I just did a quick search for this and did not find anything. I am sure it had to been covered by now, so can some one point me in the right direction?
Advanced Marksmanship light vs poi
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Re: light vs poi
Light has a couple of effects. It can effect the amount and appearance of mirage, causing contrasting bullseyes to start to wave and almost melt. This can cause you to not be aiming in the true center of the target. ETA, depending on your target type (like with free standing targets), shadows can be an issue the same way.
The other main effect is on iron sights. I'm not much of a NM style shooter, so I'm sure KraigWY or Sterling Shooter can weigh in better on that. It has to do with glint you're picking up on a non-hooded front sight causing you not to properly view the tip of the front sight post causing you to aim higher than normal. When I worked the KD ranges at Parris Island, we always had the smudge pot in use or a quick shot of sight black to combat a shiny front sight post. "Sun up-sights up" is the old saying.
On a scope, the effect is minimal unless you don't have a ARD or sun shade and you're getting glint/light magnification through your scope partially blinding you. Hats and sun shades are your friend.
Light has a couple of effects. It can effect the amount and appearance of mirage, causing contrasting bullseyes to start to wave and almost melt. This can cause you to not be aiming in the true center of the target. ETA, depending on your target type (like with free standing targets), shadows can be an issue the same way.
The other main effect is on iron sights. I'm not much of a NM style shooter, so I'm sure KraigWY or Sterling Shooter can weigh in better on that. It has to do with glint you're picking up on a non-hooded front sight causing you not to properly view the tip of the front sight post causing you to aim higher than normal. When I worked the KD ranges at Parris Island, we always had the smudge pot in use or a quick shot of sight black to combat a shiny front sight post. "Sun up-sights up" is the old saying.
On a scope, the effect is minimal unless you don't have a ARD or sun shade and you're getting glint/light magnification through your scope partially blinding you. Hats and sun shades are your friend.
Re: light vs poi
Changes in lighting conditions can cause a shooter to aim at the incorrect aiming point. What may appear to him/her as center mass on the target may in fact be several inches higher or lower, left or right. A shooter may need to adjust his rifle sights to compensate for the effects of changing light conditions. Regardless of how indistinct the target appears, maintaining a center mass hold ensures the best chances for an effective shot.
Common light conditions include:
Bright Light:
Bright light conditions exist under a clear blue sky with no fog or haze present to filter the sunlight.
Bright light can make a target appear smaller and farther away. As a result, it is easy to overestimate range.
Bright light shining from above makes the front sight post appear shorter and bright light from the side makes the front sight post appear narrower. This affects aiming because a shooter will aim at center mass using the perceived tip of the front sight post, which is altered due to the effects of light.
Haze:
Haze exists when smog, fog, dust, smoke, or humidity is present. Haze is not bright, but it can be uncomfortable to the eyes. Haze can make a target appear indistinct, making it difficult to establish sight picture.
Overcast:
Overcast conditions exist when a solid layer of clouds blocks the sun. The amount of light changes as the cloud cover thickens. Overcast conditions make a target appear larger and closer. As a result, it is easy to underestimate range.
Light Overcast:
Light overcast conditions exist when no blue sky is visible and a thin layer of clouds are present. In light overcast, both the target and the rifle sights appear very distinct. Light overcast is comfortable on the eyes with no glare present, making probably the best light condition for shooting.
Dark Heavy Overcast:
Dark heavy overcast conditions exist when the sky is completely overcast with most of the light blotted out by the clouds. As the overcast thickens, it may make it difficult to identify the target from the surroundings.
Scattered Clouds:
Scattered cloud conditions exist when the clouds are broken up into small patches with the sun appearing at times between the clouds. A shooter’s eyes may have problems adjusting between a target that is brightly lit and one that is shadowed.
