Is this delamination or fungus?

[Crater Eddie]

I took a chance on a 20x achromat objective from Armenia, I figured it was just $20, why not?
The result is what you see above.
This was not apparent when looking through the objective at a normal room scene, but looking at a white piece of paper revealed a definite problem. This image was taken using my stereo inspection scope at work, looking down into the back of the objective with it suspended above a paper and lit from above.
I will put it in the microscope tonight and see how badly it performs.
I emailed the seller, and he has offered to replace it right away. He is a popular Ebay seller with a good reputation
CE

Later...

I find surprisingly few photos online showing these issues, but I think this is severe delamination, because it really doesn't look like fungus to me.

[75RR]

In my, admittedly little, experience that does not look like delamination.
This may sound overly optimistic but could it be a liquid that has dried on the lens?

[Crater Eddie]

That was my first thought also, but the surface of the lens is pretty clean. This is definitely deep inside.
CE

[gekko]

I would say fungus. http://taiwan-photography-blog.com/2008 ... ngus-free/
Sorry

[lorez]

Mr. Gekko is correct. It is fungus. Delamination looks like a thin, well defined line that is usually (but not always) starts near the outer edge of the objective and may wind its way around the circumference of the glass. Patterns vary, but the line indicates the margin of the delamination.

lorez

[JimT]

I would say return it! Regardless of what it is it is not what you expected.

[Crater Eddie]

The seller has already agreed to send me a replacement. I offered to ship this one back to him, he said that since it was defective there was no need, he didn't want it back. So I'm not really out anything except the waiting time.
I was going to ask the seller how he could possibly have missed this very obvious defect, but since he was so gracious about the replacement I didn't.
CE

[75RR]

Since it is effectively unusable and free, you might want to try and clean it.

http://www.microscopy-uk.org.uk/mag/ind ... ungus.html

[Crater Eddie]

I found that article already, but thanks.
And yes, it is definitely unusable! I just had to have a look through it on the scope, tried it out just a while ago. Horrible of course!
When I get the replacement I'll have to do a side-by-side comparison, just for the entertainment, then I'll decide what to do with it.
CE

[einman]

Appears to be fungus. If you have some cross polars you can check for delamination. But looks like fungus to me.

[einman]

You would be surprised how many scopes I have received from an E-bay seller claiming "re-furbished" only to have it show up dirty, dusty and with fungus on the objectives. Stick with the people you know or ask questions to determine if they really know microscopes or just pick them up at auctions etc. and then try and sell them.

[Crater Eddie]

Thanks everyone for the input. I'll chalk this one down to "learning experience" and move on.
CE

[Crater Eddie]

Appears to be fungus. If you have some cross polars you can check for delamination. But looks like fungus to me.

I looked through the objective between polarizers, turned the objective, turned the polarizers, didn't see anything interesting.
Then I put the objective in the scope and looked at it with the Bertrand lens and polarizers, nothing.
CE

[einman]

Then it is fungus. Polarizers will show delamination.

[gekko]

Appears to be fungus. If you have some cross polars you can check for delamination. But looks like fungus to me.

I looked through the objective between polarizers, turned the objective, turned the polarizers, didn't see anything interesting.
Then I put the objective in the scope and looked at it with the Bertrand lens and polarizers, nothing.
CE

Did you focus your Bertrand lens throughout its focusing range when you were checking the objective? It could be that the focusing range of the Bertrand lens is too narrow to allow you to focus on the element with the fungus.

[Crater Eddie]

The Bertrand lens is not focus-able as far as I am aware.
CE

[75RR]

The Bertrand lens is not focus-able as far as I am aware.

Should be focusable. Both my Bertrand lens in my Optovar and my Phase Telescope are.
Note: Just read that this is not true of all Bertrand lens - so there may not be a focusing dial hidden somewhere. Sorry.

Polarizers will show delamination.

Never heard that before, how does one use them to reveal delamination?

[Crater Eddie]

There is no focus adjustment on mine as far as I can find. Reading the description of the HT-30 trinoc:
"A Bertrand lens is built in for observation of the back focal planes of objectives—a convenient feature allowing easy alignment of the illumination system and centering of the phase contrast annulus rings"
It sounds like it is preset for the back of the objectives only. A cost cutting measure I assume.
Oh well.

[gekko]

Did you look carefully just above or below the "switch" that puts in in and out of the optical path that there is no knurled disk/wheel (edge only shows)? The reason I think there ought to be one is to enable it to be used with objectives of different parfocal distances.

[Crater Eddie]

If there are any hidden controls then they are well hidden.

[gekko]

I may be wrong, but in the first picture, I would expect the wheel with knurled edge just under the flat part that selects the Bertrand lens (marked "B") to be movable independently of the "B" part. Or is it a single solid part? Can you insert a piece of paper between the B part and the knurled wheel? Or is there a separation that you can see with a magnifying glass? I would be surprised if that is not the focusing control. Again, I may well be wrong as I've never seen a LOMO with a Bertrand lens.

[Crater Eddie]

It is a solid knob. The positions for the other lenses are the same. The knurling is for turning the whole lens selector.

CE

[gekko]

So I was wrong. Sorry about that

[Crater Eddie]

I would have been happier if you had been right.
CE

[Rodney]

I have a special holder I use for a single objective that is held in place with a swing in or out lab stand arm mounted underneath my stereo scope to look into problem objectives. This gives me a good idea of what the general condition of the objective is; scratched up, just dirty, delamination, or glass fungal growth. If you have the procedure set up right you can focus into the objective and also reverse objective ends. Delamination looks like the cement wasted away at the edges and can be circular 360 degrees and can be a lot less with migration from any point. I have rebuilt a few objectives but they were under 200x because any alignment of very high power objectives can be very tricky and not worth the time and head aches to fix.

Rodney

[Rodney]

20x I typed in one extra 0 by mistake. I was able to rebuild one 43x objective that was hazed up inside from what I guess got ran into a dish of pond water, just a guess. Anyway this was an older simple 3 lens unit, but took days to get it aligned back right and to make sure all the elements were clean and dry going back in. Even the slightest amount of moisture trapped inside can cause the objective to fog back up. No I would not want a regular job doing this because the chance of failure can be very high, for me anyway.

Rodney

[billbillt]

With my limited experience with objectives, this does look like fungus... I have seen it once before.... May be quite a job to clean out, but you never know..

[billbillt]

Here is an attached photo from another forum of a condition very similar to yours... It was determined to be fungus....

[Crater Eddie]

Looking at this bad objective in my inspection scope at work, I am able to focus all through the elements... the defect is not on either of the outside surfaces, it is in one of the lens-to-lens interfaces deep inside. As this is just an achromat I don't think it's worth trying to fix, other than as an exercise, especially since I am getting a replacement. I think this is just a pretty paperweight.
Thanks to everyone for the participation, this is what makes this forum great!
CE

[Crater Eddie]

In the way of closure, I will say that the replacement 20x achromat arrived yesterday. The glass is clear and bright, and it produces very nice images. I'll try to put up a few photos in the next week or so.
CE