Light transmission

[Bert2368]

Please pardon my bringing this thread back again, but I have a practical, as opposed to theoretical question.

Is there anywhere available a table or list of claimed % light transmissions for all, or at least a good % of common rifle scope brands/product lines?

I can find these for a few, such as recent Leupold product lines. But a LOT of manufacturers either don't care to disclose or one must hack through quite a bit to locate a hard number online.

Additionaly, when I find a single % transmitted figure given for a whole product line which includes both fixed and variable power models? And knowing that these models have different numbers of total lens surfaces?! I suspect the number provided might not be accurate for all... unless they used lower quality coatings for the fixed powers, which I SUPPOSE might be done.

I am trying to use the % light transmitted figure along with twilight factor to get a better idea of what performance to really expect in low light.

 

[Turbulent Turtle]

I do not know of such a table, and it's pretty much meaningless in this day and age any way. A massive difference existed when optical glass first started getting coated. Coating is used to reduce the amount of light reflected back at the air/glass boundary. Uncoated glass reflects about 5% of the light at each such boundary, whereas properly coated glass will reduce that reflection by 90% or more.

The theoretical maximum for overall transmission through a riflescope is around 98%. To approach that figure, you expect the scope to have multiple coats on all the glass and for the glass to be of very high quality and have elements made of ED, Super ED or even fluorite glass.

Great riflescopes ($$$$) will have an overall transmittance around 95% and it will go down from there. The issue is that the difference between a 90% and a 95% riflescope is not something that anyone can discern, let alone measure, provided they have similar size objective lenses and are set at the same magnification.

In photography the exposure adjustments are usually measured in EVs (exposure values) and the difference between EVs is a doubling or halving of the light. You have half-EVs adjustments or third-EVs, but that still represents a much bigger difference than a piddling few percentage points in transmittance. That and the fact there is an actual sensor in the camera instead of a retina with its own autonomously adjustable pupil.

I would suggest that you concentrate on exit pupil size for the magnifications that are of interest to you. Essentially, coatings have allowed folks to have a riflescope with a smaller objective achieve the performance of an uncoated riflescope with a much bigger objective in low light conditions. Once all glass is coated and multi-coated, it becomes very difficult to see a difference in that respect.

 

[Bert2368]

Thank you all for your replies. I didn't explain my background and motives very well, my bad. I'll try to fill in a few bits below.

-----------

My dad was a physicist.

He built telescopes as a hobby, when I was young. I learned the aspects of low light performance some have mentioned long ago. Plus, I read a good bit of this thread before posting.

I'm looking at several scopes right now, which I must order online as no one carries them locally. I can't look through them and compare performance. I do understand objective Dia., exit pupil Dia. (and "twilight factor" as much or little as that may matter while comparing modern optical systems). I can interpret the commonly listed data on scope descriptions which you suggested I concern myself with. I have already done that for the models of interest.

That leaves me with at least one system design related variable, and it is potentially a big one if different companies are using different technical levels of coating schemes (and they are, especially at the end of the spectrum where I am shopping. I am not comparing Schmidt undt Bender to Swarovsky or Zeiss, quibbling over tenths of a %).

Some companies who say nada except "fully coated" (with WHAT? Calcium flouride? Dried chicken spit???) Others who say "guaranteed over 80% light transmission" (How MUCH over?). Still others who quantify light transmission of product lines to the 1/10th of a % like Leupold- But list same number for a product lines where individual models have different numbers of lens surfaces (Not inspiring my confidence in the number of significant figures given, at least without some explanation?)

And the ones who just don't care to give any numbers at all.

I really did not expect an industry wide list, but hey, you never know what's in the bottom of the pickle barrel 'lessen ya look in the bung.

I did hope for more than people's subjective opinions on 2 or 3 scopes they have looked through personally. Something derived in a testing lab.

I would wager that test data exist in all of the manufacturer's files- and that manufacturers test the competition's products as well. Probably for many the data is a trade secret, which makes your competition at least have to buy some of your equipment and WORK for the data?

 

[Bart B.]

Here's something to consider....

Focal lengths of scope's front objective lenses is typically 6 to 8 inches. If the scopes field of view is 15 feet for a given power, the field of view image focused in the first image plane will be .35 inch diameter for a 7 inch focal length objective less. Much smaller than inner tubes are.

Lenses in the erector tube will focus that image in the second focal plane where the eyepiece lens is focused at.

And yes, lenses funnel light rays. It's called focusing. Another "f" word conundrum. They funnel all the rays from each finite point of the target's field of view focussing them to another finite point in their image plane. Best example is focussing all the suns light ray's going into a 2 inch magnifying glass lens f-ing them to a single point on paper burning a hole in it.

