Small sample error.... (1 Viewer)

Just a passing thought about QC / small sample error. Those of you who saw this thread:

http://www.birdforum.net/showthread.php?t=142050

know I was looking at small porrors as a gift. I ended up getting a pair of the red Yosemite 8x30s from EO (on sale now for $81). They are quite nice, but unlike the (presumably) identical black pair I tried at Cabellas, these focus a bit past infinity without my glasses (and so are plenty usable with or w/out glasses). This seems very odd, given I tested the ones at Cabellas pretty carefully, since I was annoyed at the limited focus range. There really was a focus difference between the two pairs. I know these are lower-end bins, but I wouldn't expect that level of difference. It makes me wonder about other brands and models, ie, my ZRS HD 10x42s, which although nice, don't seem quite as stellar as SteveC's pair.....

dustyview said:

It makes me wonder about other brands and models, ie, my ZRS HD 10x42s, which although nice, don't seem quite as stellar as SteveC's pair.....

Click to expand...

Well, FrankD and myself weren't hot about the ZRS either mostly because we didn't like the color bias.

So I doubt this is a sample issue but more a preference issue which is even more difficult to fathom or compensate for except by reading a lot of the reviewers writing.

Just a thought here and I will stand corrected if wrong. There is some hand work done yet, I believe, in the final assembly of binoculars and I would bet that part of it involves the final setting of the focusing dial. This may be the reason for the differences in the amount of focus past infinity in the same binocular. It should be easy to correct by the manufacturer.
Bob

I was, and remain impressed by the ZRS HD. However, the impression they made was not so much by placing them at the top of the heap. What impressed me then and now was how much optical quality they gave for the price. It seems mine cost $179 or something. They were, and are, easily competitive with much more expensive glass. They are however a step down from the better ZEN ED.

Having said that, I tend to agree with Kevin about individual preferences. One thing I think that tends to color personal preferences (pun intended) is the color bias Kevin mentions. The ZRS is pretty reddish brown in overall color bias.

You also need to be pretty careful in evaluating binoculars from store samples. I am always amazed at how many people seem to know nothing about how to focus binoculars. I have seen a lot of display models that had something wrong with them from being continually mishandled. So, it can be a crapshoot buying optics.

The focal length of the objective lens in a 30mm binocular like the Yosemite is probably around 110-120mm. It would only need to vary by about 1mm to change the focus by about 5-6 diopters. A few diopters of focus variation in different units isn't too unlikely.

There are in fact plenty of defects in binoculars that vary from unit to unit, even the expensive ones. If we used them at high magnification (1-2mm exit pupil) the optical defects would be quite unpleasantly intrusive. Happily at normal low magnifications the same defects are mostly (but not always) invisible.

Another small sample size error could be looked at as the small sample size of one particular viewer. I might see things one way and somebody else another. Where we each are in the overall continum of human optical atributes has a lot to do with it. Another reason fo putting up as many binoculars to your eye as you can.