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Search: Posts Made By: henry link
Forum: Zeiss Saturday 9th December 2017, 22:51
Replies: 18
Views: 955
Posted By henry link
I don't think this is related to astigmatism in...

I don't think this is related to astigmatism in your eye. That would have the same effect at the 6:00 and 12:00 positions of the binocular's field edge. I've observed this same effect in most...
Forum: Binoculars Wednesday 6th December 2017, 18:30
Replies: 22
Views: 1,036
Posted By henry link
Just noticed this post. My answer above applies...

Just noticed this post. My answer above applies to telescopes as well. If the telescope's exit pupil is larger than the eye's pupil magnification is the one and only significant factor for DOF. ...
Forum: Binoculars Wednesday 6th December 2017, 16:32
Replies: 22
Views: 1,036
Posted By henry link
That question has been thrashed around a few...

That question has been thrashed around a few times here. My answer is no and yes; it depends on whether the exit pupil of the binocular is larger or smaller than the entrance pupil of the eye....
Forum: Binoculars Tuesday 5th December 2017, 14:58
Replies: 22
Views: 1,036
Posted By henry link
Well, there's an advantage to a higher focal...

Well, there's an advantage to a higher focal ratio as long as designs and glass types remain identical. You can see that in a star-test when you compare a binocular at full aperture to itself at a...
Forum: Pentax Tuesday 5th December 2017, 14:24
Replies: 18
Views: 552
Posted By henry link
Yep, you remembered correctly. That seems to be a...

Yep, you remembered correctly. That seems to be a problem with all scopes that focus by moving a prism. However, clear aperture conforming to specified aperture is never guaranteed. I tested an...
Forum: Binoculars Tuesday 5th December 2017, 13:43
Replies: 22
Views: 1,036
Posted By henry link
Thinking along these lines only works for...

Thinking along these lines only works for binoculars with simple achromatic doublets for objectives. I don't think you can make any assumptions about aberrations, reflections or even the actual focal...
Forum: Pentax Monday 4th December 2017, 20:04
Replies: 18
Views: 552
Posted By henry link
I guess it remains to be seen whether the 80mm PR...

I guess it remains to be seen whether the 80mm PR scope performs better than the 80mm PF, but the optical designs are completely different from stem to stern. On the other hand the 65mm PF was always...
Forum: Nikon Monday 4th December 2017, 15:17
Replies: 7
Views: 433
Posted By henry link
Just now I crudely measured about 6.5 diopters...

Just now I crudely measured about 6.5 diopters beyond infinity for the EII and about 9 diopters for the E. Consider those rough approximations, but the E does have more travel beyond infinity and a...
Forum: Pentax Monday 4th December 2017, 14:37
Replies: 18
Views: 552
Posted By henry link
The older XL zoom was actually optically quite...

The older XL zoom was actually optically quite simple, 6 elements in 4 groups, about the minimum for a zoom. IMO, it was not a very good eyepiece in spite of the high price. Look at the cutaway image...
Forum: Binoculars Monday 4th December 2017, 14:13
Replies: 22
Views: 1,036
Posted By henry link
Unless the optical designs, prism sizes and glass...

Unless the optical designs, prism sizes and glass types are identical I don't think much can be predicted about the optical quality of a binocular by its physical length. Look at the cutaways below....
Forum: Spotting Scopes & tripod/heads Saturday 2nd December 2017, 01:35
Replies: 11
Views: 577
Posted By henry link
One way to predict what will be visible through a...

One way to predict what will be visible through a scope like the 88mm Kowa 883/4 is to work out the resolving power of a perfect 88mm scope (1.32 arc seconds) and multiply that by the maximum...
Forum: Leica Tuesday 28th November 2017, 13:46
Replies: 39
Views: 2,147
Posted By henry link
I was around in the days before p-coating. My...

I was around in the days before p-coating. My memory is that very few people realized they were sacrificing any optical quality at all when they bought a high priced Leitz or Zeiss roof. Magazine...
Forum: Bushnell - Bausch & Lomb Friday 24th November 2017, 19:22
Replies: 64
Views: 6,970
Posted By henry link
A large number of layers is probably confined to...

