Scopes image at eye

[gazzalene]

Only used fixed magnification scope to date of 30mm objective.
If i go with a 3 -12 mag , will a 50mm give larger image than a 44mm? at same mag?

[Bunny-on-Bunnyr]

Only used fixed magnification scope to date of 30mm objective.
If i go with a 3 -12 mag , will a 50mm give larger image than a 44mm? at same mag?

Start of the summer I ended up with all my scopes off rifles and looked at this very thing for myself through:
2 off 4x40 duplex for references @ 25 and 100yrd fixed px.
3-9 x 40 35yrd fixed px
4-16 x 44 ao mildot
3-9 x 50 35yrd fixed px
4-16 x 56 sf mildot
6-24 x 50 sf mildot
all Second focal plane.
Pointing them at a pair of gaffa-tape marks spaced 30" apart on the wall 100yrd across the street...
Without the bionic mans eye, the image was Exactly the same size with all scopes set 'mag-for-mag'.

The most noticable thing was weight:
4x40 weighs 11oz.
50 / 56 weigh... 35 / 38 oz.

[TonyL]

The exit pupil will be larger. Image size / field of view will very much depend on the design of the scope, I think I'm correct in saying?

Although not as empirical an explanation as the above post, a few days ago whilst switching scopes about, the image through a certain more modern 4x32AO seemed much larger than that delivered by an older 4x40.

[angrybear]

Only used fixed magnification scope to date of 30mm objective.
If i go with a 3 -12 mag , will a 50mm give larger image than a 44mm? at same mag?

No, not as such, the diameter of the occular (eye) bell will dictate the physical size of the picture available & the eye relief is the focal length of the lens so you get the whole of the occular filled with a crisp clear picture, with no black 'fuzz' around the edges.

What might well change is the 'field of view' (FOV).
Below are the figures for the basic Hawke vantage pasted from the web site,
so the 40mm objective at 100yds has a picture size of 39ft at 3x or 12.7ft at 9x but the 50mm is smaller at 33.6ft & 11ft

So, shock horror what you need to do is read the spec's for the model of scope, some have a wider angle than others to give a wider or narrower FOV.
Sadly many people either don't bother to read them or don't actually have a clue what it means & unlike you, they don't ask.

Field of View 3-9x40
39 - 12.7ft @100yds
13 - 4.2m @100m

Field of View 3-9x50
33.6 - 11ft @100yds
11.2 - 3.7m @100m

[gunshop]

The exit pupil will be larger. Image size / field of view will very much depend on the design of the scope, I think I'm correct in saying?

Although not as empirical an explanation as the above post, a few days ago whilst switching scopes about, the image through a certain more modern 4x32AO seemed much larger than that delivered by an older 4x40.

To get the exit pupil diameter dived the objective by the magnification this gives the exit diameter in mm. When shooting during the day, your pupil is dilated around 3.5mm, of a night as it opens up to let in more light it goes to about 7mm. So if your scope gives you an exit pupil diameter of 5mm, you aren't using your pupil to its full potential of a night.

Easiest way to test this is get a variable scope, start on high magnification and then turn it down, as the mag goes down the picture gets brighter.

I used to sell a lot of 8x56 scopes for stalking as the exit pupil diameter was 7mm and gave anything up to another 1/2 hours shooting at dusk or twilight.

I will always try to explain scopes to customers when they come in to the shop to purchase them, it was handy going on a Zeiss & Swarovski training course on scopes.

[gazzalene]

Thanks for all the great info.
I think the term i was looking for was the FOV.
Using the 30mm scope at 45 yards i can see apx 50% of the backstop and attached targets. Thats fine.
After a new scope and wondered if i went upto a 44mm or 50mm ,would i then see 75% or 100% of the backstop.
So it looks like i might be able to if i read the specks? my present 30mm might be low spec with poor FOV.
Now i know the FOV is variable i will look at specs not lens dia`s
thanks

[TonyL]

To get the exit pupil diameter dived the objective by the magnification this gives the exit diameter in mm. When shooting during the day, your pupil is dilated around 3.5mm, of a night as it opens up to let in more light it goes to about 7mm. So if your scope gives you an exit pupil diameter of 5mm, you aren't using your pupil to its full potential of a night.

Easiest way to test this is get a variable scope, start on high magnification and then turn it down, as the mag goes down the picture gets brighter.

I used to sell a lot of 8x56 scopes for stalking as the exit pupil diameter was 7mm and gave anything up to another 1/2 hours shooting at dusk or twilight.

I will always try to explain scopes to customers when they come in to the shop to purchase them, it was handy going on a Zeiss & Swarovski training course on scopes.

Thank you.

And, off the topic a little........one of my customers once brought me one of his powder burners in to look at, fitted with a Swarovski. Upon looking through that scope.......wow, wow and wow!

[gunshop]

Thank you.

And, off the topic a little........one of my customers once brought me one of his powder burners in to look at, fitted with a Swarovski. Upon looking through that scope.......wow, wow and wow!

If i had the money, it would always be a Swarovski or Zeiss especially their binoculars. Once you have been around the factory and seen how things are produced it opens your eyes so to speak. The prisms in a pair of binoculars are so highly ground and polished that if two were put next to each other and a beam of light shone thorough them, the resulting bent beam would only differ by a cm or so at 2km if i remember right.

Just lately I have been impressed by the new lines of scopes coming through, they are almost as good as the German and Austrian stuff, the Hawke Sidewinders have really upped the game and Element Optics are pushing the boundaries as well.

To get the best idea of a scopes capabilities before buying, turn up at your gun shop just before dusk in a low light level, that will give you the truth on how good the optics are. I always make a point of getting my customers to look through the scopes outside wherever possible.

[TonyL]

Thank you again; excellent information and pointers.

[Bellycrawler]

I've been shooting for years & never realy thought about this & find the replies interesting. I've tried many scopes & kept things simple, I either like a scope or not. They all looked different as the OP questioned. As much as I liked my old fixed focus Hawkes I found I prefer side focus. One scope I like is my Hawke 32m ao but prefer 42/44m. Now I understand a bit more & wiser I'm going back to simple choice regardless of the science of it all. I either like the scope or I don't.

[gunshop]

Only used fixed magnification scope to date of 30mm objective.
If i go with a 3 -12 mag , will a 50mm give larger image than a 44mm? at same mag?

I tried to respond to your PM, but your inbox is full.

[Jacklurcher]

Thanks for all the great info.
I think the term i was looking for was the FOV.
Using the 30mm scope at 45 yards i can see apx 50% of the backstop and attached targets. Thats fine.
After a new scope and wondered if i went upto a 44mm or 50mm ,would i then see 75% or 100% of the backstop.
So it looks like i might be able to if i read the specks? my present 30mm might be low spec with poor FOV.
Now i know the FOV is variable i will look at specs not lens dia`s
thanks

As I understand it the rationale of having a bigger objective lens is primarily to increase the amount of light entering the optics and give a brighter image*, not to increase FOV.

* obviously the quality of the optics also affects image brightness.