aperture diaphragm, round aperture at all settings
  
• Continuously variable from 0.7mm to 11mm
  
• Eye relief approx 20mm
  
• AoV at 11mm = 300 mils (17 degrees)
  
• AoV at 11mm = 180 mils (10 degrees)

Here are some (simulated) examples.

Without Target Glasses, Eyes Focus on Fork



The fork is in focus, but the target is out of focus.

Without Target Glasses, Eyes Focus on Target



This is how people shoot. The target is in focus, but the fork is out of focus, especially in low light when your pupils dilate.

With Target Glasses, Stopped Down to Ideal Setting



You can see the target and the fork are both in focus, facilitating correct aim. The target is in better focus than without the artificial iris. The overall lighting level is corrected as well.

With Target Glasses, Stopped Down Far Too Much



If you go too far, the image becomes vignetted and occluded and the light transmission is reduced too much. Different lighting conditions require different settings, so it's best to have a range of adjustment.

I find this makes a lot of difference to me because of my cross dominance and weaker right eye.

A further refinement is to add polarisers or colour filters to improve contrast. This is not necessary when shooting at a black on white target.