Thread: Parallax Adjustment

So does this mean with say that S&B if you are looking at a target 400 metres away and parallax is set at 300 the target will actually be slightly out of focus? Ie does parallax adjustment = focus of sight picture?

Originally Posted by ebf

Do not worry about the numbers on the objective ring or side focus, those are just indicators.

+1.

No it will be perfectly focussed with ajustable scopes you can make it a problem if you set the parrallax wrongly. With ao scopes or below 10x mag it really isnt an issue. Look up parrallax to get a better understanding. I have a buggered old rangefinder that used parrallax to calculate distance. Was pretty good to 400 yards then went to 50 yard steps to 600. Mind you it was only 18 inches wide.

@spada hey mate can you run the same calculations for
300y paralax setting with a target at 50m and again 100?

@Timmay

Here you go.. are you sure you wanted 300 YARD parallax setting and 50/100 METRE ranges? The resulting error is in INCHES.

Yep, I bought a VX3i which I really didn't like so I'm going to put the Zeiss back on my 6.5 and just splash out and buy the HD5 for my 7mm.

That parallax error calculator is interesting. Probably is mathematically the last word on aiming error due to parallax. So, looking just at the focus issue ....

There are three situations where focus using the parallax knob is of interest:

Focussing error due to not relaxing eye to infinity while setting the reticle focus. The shooter may try to accommodate the eye to focus the reticle, but then adjusting the parallax knob to sharpen the target at the same time as the reticle results in an error in the range shown on the parallax dial. The zero parallax distance is then set to the number shown on the dial, not the nice sharp target. This is inevitable if the shooter has some shortsightedness (myopia) as he/she can't truly focus out as far as infinity. The short sighted shooter will therefore often notice a discrepancy between the ranges of sharp focus and zero parallax. A long sighted shooter can focus in a bit to see clearly at infinity, so should focus the reticle while looking at a scene close to infinity (eg 1000m), rather than staring out into a white background as is normally recommended..

The next situation is the aging shooter. Past the age of about 40, the lens in your eye hardens and it becomes gradually more difficult to accommodate and focus up close. Little muscles pull on the lens to flatten in it out and focus up closer. By the age of 60, most people need reading glasses to focus under 50cm; if you have cataract operation and intraocular lens then you can't accommodate at all. Typically the first eye done is set about 1 doiptre short so you can read in good light. However, this is myopia and the focus vs parallax error will occur. A shooter over the age of 40 or 50 will find the use of parallax adjustment to focus the target quite helpful.

Airgun shooters have a field target event where laser rangefinders are not allowed. They also have major drop issues past 30m. The solution to this is that they use the parallax knob to estimate range. Their scopes have evolved to have large (56mm) objectives and high (24x) power to accentuate focus effects. They don't shoot in low light and their target zones are typically 3 or 4 MOA so they don't need those high specs to shoot and in fact often dial down to 12x to take the shot. Even top of the range airgun scopes like Hawke and Leapers only cost about $400 so their optics aren't in the class of the VX-3 or Zeiss. At the short ranges they compete over (under 50m) focus can be dialled in very crisply and the range estimated well, providing they have trained themselves to good eye control. Field target airgun scopes have an extra large focus wheel, which the shooter calibrates to his/her own eyesight. However, for centerfire shooters at ranges of over 200m, using scopes under 12x and 40mm objective, it is actually very difficult to estimate range using the parallax knob. Crisp planes of focus are only really discernable under 100m.

Speaking from my own experience with a 3-12x50, which only has parallax adjustment down to 50m, This is a nuisance at 20m for dry fire practice - very blurry on 12x. I find that winding the power down to even 8x makes the target much sharper. For bush hunting, at 4x everything down to 10m is nice and sharp. Back in the day, we used fixed 4x32 scopes and none of this was an issue. I once used a 10x40 S&B with fixed parallax and that was noticeably blurry at 100m. A young shooter with good accommodation would probably be able to focus in on a much closer target, but then the reticle would be blurred. I also have a VX-1 2-7x32 which nominally has zero parallax at 100m (being a short range scope) but I find it is actually sharpest to my shortsighted eye at around 70m. This is fine for hunting but disconcerting when looking out at scenery in the distance.

Originally Posted by Bagheera

That parallax error calculator is interesting. Probably is mathematically the last word on aiming error due to parallax. So, looking just at the focus issue ....

There are three situations where focus using the parallax knob is of interest:

Focussing error due to not relaxing eye to infinity while setting the reticle focus. The shooter may try to accommodate the eye to focus the reticle, but then adjusting the parallax knob to sharpen the target at the same time as the reticle results in an error in the range shown on the parallax dial. The zero parallax distance is then set to the number shown on the dial, not the nice sharp target. This is inevitable if the shooter has some shortsightedness (myopia) as he/she can't truly focus out as far as infinity. The short sighted shooter will therefore often notice a discrepancy between the ranges of sharp focus and zero parallax. A long sighted shooter can focus in a bit to see clearly at infinity, so should focus the reticle while looking at a scene close to infinity (eg 1000m), rather than staring out into a white background as is normally recommended..

The next situation is the aging shooter. Past the age of about 40, the lens in your eye hardens and it becomes gradually more difficult to accommodate and focus up close. Little muscles pull on the lens to flatten in it out and focus up closer. By the age of 60, most people need reading glasses to focus under 50cm; if you have cataract operation and intraocular lens then you can't accommodate at all. Typically the first eye done is set about 1 doiptre short so you can read in good light. However, this is myopia and the focus vs parallax error will occur. A shooter over the age of 40 or 50 will find the use of parallax adjustment to focus the target quite helpful.

Airgun shooters have a field target event where laser rangefinders are not allowed. They also have major drop issues past 30m. The solution to this is that they use the parallax knob to estimate range. Their scopes have evolved to have large (56mm) objectives and high (24x) power to accentuate focus effects. They don't shoot in low light and their target zones are typically 3 or 4 MOA so they don't need those high specs to shoot and in fact often dial down to 12x to take the shot. Even top of the range airgun scopes like Hawke and Leapers only cost about $400 so their optics aren't in the class of the VX-3 or Zeiss. At the short ranges they compete over (under 50m) focus can be dialled in very crisply and the range estimated well, providing they have trained themselves to good eye control. Field target airgun scopes have an extra large focus wheel, which the shooter calibrates to his/her own eyesight. However, for centerfire shooters at ranges of over 200m, using scopes under 12x and 40mm objective, it is actually very difficult to estimate range using the parallax knob. Crisp planes of focus are only really discernable under 100m.

Speaking from my own experience with a 3-12x50, which only has parallax adjustment down to 50m, This is a nuisance at 20m for dry fire practice - very blurry on 12x. I find that winding the power down to even 8x makes the target much sharper. For bush hunting, at 4x everything down to 10m is nice and sharp. Back in the day, we used fixed 4x32 scopes and none of this was an issue. I once used a 10x40 S&B with fixed parallax and that was noticeably blurry at 100m. A young shooter with good accommodation would probably be able to focus in on a much closer target, but then the reticle would be blurred. I also have a VX-1 2-7x32 which nominally has zero parallax at 100m (being a short range scope) but I find it is actually sharpest to my shortsighted eye at around 70m. This is fine for hunting but disconcerting when looking out at scenery in the distance.

Very interesting.
I have focus issues @100m when my eyes are tired or in low light where either the target or recticl is blurry but not so @200M
Im long sighted?