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Meostar B1 7x50 is here (1 Viewer)

typo

Well-known member
Henry,

The distance of the eye lens to retina is typically 22mm, so a 1.8mm pupil would be f/12.2 and a 5mm pupil f/4.4.

David
 

galazie1

Well-known member
I think my technical skills do not allow me to do the star test Henry described. But for now i still enjoy the meopta every day, both on its own and in comparison with the slc. I think the difference between the two is because the meopta is good and the slc is exceptional. I and a friend xompared the slc 7x50 to the el sv 10x50 and both of us agreed they are difference but there is no better binoculars between them

The slc is remarkably bigger (longer) and heavier than the meopta. Sure there s more glass inside. Swaros should not have done that for little reason. Not to mention the 2x price difference. The size/price/performance ratio is reasonable to me.

I am still happy with the meopta and most likely it will be my travel binos. Very comfortable for a 7x50
 

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Troubador

Moderator
Staff member
Supporter
It sounds to me that you like the Meopta because there is a special magic about the view through it even though the SLC might be 'better'. Sometimes you can fall in love with a lady who is not perfect and it is the same with binoculars!

Lee
 

Alexandr33

Active member
Troubador, Really Meopta is very nice binoculars. Recently tested good binoculars. Meopta was on par with them. And for the price - quality, the best!
 

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Troubador

Moderator
Staff member
Supporter
Troubador, Really Meopta is very nice binoculars. Recently tested good binoculars. Meopta was on par with them. And for the price - quality, the best!

I agree Alex, and what a nice collection of binoculars in the pic!

Lee
 

galazie1

Well-known member
It sounds to me that you like the Meopta because there is a special magic about the view through it even though the SLC might be 'better'. Sometimes you can fall in love with a lady who is not perfect and it is the same with binoculars!

Lee

No I like it because of the handling. It feels and works so great in my hands.

the view is acceptable but to me one obvious step below the SLC. consistent with the priced difference

some BF members here suggested I have a "bad" sample. my feeling is that it isn't. but I won't be able to find out about it any time soon. For an exchange I will need to ship back and forth between Vietnam and Europe, which is too much hassle.

Maybe I'll know in 20 years when I ship it back to Meopta for maintenance. or until I buy another Meopta.

again the Meopta is my best binoculars until now in terms of ergonomics
 

henry link

Well-known member
No I like it because of the handling. It feels and works so great in my hands.

the view is acceptable but to me one obvious step below the SLC. consistent with the priced difference

some BF members here suggested I have a "bad" sample. my feeling is that it isn't. but I won't be able to find out about it any time soon. For an exchange I will need to ship back and forth between Vietnam and Europe, which is too much hassle.

Maybe I'll know in 20 years when I ship it back to Meopta for maintenance. or until I buy another Meopta.

again the Meopta is my best binoculars until now in terms of ergonomics


Hi Galazie1,

I guess I'm the BF member who suggested that your Meopta is probably a "bad" sample. I'll suggest a quick and easy star-test one more time and then I'll shut up.

I promise it won't be that hard to do, especially if you use an artificial star like a small shiny ball set up at maybe 20 meters away in sunlight to produce a tiny glitter point of the sun. Of course, the binocular needs to be kept still, either tripod mounted or just propped on something. The second binocular for boosting the magnification can be handheld behind the eyepiece of the tested binocular. The star needs to be carefully centered in the tested binocular, but alignment between the two binoculars doesn't have to be perfect. You'll see that the diffraction pattern of the "star" will remain stable over a surprisingly wide range of misalignment. Its shape will start to distort only if you wander too far out of line. Also test your 7x50 Swarovski as a reference.

Your impression of a degraded image in daylight is what nearly convinces me that the Meopta has a problem. 7x50s, because of their large exit pupils have a very easy time producing a good image in sunlight since they are stopped down by the eye to a very small effective aperture of around 17-18mm with an effective focal ratio above f/10. Even bad ones tend to look good when such a small central area of the objective lens is the only part contributing to the image quality.

The star-test won't eliminate every possibility. For instance, small collimation and diopter adjustment problems won't show up, but even if I'm wrong you should come away with a new skill for evaluating binocular purchases.

Henry
 
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yarrellii

Well-known member
A little off topic here, but since there are not that many threads regarding the Meopta B1 7x50... anyone with experience with the B1 and the Vixen Foresta CF porro is able to give a first hand experience comparison, even if it is just a couple of general ideas?

I remember the Foresta CF stirred quite a lot of interest both here and in CN back in the day. The price is less than half of the Meopta, but according to many reviews and opinions, the performance is supposed to be pretty high. I wonder how close does it come to the Czech binoculars.
Thanks!
 

galazie1

Well-known member
Hi Galazie1,

I guess I'm the BF member who suggested that your Meopta is probably a "bad" sample. I'll suggest a quick and easy star-test one more time and then I'll shut up.

I promise it won't be that hard to do, especially if you use an artificial star like a small shiny ball set up at maybe 20 meters away in sunlight to produce a tiny glitter point of the sun. Of course, the binocular needs to be kept still, either tripod mounted or just propped on something. The second binocular for boosting the magnification can be handheld behind the eyepiece of the tested binocular. The star needs to be carefully centered in the tested binocular, but alignment between the two binoculars doesn't have to be perfect. You'll see that the diffraction pattern of the "star" will remain stable over a surprisingly wide range of misalignment. Its shape will start to distort only if you wander too far out of line. Also test your 7x50 Swarovski as a reference.

