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

Single Speed vs. Dual speed focusers (1 Viewer)

A

aeajr

Active member
Single Speed vs. Dual Speed Focus

I am looking at spotting scopes. This will be my first.

looking at 80 mm 20-60X models under $300 US.

I note that some have single speed focus and some have dual speed focus. Any opinions on the value of dual speed focus? Should I give this a priority or is it just a nice but not necessary feature?
 
Last edited:
Hi Aeajr,

aeajr said:
Any opinions on the value of dual speed focus? Should I give this a priority or is it just a nice but not necessary feature?
Click to expand...

I like the setup with two different knobs for two different speeds, but I have to admit that I hardly ever use the fast speed on my Kowa 883 since the "slow" speed actually is quite fast already.

I wouldn't miss the fast speed much, though occasionally it comes handy, usually when re-configuring from, for example, watching shorebirds at the horizon, to identifying a small bird that suddenly lands in right front of the hide.

While I never tried one in the field, I occasionally use Zeiss scopes with their "two speeds on one kob" approach at a Zeiss-sponsored and -equipped site, but that's very 20th century in expecting the users to adapt to the ideosyncracies of a mechanical device that's purely reactive in nature. I'd rather have single speed only than that.

Regards,

Henning
 
Hi,

in my opinion you don't need a two speed focus drive if the single speed has the correct ratio and the instrument is good. Often the wish for a fine focus comes from the fact that good focus at higher magnification is difficult to reach due to optical aberrations.

On my old Kowa TSN-3 the focus pops at 52x (which is the maximum with the EP I use), so the single speed focus is ok. I have seen too many examples of premium and not so premium scopes where good focus at that magnification was hard to impossible to reach even with a two speed drive.

TLDR: Buy optics with a good money back option or in person, if used.

Joachim
 
Thanks for your responses. I know in astronomy the dual speed focuser is highly valued, but was not sure if it would be different for birding.
 
The Zeiss dual speed focus in a single knob has been mentionned already. Then there are also the large focus wheels of Swarovski, Meopta and others (single speed) as alternative to the small knobs. And I believe Zeiss' new Harpia will have the dual speed focus integreated into a large wheel as well. Many options... and the preference is purely personal. Your choice...
 
I have an old Diascope with separate knobs for fast and fine focus and only use fine. But I have seen folks at British Bird Fair using the combined single-wheel to great effect and advantage.

Lee
 
Hauksen said:
Hi Aeajr,



I like the setup with two different knobs for two different speeds, but I have to admit that I hardly ever use the fast speed on my Kowa 883 since the "slow" speed actually is quite fast already.

I wouldn't miss the fast speed much, though occasionally it comes handy, usually when re-configuring from, for example, watching shorebirds at the horizon, to identifying a small bird that suddenly lands in right front of the hide.

While I never tried one in the field, I occasionally use Zeiss scopes with their "two speeds on one kob" approach at a Zeiss-sponsored and -equipped site, but that's very 20th century in expecting the users to adapt to the ideosyncracies of a mechanical device that's purely reactive in nature. I'd rather have single speed only than that.

Regards,

Henning
Click to expand...

I don't know, what is '20th-century' with the Zeiss DSF?? I'm using the DiaScope85 since 2011 (21st-century), and the DSF works great. I'm using a MM4-60 with a fine-focus-knob, and it works great. It's personally experience, and a good 'one-for-all-focus-knob' may also be fine in the field. But there should be no backlash while focussing back and forth.
I've heared that some people don't like the DSF, that's a cognitive problem in my opinion. Some people don't like the big focus-Wheel like the Swarovski or Meopta (and I don't like them), because there could be too much wobbling by using the whole hand and not only one finger.
You have to try by yourself…

best regards
Manfred
 
I would agree with the sentiments on here, you need to try and see what works best for you.

I previously owned a Leica Televid 77 with the dual focus and I loved it, the gear ratio was perfect for me. I then swapped to a Nikon ED82 which I despised as the focus was so tight that I struggled to get a sharp focus a lot of the time.

I now use a Kowa 663, which I love. I don't think I really miss the dual focus, except maybe at high magnification and poor light.

I often tended to find that I would fiddle too much with the fine focus on the Leica, I can usually get a sharp focus with the Kowa straight away.

