Click here if you are having trouble logging into the forums
Privacy Policy |
Please read our Terms
of Service | Signup and
Troubleshooting FAQ | Problems? PM a Red or a Green Gu.... uh, User
Anonymous
Unregistered
|
|
It is interesting - to me anyway - that whilst a laboratory might give one result, in the field tests depend heavily on other factors, which are thus of equal importance to absolute optical quality.
I tested the Nikon 8x32 SE against a Swaro 8.5x42 EL, and at large distances I could not distinguish between the two, at least as far as resolving detail went. There might have been a difference, but it was so small as to be academic. At close distances the Nikon appeared noticeably less sharp, by which I mean that when I used binoculars to read writing on a nearby soya sauce bottle, the Swaro clearly revealed more detail, and allowed me to read small text that was indistinct through the Nikons. However, see below.
I am prepared to believe that the long distance tests might have been inadequate for precise comparisons. At large distance it is hard to find a suitable subject. (I am talking daytime use, speaking as a birder.) Sadly we have a shortage of 100 foot tall soya sauce bottles.
Having thought a bit about the close distance tested, I have realised that the focus on the Nikons is very coarse, and this makes achieving accurate focus at near distances, when DOF is shallow, rather difficult. In fact when I repeated the tests, taking care to spend a bit longer adjusting the focus, the results were closer, though I am still of the opinion that the Swaro resolved more of the text.
I am a little surprised by my conclusions, namely that mechanical issues such as the focus throw can appear to influence the perceived resolution of an instrument! This makes me think of the review of the B&L Elite 8x42 binoculars by Steve Ingraham. He concluded that they had good DOF, despite reviews to the contrary. He also stated that he thought the explanation for this was probably the coarseness of the focus throw giving the psychological impression of shallow DOF!
|
nemo
sage
Reged: 06/09/03
Posts: 388
Loc: Eugene,Oregon
|
|
Kenny and Wilash,
Reading the above I am reminded of the following paraphrase. "When it comes to a pinch between the practical and the ideal the loss is almost always at the expense of the ideal." I am thinking that whenever human factors enter into the quantification and qualification of a given set of variables such as Contrast versus Resolution there is a certain loss in translation. It often seems like anytime a rule fails to have a certain amount of the human factor inherent in it-included; there is a good chance that the rule will fail due to lack of flexibility in its application. As we know in order to empirically examine concepts in this discussion there must be a method of measurement for the given phenomena. The need for this may or may not reflect experiential aspects with a particular instrument and other external variables. This may be due to the basic subjectivity present in the observer.
Sorry for the blather. I am learning allot from this thread and not all of it about contrast and resolution.
R/S,
Dan
--------------------
"Humility is not thinking less of your self-it is about thinking of yourself less."
|
KennyJ
Reged: 04/27/03
Posts: 10163
Loc: Lancashire UK
|
|
Wilash,
I certainly owe you a big thank you for taking the time to explain all this -- but to be honest -- some it IS and some of it is NOT, sinking into my cranium or sitting comfortably therein if it does descend to such depths.
Perhaps the bottom line is that my understanding of the term "resolution" is completely and utterly flawed.
Unfortunately , the British National Health Service is already under more than enough pressure without being troubled with the additional problem of funding the brain transplant that would surely be necessary to render me capable of fully understanding such thesis.
However not of this alters the truth of what I tried to explain in last night's post -- it's just my reference to terminology that is flawed.
Perhaps we all ought to "sign up" to the new "pay per view" in depth articles sections , and take a good long look at "Professor Ed's" latest epic on Resolution.
P.S Belated thanks to other contributors to this thread.
Regards -- Kenny.
Thanks again -- Kenny.
--------------------
If everyone is thinking the same thing , no-one is thinking - General George S.Patton
Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
Helios 15 x 70 Observation
Strathspey 20 x 90
Televue 76 APO
Zeiss 85 Diascope
Helios 102 f5 refractor
Various eyepieces barlows tripods mounts etc.
Panasonic Lumix DMC - TZ5 digital camera
|
wilash
Fairy Godmother
Reged: 09/30/03
Posts: 5746
|
|
I think it is good to know what the concerpts of resolution and contrast are. The simple formula that show relationships help to make judgements on the strengths and weaknesses of certain specifications. But none of this tell you how a particular optical system will work.
Image quality has always been subjective - if you think optics are good, then they are. When Kodak was working on tone reproduction in films they basically made a series of different prints with different processing, decided which looked the best. made some measurements, and then came up with criteria for processing. But it all came down the a subjective judgement. And of course this can be the only way because optics are made for human beings. Image quality does not have any abosolute meaning beyond our experience. This, by the way, is the problem of MTF curves. They give numbers but no imformation on how it will be perceived.
|
KennyJ
Reged: 04/27/03
Posts: 10163
Loc: Lancashire UK
|
|
Friends,
I joined the "pay to view" LAB Tests section earlier today and must say that for the modest contribution of $20 US for one whole year ,in my opinion the option represents tremendous value for money , in addition to providing the subscriber with a sense of "helping out" albeit in a very small way , with the inevitable running costs of such comprehensive works.