A large number of layers is probably confined to the prism mirror coating. The graphic below shows the number of layers for Swarovski coatings as they were about 10-15 years ago. The last column...
Forum: Bushnell - Bausch & Lomb Monday 20th November 2017, 17:58
Replies: 64
Views: 6,970
Posted By henry link
I didn't intend to change the thread subject...

I didn't intend to change the thread subject either. The photo was just to illustrate how to determine if the optics of two instruments are identical.

I doubt that the copying of the Swarovski...
Forum: Bushnell - Bausch & Lomb Monday 20th November 2017, 15:34
Replies: 64
Views: 6,970
Posted By henry link
Thanks for the photos, Bruce. Based on them I...

Thanks for the photos, Bruce.

Based on them I would say the ED3 eyecups are now nearly or exactly the same length, however looking at your photos in post #19 as well as post #25 I have some doubts...
Forum: Bushnell - Bausch & Lomb Sunday 19th November 2017, 13:59
Replies: 64
Views: 6,970
Posted By henry link
I just noticed the speculation on this thread...

I just noticed the speculation on this thread about the Zen-Ray ED3 and the Bushnell Legend M being the same binocular. I tested the 10x43 ED3 about six years...
Forum: Leica Friday 17th November 2017, 14:02
Replies: 14
Views: 934
Posted By henry link
I bought a few old Leitz Porros about 15 years...

I bought a few old Leitz Porros about 15 years ago (Bidoxit, Binuxit and Marseptit). All had the same eyecup threads. Leica supplied me with fold down rubber eyecups with the same thread that were...
Forum: Binoculars Wednesday 15th November 2017, 15:08
Replies: 22
Views: 1,264
Posted By henry link
If it's one of those old beat-up jobs from...

If it's one of those old beat-up jobs from Cremona send it to me and I'll supply you a brand new one with all the latest improvements. ;)
Forum: Spotting Scopes & tripod/heads Wednesday 15th November 2017, 13:18
Replies: 12
Views: 592
Posted By henry link
This version of the Manfrotto 128 is still...

This version of the Manfrotto 128 is still available.

https://www.manfrotto.us/micro-fluid-two-way-video-head

It's cheap, doesn't have a built in QR plate and in my experience is quite stable,...
Forum: Spotting Scopes & tripod/heads Monday 13th November 2017, 13:05
Replies: 13
Views: 1,078
Posted By henry link
I agree with Kimmo. I sometimes use an outdoor...

I agree with Kimmo. I sometimes use an outdoor setup of about 30 yards, with the target and the scopes placed well above a grass lawn. I make certain the the air is steady enough by including a...
Forum: Binoculars Monday 13th November 2017, 12:39
Replies: 61
Views: 3,395
Posted By henry link
That would explain some of the dubious...

That would explain some of the dubious transmission data in the first couple of years after they began making measurements with a spectrophotometer. But, in 2010 when the Nikon 10x42 SE was reviewed...
Forum: Spotting Scopes & tripod/heads Monday 13th November 2017, 02:57
Replies: 13
Views: 1,078
Posted By henry link
Predictions like that don't work in the real...

Predictions like that don't work in the real world because different specimens of the same scope have a wide range of resolution measurements running from lemons to cherries.

If we accept the...
Forum: Binoculars Saturday 11th November 2017, 14:58
Replies: 9
Views: 1,034
Posted By henry link
Here's a method for measuring pupil size by using...

Here's a method for measuring pupil size by using a binocular of known magnification with an exit pupil larger than your eye's pupil, a star (artificial or real) and two pieces of opaque sticky tape....
Forum: Spotting Scopes & tripod/heads Tuesday 7th November 2017, 14:48
Replies: 15
Views: 1,414
Posted By henry link
That's definitely not normal. It's a strong...

That's definitely not normal. It's a strong indicator that your scope is defective. I doubt that the eyepiece is at fault, but a quick check at high power with a different eyepiece would settle that...
Forum: Spotting Scopes & tripod/heads Thursday 2nd November 2017, 11:17
Replies: 25
Views: 1,150
Posted By henry link
yakyakgoose, I would recommend treating both of...

yakyakgoose,

I would recommend treating both of these claims with high skepticism. I don't know where they got the idea that there is a 60mm Zeiss Fluorite scope.

There are easy objective tests...
Showing results 1 to 25 of 1000
 

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