Alpha IS? (1 Viewer)

[Binastro]

Second more accurate attempt gives a more reasonable 1/14 area using a half angle of 40 degrees, although 40.5 degrees may be nearer the mark.

This is 7%.

This gives 16x40.5 as the equivalent area subject to vignetting.

This looks more reasonable to the eye.

In addition, a very accurate measure of the cut out and front aperture is needed to perhaps 0.1mm.

Also the exit pupil and accurate magnification of the binocular.

Sorry, for being lazy initially, but I don't have log tables that used to be so useful.

Perhaps someone can do an accurate calculation, or I may try another day.

Regards,
B.

 

[John A Roberts]

IS Models - Porro Prism or Schmidt Pechan Roof Prism?

As Henry’s noted, the Zeiss 20x60S uses Porro prisms along with a rhomboid prism in each eyepiece.
And most Canons use a Porro Type II prism *


In contrast, both the OEM manufactured 16x42 offered under a variety of brand names, and the Fujinon TS 16x28,
use roof prisms (SP) in conjunction with a rhomboid prism in each eyepiece.

With the Fujinons, the use of roof prisms is clearly indicated in a recent catalogue:




And it’s easy to visually verify that the Fujinon 16x28 doesn’t use Porro prisms - but a roof prism/ rhomboid prism combo - since:
• the binocular body is parallel and compact both side-to-side and top-to-bottom, and;
• there is the offset of the eyepieces.



. . . So the same configuration as the latest iteration of the OEM 16x42, shown back in post #20 of this thread.


John


* For images showing the optical construction of the Zeiss and some Canon models, see: High end porro's

For more on the fabulous mechanical Zeiss, see: Roger Vine's Zeiss 20x60S review
And posts #58 to 60 at: Zeiss: Collection of cross-section and cutaway images

And for more images of the Canon 10x42 internal construction, including a labelled diagram of the optics,
see post #23 at: Canon 10x42 IS L cutaway view

 

[Binocollector]

@[email protected]
Does the Zulu have field flatteners? That would be an extra lense probably so more light loss. Coatings might make a difference, too. I have a 10x60 porro (Oberwerk) that is dimmer than a 10x56 roof (DDoptics). The roof was more than 2x as expensive but obviously the coatings are way better.

 

[normjackson]

@[email protected]
Does the Zulu have field flatteners? That would be an extra lense probably so more light loss. Coatings might make a difference, too. I have a 10x60 porro (Oberwerk) that is dimmer than a 10x56 roof (DDoptics). The roof was more than 2x as expensive but obviously the coatings are way better.

Don't forgot, though, that Oberwerk model could be substantially stopped down :

Small Binocular Reports: The 10 x 50s - Binocular Reports

Nikon AE 10x50 PentaxPCFWPII 10x50 Orion Ultraview 10x50 Small Binocular Reports The 10x50s Ed Zarenski 3-6-08 This is one in a series of Small Binocular reports that will detail and summarize all my findings...

www.cloudynights.com

 

[Binastro]

Using a calculator and taking the half angle of the sector as 40.5 degrees I make the loss of area 6.79%.

Actually, using 37mm and 42mm gives a half angle of 40.37 degrees, so the area loss is slightly less.

Subject to someone else checking.

That is assuming the objectives are the size given and not stopped down.

My estimate of 37 degree half angle is because I forgot my tan tables of long ago.

The sleepless night was worth it, as there was a major noctilucent cloud display up to 30 degree elevation.

I did then sleep four hours.

Regards,
B.

 

[henry link]

Thanks for your efforts, Binastro. The sliced objective lens of the 16x42 is such an odd feature that it might not even show up in a light transmission measurement using ISO protocols, but it would certainly create a dimmer image for an observer at almost all light levels since the exit pupil is so small and therefore likely to usually be smaller than the eye's pupil. I think it's safe to say that the lopped lens combined with the lossy prism design taken together probably reduce the light throughput by around 8-10% compared to the very same binocular, but with a high transmission prism and fully round objective lenses. Images in the 10x30 really should look brighter than the 16x42 since the 10x30 objectives lenses are not clipped and its exit pupil, while small, is larger than the tiny exit pupil of the 16x42.

Sig Sauer is not very forthcoming with details useful for guessing at total light transmission (like what mirror coating is used or how many lens groups there are), but owners could observe some tells by looking into the binoculars from the front. Is there a flat optical window in front of curved objective lenses? Do the the objective lenses move when the focusing knob is turned or is there a smaller focusing element further back that moves? How many reflections of a small light source return from the object lens group(s)?