Moving Clouds:
Moving clouds exist when scattered clouds move across the sky rapidly, making the sun appear periodically. Rapidly moving clouds can fatigue the eyes due to the rapid changes from bright light to shadows. This condition is probably the most difficult to contend with because the light changes rapidly. If the situation permits, this condition can be compensated by selecting one of the two light conditions (bright light or shadow) in which to fire. Best results are obtained, if each shot is fired under the same light condition.
<span style="color: #33CC00">Record Light Condition in the Data Book: A shooter should record a significant change in light condition in their data book. This information helps to study and determine how a type of light conditions or change in conditions affects a particular shooter. </span>
Changes in lighting conditions can cause a shooter to aim at the incorrect aiming point. What may appear to him/her as center mass on the target may in fact be several inches higher or lower, left or right. A shooter may need to adjust his rifle sights to compensate for the effects of changing light conditions. Regardless of how indistinct the target appears, maintaining a center mass hold ensures the best chances for an effective shot.
Common light conditions include:
Bright Light:
Bright light conditions exist under a clear blue sky with no fog or haze present to filter the sunlight.
Bright light can make a target appear smaller and farther away. As a result, it is easy to overestimate range.
Bright light shining from above makes the front sight post appear shorter and bright light from the side makes the front sight post appear narrower. This affects aiming because a shooter will aim at center mass using the perceived tip of the front sight post, which is altered due to the effects of light.
Haze:
Haze exists when smog, fog, dust, smoke, or humidity is present. Haze is not bright, but it can be uncomfortable to the eyes. Haze can make a target appear indistinct, making it difficult to establish sight picture.
Overcast:
Overcast conditions exist when a solid layer of clouds blocks the sun. The amount of light changes as the cloud cover thickens. Overcast conditions make a target appear larger and closer. As a result, it is easy to underestimate range.
Light Overcast:
Light overcast conditions exist when no blue sky is visible and a thin layer of clouds are present. In light overcast, both the target and the rifle sights appear very distinct. Light overcast is comfortable on the eyes with no glare present, making probably the best light condition for shooting.
Dark Heavy Overcast:
Dark heavy overcast conditions exist when the sky is completely overcast with most of the light blotted out by the clouds. As the overcast thickens, it may make it difficult to identify the target from the surroundings.
Scattered Clouds:
Scattered cloud conditions exist when the clouds are broken up into small patches with the sun appearing at times between the clouds. A shooter’s eyes may have problems adjusting between a target that is brightly lit and one that is shadowed.
Moving Clouds:
Moving clouds exist when scattered clouds move across the sky rapidly, making the sun appear periodically. Rapidly moving clouds can fatigue the eyes due to the rapid changes from bright light to shadows. This condition is probably the most difficult to contend with because the light changes rapidly. If the situation permits, this condition can be compensated by selecting one of the two light conditions (bright light or shadow) in which to fire. Best results are obtained, if each shot is fired under the same light condition.
<span style="color: #33CC00">Record Light Condition in the Data Book: A shooter should record a significant change in light condition in their data book. This information helps to study and determine how a type of light conditions or change in conditions affects a particular shooter. </span>
Re: light vs poi
And there is your in depth answer. Good info.
And there is your in depth answer. Good info.
Re: light vs poi
Addressing the topic with regard to iron sights only, I disagree with parts of what Redman and Jager posted.
The sun does not affect the sharpness of focus on any part(s) of the front sight if your sights are properly blacked. Hooding of the front sight yields no effect. Here's why:
What the increased intensity of light does do is cause the shooter's iris to reduce in aperture and make the bull appear to be a smaller size than it really is to the shooter's eye: the edges of the black bull blur, white and black light mix, forming a ‘halo’ around it, and the bull appears to be smaller. In reduced light intensity conditions, the effect is reversed. Thus the bull appears to be smaller with more light and larger with less light.
When a shooter uses a 6 o'clock hold (aiming at the bottom of a circular bull), the bull's perceived size change will move the groups because the shooter's point of aim is changing with the diameter of the bull: when it's bright, the bull appears a smaller diameter than it really is, and the bullets will impact high if you've zeroed when it was overcast. When it's overcast, the bull appears larger and the bullets will impact low if you've zeroed when it was bright.
