POI shift spec’ula­tion

Air Gunner - - Your Letters -

Two things about glasses: I did an ex­per­i­ment be­cause my dis­tant vi­sion is fine, but I wear glasses for close-up work so I have var­i­fo­cals. I shot a few tar­gets at 30 yards with my glasses on – all fine – and then shot a cou­ple of groups with glasses re­moved. To my sur­prise, I had a 1cm group shift to the right – I am a lefty – so I put my glasses back on and the group re­turned to the orig­i­nal po­si­tion! Also, I have tran­si­tion lenses and they are a bad thing for air­gun­ners, in my opin­ion. When I need them most, I’m sit­ting in my car and they don’t work due to the wind­screen UV fil­ters, so if you are go­ing to do FT or HFT, do not use tran­si­tion lenses. You can sit

in the sun, the tar­get also in the sun, with no prob­lems, but your next tar­get might be in a heav­ily shaded area whilst you are still sit­ting in the sun; your glasses will still be max­i­mum dark brown and you will strug­gle to see it.

Go­ing back to point one above, if you re­move your glasses for this shot so you can see the tar­get, you will prob­a­bly miss it and won­der why – POI shift. Peter Finch

Do our spec­ta­cles cause POI shift? Peter Finch be­lieves so

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