Is there much difference in "practical" light gathering ability? Which of these scopes do you guys like better.

Elmo

The 1.75x6 is the better choice...larger exit pupil and larger objective lense for more light.

Some people have complained about running out f adjustment ont the 1.75x6...I have never seen it happen others think the 1.5x5 "looks" cooler.

I think the 1.75x6 is an all around better scope

I agree with Mike.

I have a 1.75 X 6 with QD mounts on a 416 Rem Mag, been to Africa twice, has worked without a hitch.

I've got the new 1.5-5 VX-III with illuminated reticle. Like the 30mm tube and the very compact size (9.3" OAL, vs 11.23" on the 1-6 x 32) Shoots good so far, but can't honestly say it's any better than the other. Light gathering?? the 32mm is most likely better there (technically speaking).

If you are wanting to really see a difference then you might consider the 2.5-8 x 36 VXIII it's only 2 10ths of an inch longer but is a big step up in optical performance, esp light gathering.

As for my 1.5-5, "jury's-out". I'll report back after a couple of months use.

JW

I have both & like both. If you are looking for max. eye relief, then the 1.5x5 is the way to go. For a .375 class rifle, the 1.75x6 would be great.

I have the 1.75X6 and ran out of adjustment room. My gunsmith shimmed the mount so I was able to adjust just fine after that. I've had no trouble at all with it other than that. It's assisted me in killing a lot of game, I am happy with it. Seems to have lots of eye relief too.

Elmo,

You will have about 40% higher twilight factor with the 1.5-6X; this probably is important only if you are shooting leopard after dark.

jim

elmo,

I've used 5 diferent scopes in Africa from 1x4 through 3.5x10 and probably contrary to a lot of people's opinion I think the 1.75x6 to be the best of the lot. 1.75 gives you plenty of field of view and 6 gives you a good look at that leopard on the bait or a distant Tommie. With the 1.75x6 on a 375 I would feel comfortable doing the whole safari with just one rifle and I have.

Regards,

Mark

quote:

Is there much difference in "practical" light gathering ability?

There is no difference between the scopes in their light gathering ability. There are no scopes on the market that I am aware of that have light gathering technology. You may want to check light transmission though.

Light gathering is just some mistake in verbage that got going and will go on forever. You can not "gather" light but you can use what ever available light is there. Some optics will be able to transmit the avaiable light better than others. Other wise you need to turn on the light, raise the window shade, wait until it is daylight or something.

I use the 1.5x5, 1x4 and 3X fixed on all my guns..I like a 20 MM objective lens because the hold a zero better with rough treatment....and they look good on a big bore rifle and I have yet to find a circumstance where they didn't work and those that supposedly have had problems with light etc., I think was more of an excuse than a reality....

Yeah Ray!

Those little buggers really do work!

I have the 2x on my Hoenig...I'ts fast, but will opt to use Iron this summer on Mr. B.

Jeff

PS - Butch says howdy....booked a .470 sidelock with him yesterday!

quote:

Originally posted by M16:

quote:

Is there much difference in "practical" light gathering ability?

There is no difference between the scopes in their light gathering ability. There are no scopes on the market that I am aware of that have light gathering technology. You may want to check light transmission though.

Well a rifle scope is really a telescope, so:


------------------------------

The Powers of a Telescope

A telescope can aid our eyes in three ways. These are called light-gathering power, resolving power, and magnifying power.

Most interesting celestial objects are faint sources of light, so we need a telescope that can gather large amounts of light to produce a bright image. Light-gathering power refers to the ability of a telescope to collect light. Catching light in a telescope is like catching rain in a bucket - the bigger the bucket, the more rain it catches. This is why astronomers use big telescopes and why they refer to telescopes by diameter.

The second power, resolving power, refers to the ability of the telescope to reveal fine detail. Whenever light is focused into an image, a blurred fringe surrounds the image. Because this diffraction fringe surrounds every point of light in the image, we can never see any detail smaller than the fringe. There is nothing we can do to eliminate diffraction fringes; they are produced by the wave nature of light. If we use a large diameter telescope, however, the fringes are smaller and we can see smaller details. Thus the larger the telescope, the better its resolving power.