Regarding light transmission, I doubt anyone can tell the difference in image brightness between 97% and 93% light transmission. And that relative brightness formula assumes 100% transmission through each lens.

 

[Turbulent Turtle]

Thank you all for your replies. I didn't explain my background and motives very well, my bad. I'll try to fill in a few bits below.

-----------

My dad was a physicist.

He built telescopes as a hobby, when I was young. I learned the aspects of low light performance some have mentioned long ago. Plus, I read a good bit of this thread before posting.

I'm looking at several scopes right now, which I must order online as no one carries them locally. I can't look through them and compare performance. I do understand objective Dia., exit pupil Dia. (and "twilight factor" as much or little as that may matter while comparing modern optical systems). I can interpret the commonly listed data on scope descriptions which you suggested I concern myself with. I have already done that for the models of interest.

That leaves me with at least one system design related variable, and it is potentially a big one if different companies are using different technical levels of coating schemes (and they are, especially at the end of the spectrum where I am shopping. I am not comparing Schmidt undt Bender to Swarovsky or Zeiss, quibbling over tenths of a %).

Some companies who say nada except "fully coated" (with WHAT? Calcium flouride? Dried chicken spit???) Others who say "guaranteed over 80% light transmission" (How MUCH over?). Still others who quantify light transmission of product lines to the 1/10th of a % like Leupold- But list same number for a product lines where individual models have different numbers of lens surfaces (Not inspiring my confidence in the number of significant figures given, at least without some explanation?)

And the ones who just don't care to give any numbers at all.

I really did not expect an industry wide list, but hey, you never know what's in the bottom of the pickle barrel 'lessen ya look in the bung.

I did hope for more than people's subjective opinions on 2 or 3 scopes they have looked through personally. Something derived in a testing lab.

I would wager that test data exist in all of the manufacturer's files- and that manufacturers test the competition's products as well. Probably for many the data is a trade secret, which makes your competition at least have to buy some of your equipment and WORK for the data?

I enjoyed reading your response and seeing that you have been a member here since 2013 and have only posted 7 times just makes me long for more of your contributions because you write well and make lucid arguments.

Of course, your father the physicist would probably chastise you over your misspelling of "fluoride", a rather important word.

I'm sad that you didn't get the information that you were hoping to get; as I said earlier, I know of no such table and even if you were to piece it together from various websites and documents, it would be out of date by the time you were halfway though it; there is way too much variety and changes to keep track of it.

The only time I ever saw anything approaching that was in an on-line article at a German website called "Der Viser" in the mid 2000s. They compared around a dozen riflescopes ranging from highfalutin S&Bs and Swaros to lowly Leupolds and Nikons. They were shocked to find out that the riflescope with the highest light transmission was the $400 Nikon Monarch at 92%+ and one of the worst ones was the Nightforce at 88%. These tests were done in a lab at S&B. This was over 12 years ago.

I've seen a lot of claims at various websites since then, but as you can see the numbers were pretty high then, with not much room to climb to that 98% limit. We're talking about a scant few percentage points now.

Some of the current optical differentiators are resolution, chromatic aberration control and of course coating for all wavelengths. Differentiators for the mechanics of a scope are zoom range, adjustment range, focus distance, repeatability and the various reticles.

 

[Bart B.]

Some of the current optical differentiators are resolution, chromatic aberration control and of course coating for all wavelengths. Differentiators for the mechanics of a scope are zoom range, adjustment range, focus distance, repeatability and the various reticles.

Good post.

I'll add the lenses have focal length tolerances which means the image size at each respective focal plane won't be exactly the same across all of a given model. And that's why their adjustments don't move focus and line of sight exactly as specifications and scales state.

 

[Bart B.]

Here's a good write up on scope image quality:

https://precisionrifleblog.com/2014...ptical-performance-field-test-results-part-1/

Interesting thing to note is the scope with best optical or image quality had a small zoom range. That's normal as lens tolerances add up as zoom range increases. Fixed power scopes can deliver best optical/image quality.

 

[Bert2368]

Interesting thing to note is the scope with best optical or image quality had a small zoom range. That's normal as lens tolerances add up as zoom range increases. Fixed power scopes can deliver best optical/image quality.

Yes indeed!

And that (along with the lower # of lenses and hence lossy optical surfaces) is why one of THESE is arriving here this week- A fixed 8 X 56mm scope with 7mm exit pupil and an illuminated reticle.



https://kalinkaoptics.com/rifle-sco...-and-1000m-dragunov-rangefinding-reticle.html

I would have liked to try out Meopta's version, but this is 25% the cost.

Considering that the USSR looted the whole equipment inventory of the Zeiss factory in 1945, relocating them to the mother land- I am guardedly hopeful. They DO repeatedly mention on the English language site that they are "in the tradition of Zeiss".

