Roger Vine's thoughts on the 7x21 Curio? (1 Viewer)

[John A Roberts]

Roger has just posted a detailed review. And at the end he compares the Curio's performance to that of the Zeiss 8x25 Victory.
See at: Swarovski 7x21 Curio Review


John

 

[Swedpat]

Thanks for link! Curio 7x21 is really compact, which one can see in comparison to Zeiss Victory 8x25.

There is a wrong statement in the review, though.

"These are are notably bright for compact bino’s in full daylight – significantly better than my old reference standard, Nikon’s 8x20 HGLs. Mostly that’s due to the higher transmission optics, but the extra 1mm aperture actually gathers 10% more light too. Consequently, they do work better at dusk or in dim woodland than most 8x20s, but fall short of 8x25s or 8x30s in really low light".

It's correct that 21mm aperture gathers ~10% more light than 20mm. But the main reason to brighter image is the larger exit pupil. 3mm means 44% brighter image than 2,5mm with equal light transmission. So it's mostly due to larger exit pupil.
And 7x21 actually has 92% of the brightness as 8x25 so it falls short VERY slightly. Compared to 8x30 the difference is more noticeable, though.

 

[dorubird]

Olso it is a wrong statement in the review about size:
"Body

These really are tiny – just about the smallest binoculars I’ve ever seen. They are noticeably shorter but a little wider and marginally heavier than Leica’s 8x20 Trinovids, but smaller and lighter than the rest."

In reality Leica Trinovid 8x20 are litlle shorter than Curio, and overall smaller too! Trinovid 8x20 it is still the smallest🤏
Anyway, I like the review!

 

[Gijs van Ginkel]

Swedpad, post 2,
We have investigated the 7x21 Curio as well as the Zeiss Victory 8x25, see our test of the Curio and other compacts on the WEB-site of House of Outdoor.
We measured light transmission values of 93% for the Curio over a broad spectral range and we found the same transmission values for the Zeiss Victory 8x25. That means that the light gathering properties of both binoculars are the same, since both binoculars have similar exit pupils of 3 mm.The photographs in our test report do not support evidence that the Curio is smaller compared to the Leica/Zeiss 8x20 compacts.
Gijs van Ginkel

 

[tenex]

There is a wrong statement in the review, though.

I've long been curious why Roger keeps saying in binocular comparisons that extra aperture gathers more light, while ignoring exit pupil. Presumably it's some sort of carryover from his astronomy background that he hasn't noticed.

 

[[email protected]]

I've long been curious why Roger keeps saying in binocular comparisons that extra aperture gathers more light, while ignoring exit pupil. Presumably it's some sort of carryover from his astronomy background that he hasn't noticed.

Yes, usually astronomers think of aperture size in telescopes and binoculars in terms of how much light they gather instead of exit pupil size. Really, it means the same thing. Either way, you are bringing more light to your eyes. In astronomy, aperture size rules everything where you are using a telescope at night but not so much in a daytime birding binocular.

 

[b-lilja]

OK, that did it...I'm buying a pair. Had an order in and cancelled it...but gonna do it this time. We'll see how they compare to my Uvid 8x20s.

The main thing I'm nervous about is that I have Reynaud's Syndrome - don't know if the exposed metal will trigger - we'll see.

 

[Swedpat]

Yes, usually astronomers think of aperture size in telescopes and binoculars in terms of how much light they gather instead of exit pupil size. Really, it means the same thing. Either way, you are bringing more light to your eyes. In astronomy, aperture size rules everything where you are using a telescope at night but not so much in a daytime birding binocular.

When it comes to stars, who remain pointsources, a smaller exit pupil due to high magnification is often to prefer. Because the sky background becomes darker which increases the contrast. This can help to see fainter stars.

But on faint surface objects like nebulas and galaxies a larger exit pupil is often desirable. Here a higher relative brightness is good, providing the sky is dark and not polluted.

But yes, in either case larger aperture is preferable.

At all situations when we watch surface objects the exit pupil is the basic determining factor for the image brightness.

 

[mwhogue]

To keep it short:

IMO Roger nailed it in the summary. Between the two if birding is the primary purpose the VP 8x is the best choice. If all around general use in a pocket is the goal the Curio is the way to go.

Thanks John for posting the link.

Mike

 

[adhoc]

John, thanks for the heads-up. First looked for something critically important to me: CA control against backlighting. "Stray Light and Ghosting//I couldn’t get much in the way of ghosts, veiling flare or stray light problems from the Curios." Understood. But then under Chromatic Aberration is this: "...You can sweep through silhouetted branches without trouble from jazzing false colour."

Looked up "jazzing", "verb jazz", etc. in formal and informal internet dictionaries but not much help in this it seems to me. Clarification, Roger Vine or anyone else? Should be generally useful. Thanks!

 

[Richard D]

I took it to mean that with a quick sweep through contrasting branches you won't see flashes of colour.

I've not tried the curio but if CA is as well controlled as it's older big brother the CL 8x25 the CA won't be an issue even for those sensitive to CA. In the 8x25's you can force the merest hint, but you have to try very hard.

 

[pm42]

I've not tried the curio but if CA is as well controlled as it's older big brother the CL 8x25 the CA won't be an issue even for those sensitive to CA

CA is very well controlled indeed. I hardly see it and I just compared with the NL Pure 8x32.

 

[Troubador]

OK, that did it...I'm buying a pair. Had an order in and cancelled it...but gonna do it this time. We'll see how they compare to my Uvid 8x20s.

