I had someone tell me that objective size correlates to Field of View. Does objective size directly relate to Field of View? I would think that changing the curvature of the lens would also widen the FOV but would add optical distortion. Objective size also increases light transmission, but are these the only two functions of the objective size?
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Rifle Scopes Objective size
- Thread starter dega37
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Re: Objective size
Objective size alone does nothing for FOV. For example, check the NXS line, same FOV with 50 vs 56 mm objective.
Objective size alone does nothing for FOV. For example, check the NXS line, same FOV with 50 vs 56 mm objective.
Re: Objective size
So, light gathering ability is the only advantage of a larger objective? What about my thoughts on lens shape, not correct?
So, light gathering ability is the only advantage of a larger objective? What about my thoughts on lens shape, not correct?
Re: Objective size
If everything else remains constant:
more magnification = less FOV
more FOV = less eye relief
Objective size does not affect this, only pros for a bigger objective are more light gathering ability and bigger exit pupil at a given magnification. Exit pupil diameter is: objective diameter/magnification, but many times in zoom scopes the exit pupil is a bit less than this due a the lowest setting due to design constrains.
If everything else remains constant:
more magnification = less FOV
more FOV = less eye relief
Objective size does not affect this, only pros for a bigger objective are more light gathering ability and bigger exit pupil at a given magnification. Exit pupil diameter is: objective diameter/magnification, but many times in zoom scopes the exit pupil is a bit less than this due a the lowest setting due to design constrains.
Re: Objective size
I don't know the answer to some of the questions that you're asking, but I know that some more specialists will come along and verify or offer more answers. I do know for a fact resolution is related to objective size. Obviously it's not the only thing that effects resolution, but it is an important factor.
I don't know the answer to some of the questions that you're asking, but I know that some more specialists will come along and verify or offer more answers. I do know for a fact resolution is related to objective size. Obviously it's not the only thing that effects resolution, but it is an important factor.
Re: Objective size
@Tiro, Good info, and the exit pupil makes it easier to get behind a scope and have no shadow correct?
@Tomcat That makes sense to me because, more light would equal more information if all else was constant.
@Tiro, Good info, and the exit pupil makes it easier to get behind a scope and have no shadow correct?
@Tomcat That makes sense to me because, more light would equal more information if all else was constant.
Re: Objective size
T2CH - the tube size has nothing to do with light gathering. Tube size translates to erector movement and the larger tubes generally have more elevation and windage but not more light gathering. The light gathering has to do with the objective size but not the tube.
T2CH - the tube size has nothing to do with light gathering. Tube size translates to erector movement and the larger tubes generally have more elevation and windage but not more light gathering. The light gathering has to do with the objective size but not the tube.
Re: Objective size
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tomcat088</div><div class="ubbcode-body"> I don't know the answer to some of the questions that you're asking, but I know that some more specialists will come along and verify or offer more answers. <span style="font-weight: bold">I do know for a fact resolution is related to objective size.</span> Obviously it's not the only thing that effects resolution, but it is an important factor. </div></div>
Objective diameter has no practical influence in resolution.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tomcat088</div><div class="ubbcode-body"> I don't know the answer to some of the questions that you're asking, but I know that some more specialists will come along and verify or offer more answers. <span style="font-weight: bold">I do know for a fact resolution is related to objective size.</span> Obviously it's not the only thing that effects resolution, but it is an important factor. </div></div>
Objective diameter has no practical influence in resolution.
Re: Objective size
larger objective gives more light and larger exit pupil.
For exit pupil, divide objective lens size by magnification.
larger objective gives more light and larger exit pupil.
For exit pupil, divide objective lens size by magnification.
Re: Objective size
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TiroFijo</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tomcat088</div><div class="ubbcode-body"> I don't know the answer to some of the questions that you're asking, but I know that some more specialists will come along and verify or offer more answers. <span style="font-weight: bold">I do know for a fact resolution is related to objective size.</span> Obviously it's not the only thing that effects resolution, but it is an important factor. </div></div>
Objective diameter has no practical influence in resolution. </div></div>
well that is a blanket statement. if you are in low light conditions objective size has everything to do with resolution.
As with all things it depends what you are trying to do. if it is bright out and you have a large objective it can be advantagious to block some part of your objective to increase your resolution.
I know in Astronomy my scope needs to have the largest objective that I can. However when using it during the daytime-- I need to cut the size of the objective down to regain contrast.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TiroFijo</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tomcat088</div><div class="ubbcode-body"> I don't know the answer to some of the questions that you're asking, but I know that some more specialists will come along and verify or offer more answers. <span style="font-weight: bold">I do know for a fact resolution is related to objective size.</span> Obviously it's not the only thing that effects resolution, but it is an important factor. </div></div>
Objective diameter has no practical influence in resolution. </div></div>
well that is a blanket statement. if you are in low light conditions objective size has everything to do with resolution.
As with all things it depends what you are trying to do. if it is bright out and you have a large objective it can be advantagious to block some part of your objective to increase your resolution.
I know in Astronomy my scope needs to have the largest objective that I can. However when using it during the daytime-- I need to cut the size of the objective down to regain contrast.
Re: Objective size
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lightwind</div><div class="ubbcode-body">T2CH - the tube size has nothing to do with light gathering. Tube size translates to erector movement and the larger tubes generally have more elevation and windage but not more light gathering. The light gathering has to do with the objective size but not the tube. </div></div>
Physics says otherwise.
Dig a hole in the ground, get in the hole. Place a funnel so the "big end" is level with the surface. Lets say the big end at the surface is 10' wide. The tube is 1' in diameter. Measure the light in the hole.
Now do the same but change the tube to a 5' dimeter tube. Measure the light in the hole.