The old maxim "Light's up, sights up" refers to raising the front sight, thus bringing the point of impact back down where it belongs, when you've zeroed under overcast skies earlier in the morning and the sun comes out in the afternoon.
This can be better remedied by switching to a center mass hold, or a front aperture sight, for all conditions.
Addressing the topic with regard to iron sights only, I disagree with parts of what Redman and Jager posted.
The sun does not affect the sharpness of focus on any part(s) of the front sight if your sights are properly blacked. Hooding of the front sight yields no effect. Here's why:
What the increased intensity of light does do is cause the shooter's iris to reduce in aperture and make the bull appear to be a smaller size than it really is to the shooter's eye: the edges of the black bull blur, white and black light mix, forming a ‘halo’ around it, and the bull appears to be smaller. In reduced light intensity conditions, the effect is reversed. Thus the bull appears to be smaller with more light and larger with less light.
When a shooter uses a 6 o'clock hold (aiming at the bottom of a circular bull), the bull's perceived size change will move the groups because the shooter's point of aim is changing with the diameter of the bull: when it's bright, the bull appears a smaller diameter than it really is, and the bullets will impact high if you've zeroed when it was overcast. When it's overcast, the bull appears larger and the bullets will impact low if you've zeroed when it was bright.
The old maxim "Light's up, sights up" refers to raising the front sight, thus bringing the point of impact back down where it belongs, when you've zeroed under overcast skies earlier in the morning and the sun comes out in the afternoon.
This can be better remedied by switching to a center mass hold, or a front aperture sight, for all conditions.
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Re: light vs poi
I am really interested in hearing this discussion as well.
Last week I experienced roughly a 1 moa change in poi on a target at 675yds that was going in and out of the shade on a bright sunny day. It was like clock work, if I shot a round at the target in the sun using my "shade" dope, it would go 1 moa high, make a correction and it was dead on.
Every other range until 675 was in bright sunlight so I obtained solid zeros for sunny conditions, but this leads me to another question.
Say I take shot at a 500yd target using my sunny dope, will I experience such a dramatic change in poi?
How do most tactical long range shooters compensate for this? record data for both sunny and shady targets? Or get data in both conditions and average?
FWIW, I am running a scope.
I am really interested in hearing this discussion as well.
Last week I experienced roughly a 1 moa change in poi on a target at 675yds that was going in and out of the shade on a bright sunny day. It was like clock work, if I shot a round at the target in the sun using my "shade" dope, it would go 1 moa high, make a correction and it was dead on.
Every other range until 675 was in bright sunlight so I obtained solid zeros for sunny conditions, but this leads me to another question.
Say I take shot at a 500yd target using my sunny dope, will I experience such a dramatic change in poi?
How do most tactical long range shooters compensate for this? record data for both sunny and shady targets? Or get data in both conditions and average?
FWIW, I am running a scope.
Re: light vs poi
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: m1ajunkie</div><div class="ubbcode-body">I am really interested in hearing this discussion as well.
Last week I experienced roughly a 1 moa change in poi on a target at 675yds that was going in and out of the shade on a bright sunny day. It was like clock work, if I shot a round at the target in the sun using my "shade" dope, it would go 1 moa high, make a correction and it was dead on.
Every other range until 675 was in bright sunlight so I obtained solid zeros for sunny conditions, but this leads me to another question.
Say I take shot at a 500yd target using my sunny dope, will I experience such a dramatic change in poi?
How do most tactical long range shooters compensate for this? record data for both sunny and shady targets? Or get data in both conditions and average?
FWIW, I am running a scope. </div></div>
Very interesting. Where was the sun at(in relation to you)when you were hitting high?
I am also running a scope so this is good info.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: m1ajunkie</div><div class="ubbcode-body">I am really interested in hearing this discussion as well.