The main thing I'm nervous about is that I have Reynaud's Syndrome - don't know if the exposed metal will trigger - we'll see.

I have Reynaud's too. In cold weather the exposed metal would be a risk but hopefully wearing gloves would prevent this, although pocket binoculars are not always easy to handle wearing gloves. Could be they are best saved for warm weather.

Lee

 

[pm42]

but hopefully wearing gloves would prevent this, although pocket binoculars are not always easy to handle wearing gloves.

They are really small so I'm not sure about gloves. I covered mine with tape to avoid contact with metal and to protect them:

CL Curio 7x21: protection for apparent metal

Hi, For some reason, the designer of the CL Curio never used binoculars. Because he should now that apparent anodized metal is a bad idea when it's cold but it wears quickly. As I put my compact binoculars in my pants pocket, I've noticed it after just a few days. So I designed a pattern...

www.birdforum.net

But if metal is really an issue, the Ultravid 8x20 are excellent but with less FOV and the Victory 8x25 are close to perfection, only slightly bigger. My wife prefers the Zeiss because of this, she finds them easier to handle.

 

[Troubador]

They are really small so I'm not sure about gloves. I covered mine with tape to avoid contact with metal and to protect them:

CL Curio 7x21: protection for apparent metal

Hi, For some reason, the designer of the CL Curio never used binoculars. Because he should now that apparent anodized metal is a bad idea when it's cold but it wears quickly. As I put my compact binoculars in my pants pocket, I've noticed it after just a few days. So I designed a pattern...

www.birdforum.net

But if metal is really an issue, the Ultravid 8x20 are excellent but with less FOV and the Victory 8x25 are close to perfection, only slightly bigger. My wife prefers the Zeiss because of this, she finds them easier to handle.

On really cold winter days I could imagine that tape would not give sufficient insulation to prevent the cold metal triggering Reynaud's.

For handling I also preferred Zeiss's Victory Pockets. I had a twin-hinge pocket for years that I could never get used to as every time I applied sufficient pressure to move the focus wheel, the hinges started moving..........

Lee

 

[dorubird]

About exit pupil (aperture/power) and brightness image perception:

In reality, between two binoculars with same optical quality and same exit pupils, the binoculars with larger aperture and higher power will show more information than smaller one, especially in low light when the light is crucial. Because the larger surface of the front lenses will capture more light, and the power will help resolve more image details.
So VP 8x25 will behave better in low light than Curio 7x21, even if they share the same exit pupils. But they dont't even have exactly the same exit pupils, they are almost identical (3.125mm vs 3mm)

 

[Swedpat]

One way to understand the importance of exit pupil is that it just corresponds to your eye pupil size or looking through a hole. For example if you watching an object at 100m with naked eyes compared to binoculars or telescope:

8x20 corresponds to standing at 12,5m looking through a 2,5mm hole.

7x21 corresponds to standing at 14m looking through a 3mm hole.

6x30 corresponds to standing at 17m looking through a 5mm hole.

8x40 corresponds to standing at 12,5m looking through a 5mm hole

7x50 corresponds to standing at 14m looking through a 7,1mm hole

10x50 corresponds to standing at 10m looking through a 5mm hole

20x80 corresponds to standing at 5m looking through a 4mm hole

25x100 corresponds to standing at 4m looking through a 4mm hole

50x50 corresponds to standing at 2m looking through a 1mm hole

Here it's easy to understand that a higher magnification can help to see details even if the image is dimmer. But if it becomes too dim, higher magnification will not help. Because magnified darkness = darkness.

And if you compare a 6x30 to a 10x50 the 10x50 will reveal more details due to the higher magnification. But if it's too dark to see any details with 6x30 you will not see any detail with 10x50 either.
8x25 has a VERY VERY slight advantage compared to 7x21 here, the difference between 3 and 3,125 mm exit pupil is almost negligible.

 

[adhoc]

Richard D,
Thanks, it now makes sense, sorry if I was daft.

 

[Gijs van Ginkel]

Swedpat, post 17,
Have you tried this theory? I ask it since I do not believe it will be published in optical text books and in the text books I know it is not mentioned..
Gijs van Ginkel

 

[Swedpat]

Gijs,

It's just the conclusion I draw based on the optical laws.
In physics we know the law that what you gain in force you lose in distance (I don't know the best way to express this on english but you know what I mean).
In optics the law is that what we gain in increased apparant object area we lose in relative brightness. With same light transmission every binocular/telescope with same exit pupil provides same brightness.
So, let us compare 8x20 at 10m and 80x200 at 100m.
If we exclude the possible impact of more air mass between the instrument and object(I think it requires a very polluted air to be a noticeable factor at 100m) there will be absolutely no difference. The images will have completely identical brightness.
I have not specifically compared these configurations but I accept the challenge to prove if I am wrong. If I am, it also has to be possible to prove from a mathematical formula.

I also support my statement by my experience of my 5x25 and 6x32 binoculars. I can see that these have a brightness in dim conditions similar to 8x42 and 10x50. Just lower magnification.

It's common that people think that a large instrument is brighter than a small despite same exit pupils. That misconception is probably caused by that they have mixed up brightness and light amount. For example: the view in a 10x50 will be more dazzling than a 6x30 when aiming at a light source. It has to be, if the surface intensity is the same but the apparant area of the light source is 2,78 times higher. So I believe this is a reason to the misconception.
But watch against an even colored surface which fills up the entire FOV(here you can compare a 10x25 to a 20x50 to be sure you make use of the entire exit pupil), like a white wall, or the blue sky, and you will see it's the same.