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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

Loss Of Brightness With 8X42 RF (HT) (1 Viewer)

dwever

dwever

Well-known member
I know I will lose some image brightness between an HT Zeiss 8X42 and the HT based Victory RF Laser Rangefinder.

It used to be a significant loss with the FL’s. Now with the new HT based redesign that’s been out a number of months how perceptible is the difference?

I am not a hunter but have various uses for laser ranging in Alaska including safety knowing how far the bear was from us in April (Pic 3).
 

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Hi Dwever,

I was curious about this same thing so I asked Zeiss about a year ago. Following is my email conversation with a Zeiss Customer Care Representative:

Me: What is the light transmission by percent of the new victory rf 10x42 rangefinding binoculars? Are they as bright as the victory ht binoculars?

Rep: The new RF's have FL glass with a light transmission of 92% while the HT has 95%.You would be hard pressed to notice the difference.

So, Zeiss claims that you would probably not notice the difference. I've never seen a pair of RFs much less looked through them, so I can't attest to the truthfulness of the statement.
 
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Hi,

I agree with Zeiss that you will not notice 3% less transmission unless you use a lab fitted for this kind of measurements.

Joahim
 
Essentially the same response I’ve gotten from Zeiss. Virtually every Sportsman’s Warehouse in Alaska has the 10X42, and they are pretty impressive. I’ll be ordering the 8X42.
 
Binastro, post 6,
No both barrels do not have the same transmission. That is due to the system Zeiss uses for the rangefinder: a reflecting glass plate/mirror, which transmits part of the light to the viewer and a small part to the detector for the rangefinder. That system is chosen (according to the information I have received) to avoid use of patents of the systems used by other binocular producers.
Gijs van Ginkel
 
I confirm Gijs' explanation.

Looking through the right tube from the objective side, you can easily see the glass plate / mirror mentioned by Gijs (see photo; I used a yellowish light source to make it better visible).
The system used by Leica in those Geovid models that feature Perger prisms avoids such an "obstruction" in the light path (one of the big advantages of the Perger prism, among others).
And by the way: somewhere earlier in this thread, the question was asked whether the RF is as bright as the HT. Zeiss gave the answer that transmission figures are 3% lower in the RF, which is usually not enough to spot the difference. If the RF nevertheless appears slightly less bright than the HT, that has mainly to do with the fact that the RF exhibits a distinctly warmer image tone than the HT.

Canip
 

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Is the average transmission 3% less?

Or is one barrel 6% less and the other 3% less?

Or is one barrel 3% less and the other 0% less?
:)

B.
 
Binastro, post 10,
We measured roughly 10% transmission difference between both barrels. Lower transmission occurred in the tube which contains the beamsplitter.
Gijs van Ginkel
 
For those interested, Gijs' tests are at: https://www.houseofoutdoor.com/verrekijkers/verrekijkers-testen-en-vergelijken/

And at least 4 include info about laser rangefinder binoculars:
- Meopta Meorange 10x42 (Meopta test, July 2017)

- Leica Geovid HD 8x42, Swarovski EL Range 8x42 and 10x42, Zeiss Victory RF 8x45 (in ‘Testresultaten van de Leica Geovid 8x42HD . . . ; from Jan 2012)

- Leica Geovid 15x56, Leica Rangemaster 1200 7x24 monocular, Swarovski Laser Guide 8x30 monocular (in ‘Test rapport van 56 mm kijkers . . . ; a 2007 test updated Jan 2012)

- Zeiss Victory RF 8x45, Leica Geovid 8x42, Leica Geovid HD 8x42 (in ‘Testrapport 42mm kijkers’; May 2011 test; near the bottom of the list)


I’ve attached a copy of the Zeiss Victory RF 8x45’s graph (i.e. not the current HT 8x42 version)
While it’s an earlier generation, it shows the effect that the internal system described by Gijs in post #8 has in relation to the 2 barrels

I’ve only seen one Zeiss RF cross-section (again the previous generation x45 version), and for reference I’ve attached a copy


Neither the first generation Zeiss, nor the Swarovski EL Range use HD glass. In contrast, some of the 2nd generation and all of the 3rd generation Leica's do
This seems to be possible as the laser is externally mounted between the barrels (and so is not projected out through the optics)

The current Zeiss HT rangefinder brochure indicates that it does use FL glass, which may be possible due to the differences between it and the Swarovski system
e.g. in contrast to the Zeiss system, see the similar transmission of the 2 barrels in the EL Range 8x42 graph


John


ADDITION: the Zeiss patent for the system that it uses in RF binoculars is now available from Google Patents as a PDF (previously it was in a non-saveable form)
I've also included an English translation of the text
 

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Thanks Gijs, Canip and John.

A 10% transmission difference is noticed by eye. At least by testing the rangefinder binocular right way up and then upside down, as our two eyes differ. Hopefully the rangefinder works upside down.

It seems that the 3% transmission difference quoted by Zeiss needs to be taken with a pinch of salt.

For me, the old Leica 1200 monocular laser rangefinder has worked well for many years. Maybe 7x21 monocular of good quality.
The Leica Disto is very good for ranges up to about 120 metres? I think very accurate.

