Curio 7x21 vs. CL 8x25 pocket (1 Viewer)

[ReinierBos]

The looks of binoculars are important for me as well. The CL 25 is good looking as well as the Curio. The Pentax 6.5x21 does not have a change, although the price is nice.
For now I will be satisfied with the Terra 8x25 and after a while I might experience with I am missing. Is it the weight? The size? The magnification? The quality? The looks? The comfort? I am not sure yet. Let's figure it out before I open my wallet again.
However, I see the value of pocket bins now. When I was on holiday with small children, I wasn't there for bird wachting. So it was nice having a lightweight pair of bins with me. I hardly used my 8x42 and 10x32, although the quality is better.

 

[ReinierBos]

In terms of the eyecups, I like the UV better than the older version of the CL.

Am I right that of all the pocket bins you think the UV 8x20 has the better/more comfortable eyecups? Also compared with the Curio and the Trinivod 8x20?

 

[mwhogue]

Am I right that of all the pocket bins you think the UV 8x20 has the better/more comfortable eyecups? Also compared with the Curio and the Trinivod 8x20?

Reinier,

Just based on frequent use, as opposed to directly comparing comfort of the different eyecups, the UV and Trinovid eyecups are my favorite. There is not much if any difference between the two in terms of comfort although the design is a bit different. On a related note, I have come to prefer the pull up function of the Leica eyecups as opposed to the twist up function of all the others. Your question has piqued my interest and over the next several days I'll do some direct comparison and report back with pictures if I find anything which may be helpful.

Mike

 

[ReinierBos]

Thank you! With pocket bins it is all about compromise. I would like the bins as small and light as possible. I would like comfortable eyecups too and a decent AFOV. I now have the Terra 8x25 and they are still quite hlarge and heavy. Good enough during winter for the pocket of my winter coat, but not during summer.
And the optics are quite good, but I prefer them to better... I am spoiled already. So a Leica 8x20 would be nice and if the Trinovid 8x20 would be as comfortable as the Ultravid 8x20, it may be a good buy. The Curio 7x21 would be nice as well, although I prefer 8 power. Still, 3mm EP would be nice. 7 power has better DOF as well.

 

[mwhogue]

Thank you! With pocket bins it is all about compromise. I would like the bins as small and light as possible. I would like comfortable eyecups too and a decent AFOV. I now have the Terra 8x25 and they are still quite hlarge and heavy. Good enough during winter for the pocket of my winter coat, but not during summer.
And the optics are quite good, but I prefer them to better... I am spoiled already. So a Leica 8x20 would be nice and if the Trinovid 8x20 would be as comfortable as the Ultravid 8x20, it may be a good buy. The Curio 7x21 would be nice as well, although I prefer 8 power. Still, 3mm EP would be nice. 7 power has better DOF as well.

In terms of overall size of the bins including the outer diameter of the eyecups, the Trinovids are the smallest and lightest followed by the UV (both are BL models not BR which are are slightly larger overall) and then the Curio. But the differences in size are very small and probably will not matter or even be noticed in actual use for most people. All three are true "shirt pocket" models. I find the UV eyecups most comfortable by a tiny margin. I prefer the optical performance of the Curio followed closely by the UV and then the Trinovid.

Of course the Terra is much larger, relatively speaking, in all dimensions including diameter of the eyecups. The Terra's optical performance is excellent to the point that IMO the most meaningful difference between the Terra and the 20/21 mm models in practical terms is down to size and weight especially since you prefer an 8 to a 7x.

Hope this helps with your search.

Mike

 

[Elkhornsun]

The light transmission is primarily a function of the surface area of the objective lenses. A 25mm provides an area gain of 56% over a 20mm objective. I don't consider any bino with objectives smaller than 25mm.

Actual size when folded varies with the different bridge and hinge design and I like how very compact the Swarvo 8x25 and 10x20 CL binos when folded and in their carry case.