Which one do you think will transmit more light into the hole?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lightwind</div><div class="ubbcode-body">T2CH - the tube size has nothing to do with light gathering. Tube size translates to erector movement and the larger tubes generally have more elevation and windage but not more light gathering. The light gathering has to do with the objective size but not the tube. </div></div>
Physics says otherwise.
Dig a hole in the ground, get in the hole. Place a funnel so the "big end" is level with the surface. Lets say the big end at the surface is 10' wide. The tube is 1' in diameter. Measure the light in the hole.
Now do the same but change the tube to a 5' dimeter tube. Measure the light in the hole.
Which one do you think will transmit more light into the hole?
Re: Objective size
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: T2CH</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lightwind</div><div class="ubbcode-body">T2CH - the tube size has nothing to do with light gathering. Tube size translates to erector movement and the larger tubes generally have more elevation and windage but not more light gathering. The light gathering has to do with the objective size but not the tube. </div></div>
Physics says otherwise.
Dig a hole in the ground, get in the hole. Place a funnel so the "big end" is level with the surface. Lets say the big end at the surface is 10' wide. The tube is 1' in diameter. Measure the light in the hole.
Now do the same but change the tube to a 5' dimeter tube. Measure the light in the hole.
Which one do you think will transmit more light into the hole? </div></div>
What you're saying may be true IF the larger main tube were accompanied with a larger erector tube AND the objective lens were larger such that the exit pupil were larger than the erector tube.
Unfortunately, that isn't the case with a scope.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: T2CH</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lightwind</div><div class="ubbcode-body">T2CH - the tube size has nothing to do with light gathering. Tube size translates to erector movement and the larger tubes generally have more elevation and windage but not more light gathering. The light gathering has to do with the objective size but not the tube. </div></div>
Physics says otherwise.
Dig a hole in the ground, get in the hole. Place a funnel so the "big end" is level with the surface. Lets say the big end at the surface is 10' wide. The tube is 1' in diameter. Measure the light in the hole.
Now do the same but change the tube to a 5' dimeter tube. Measure the light in the hole.
Which one do you think will transmit more light into the hole? </div></div>
What you're saying may be true IF the larger main tube were accompanied with a larger erector tube AND the objective lens were larger such that the exit pupil were larger than the erector tube.
Unfortunately, that isn't the case with a scope.
Re: Objective size
kevlars, <span style="font-weight: bold">in low light</span> your are right, but in practice the differences are small. Take a look at this:
https://snipershide.com/forum/ubbthreads...593#Post2276593
<span style="font-weight: bold">"When you have two variable scopes with different size objective lenses, the bigger objective will allow you to use a bit more magnification in low light, that's all. Assuming your eye pupil opens to 6mm when adapted to low light conditions, a 56mm objective will allow you to crank magnification to ~9,3x without the image getting dimmer, while a 50mm objective will a low a magnification of ~8,3x. Since more magnification means more resolution of detail, the image with more magnification at the same brightness allows you to see more detail of the target.</span>
Below those magnifications, the image will be equally bright with both scopes, only the one with the bigger objective will allow a little more error when aligning the eye pupil "inside" the bigger exit pupil of the scope, making for an easier sight picture."
T2CH, you forget to take into account that the optical path concentrates light cones into tiny cirles inside the scope's internal lenses, and that for all practical purposes regarding light transmission it makes no difference the diameter of these internal lenses. Take a look at this:
<span style="font-weight: bold">"As has already been mentioned, tube diameter does not play a role in this, the fact that the more low light-capable scopes tend to have bigger tubes is more of a coincidence due to other factors (reticle adjustment range, FOV in variables)."</span>
All these questions have been answered in detail before by David S., a professional scope designer that contributes to this site. I recommend a search
kevlars, <span style="font-weight: bold">in low light</span> your are right, but in practice the differences are small. Take a look at this:
https://snipershide.com/forum/ubbthreads...593#Post2276593
<span style="font-weight: bold">"When you have two variable scopes with different size objective lenses, the bigger objective will allow you to use a bit more magnification in low light, that's all. Assuming your eye pupil opens to 6mm when adapted to low light conditions, a 56mm objective will allow you to crank magnification to ~9,3x without the image getting dimmer, while a 50mm objective will a low a magnification of ~8,3x. Since more magnification means more resolution of detail, the image with more magnification at the same brightness allows you to see more detail of the target.</span>
Below those magnifications, the image will be equally bright with both scopes, only the one with the bigger objective will allow a little more error when aligning the eye pupil "inside" the bigger exit pupil of the scope, making for an easier sight picture."
T2CH, you forget to take into account that the optical path concentrates light cones into tiny cirles inside the scope's internal lenses, and that for all practical purposes regarding light transmission it makes no difference the diameter of these internal lenses. Take a look at this:
<span style="font-weight: bold">"As has already been mentioned, tube diameter does not play a role in this, the fact that the more low light-capable scopes tend to have bigger tubes is more of a coincidence due to other factors (reticle adjustment range, FOV in variables)."</span>
All these questions have been answered in detail before by David S., a professional scope designer that contributes to this site. I recommend a search
Re: Objective size
T2CH, I think the main problem with your cone and digging a hole theory is that the objective lens, narrows/intensifies the light through that smaller hole.
I still would like to know about the shape of the lens, because I am fairly certain that in camera lenses, they change the shape of the objective in order to gain a wider perspective, but the downside is that there is optical distortion known as fish eye.
T2CH, I think the main problem with your cone and digging a hole theory is that the objective lens, narrows/intensifies the light through that smaller hole.
I still would like to know about the shape of the lens, because I am fairly certain that in camera lenses, they change the shape of the objective in order to gain a wider perspective, but the downside is that there is optical distortion known as fish eye.