Looking at the Sig specs suggests that the eyepieces in the 10x30 and 12x42 are simpler designs than the 16x42/20x42 because of their much narrower apparent fields, perhaps as simple as 3 elements in 2 groups, while the wider field models almost certainly have at least 3 groups, maybe 4 or 5 if there are any field flatteners (which are not mentioned).

 

[Paultricounty]

I think the major flaw with all these IS binos with anything under 3mm exit pupal is how dark they are. Seems to me the 10x 30/32/36 is acceptable , maybe throw in the 12x as well, especially in 42mm. I believe the technology isn’t quite there yet in the higher magnifications when it comes to transmission due to all the multiple lenses and complex designs. The 12x42 Zulu has been on my radar for a while, would love the 16mm, but I think (haven’t tried yet) would be way to dark. I will say (imo) the best of the half dozen IS I’ve tried and two that I’ve kept, the Canon 10x42L is as good as it gets as a complete package and combination of optics, brightness, sharpness to the edge and barely a hint of CA. A shames it’s in the form of a heavy plastic brick.

Paul

 

[henry link]

Paul,

Take a look at the FOV of the 12x42 Zulu - 3.8º. Using the simple formula that works out to a 45.6º AFOV and it would measure even smaller once distortion is included. Maybe it's a typo.

Henry

 

[Paultricounty]

Paul,

Take a look at the FOV of the 12x42 Zulu - 3.8º. Using the simple formula that works out to a 45.6º AFOV and it would measure even smaller once distortion is included. Maybe it's a typo.

Henry

I know I was looking at that as well. Interesting that 16x42 has the same FOV spec.

 

[William Lewis]

Maybe or maybe not. The kite's are the same, the 12x42 actually had less fov than the 16x. 67m at 1000m for the 12x and 68m for the 16x. I suspect they are a more similar design optically than the form factor suggests.

The kites were also originally made in China before switching to Japan.

Will

 

[Paultricounty]

Maybe or maybe not. The kite's are the same, the 12x42 actually had less fov than the 16x. 67m at 1000m for the 12x and 68m for the 16x. I suspect they are a more similar design optically than the form factor suggests.

The kites were also originally made in China before switching to Japan.

Will

Maybe the Kites would be a better alternative if one is averse to MIC. Averse or not would still prefer MIJ anytime. I’m going to take another look at the Kites.

 

[Binastro]

Thanks Henry,

The calculation is very sensitive to the angle of the sliced pizza section.

At 40.37 degree half angle the loss is, I think, 6.72%.

I also think it would be very sensitive to the actual measurements to 0.1mm.

Then, if there is some obstruction, even small, to the objectives, the loss is quite different.

Incidentally, Horace Dall's superb 8 inch Maksutov primary was not round.
It was rough hewn as near circular as possible.
It is probably the best telescope I have looked through.

Too much is made of perfect star tests, and those with fast optics are anyway suspicious.

I must try to view a planet with a telescope that has the objective sliced in two, i.e a half obstruction mask.
I wonder how bad or good the image or detail is.

I don't think a small slice as in the Kite/Sig Saeur and clones makes much difference, except in light loss in poor light terrestrially.

I doubt it would be seen astronomically.

I have three identical 120mm refractors, two single coated on four surfaces and one uncoated.
They give almost identical views and I sometimes am not certain which the uncoated one is.

Regards,
B.

 

[henry link]

Looks like the FOV spec for the 12x42 is probably right. Its real field is the same as the 16x42 because both use the same focal length objective lenses and the same size eyepiece fieldstops. Only the focal lengths of the eyepieces are different.

 

[Hermann]

I will say (imo) the best of the half dozen IS I’ve tried and two that I’ve kept, the Canon 10x42L is as good as it gets as a complete package and combination of optics, brightness, sharpness to the edge and barely a hint of CA. A shames it’s in the form of a heavy plastic brick.

Agreed. You might add the AFOV to your list of the strong points of the 10x42L.

BTW, the only stabilized binocular with an exit pupil below 3mm that I quite like is the Canon 8x20 IS. Small, light, cheap, with surprisingly good optics. I often put it in my pack when I'm shopping and so on.