Last week I experienced roughly a 1 moa change in poi on a target at 675yds that was going in and out of the shade on a bright sunny day. It was like clock work, if I shot a round at the target in the sun using my "shade" dope, it would go 1 moa high, make a correction and it was dead on.
Every other range until 675 was in bright sunlight so I obtained solid zeros for sunny conditions, but this leads me to another question.
Say I take shot at a 500yd target using my sunny dope, will I experience such a dramatic change in poi?
How do most tactical long range shooters compensate for this? record data for both sunny and shady targets? Or get data in both conditions and average?
FWIW, I am running a scope. </div></div>
Very interesting. Where was the sun at(in relation to you)when you were hitting high?
I am also running a scope so this is good info.
Re: light vs poi
The sun was at about the 4- 6 o clock postion from about 10am- 12 noon here in GA.
The area I was shooting at was an open field (100-650ysds) until you get to the 675 yd target. It is cut back in a grove of trees that cast lots of wierd shadows, but I was able to shoot a couple of tests over about 2 hours when the shade would come and go.
I was amazed as I thought having an optic would mitigate the effects of the sun, but after confirming the effect I could look at the target and dial the correct dope either shade or sun and I could make a solid hit within 3-5" of the red bullseye.
I only gathered this info on a single trip, but it was still consistent throughout that trip.
The sun was at about the 4- 6 o clock postion from about 10am- 12 noon here in GA.
The area I was shooting at was an open field (100-650ysds) until you get to the 675 yd target. It is cut back in a grove of trees that cast lots of wierd shadows, but I was able to shoot a couple of tests over about 2 hours when the shade would come and go.
I was amazed as I thought having an optic would mitigate the effects of the sun, but after confirming the effect I could look at the target and dial the correct dope either shade or sun and I could make a solid hit within 3-5" of the red bullseye.
I only gathered this info on a single trip, but it was still consistent throughout that trip.
Re: light vs poi
Jaeger308 and tullius covered it all, as it might effect a Service Rifle shooter, who is capable of building a consistent position, but is not conscious of the possible effect of changing light. For an inexperienced shooter, in all matters of what's important to good shooting; however, an elevation problem can be the result of a multitude of errors, in addition to light. These are associated with external ballistics and position matters, and can include, but are not exclusive to: temperature, butt-to-shoulder position, stockweld, perspective of aim, and perception of hold. Also, using a match aperture front sight or scope, the error associated with changing light may not manifest itself, since holds with such sights are typically center of mass.
Recording all conditions in a score or data book will aid the shooter who needs to build consistency. Recording starting zero, as well as what is determined by shots to be correct for conditions will inspire marksmanship development and proper shooter/target analysis. For sure, inferences from observations are more trustworthy when found to be consistent with score book data.
Jaeger308 and tullius covered it all, as it might effect a Service Rifle shooter, who is capable of building a consistent position, but is not conscious of the possible effect of changing light. For an inexperienced shooter, in all matters of what's important to good shooting; however, an elevation problem can be the result of a multitude of errors, in addition to light. These are associated with external ballistics and position matters, and can include, but are not exclusive to: temperature, butt-to-shoulder position, stockweld, perspective of aim, and perception of hold. Also, using a match aperture front sight or scope, the error associated with changing light may not manifest itself, since holds with such sights are typically center of mass.
Recording all conditions in a score or data book will aid the shooter who needs to build consistency. Recording starting zero, as well as what is determined by shots to be correct for conditions will inspire marksmanship development and proper shooter/target analysis. For sure, inferences from observations are more trustworthy when found to be consistent with score book data.
Seeing this photo reminded me of this thread. Check it out, obviously all the targets are identical, but some bulls appear larger and some smaller: which ones appear smaller?
Then I went back, reread my post above and realized I got the effect of light reversed in explanation.. mea culpa. Should be correct now..
Then I went back, reread my post above and realized I got the effect of light reversed in explanation.. mea culpa. Should be correct now..