The article on Resolution alone by Ed.Zarenski contains much more technical information than I've ever seen in any BOOK obtainable for the equivalent of what $20 US represents at the current UK exchange rates , and that is just ONE article of several available within the first month of the section's existence.
I therefore greatly urge any fellow member remotely interested in a more in depth study of this complex subject to follow my lead and sign up.
Web site rules and copyright prevent me from quoting any information contained therein , and I cannot pretend to give the impression that I actually understand all that is written , so therefore cannot say that I either agree or disagree with every assertion presented.
Wha I can say is that there is clearly a distinct difference between the "kind" of Resolution the author defines and explains so deeply and what is implied by "Resolution" in for example ,the NEED charts drawn up by Stephen Ingraham on the Better View Desired Birding Optics web site.
This is another example of the differences in understandings of definition as touched upon in previous posts to this thread.
It is interesting to note that Ed makes mention of the fact that during his extensive research for this paper , very little if anything of an authoritative nature could be found which had been written specifically to address the effects of the situation when the human entrance pupil is smaller than the exit pupil of an optical train.
I too spent hours last year trying to find anything written on this specific scenario ,and to no avail.
At the end of the day ,I will continue to trust my own eyes and judgment above scientific theorising.
It is interesting to note that at least one person I know who firmly believes in the "wasted aperture" theory , like myself, chooses and prefers to use 7 x 42 binoculars for most daylight observing.
Regards -- Kenny.
--------------------
If everyone is thinking the same thing , no-one is thinking - General George S.Patton
Zeiss 7 x 42 BGAT
Captain's Helmsman 7 x 50
Nikon 10 x 42 Superior E
Swift Audubon Kestrel 10 x 50
Helios 15 x 70 Observation
Strathspey 20 x 90
Televue 76 APO
Zeiss 85 Diascope
Helios 102 f5 refractor
Various eyepieces barlows tripods mounts etc.
Panasonic Lumix DMC - TZ5 digital camera
|
EdZ
Professor EdZ
Reged: 02/15/02
Posts: 12601
Loc: Cumberland, R I , USA42N71.4W
|
|
Having just returned from a lengthy vacation and with a great deal to do preparing for the upcoming week, I cannot enter this great discussion at this time, but to support these few statements made by others above.
Higher contrast most definitely improves the ability of the eye to percieve resolution.
Brightness increases the perception of resolution. In very low brightness conditions there could appear to be no resolution at all.
Resolution will diminish with distance from the object. Resolution is dependant on light gathering and the further you are from the object the more difficult it is to gather light from the object. The light from terra objects will not appear with the same brightness if moved to a distance 10x farther away. The same would be true if a point source star were moved 10x further away.
Using stars as an example to depict a similar condition to terra objects moved further away:
A double star with equal components is close enough to appear as 6th magnitude. If separated by 1 arcsecond, they can be completely resolved with a 5.45" scope. Now, another double star with apparent separation of 1 arcsecond, with exactly equal components is much further away so that it appears as a pair of 9th magnitude stars. The two stars are exactly equal to the first pair, but distance reduces the apparent brightness to 9th magnitude. It would take about 50% greater aperture, or 5.45 x 1.5 = 8.17" to resolve these two distant components. The diminished light reaching the lens requires greater resolving power. Objects moved further away do not appear as bright, therefore it requires greater resolution to see the objects.
There are several posts in the double star forum that were portions of the original writings I used to develop my paper "Understanding Resolution". Although it is far less than the whole, you may access those and if those posts have what you are looking for, quote to your hearts content.
edz
--------------------
Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
member#21
Edited by EdZ (02/22/04 08:27 PM)
|
nemo
sage
Reged: 06/09/03
Posts: 388
Loc: Eugene,Oregon
|
|
Kenny,
"I there fore greatly urge any fellow member remotely interested in a more in depth study of this complex subject to follow my lead and sign up."
Well I followed your advice Kenny and signed up for a year. Given the quality of content it seemed like an inexpensive way to show a little support.
R/S,
Dan
--------------------
"Humility is not thinking less of your self-it is about thinking of yourself less."
Edited by nemo (02/22/04 06:33 PM)
|
|
8 registered and 16 anonymous users are browsing this forum.
Moderator: EdZ
Print Thread
|
Forum Permissions
You cannot start new topics
You cannot reply to topics
HTML is disabled
UBBCode is enabled
|
Thread views: 1170
|
|
|
|
|
|
|
Previous
Index
Next
Threaded
[Re: 
Edit
Reply
Quote