There is snow on the ground and the moon is waxing, we're going to do some low light testing.

 

[Bart B.]

Another element of optical quality is image contrast. Two scopes with the same resolution, power and objective diameter, the one with the highest contrast image can appear to have the sharpest image.

In my opinion, the 2 most common causes of poor image in scopes is their eyepiece lens(es) are not perfectly focused on the reticle and the objective lens(es) are not perfectly focussing the target on the reticle. Target range focussing adjustments move the lenses a fixed amount from infinity to some closer range exactly the same amount across all scopes of a given make/model. But their lenses in each respective place between the eyepiece focal point forward have tolerances in their focal lengths. Which means, for example, to focus a 600 yard target perfectly on the reticle eliminating parallax, the scope range focus may need be set to someplace between 500 and 800 yards. That's about a .002" change in typical objective lens(es) focus point. On a barrel focus objective lens with 40 threads per inch, it moves .025" per turn. Side focus scopes must change their inner lens positions to change 2 lens positions some amount to make the same change in their system.

 

[Turbulent Turtle]

Yes indeed!

And that (along with the lower # of lenses and hence lossy optical surfaces) is why one of THESE is arriving here this week- A fixed 8 X 56mm scope with 7mm exit pupil and an illuminated reticle.

https://kalinkaoptics.com/rifle-sco...-and-1000m-dragunov-rangefinding-reticle.html

I would have liked to try out Meopta's version, but this is 25% the cost.

Considering that the USSR looted the whole equipment inventory of the Zeiss factory in 1945, relocating them to the mother land- I am guardedly hopeful. They DO repeatedly mention on the English language site that they are "in the tradition of Zeiss".

There is snow on the ground and the moon is waxing, we're going to do some low light testing.

I'm not clear as to why you chose to post the above in a thread entitled "Light Transmission" on a forum dedicated to accurate shooting. Perhaps you meant it was an example of the reverse of light transmission, for which I think this scope will definitely by the poster child.

I do not mean to urinate in your Cheerios this morning, and so don't take this the wrong way, but buckle up; it's going to be a rough ride.

I went to the website you posted and I read the information a few times. One thing I noticed right away, there is a definite dearth of useful information about the product. The data that is provided, with a lot of unnecessary words, only says this is an ordinary very low-end scope.

Saying that it is made in the Zeiss tradition is meaningless. A Zeiss scope from 1945 is junk compared to even ordinary modern scopes for one specific reason; coating. I also notice that word is not used anywhere on that page. (Ctl-f coat, returns nothing.) The only mention about the optical properties of the scope is: "The optics are very clear,... grid... They never mention coat, coating, coated, multicoated or fully multicoated. So, this scope is built with uncoated glass. There's a reason it comes with a 56mm objective at only 8X; at 5% loss at each air/glass surface, you have to start with the biggest objective possible to have anything left at the end to transmit to the eye.

Of course all the other coatings use for hardening, protecting, rain, etc, are not found on this scope. We're talking pure unadorned glass. Your first test should be to look through in the general direction of (not directly at) the sun. You will see a whole set of artifacts in the eyepiece.

My experience with optics prior to coating is that the contrast will be very soft and the image will be dull; no colors will pop. There may even been a red or blue shift in the image.

So, it's a one-inch tube scope with 1/4 MOA (+/- 0.2) clicks for windage and a mil-based reticle with marks for longer distances. The adjustment range is not specified. It has an adjustable objective, which is the original and still the best method for parallax adjustment, what they call independent focus, but that is not "advanced focusing technology." The knob on the left is for turning on/off the illuminated reticle. The picture shows a minimum focus range of 10 meters.

The reticle allows for some form of range estimation, what they call "kill distance" and has a fancy curve on the left side to help you with that.

Speaking of knobs, I see the directions of adjustments are in Russian; I do not know what U or V mean but I think one is Left and the other is Right. Same with the elevation knob, H and B; I do not know which one is Up or Down.

There is a reason that it is 25% of the cost of a Meopta.

I tried to download their translated owners manual, but I had no luck.

 

[Billy 30-06]

One evening at the hunting club we compared a hand full of scopes in the failing light and found the more expensive euro scopes to have better resolution in good or poor light. The best were an older model Swarovski PH 2-1/2-10x56 and a Docter Unipoint 3-12x56. The Docter has the advantage with the illuminated dot. The newer 2nd focal plane Swarovskis have great optics but were out classed by the older 1st focal plane PH in poor light.
Billy

 

[Turbulent Turtle]

One evening at the hunting club we compared a hand full of scopes in the failing light and found the more expensive euro scopes to have better resolution in good or poor light. The best were an older model Swarovski PH 2-1/2-10x56 and a Docter Unipoint 3-12x56. The Docter has the advantage with the illuminated dot. The newer 2nd focal plane Swarovskis have great optics but were out classed by the older 1st focal plane PH in poor light.
Billy

I was reading your post and getting all your information and then at the end you went newbie on me You gave the exact information about the older Swaro and the Docter and nothing about the new Swaro, so we have no idea as to what you compared.

