Nikon premier LX Japan Leaded glass? (1 Viewer)

henry link said:

I've tried to photograph the longitudinal CA ............

Henry

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Henry,


I think that measuring longitudal CA would be extremely difficult. Since the CA would fall in front of, or behind the image plane, and by a distance that would be well within the depth of field of low power instruments that, when viewing axially, would have insufficient defocus to see. Plus, a color may obscure another. I find that I can very seldom get to where I see fringing all the way around (longitudal) the target, usually just in one direction.

You may be able to do it by using a very small dot or cross at as close a distance as you can focus on (minimum depth of field), placing the optical axis of the optic on that spot, then boosting the daylights out of it. You may get enough defocus of the longitudal error that way to tell something about it.

I have done some lateral CA measurements along with the MTF stuff and find the optical axis/target alignment quite critical. You also have to choose your white for consistency (illuminant A will have more red than D65) and be sure to use the same illuminant and intensity for the tests so as to make sure you have the same levels of red, blue and green. Attached is an old test of an Ultravid. I missed the optical axis 5% above, but since using a vertical line, I kept it, but it is not good enough to use as comparison data because I did not use a reference light source. I captured this data while doing comparison MTF’s for a group of bino’s.

If we were to standardize the light source and do a better job of aligning the axis, pictures, such as posted in the 7x36 ED2 posts showing some fringing on the concentric rings at (one degree increments) from the center might make a useful transverse CA comparison tool. Though not on optical axis, note 3 degree left of center and 3 degree right of center of the two crops.

Different light levels, colors, magnifications, backgrounds, viewers’ eyes, front lit, back lit, etc. make visual perception comparisons of CA pretty vague except for present, or not present, IMO.

FWIW, CA just does not bother me, so I spend little time trying to measure it.

Ron:


It seems that this leaded glass vs. non-leaded thing is quite impossible to determine.

To simplify things here a bit, if you have a view through a binocular that you like,
then don't worry, be happy. That means if the CA is severe enough, it probably will degrade the view, if it isn't within a tolerable range, then don't worry about it. There may be a small population that cannot stand it, and I respect their views.

As for as the practical aspects to using lead and the heavy metals, thinking about the guy that has to hand paddle and mix the glass in the melting pot, with his mask and respirator, he may prefer the newer ingredients.

And also those down below where they used to dump things down the river.

It seems the Chinese, are still trying to use lead paint on various toys and such being
exported. It is widely known that lead gives that nice gloss and finish to paint that you just can't get with anything else. I guess as long as you aren't a toddler allowed to munch on it you will not be harmed.

So much to digest here while on the discussion of lead.

For me, if you like the view through a bin that has lead content in the lenses, great,
that is fine with me. That is the way the construction of many fine optics was made.

Jerry

Hi Jerry;

Most of my comments were for Henry, whom, it appears, is getting ready to make a serious run at quantifying longitudal CA.

I was just commenting of some of the issues that made it hard for me to come up with a satisfactory method.

Henry always comes up with some unique and surprising work a rounds though, so I look forward to his results and methods.

Ron,

Sorry I didn't reply sooner. Actually I don't have any plans to try to measure longitudinal CA. I've virtually given up on even trying to photograph it accurately.

I think my black and white target, used visually in sunlight with boosted magnification does pretty well at revealing differences in longitudinal CA, like the difference between a binocular with a conventional achromat and an ED objective, and if I'm very careful about pupil positioning I feel some confidence using it to compare coarse differences in lateral color at normal magnification. But that's as far as it goes. I'm waiting for you to give us some real measurements ;-))

Henry

I think the leaded vs non leaded thing is a ghost hunt. Not that I'd ever argue that Brock or anybody else didn't actually see what they claimed to see. But the "eco glasses" were developed to be sufficiently identical replacements for their heavy metal antecedents that they could simply be substituted in any design, no reworking necessary. How many decimal places do you need? Do you think the specs are in error, or lies?

Now, for me to take this attitude, admittedly means that I have to believe in something. I don't pretend to prove every little thing to myself to be sure it's right. But I will go on record here as believing in science, and the technical records of the glass producers for getting it right, making it good, and telling the truth.

So, whatever Brock and the other proponents of leaded glass are seeing is not due to a difference in glass types, but something else, and to search scientifically for a leaded/non-leaded difference, in such a complex system as a binocular, when there are completely trustworthy specifications telling you there is no difference, is a waste of time. Even if somebody as measurement bent as Henry or Ron found a difference in the color correction of the the older and new Nikon, for example, I would not believe for a second that it was due to a difference between the optical properties of leaded and non leaded glass.

We are supposed to know a little bit about basic optics here. If you don't believe the numbers in the glass tables describe the passage of light through the material, but that there are angels or devils at work in addition, you have not quite arrived. Let's get past superstition, is all I'm saying.
Ron

ronh said:

I think the leaded vs non leaded thing is a ghost hunt. Not that I'd ever argue that Brock or anybody else didn't actually see what they claimed to see. But the "eco glasses" were developed to be sufficiently identical replacements for their heavy metal antecedents that they could simply be substituted in any design, no reworking necessary. How many decimal places do you need? Do you think the specs are in error, or lies?

Now, for me to take this attitude, admittedly means that I have to believe in something. I don't pretend to prove every little thing to myself to be sure it's right. But I will go on record here as believing in science, and the technical records of the glass producers for getting it right, making it good, and telling the truth.

So, whatever Brock and the other proponents of leaded glass are seeing is not due to a difference in glass types, but something else, and to search scientifically for a leaded/non-leaded difference, in such a complex system as a binocular, when there are completely trustworthy specifications telling you there is no difference, is a waste of time. Even if somebody as measurement bent as Henry or Ron found a difference in the color correction of the the older and new Nikon, for example, I would not believe for a second that it was due to a difference between the optical properties of leaded and non leaded glass.

We are supposed to know a little bit about basic optics here. If you don't believe the numbers in the glass tables describe the passage of light through the material, but that there are angels or devils at work in addition, you have not quite arrived. Let's get past superstition, is all I'm saying.
Ron

Click to expand...

+1. Kind of like looking for a bucket of prop wash.

I've used Nikon optics for years and know that company produces consistently high quality equipment. That image is widely known because Nikon has carefuly honed it in the marketplace over many decades. I would be utterly amazed if Nikon were to begin delivering expensive binoculars that use a lower performing unleaded glass. In the highly competitive binocular market that would be corporate suicide.