Hermann

 

[4th_point]

I think the major flaw with all these IS binos with anything under 3mm exit pupal is how dark they are. Seems to me the 10x 30/32/36 is acceptable , maybe throw in the 12x as well, especially in 42mm. I believe the technology isn’t quite there yet in the higher magnifications when it comes to transmission due to all the multiple lenses and complex designs. The 12x42 Zulu has been on my radar for a while, would love the 16mm, but I think (haven’t tried yet) would be way to dark. I will say (imo) the best of the half dozen IS I’ve tried and two that I’ve kept, the Canon 10x42L is as good as it gets as a complete package and combination of optics, brightness, sharpness to the edge and barely a hint of CA. A shames it’s in the form of a heavy plastic brick.

Paul

Hi Paul,

I bought the 10x30 and 16x42 over a year ago, and used them for several months before eventually selling both. In use, I didn't find either especially dark. I didn't have another 15x/16x to compare brightness to, but I had a few 10x42 and the SIG 10x30 did much better in low light than I expected. I was especially concerned with the 10x30 because I had a CL 8x25 that seemed extremely dim in low light.

Overall, I thought that the 10x30 and 16x42 were light, handy, and with effective stabilization. However, I moved on to an 8x42 (non-IS) and Canon 15x50 and don't miss either now.

Jason

 

[Paultricounty]

Hi Paul,

I bought the 10x30 and 16x42 over a year ago, and used them for several months before eventually selling both. In use, I didn't find either especially dark. I didn't have another 15x/16x to compare brightness to, but I had a few 10x42 and the SIG 10x30 did much better in low light than I expected. I was especially concerned with the 10x30 because I had a CL 8x25 that seemed extremely dim in low light.

Overall, I thought that the 10x30 and 16x42 were light, handy, and with effective stabilization. However, I moved on to an 8x42 (non-IS) and Canon 15x50 and don't miss either now.

Jason

Jason , why did you sell them and move on to the non IS 8x42 and the 15x50 Canon?

 

[4th_point]

Jason , why did you sell them and move on to the non IS 8x42 and the 15x50 Canon?

Good question, Paul. I wasn't overly thrilled with the 16x42 SIG image and sold it. I had used it for several months on my local walks and a backpacking trip where I viewed wildlife at extended distances where I didn't want to bring a scope and tripod. It was certainly functional, but I had more money invested into it than I thought it was worth (and I got it on sale for a very good price).

I did miss that magnification range and the IS though, so gave the 15x50 Canon a shot. I have been happy with the Canon overall since last fall, and just recently compared it to a different 16x42 SIG. I hadn't looked through a 16x42 since I sold mine, but side by side the Canon image is noticeably better to me and confirmed what I suspected. The SIG being much lighter and handier though.

I was somewhat tempted to keep the 10x30 SIG for my children to use. It showed a lot of heat haze compared to other 10x binoculars that I had on hand, but overall was still worth keeping for my kids just for the IS. In the end I sold that one too. I also bought the 10x30 on sale, but again felt that the image was not worth the money that I had invested in it.

For my needs, the 10x30 was somewhat similar to a Kowa 8x33 that I also had. About the same size. The Kowa with 2x less magnification obviously, but fairly steady for me. Neither had a stunning image to my eyes though, but maybe that is unrealistic for either. The Kowa was definitely better in low light but the 10x30 SIG was much better than I expected and really not that far behind for my eyes.

I'm still looking for a binocular for my kids - maybe the 6.5x Kowa - but I greatly prefer the image from my 8x42 over the 10x30, and a few 10x42 that I was trying out. I could actually see more detail at distance with the 8x42 than the 10x30 and those 10x42. The view is bright and just really stunning to my eyes.

The 8x42 is steady enough for me, and I just value a beautiful image over the IS for most of my uses. I do use a tripod on occasion though. I tend to view wildlife for extended periods of time, enjoying the view, colors, and their behavior. I am not into identifying or checking birds off of a list. I just sit and observe so that might explain my preference for a certain image quality. I suspect that if I simply needed to ID objects that I would perhaps not be so obsessed with certain image characteristics.

I would not say that the image from the 15x50 Canon is stunning though. Definitely sharp close to the edges compared to the 16x42 SIG, and flat, but more of a utilitarian instrument. I actually prefer the 15x56 SLC image for brightness and contrast, but for that application I do favor the IS over the pleasing image. I could see myself owning both the 15x50 Canon and 15x56 SLC though! The SLC would be used on a tripod.

Jason