 

[Bert2368]

The VOMZ Pilad 8X56 arrived. I received it after dark, will do daylight test soon.

I immediately took it outside and did a quick check on low light performance- It is not so bad as one of you feared, nor as good as might have been hoped (is anything?).

(I had no trouble downloading the Enlish language manual PDF, but can't upload it here. What parts would you like to see?)

In the dark with 1/4 moon, snow cover and second to lowest reticle brightness, shooting coyotes at 200 yards without artificial light looks quite do-able.

The lower settings of reticle illumination are very good, set at the minimum, it will go dimmer than my fully dark acclimated eyes can see. Only when I mounted a night vision scope cam to the ocular could I verify the minimum setting was even on.

Looking around in the warehouse at work with the lights on, no problems so far, but the distance available was only to 120'. Contrast is better than some other scopes I own which cost about as much, edges of field are good. "Eye box" is not as forgiving as some scopes claiming the same exit pupil.

Is it junk? No. Is it going to put Zeiss out of bsiness? Definitely not. Worth the money? Probably, will know more after I get to use it for the intended purpose.

Which is varmint hunting without artificial light, my state forbids use of artificial light (including the IR illuminators on night vision scopes!) for shooting ANNYTHING except coyote, which can be done only with SHOTGUNS and that for ONE MONTH OF THE YEAR (January). Weird, but I will stay within those parameters. Coyotes around here are not coming within shotgun range in my experience! My only other alternative might be passive infrared, and I REALLY can't afford that.

 

[Billy 30-06]

I was reading your post and getting all your information and then at the end you went newbie on me You gave the exact information about the older Swaro and the Docter and nothing about the new Swaro, so we have no idea as to what you compared.

The scopes were Z6 5-30x50P BTL and Z6 3-18x50P BTL.
Billy

 

[Turbulent Turtle]

The scopes were Z6 5-30x50P BTL and Z6 3-18x50P BTL.
Billy

Billy, thank you for coming back and adding the information.

I suspect that as you were posting it you realized why you and your friends at the hunting club found that the scopes with a 56mm objective lens were better in poor light than the ones with a 50mm objective lens. The 56mm objective is 25% larger than the 50mm one and that makes a difference.

 

[JD9000]

Billy, thank you for coming back and adding the information.

I suspect that as you were posting it you realized why you and your friends at the hunting club found that the scopes with a 56mm objective lens were better in poor light than the ones with a 50mm objective lens. The 56mm objective is 25% larger than the 50mm one and that makes a difference.

I guess the larger objective does gather more light.

 

[Nature Boy]

This is my Swarovski Z6i 3-18x50, 3x at 5:30 PM

Not sure how to measure it objectively, but my eyeball says it’s the best scope I’ve ever had in low light conditions

 

[Turbulent Turtle]

This is my Swarovski Z6i 3-18x50, 3x at 5:30 PM



Not sure how to measure it objectively, but my eyeball says it’s the best scope I’ve ever had in low light conditions

Is it just me or is the scope reticle canted to the right just a bit?

 

[Bert2368]

Judging from your photo, the 3X image is noticeably brighter than the nearby (and presumably equally illuminated) area to the left of the occular

Check how bright the image looks compared to that 3X setting at whichever magnification where exit pupil will have been reduced to about 7 to 8 mm.

Using a 3-15X50 Weaver Tactical scope this fall, it was brightest (subjectively, as it appeared to my eyes) around 5 or 6X.

https://www.opticsplanet.com/weaver-tactical-3-15x50-mil-dot-30mm-riflescopes.html

That discovery worked out poorly for a couple of deer approximately 200 and 240 yards out, who decided it was dark enough to safely leave the treeline on an overcast day within the last 5 minutes of legal shooting hours.

All but 2 deer out of 15 taken in the last 10 years have been shot less than 30 minutes after the beginning of legal shooting hours or less than 30 minutes before the end. Usually VERY close to either the beggining or end.

The two taken in full lightwere bucks, thinking about sex rather than safety.

Oddly enough, the small Vortex 8X36 "Solo" scope I use has at least as good apparent brightness as that scope- Manufacturer claims it has a 5mm exit pupil, fully coated lenses. I wonder how MANY lenses less this has than that variable Weaver? For the money, this thing is decent.

 

[Nature Boy]

Is it just me or is the scope reticle canted to the right just a bit?

It’s just the picture making it look that way. The rifle is probably canted a bit