Your impression of a degraded image in daylight is what nearly convinces me that the Meopta has a problem. 7x50s, because of their large exit pupils have a very easy time producing a good image in sunlight since they are stopped down by the eye to a very small effective aperture of around 17-18mm with an effective focal ratio above f/10. Even bad ones tend to look good when such a small central area of the objective lens is the only part contributing to the image quality.

The star-test won't eliminate every possibility. For instance, small collimation and diopter adjustment problems won't show up, but even if I'm wrong you should come away with a new skill for evaluating binocular purchases.

Henry

Hi Henry,

Don't worry it's not only you :)

And I welcome those suggestion. I take your words seriously. I just don't want to have a bad Meopta sample. Why must it be me? hehe.

I am back from long trip. now i am thinking how to execute your test. I mounted the meopta on my tripod. but no stable artificial stars. they change every 5 minutes as the sun light direction changes.

is it OK to do the test at night using a real star? or a distant street light?

or is it better to do in day time?

also. BIG question: what am I expecting from the star test? I understand I will handhold another binoculars behind the mounted one. what will I do with the hand-hold binos: focus, defocus...? what will the star image be like to expect? what is good result and what is bad result?

sorry for my poor technical skill.
 

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galazie1

Well-known member
Henry

In the evening. Mounting the Meopta, I focus on a very bright street light about 1km away. Using a 7x42 handheld to look through the Meopta, I saw a thick, concentric ring that can not be focused to a point.
 

galazie1

Well-known member
When i defocused the streetlight in the mounted Meopta (to both directions). In the handheld 7x42 it became a big perfect round disk of light, evenly lit, that changed little when i focus or defocus the handheld binos
 

galazie1

Well-known member
Pointing them towards a bright star in the sky. The focused star in the mounted Meopta became a big round disk of light in the handheld binos. The disk had thick rim, like a pizza

It was exactly the same with the slc
 

henry link

Well-known member
Sounds like you are defocusing too much. The defocused disk should be small, not large. You want to see only a few diffraction rings when you defocus and those may be visible only on one side of focus and not the other.

Begin by setting the handheld binocular to infinity focus and leave it there. Then use only the focuser of the mounted binocular to defocus the star.

The street light might not be small enough to act a true point source.
 
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galazie1

Well-known member
now maybe I see what you mean.

tonight:

1- i set the handheld binos to infinity focus

2- i mounted the meopta on tripod and point to a bright star. used the handheld binos to look at the star image through the meopta.

3- put my other hand on the meopta and slowly focused/defocused on both directions.

when focused the meopta on the star, the image in the handheld binos was a point of light.

when slowly defocusing the meopta to the "left" (to the close focus direction), the star (in the handheld binos) got spiky before becoming a disk

when defocusing the meopta towards infinity, it was different. now maybe I saw what you called "diffraction rings". However, only the outer ring was clear, the inner few rings were very faint - or maybe i imagined them. If they are truly rings, they appeared to be concentric.

now what should I expect? if there is an error, what should it look like?
 

henry link

Well-known member
Well, the "spiky" look might indicate a poorly made roof prism or maybe astigmatism and the hollowed out look when defocusing in the opposite direction suggests a large amount of spherical aberration, but that's not so unusual in a 7x50 at full aperture. What does the Swarovski look like when you test it?

Could be that you just won't be able to figure out what's wrong on your first attempt at star testing.

BTW, photos of the star test are possible by simply pointing a camera through the binocular eyepiece. There are a few in this review:

https://www.birdforum.net/showthread.php?t=285414
 

galazie1

Well-known member
Thanks, Henry. The linked star test is eye-opening!

I take your photos of your Zeis FL result.

For the SLC 7x50, when defocused towards infinity, it looks like the 1st photo (circled), but much better. the rings are much more pronounced. when defocused towards near focus, it looks like the 2nd photo (circled), but without the green outer fringe.

For the Meopta 7x50, when defocused towards infinity, it also looks like the 1st photo (circled), but clearly worse. The inner rings were much less pronounced. but it was still much better than the HT results in your star test. when defocused towards near focus, it also looks like the 2nd photo (circled), but without the green outer fringe, AND IT WAS NOT A ROUND DISK, BUT AN OVAL SHAPE.
 

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henry link

Well-known member
Keep in mind that photos never show the diffraction patterns as clearly as the eye sees them. More pronounced rings are not necessarily good. What's wanted is identical looking rings on both sides of focus. As the rings weaken on one side they tend to become harder and clearer on the other side. Very weak or no rings on one side and hard rings on the other means high spherical aberration. The worst you're likely to see looks like the full aperture HT photos, with a bright central area with no rings on one side and a bright outer ring with a hollowed out dark center on the other side.

A diffraction disk with an oval shape indicates astigmatism, best seen at only 2-3 rings of defocus. The axis of the oval shape should change by 90ยบ on the other side of focus. You can see that clearly in the right side/full aperture photo of the HT in the link. High spherical aberration and astigmatism may be all the explanation that's needed.

If you can make a stop down mask for the objective lens with a diameter around 16-20mm that will tell what the aberrations look like in daylight when your constricted pupil effectively stops down the binocular objective.
 
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galazie1

Well-known member
Thanks, Henry. It will take me some time to do this

Meanwhile, so far, has anything pointed you to any significant flaw of this bins, that explains the situation I conceived?

I am thinking of shipping the binos to you for your help on a conclusive check. Of course if you have time and like to do that.
 
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