Two other factors - optical quality and atmospheric conditions - limit the detail we can see. A telescope must contain high-quality optics to achieve its full potential resolving power. Even a large telescope shows us little detail if its optics are marred with imperfections. In addition, when we look through a telescope, we look through miles of turbulent air in Earth's atmosphere, which makes the image dance and blur, a condition called seeing.

The third and least important power of a telescope is magnifying power, the ability to make the image bigger. Since the amount of detail we can see is limited by the seeing conditions and the resolving power, very high magnification does not necessarily show us more detail.


Gathering light is like catching rain in a bucket. A large diameter telescope (large aperture) gathers more light and has a brighter image than does a smaller telescope of the same focal length.

http://www.twcac.org/Tutorials/powers%20of%20a%20telescope.htm

-----------------------------

So yes, a rifle scope does, just like any telescope, have light gathering power. However, most rifle scopes are commonly used during the daytime so the image usually appears bright enough. But, a larger diameter objective lens does gather more light (photons) than a smaller one. I think a lot of people get light gathering power confused with how efficiently a particular scope's optics transmit the light through the scope to the eye piece. (Basically efficiency of light transmission. 95% or 98% etc.)

-Bob F.

Also see:
http://www.astronomynotes.com/telescop/chindex.htm
and
http://www.star.ucl.ac.uk/~idh/STROBEL/telescop/telescpb.htm
for more information about telescopes.

quote:

So yes, a rifle scope does, just like any telescope, have light gathering power

I'll have to wave the bullshit flag on this one. Please explain just how they go and gather light. Don't believe everything you read on the internet.

M16,

Then I suggest you go to the library and check out some books on astronomy and telecopes. The graphic I provided above explains it. A larger diameter objective lens gathers more photons than a smaller lens. That's it; period. Here's another graphic:



Light Gathering Power
"The ability of a telescope to collect a lot more light than the human eye, its light gathering power, is probably its most important feature. The telescope acts as a 'light bucket', collecting all of the photons that come down on it from a far away object. Just as a bigger bucket catches more rain water, a bigger objective collects more light in a given time interval. This makes faint images brighter. This is why the pupils of your eyes enlarge at night so that more light reaches the retinas. Very far away, faint objects can be seen only with BIG objective telescopes. Making faint images brighter is critical if the light is going to be dispersed to make a spectrum."

From:
http://www.star.ucl.ac.uk/~idh/STROBEL/telescop/telescpb.htm


Also, you might want to actually check the links that I provided. As in:

http://www.star.ucl.ac.uk/
http://www.star.ucl.ac.uk/~idh/STROBEL/telescop/telescpb.htm

"The Astrophysics group at UCL ( http://www.ucl.ac.uk/ ) forms part of the Physics and Astronomy Department. It is one of the largest Astrophysics groups in the UK (incorporating the Atmospheric Physics Lab, the Optical Science Lab and the University of London Observatory) with research programmes in hot stars, star formation, circumstellar matter, astro-chemistry, cosmology, atmospheric physics and instrumentation."

-Bob F.

I did physics for my undergrad degree, and I am going to state flatly that the telescope's objective lens does gather light -- in the sense that it can capture more photons than your naked eye can.

The cross-section for capture goes up as the square of the objective lens diameter as Bob noted above. You can think of your eye as a "scope" with a 7 mm objective by the way.

jim

Atkinson, Excellent point concerning the durability of a 20mm objective. I need a scope to top of my southpaw M70. The decision is made!

Good one Bob

Here's the deal. I have a 1.75x6 on my .376 Steyr, in Leup dual dovetail mounts right now. I've ordered a set of leup QR mounts to replace the DD mounts. But if the SWFA's promo photo is correct,(HunterJim???) the rings will move foreward about 9/10ths of an inch, with the QD mounts. I've ordered extension rings but I'm still concerned that the objective bell on the 1.75x6 will keep the scope too far foreward, as I use a long length of pull. That's why I'm considering the 1.5x5 as I think it move farther aft in the rings.