The only new rangefinding binocular I fancy is the Swiss one measuring up to 20kms about. But a bit expensive and possibly restricted user. Also maybe the 3 in 1 thermal imager, image intensifier and visual light binocular would be nice, though a bit heavy.

Regards,
B.
 
Binastro said:
?....
.....
.....
.....
A 10% transmission difference is noticed by eye. At least by testing the rangefinder binocular right way up and then upside down, as our two eyes differ. Hopefully the rangefinder works upside down.

.....
Click to expand...

Of course the rangefinder works upside down, you just have to get used to reading the numbers upside down ... ;)

Joke aside, the rangefinder does work at all angles, even upside down.
And yes, the 10% (or whatever the value for the latest model is) transmission difference is clearly visible; not that the image in the right tube appears much darker, but it appears distinctly yellower than the one at left.

Canip
 
Gijs indicates in post #8, that there is still a significant difference between the transmission of the 2 barrels (a consequence inherent to the rangefinder design used by Zeiss)

However, as to:
- how perceptible the difference is in use, and
- what effect that has on viewing comfort and usability
seems to vary markedly between individuals

See the difference in these comments: https://www.birdforum.net/showthread.php?t=373583
And also the comments of Canip here in posts #9 and #14
(I Googled around but couldn’t find any other useful comments on the transmission disparity)


To my knowledge, Zeiss has not published any detailed information about the primary optical system of the current generation rangefinders
However, I’ve noticed several comments where it’s assumed to be the same as that of the current HT binoculars (see the image of an HT x42)
And if only for the sake of production simplicity that would seem to be a reasonable assumption
Additionally, based on the cross-section in my previous post, the optics of the previous generation RF’s do appear to have been similar to their non-RF counterparts

However, similar - in terms of the numbers of lenses and groups - is not identical e.g. lens curves and thicknesses, composition and spacing
And it’s unknown what alterations may have been needed to incorporate the RF function


Interestingly, both the current rangefinders and the HT binoculars have the same overall length in their respective x42 and x54 pairings,
so I cobbled together a comparison image of the x42’s
From the front of the focuser going rearward, the handling would appear to be similar
And forward of the focuser, the RF's barrels are obviously expanded to incorporate electronics, with the battery housed in the lengthened bridge arms (see the image from the manual)


John
 

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Thank you, John.

From what I know, I agree with your findings resp. interpretations.
Your pictures also show that the RF further improves on the - already excellent - HT ergonomics: the focus wheel is placed even further forward, so your index or middle finger, depending on how you hold the binocular, falls naturally onto the focus wheel. I personally like the new RF best among the current three top rangefinders (EL, Geovid) when it comes to handling.

By the way: the rangefinder technology of the RF is in my (limited) experience quite „robust“, perhaps even more so than the one of the others. Day or night, sunshine, cloudy, overcast weather: within the specified range, the RF rarely shows you the „three dots“, indicating that the measurement failed. In the Geovid, this seems to happen more frequently, esp. when I don’t hold the bino very still. The EL is somewhere in the middle, more like the RF.
What I prefer in the Geovid, however: first pressing of the button turns on, only the second one measures. In the RF and the EL, the first press turns on AND measures, while I am still trying to move the red circle (which only becomes visible with pressing the button) over the target.

Regarding image brightness (perceived!): the EL comes first in my view, the Geovid second, the RF last. However, I do like the somewhat warm, slightly „contrast enhancing“ color tone (and excellent central sharpness) in the RF.

fwiw Canip
 
I went through Gijs’ data and copied the transmission graphs for the various brands of x42/45 rangefinder binoculars that he’s tested
And I’ve arranged them in the order of: those with the least consistent, to those with the most consistent transmission from the two barrels

What’s striking in relation to most is:
- the significant differences in the left and right barrel readings, and
- the abrupt changes in transmission values across the wavelengths
Both are obviously the unavoidable effects of the particular way in which each manufacturer has integrated the rangefinder function

As such, both the consistency and evenness of the Swarovski’s values are striking, and
1) It’s the only one with the generally moderately curved transmission shape that we expect from quality non-rangefinder binoculars, and
2) It’s overall transmission percentages are significantly higher then the others

In relation to the first point, clearly this is a significant advantage for Swarovski’s rangefinder system

But in relation to the second point, keep in mind that:
- the Zeiss and Leica units were tested in 2010, so it’s reasonable to expect that later production may have higher transmission figures
(though with much the same shape and separation to the curves), and
- the Swarovski from 2012 already had a very high transmission level, so Swarovski may have since concentrated on improving the flatness of the curve
(i.e. evenness of transmission verses a higher peak value)

The tables should also provide useful context when Gijs publishes his results about the new generation Zeiss rangefinders
And it will be interesting to see in the future how the newest generation of Perger prism Leica’s fit in ( . . . now if that’s not a subtle hint to Gijs!)


John


From left to right:
Zeiss Victory RF 8x45 (2010 test); Meopta Meorange 10x42 (2017 test); Leica Geovid 8x42 (2010 test); Leica Geovid HD 8x42 (2010 test); Swarovski EL Range 8x42 (2012 test)
 

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John, post 19,
Very good work, thank you.
We have already tested Leica-Perger rangefinders and 42mm and 54 mm HT's, but due to severe computer problems I am a little slowed down with my planning.
Gijs van Ginkel
 
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