 

[ReinierBos]

Now I wonder. You have a CL 10x25 with 2.5 mm exit pupil. The CL 7x21 has 3 mm exit pupil. Doesn't that mean that the light gathering is larger in the 21mm compared with the 25mm? (At least when you're own pupil is larger than 2.5mm)
Doesn't that mean that the CL 7x21 is a bit more useable at dawn/twilight than the CL 10x25?

 

[tenex]

Light gathered is a function of objective size.
Transmission is a percentage of that, dependent on number of elements, coatings etc, typically close to 90% these days.
Perceived brightness is further reduced when the user's pupil (around 2.5mm in daylight) is smaller than the exit pupil.

Conclusion: assuming roughly equal transmission, in lower light with >3mm eye pupil, 10x25 should be about 40% brighter than 7x21, and the magnification should give better detail as well. (7x21 could actually be 10% brighter than 8x20 due to objective size, but that's a different comparison.)

 

[ReinierBos]

So you are saying the exit pupil doesn't play a role here? A 8x25 or a 10x25 has the same brightness, even in lower light?
I have heard other people saying that for instance the 8x42 should appear brighter than a 10x42.
I remain puzzled about this. Some people say that the exit pupil is the most important feauture for low light (a reason why people love 7x42 bins as low light bins) and other people say that the object size is the most import, regardless of the magnification. The magnification will even help for better details.

 

[William Lewis]

Brightness is dependent on transmission and exit pupil size.

Exit pupil size is aperture divided by magnification and transmission is measured by someone with access to some rather expensive equipment, it's also usually stated by the manufacturers.

If you think of it this way- your eyes on there own will adapt the pupil size for the light conditions so on a bright summer day you pupils may be contracted to say 2.5mm or so. In these circumstances a 10x25 binoculars will be just as bright as a 10x56 binoculars IF both binoculars have the same percentage transmission - the 10x56 will have a bigger exit pupil but your eye will only be using 2.5mm of it anyway.

More magnification reduces the exit pupil for a given aperture so in the case above providing your in light conditions where your pupil is dilated to more than 2.5mm the 7x21 curio will appear brighter providing it has the same or greater transmission values than the 10x25.

The rest regarding magnification making details more visible in the 10x25 or the stability of the 7x revealing more detail is down to user preference, optical quality of construction and collimation, how stable their hands are and if either optic has image stabilization.

In practical use a difference of 0.5mm will be minimal either way!

Will

 

[ReinierBos]

Yes, those were also my thoughts William. But Tenex was saying something differently: the 10x25 is brighter than the CL 7x21 because of the bigger objective size...

 

[Gijs van Ginkel]

A lot of confusion about brightness. Brightness is a psychological phenomen which is determined by:
-a- the amount of light
-b- the color distribution of the incoming light. Our eyes judge some colors as bright and others less so. (blue and green are "bright colors", red and far red not). To help the discussion in this matter I have a composed a review paper entiteld ""Color distribution, brightness, resolution and contrast in binocular images", May 2013. It can be found on the WEB-site of House of Outdoor.

Reinier Bos, post 29,
An 8x25 binocular has an exit pupil of 3,125 mm, the 10x25=2,5 mm so the "beam of light" (the amount of photons ) of an 8x25 is larger than that of a 10x25. So with the same transmission curves you will not see more in low light with a 10x25.
Gijs van Ginkel

 

[gweller]

Other factors come also into play, like it is easier to hold the 7x21 steady than the 10x25, making it likely that you will see more detail with the lower mag. bin.

 

[William Lewis]

Yes, those were also my thoughts William. But Tenex was saying something differently: the 10x25 is brighter than the CL 7x21 because of the bigger objective size...

Talking about low light, dilated pupil performance. If you think of an objective lens (usually lenses) with no binoculars behind it it doesn't matter how big it is, they're all more than 7mm - it's the jiggery pokery behind it that makes it brighter or dimmer, primarily with modern glass and coatings its just the magnification as the % differences in lens surface area dwarf the % differences in transmission assuming equal quality materials and construction.

Having said that the difference is small - even between my 8x30 and 8x56 it's only really giving me a better view right at the start and end of the day, or for the stars. The instant comfort with a large exit pupil is also a nice thing to have but it comes at a hefty cost in weight!