• Welcome to BirdForum, the internet's largest birding community with thousands of members from all over the world. The forums are dedicated to wild birds, birding, binoculars and equipment and all that goes with it.

    Please register for an account to take part in the discussions in the forum, post your pictures in the gallery and more.
ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

Kern Focalpin (1 Viewer)

Henry,

In post #4 you compared your mint Focalpin 7 to the Leitz 7x50 Marseptit. But only on one aspect. Could you elaborate some more on them? As we both happen to love large exit pupil binoculars (in fact you showed me the glorious path) maybe the Marseptit could be a good choice. I own a Leitz 8x30 Binuxit and if the Marseptit gives me comparable clarity, contrast and center sharpness I won't look any further.

best regards,

Renze
 
Ron,

OK, I thought you meant the cutaway I posted. I don't think the right image in Renze's post is supposed to be a really accurate representation of the optics. The prisms, for instance, look like a generic Porro, not the shape and size of the actual prisms.

I know my idea is crazy, but we all know how wild and crazy the Swiss are! LPT could put me out of my misery by either measuring the angles or photographing the prism straight on from the side so we could get our protractors out and see how those reflection angles compare to the prism shelf.

Renze,

I'll send you a PM about the Marseptits.

Henry
 
Ok you talked me into it (you don't need to twist my arm very had to either convince me to purchase another binocular or take one apart). I'll post something later today.

henry link said:
Ron,
LPT could put me out of my misery by either measuring the angles or photographing the prism straight on from the side so we could get our protractors out and see how those reflection angles compare to the prism shelf. Henry
Click to expand...
 
Oh those Swiss. Looks like Henry's correct. Have a look at this:
http://www.flickr.com/photos/binocwpg/6468086075/in/photostream
The left-hand slope is the coated one and I don't think it's quite 45 degrees from the base. The prism slopes are also asymmetrical, the coated one being larger. I would have liked to take the prism out, but didn't want to break the glue securing it. Note the metallic gold/brown coloring on the side of the prism. It looks very much like tarnished silver to me.
This must have been done to make the binocular more compact and lighter, but, really, how much larger would it have been if a conventional Porro I prism were used? Considering the extra cost involved and the probable effect on image color, it doesn't seem worth it.

LPT said:
Ok you talked me into it (you don't need to twist my arm very had to either convince me to purchase another binocular or take one apart). I'll post something later today.
Click to expand...
 
Last edited:
Huh!Huh!Huh!Huh! I'm the MAN!!!!

And yes, it's a completely screwball thing to do. The designer must have eaten too much chocolate that day.
 
Way to go Henry, you're right. And thank you LPT for doing the disassembly and taking this nice photo.

But coating that face still doesn't make sense to me. It appears to be the one first encountered by the light, and tilted so the angles of incidence are more acute, not more grazing, than in a normal 45-45 prism. That would make TIF easier, not harder, and make the coating least necessary on that face. The following face might need help though. Help me here, what am I missing?

Ron
 
Ron,

The way I see it the first face (left) leans to the right less than 45 degrees, making it closer to perpendicular to the direction of the light coming up from the objective than a 45 degree face would be, so its angle of reflection would be less than the 90 degrees needed for TIR. Am I missing something?

And thanks for your work on this, LPT. It took a team effort to solve this mystery.

Henry
 
Last edited:
I now realize my mistake. TIF works better at more grazing angles, so the odd tilt of that first face would benefit from a reflective coating, if that coating was indeed reflective enough.

This was a very interesting thread, Focalpin owners. Such a noble concept it was.
Ron
 
Renze,

Your PM box is full, and thanks for all the excellent information you posted. This has to be the ultimate Focalpin thread.

Ron,

I started to post an answer last night, but I thought you would figure it out by this morning.

Henry
 
This has been fun and I've learned a lot about optics as well as Focalpins. In spite of its optical shortcomings I like the Focalpin quite a bit and even more now that I know more about it. Thank you all.
 
Yeah, discussions like this stimulate appreciation. Today I saw my Focalpin 7 in a whole new light. From the side. Isn't she beautiful?

Renze
 

Attachments

  • L1000881 (583x800).jpg
    L1000881 (583x800).jpg
    269.9 KB · Views: 87
Last edited:
henry link said:
.......I know my idea is crazy, but we all know how wild and crazy the Swiss are! .......

Henry
Click to expand...

Interesting to see how you fellows judge us Swiss. ;) But we should better take that with a grain of salt. Anyway, there are certainly not more "wild and crazy" ones in our country than in other countries. Unless we get more immigrants that are definitely different from the average. But the Swiss are basically rather conservative. Fortunately, with a genius spread in at times. But following the discussion and evaluation in this thread, it would seem that there was more "crazy" than "genius" in this Focalpin construction.

The Focalpin binoculars have always impressed me as being very elegant (for the time). But what good it that when the optical performance suffers. However, my first Leitz Trinovid 10x40 suffered from the same basic problem. Light and elegant, but far from a stellar view. I have mentioned it earlier somewhere that I had always wondered how a decent but not exceptional porro Fujica Meibo 8x42 was able to provide a view that I felt as being at least equally good as my Leitz (albeit with 8x vs 10x ). Of course, the problem were the uncoated prisms, as we now know. But Leitz/Leica certainly hid that well for a considerable time.

Thank you Henry and Renze for your help in making me finally cross the hurdle regarding the focus mechanism. My German definitely got in the way to even realize what Focalpin means. It was always clear that the "alpin" was meant as having something to do with the Alps. In German alpin is the same as alpine in English. And the German pronunciation of the seemingly German language name did not help to cast any doubts on this interpretaion either. Of course, "foc" then did not mean anything. But I am equally at a loss when trying to analyze other names like "Trinovid". Anyway "focal" and "pin" now opened my eyes and my mind as well.
 
Last edited:
henry link said:
Robert,

Sorry, just having a little fun with the stereotype of you Swiss as all sober bankers and watchmakers.

Coincidently I ran into the official Leica explanation of the term Trinovid yesterday. It's in the paragraph of this history of Leica binoculars covering the first Trinovid models from 1958.

http://en.leica-camera.com/assets/file/download.php?filename=file_2550.pdf

Henry
Click to expand...

Interesting coincidence indeed. Thanks for sharing. It's an interesting brochure as well. I think the Trinovid name then was a typical maketing hype, nevertheless. Looking back at least, that "superlative optical performance" must have been less stellar than a similar porro would have provided.

As for the Swiss character, we can live quite well with those stereotypes. ;)
 
Gentlemen,

Thus far I thought the Kern Focalpin (1950) was the first porro prism binocular with completely internal focusing. However, could the Kershaw Vanguard possibly be even earlier?

Renze
 
Warning! This thread is more than 11 years ago old.
It's likely that no further discussion is required, in which case we recommend starting a new thread. If however you feel your response is required you can still do so.

Similar threads

has530
SVBONY SA205 Review
Replies
3
Views
625
has530
has530
D
Sky Rover Banner Cloud 8x42 APO Review
2
Replies
29
Views
4K
dries1
dries1
T
Dielectric Coatings - Potential Drawbacks?
Replies
5
Views
1K
wllmspd
W
MartinDCZ
Vanguard Endeavor ED IV 10x42 is a disappointment
Replies
4
Views
1K
Chris Pringle
C
D
Recommendation for a binocular
Replies
6
Views
537
MiddleRiver
MiddleRiver

Users who are viewing this thread

Total: 2 (members: 0, guests: 2)
Back
Top