It seems like a lot of lower cost modern scopes have dual focus, my personal opinion is that in some cases it is compensating for lower quality optics. Also the gear ratio on some is ridiculous, the ones that I have tried with an 8:1 or 9:1 ratio do nothing for me, it feels like the fine focus is a spinning wheel.

I'd rather have high quality glass with single speed focus, than dual focus on a scope where the glass doesn't quite cut it.

My two penneth.
 
Moin!

bioscope said:
I don't know, what is '20th-century' with the Zeiss DSF??
Click to expand...

Let me try to explain :)

Basically, when I start adjusting focus, I do know whether I need fast or slow adjustment, but the scope doesn't.

With the Zeiss System as I understand it (and please correct me if I'm wrong), whatever I actually want, I get "slow" at first. After turning the slow knob for a while, the scope, still not knowing what I want, kicks me to "fast".

This is infallibly either late, if I actually wanted "fast", or wrong, if I wanted "slow".

That's a hardware-only system incapable of processing the information required for correctly addressing the task at hand ... 20th century, Meccano kit technology.

Not to say I'd be happier with a millenial-style "auto focus on smiling bird" app running on my scope, but you get the idea ;-)

bioscope said:
I've heared that some people don't like the DSF, that's a cognitive problem in my opinion.
Click to expand...

I'll readily admit that it has a cognitive aspect. I'll still maintain that the system has objective shortcomings, but I'm aware that many people just get used to it and maybe find something positive about it (as in some situations, it's admittedly faster than single-knob only).

Personally, I'm not very good at "just getting used to it". That's a cognitive thing for sure, quite inconvenient for myself at times, but it also drives the innovative "Tüftler" side of me ... :)

Regards,

Henning
 
Hi again,

Hauksen said:
With the Zeiss System as I understand it (and please correct me if I'm wrong), whatever I actually want, I get "slow" at first. After turning the slow knob for a while, the scope, still not knowing what I want, kicks me to "fast".
Click to expand...

Since I just happened to come across what I believe is the relevant Zeiss patent, here the Google Patents link for reference:

https://patents.google.com/patent/DE102016112863A1/de

I was a bit suprised it dates to 2016 ... I had thought it had been around for a while.

Regards,

Henning
 
Henning

This is not how I find the Zeiss one knob / 2 speed system. If you push the knob hard and fast you get fast focus, if you push it gentle and slow you get slow focus.

The recent patent must include some new feature or design element.

Lee
 
Hi Lee,

Troubador said:
This is not how I find the Zeiss one knob / 2 speed system. If you push the knob hard and fast you get fast focus, if you push it gentle and slow you get slow focus.
Click to expand...

Ah, thanks for the clarification. In that case, my above criticism of the system is inaccurate as in the limited time I used it, I formed a wrong mental model of how it operates.

Ironically, the new patent is consistent with my old mental picture as it always starts slow now matter how fast you turn the wheel, and then switches over to the fast speed after a certain turning angle.

Regards,

Henning
 
Hauksen said:
Hi Lee,

Ah, thanks for the clarification. In that case, my above criticism of the system is inaccurate as in the limited time I used it, I formed a wrong mental model of how it operates.

Ironically, the new patent is consistent with my old mental picture as it always starts slow now matter how fast you turn the wheel, and then switches over to the fast speed after a certain turning angle.

Regards,

Henning
Click to expand...

Actually Henning I think I need to apologise to you. Thinking more carefully about the one-knob system, if you make a big movement with the knob you get coarse (fast) focusing speed then if you slow down to small focus knob movements it changes to fine (slow) focus. So I was wrong to suggest it is sensitive to the torque applied, it interprets the size of the rotation of the knob.

Lee
 
Hi Lee,

Troubador said:
Actually Henning I think I need to apologise to you.
Click to expand...

No need to apologise, I wasn't entirely sure of my interpretation either.

Perhaps your idea of a torque-sensitive focus ratio adjustment actually would be a way to take the variable-speed focus wheel to the next level :)

Another idea would be to switch to fast gear if you squeeze the knob slightly while turning. That would eliminate the unwanted slow movement at the beginning of the focus change. It would rely on a two-finger grip on the focus knob, though.

Regards,

Henning
 
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