This brings up the questions....

Are there any problems with placing the 20mm objective lens right under the foreward ring and torqueing that ring down. Gives me the willies just thinking about it.

And

All theoretical and semantic issues aside...
Can your own eyeball tell the difference in light gathering/transmission between the two scopes.

BONUS QUESTION...WIN FABULOUS PRIZES

How many Photons can you gather in a 5 Gallon Bucket?

Winner gets two free drinks at Reno next year.
Winner must be present to receive prize.
Void where common sense prevails

Elmo

How much light can the human eye "use" of an exit pupil calculation... ?

"The University of Houston College of Optometry research (William J. Donnelly III and Austin Roorda) showed that 4.3mm of pupil size is "the optimal pupil size for axial resolution."

So... is anything more than 4.3mm "wasted?"

Elmo,
I ran into just the concern you expressed. My gunsmith tried to mount a Leup 1.5X5 on my Mod 70 Win Classic in .375 using Talley quick detachables. The ring spacing required that he put the objective lens directly under the front rings. This resulted in cracking the lens when tightening the rings sufficiently to prevent movement from the rifle's recoil. Bottom line solution, I switched to the Leup1.75X6 which worked great. Hope this helps.

I hope you found a new gunsmith,

Ram, that doesn't sound a bit good to me. I'm surprised it had to go that far.....

I have a Leupold 1.5-5X on my .416 Rem., and consider it to be just about a perfect scope for that rifle.

I have a pair of 1.75-6X Leupolds for my .375 H&H, each in it's own set of detachable rings, and I'm very pleased with that scope as well.

The 1.75-6X is just a smidge brighter early and late, but the difference really isn't all that pronounced. Take your pick.....

AD

The human pupil generally does not expand above 5.5-6.0 mm under low light conditions. Expansion of the pupil above 6.5mm is one of the objective symptoms of being under the influence of methamphetamine or cocaine.

AD, Ray and other 1.5x5 users....

Tell me about the 20mm objective lens under the ring issue. Where are yours located and any problems?


Ramhunter

Thanks for your post and welcome to the assylumn. Now my willies have turned into WILLIES


Thanks

Elmo

Elmo,

The problem first starts because of the recoil of the 375 most folks really tighten up their rings actually slightly "deforming" the scope body. If the scope is placed to far forward the pressure from the back ring impedes the movement of the variable power adjustment mechanism so folks move the scope back often making the front edge of the scope tube just barely protruding or flush with the front edge of the front ring...and when you over tighten...Voila! cracked objective lense.

One should not be tigtening so much as to defrom the scope body. Either plain rosin or rosin mixed with rubbing alcohol into paste can be "painted" inside the rings to add better gripping.

If you need some rosin email your address all throw some into a ziploc and mail it to you. brownells sells a 1 lb can which will be enough for me a six friends for a lifetime.

Also I would not recommend lapping your rings. Ihave spoked with several gunsmiths that I respect who state that your are 1) smothing up the surface to the point losing "grip" and 2) the lack of perfect "roundness" actually helps the "holding" of the scope under recoil.

Mike

That's mighty generous of you

PM on the way

Thanks

Elmo

I just saw an interesting Leupold add in Rifleshooter magazine. Quote:

Debunking the Myth of "Light Gathering"

Chances are, you've heard that one riflescope "gathers more light" than another. Here are the facts: optics do not gather light. Optics transmit light. The lenses focus the light into a beam, and what makes one scope brighter than another is how efficiently it transmits that light to the shooter's eye. Leupold achieves this through proper light management and outstanding riflescope design and construction.

Alright B. Faucett and Hunter Jim. You are the ones that said scopes can gather light. Is Leupold lying. False advertising?

