in the last couple of days i have noticed a small amount of resistance when focusing from near focus to infinity on my opticron imagic porro prisms.it's not much and does'nt detract from the view but it's a little more noticable in warm weather.in short the focus wheel runs easiar in one direction than the other.just wondered if any other porro user's get the same thing.i presume a pair of roof prisms would not suffer from this because of the internal focusing mechanism?.i dont really want to send them for an unneccasory service as i dont have a spare back up pair.any advice.matt
[QUOTE=matt green]in the last couple of days i have noticed a small amount of resistance when focusing from near focus to infinity on my opticron imagic porro prisms.it's not much and does'nt detract from the view but it's a little more noticable in warm weather.in short the focus wheel runs easiar in one direction than the other.just wondered if any other porro user's get the same thing.i presume a pair of roof prisms would not suffer from this because of the internal focusing mechanism?.i dont really want to send them for an unneccasory service as i dont have a spare back up pair.any advice.matt[/QUOTE]
Hi Matt
Interesting post
I too notice with my Zeiss 10 x 50 MC Jenoptem porros that on warm days the focus wheel runs a little easier generally
Also there is a distinct "default focus position" which the bins slot into (possibly wear or due to my average view distance being similair) again this is more noticeable on the warmer days
Of course these are quite old (87-88 i think according to serial no) and DDR built so the focus mechanism is more primitive and perhaps not as advanced as Opticron variants
I suspect porro's focussing travel/resistance will always be a little more prone to temperature than the totally internal sealed roof types
In general terms probably the better models should suffer less fluctuation if the engineering/build quality is relative
There is the argument that as long as a focus mechanism is a "sealed unit" it should last a "lifetime" and perform with complete consistence but i have already experienced even in my relatively short birding involvement several focus movement quirks in both cheap and expensive porro and roof bins which makes me wonder
However i can say, that based on recent useage and without brand promoting my Nikon 10 x 42 SE's have tended to be very consistent and i have only really noticed a slight increase in focus resistance when out at Bempton Cliffs in mid winter
(and it was bloody cold then !!) i think my entire body had resistance to movement never mind the bins !!!
Wouldnt have thought the service is necessary just yet unless there is a definite increase or frequency in the problem
Regards
Rich
I have one Swift 820 which has never been smooth, and another (well, the ED version) which has always been smooth. In the Swift, I put it down to a slightly duff sample. I do know somebody who has a pair of Ace Avian roof prism binoculars they are very happy with, except that now they squeak slightly on focusing - so I guess roofs can have their troubles too.