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Focus rotation for 3m to infinity for a range of binoculars (1 Viewer)

Kevin Purcell

Kevin Purcell

Well-known member
kabsetz said:
When comparing focus speed, it would be useful if people would specify two things to make the reports easily comparable. One is of course the amount of turning of the wheel, in rotations and fractions thereof (e.g. 1 1/4 turns) or in degrees (450, 205, whatever it happens to be), but the other and equally important one, often missing, is the distance range which that amount of turning covered. For the latter, I would suggest using 5 meters to infinity as a practical range that would give meaningful information, although the ones among you who have good memory and have read my previous stuff may recall that I have thus far used 10m-1km as the range.

[...]

I'm suggesting this because it is cheap, fast and easy to do, and makes different users' reports meaningful and comparable from model to model. And, as long as the range is mentioned by the person reporting the focus speed, it doesn't even matter if the range is the same or different from what I or anyone else uses - one can always take their reference binoculars and check how fast they focus over the range someone else had reported.

Kimmo
Click to expand...

and I responded

Kevin Purcell said:
I do just what Kimmo suggests but I'd suggest use decimal notation for the turn counting. It's less restrictive ... is that 1 3/8 or 1 1/4 turns or 1.3 turns ... tenths are easy to estimate too.

And use 3m/10 feet to infinity which I feel is a more typical distance range for people who bird over a range of habitats (from woodland to open spaces). It's also a typical maximum focus distance for "older" bins. I think most people would agree 3, as a "maximum" minimum close focus for a birding bin.

Which is what I use in all of my reports (including the one on this thread ;) )
Click to expand...

So here's a thread for people to report these rotation measured from their own binoculars to change focus from 3m/10 feet/3 paces to infinity in decimal notation.

Multiple reports are good (are we consistent?).

Collect the set. ;)
 
Swift Eaglet CFT 7x36 0.4 turns

Pentax DCF HS 8x36 0.9 turns

Zen Ray ED 8x43 1.3 turns
Hawke Frontier ED 8x43 1.3 turns
Promaster Infinity ELX ED 8x42 1.3 turns
 
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Great idea Kevin. One thing I would like to see added is the direction of the turn from close to infinity. Clockwise (CW) or CounterClockwise (CCW)

My contribution:

Canon 12x36 IS II (from minimum 6 meters) to infinity 0.9 turn CW
Nikon 8x32 SE 1.0 turn CW

Cheers Peter
 
Swift Eaglet CFT 7x36 = 0.3 turns CCW

This appears to be the fastest focusing bin I have. Perhaps a bit too fast for me.

Zen Ray ED 8x43 = 1.3 turns CW
Hawke Frontier ED 8x43 = 1.2 turns CW
Promaster Infinity ELX ED 8x42 = 1.2 turns CW

These I suspect are the slowest (though my Celestron Ultima DX porro might be slower, I have yet to measure that one).

Zen Ray ZRS 8x43 = 1.0 turns CCW

Pentax DCF HS 8x36 = 1.0 turns CW
Pentax DCF WP 8x32 = 0.5 turns CCW
Pentax DCF SP 8x32 = 0.6 turns CCW

Bushnell Elite 8x43 = 1.1 turns CCW
Bushnell Legend 8x42 = 0.7 turns CCW

Zeiss Victory 8x40 = 1.1 turns CCW

Leupold Cascades porro 8x42 = 1.8 turns CCW

The Leupold Cascades internal focus porro is an interesting case for 3m to infinity as it's close focus is just at 3m so the focus range includes the slow "close focus range". One you get to 10m to infinity the rotation required is less than half a turn.

I think my accuracy is perhaps better than 0.1 turn. Perhaps a bit better now I've refined my technique. But it's easier to measure the ones that have a dial that spins too (both Hawke and the Zen Ray have a fancy no spinning dial with a logo on it hence the slight over estimate previously).
 
Last edited:
Changed for "Design Selection compacts". Anyway, the article is considered for deletion so I think I'll create a shared document instead.
 
Alexis Powell said:
And while you're at it, another very relevant spec is the diameter of the knob. Spinning a little knob one turn can be as easy as spinning a big knob 1/2 a turn.

--AP
Click to expand...

Look, this is a family website, can we not have guys on here bragging about big knobs or moaning about little ones.

:eek!:

Lee
 
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