Try a Burris and you will sell your Leupold

I have a 1.75-6X on my .375 H&H, and a 1.5-5X on my .416 Remington. I wouldn't change scopes on either one of those rifles. The 1.75-6X seems a bit brighter, but it's a might small difference.

The 1.5-5X is a scope that I've used much more than the 1.75-6X. It has more eye-relief than any variable scope that I've ever used or am familiar with, and of course it has an extremely wide field of view at the low end. It's also and extremely tough scope that has never caused me any trouble at all on any of the .375, .458, or .416 rifles I've used it with over the years. It's probably the toughest, most reliable variable I've ever used.

AD

Another vote for the 1.75/6. A helluva lot better scope for basically the same money. And, people who say there is very little difference in the low light abilities haven't tried them side by side in deep twilight like I have. Although these were not the latest iterations, the difference is obvious and if late shooting is a consideration, it makes the choice a "no contest".

Well, yeah, I've tried 'em own, 'em, and have used 'em both under low-light conditions. I guess my eyes and judgement aren't as technically sophisticated as yours........

AD

Obviously. Would you like to try to read a test pattern in the near dark with your 1.5x5/20 mm and let me use my 1.75x6/32mm and bet on which one does better.

M16,

Bob really is right for all practical purposes...the larger the objective, the more light that can fall on that given area and the more light that can be "transmitted" through the scope, all other factors being equal. The last bit is very important!

None of these formula for "exit pupil" nor the "twighlight factor" take into account the quality of the lens or the coating used nor the amount of lens used....As an example I had a 6x42mm Swarovski Habitch scope that was at least as bright maybe a touch brighter than a 7x50mm Meopta...according to the various formula, the 7x50mm should have been brighter, but it simply did not take into account of the quality difference between the two scopes.

With rgards the size of the exit pupil alot of folks say having one larger than 6mm or 7mm is wasted espcially on old eyes...not so, you may not fully appriciate the extra brightness, but a larger exit pupil also makes eye alinement much less critical...

Regards,

Pete

It depends on what you plan to do with it. For plainsgame it doesn't matter. Shoot leopard in the daylight and it doesn't matter.

For buff and lion, I wanted all the field of view I could get and that is the 1.5-5X.

If you hunt elephant with any scope, what shouldn't I say?

quote:

Originally posted by Will:

If you hunt elephant with any scope, what shouldn't I say?

Hunting elephant with a scope is like going swimming with a T-shirt on. (Yes, I have done both.)

My vote goes to the 1.5x5! I have both and have run out of adjustment with the 1.75x6. The difference in adjustment is 65MOA versus 35. There is also a little more tube available to position your scope on the 1.5x5 and it seems to me in practice to have more eye relief. If I wanted greater magnification, I would go to the 2.5x8 which is versatility in spades! Someone suggested a Burris, too heavy! I don't think either Leupold is a bad choice but without info on the gun and mounting system the 1.5x5 is a safer bet. Good luck!

I have a 1.5x5 and my wife has a 1.75x6. Both have the heavy duplex, which on a DGR I much prefer.
When my brother was chosing a scope for the SAKO 375 he got from me I talked him into the 1.75x6. It is "brighter".
Go to the store look at both scopes and get the one you like the best.
I also have a 2.5x8 Leupold on my 9,3x74R double rifle with the heavy duples. It does not cause any aiming problems even of a coyote at 271 yards. It really shows up great in heavy brush and in low light.

Will

When I hunt elephant again knowing that I am not a REAL elephant hunter in your eyes because I used a scope will diminish my total experience considerably. NOT!!!

You are an opinionated old prick which I am sure you will take as a compliment and I have thoroughly enjoyed reading your cryptic posts.

Regards,

Mark

Mark,

Anything I can do to annoy the masses!

I fortunately I have never experienced the "mass onslaught" when ele hunting. If I ever do, I hope I come out of it alive and don't pee on myself. It is no place for a scope; so there might be a practical reason for not using a scope, besides tradition.