I am sure that, like some of you, I spend a good deal of time not only using binoculars but also thinking about them as well. One area that has plagued me for some time is the issue of a binoculars’ subjective optical performance. This may sound simple at first but it is not. It tends to fall into the range of discussion in perception but not entirely.
I have tried to put some type of terminology to what I am referring to but have had difficulty finding just the right terms. So, for lack of a better phrase let me clarify what I mean by “object performance, field performance and overall performance”.
Object performance refers to the binoculars’ visual presentation of a specific object. Simple right? So, if you are looking for a Snowy Owl in the middle of cornfield then the way the binocular represents the Snowy Owl to your eyes is the binoculars’ object performance. The distinction here is between object performance and the other two types. Object performance does not necessarily depend on issues such as the type of distortion surrounding the other edge of the field of view….assuming that the object fits snugly into the sweet spot of the binoculars’ image. It does depend on issues such as apparent sharpness, apparent contrast and color representation. A perfect example of this was noted in a discussion I had with another forum member a few weeks ago. He objected to the type of edge performance a particular model displayed when he was scanning the open sky looking for raptors. What he stated was “…it bothers me but when I find a bird and focus the binoculars on the bird then the edge performance issues disappear because all of my attention is focused on the bird itself (object).”
This is distinctly different from what I want to call “Field performance”. Field, in this case, is referring to the overall impression that the binoculars full field of view provides to the user. This is extremely dependent on the width of the binoculars apparent and true field of view. Case in point, I have really been dabbling with some of the older model 7x35 porros lately. Because of their use, many times, of both single coated lenses and possibly Bk-7 prism they do not excel in the optical performance areas that many of us take for granted these days. They are not as bright or as filled with contrast as modern roofs nor do they typically have the neutral color representation. Images appear slightly yellow in comparison.
These shortcomings do take away a bit from their “object performance” but their design does contribute greatly to very good “Field Performance”. Because their field of view is generally huge (10-12 degrees) and because they offer the porro 3D-effect the image is exceptionally relaxing and easy to use. They just have that natural “oh, here is what I typically see when I look at something without binoculars just much closer” feeling to them. I am guessing this correlates with a human’s normal width of focused, unaided attention.
Overall optical performance is a term I would use to describe binoculars which have great object performance but also provide better edge performance. Many of the Alpha binoculars would fall into this group. Models such as the Nikon SE, Premier LXL and EDG, the Swarovision, etc… The only issue these binoculars are lacking is in a true “ultra wide angle” field of view. To accomplish this, in my opinion, their fields of view would have to approach or exceed 70 degrees.
Now, you are probably wondering why I am taking the time to relate any of this. Well, the answer is not too complicated. As I mentioned I have been having a hard time putting some of my experiences into words. There have been several binoculars whose levels in “object performance” areas have been first rate….on par with binoculars costing quite a bit more. Other models I have been trying offer an equally satisfying viewing experience but lack in certain object performance areas.
I guess what I am trying to say is that different binoculars can please us for different reasons. Depending on what type of activity you intend to use them for you may find one type of performance equally appealing to another.
Just something to think about.
For me, there is only one primary need for a bin. to deliver to be worthy, they must give outstanding views of birds.
I may spend the better part of a day in the field looking at rocks and roofs for CA, or reading signs and testing the size of the sweet spot or edge performance, or trying to invoke glare or flare from some absurdly backlit situation.
There are times, during these ''inspections'', that I may find some apsects of the bin lacking. Then, I start looking at birds again and [in the case of my FL] they just look gorgeous, perfect, accurate. You can push a bin to perform in many non real world situations, while ignoring the simple fact that these are birding glasses and they must perform [for me] as such.
That's why I still sing the praises of my FL, as [sure] it doesn't have the edges of the EDG or SV, but the view of a bird is so pristine, so elegant and so satisfying, I do not feel the need to look for something else.
James,
Thank you for sharing your experiences. That is exactly what I was referring to. Different folks look for different optical performance areas in their binoculars. No one binoculars is going to please everyone as we each tend to put emphasis on different issues.
I was just looking to put terminology to some very specific subjective experiences.