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Also worth remembering the Service Rifle shooters adage, "lights up, sights up!" The rule is that when the light is bright, the target itself appears bigger, causing you to displace the front sight post lower on target, shifting the POI low. Click up a bit to compensate, and you should be back in the center again. Works the other way when you're dealing with darker days, and you need to adjust the other way to compensate.
Remember the adage, but don't believe it until you've verified that this is the way it affects YOU. It doesn't affect everyone the same, and there are some shooters that it works the other way around on. This applies to post front sights only, as aperature sights like those on most match rifles won't generally see much change, one way or the other. Rely on your data book, and see what the various lighting conditions do to you, personally.
Remember the adage, but don't believe it until you've verified that this is the way it affects YOU. It doesn't affect everyone the same, and there are some shooters that it works the other way around on. This applies to post front sights only, as aperature sights like those on most match rifles won't generally see much change, one way or the other. Rely on your data book, and see what the various lighting conditions do to you, personally.
Yup its Sun Up, Sight up, Sun down Sight down. Also applies to windage.
When its bright, the sight has a tendency to bleed into the target, the bull appears smaller. Then when a cloud passes over the bull looks bigger and one tends to shoot lower. The same for the sun coming from the left or right. If you're shooting north, in the morning the sun will shine from the right (east) so the same applies, you click into the sun. Later in the afternoon the sun comes from the left or west, you click the other way.
I've found shooting 308s for over 35 years I need to click on MOA into the sun. Some people may be different, some may click less, some may click more.
The most important part is to record the light conditions in your score book. HP score books have a spot for recording light conditions. Simply point the top of the book to the target, hold your pencil straight up and look at the shadow. Draw an arrow indicating the light direction. It doesn't take many matches to see how light affects you.
Me I know my zero and its set on bright sunlight, I take that into account with I fire my first shot. If its sunny, I go with my zero, if its cloudy, I click down. My windage zero was obtained about noon, so if I start shooting in the morning, (assuming I'm facing north) I click right or into the sun.
But I mark my changes, and indicate why, indicating if its the light that caused the change. I make the wind adjustments from there.
Again the most important part is to RECORD it. Record everything, and indicate why you made any changes you made.
If you make a change for the light, you don't want to confuse it with your wind changes.
When its bright, the sight has a tendency to bleed into the target, the bull appears smaller. Then when a cloud passes over the bull looks bigger and one tends to shoot lower. The same for the sun coming from the left or right. If you're shooting north, in the morning the sun will shine from the right (east) so the same applies, you click into the sun. Later in the afternoon the sun comes from the left or west, you click the other way.
I've found shooting 308s for over 35 years I need to click on MOA into the sun. Some people may be different, some may click less, some may click more.
The most important part is to record the light conditions in your score book. HP score books have a spot for recording light conditions. Simply point the top of the book to the target, hold your pencil straight up and look at the shadow. Draw an arrow indicating the light direction. It doesn't take many matches to see how light affects you.
Me I know my zero and its set on bright sunlight, I take that into account with I fire my first shot. If its sunny, I go with my zero, if its cloudy, I click down. My windage zero was obtained about noon, so if I start shooting in the morning, (assuming I'm facing north) I click right or into the sun.
But I mark my changes, and indicate why, indicating if its the light that caused the change. I make the wind adjustments from there.
Again the most important part is to RECORD it. Record everything, and indicate why you made any changes you made.
If you make a change for the light, you don't want to confuse it with your wind changes.
Seeing this photo reminded me of this thread. Check it out, obviously all the targets are identical, but some bulls appear larger and some smaller: which ones appear smaller?
Then I went back, reread my post above and realized I got the effect of light reversed in explanation.. mea culpa. Should be correct now..
The targets appear smaller in the sun to me and the post below states the opposite?
Seeing this photo reminded me of this thread. Check it out, obviously all the targets are identical, but some bulls appear larger and some smaller: which ones appear smaller?
That looks like miami rifle and pistol at the three hundred line to me. And yes the bulls in the shade appear to be bigger to me as well.
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