Fungos?

I have a binocular Pentax 10x50 PCF WP II.
When I breathe on the objective lens I see what looks like pale circular stains. Can it be fungus or it just means that I should clean the lens?

Sorry I do not know how to attach a pic to show that!

Thanks,

Alex.

That doesn't sound like fungus (that appears more like a spider's web of thin random veins) but it does sound like seperation of the elements. Glass elements are bonded together with a special glue and when the glue starts to let go (which could be for a number of reasons) then you see a pale circular patch like the one you describe.

If the binoculars are still under warranty then you could get them changed, if not then the cost of repair is likely to be higher than the cost of a new pair - sorry!

The stains seem to be on the external lens surface...
Nevertheless, I will check it again.

Many thanks,
Alex.

Looking into the front lens I can see reflections of a lamp bulb (in my bed room) at the prism surface. At the moment what, is confusing me is that I see three (main) reflections looking into the left objective and four reflections by looking into the right objective:
* left objective: one white (smaller / near) the other light-green and green (larger / far);
* right objective: the first is light-green (and smaller), next is white and light-green (two reflections almost side by side) and at the far end is green.

Since glass elements are bonded together with a special glue, can the difference of the number of reflections be a problem of separation of optical elements? (the difference between the left and right objective be an extra optical surface -- resulted from the separation of two elements).


Sorry for changing the topic..


Alex.

What you're seeing sounds quite normal. Don't forget, the two lenses aren't in *exactly* the same position when you view them - imagine holding two mirrors a couple of centimetres apart; they would reflect the same scene but from different angles so the reflections would be staggered in terms of what they show.

From the angle that you're viewing you're simply missing the first (light green) reflection on the left because you're viewing it at a slightly different angle to the right hand lens. These lenses have combinations of concave and convex surfaces so the tiniest movement makes a big difference to what you see reflected!

Check again, but this time look at one objective at a time: When you've noted what you see in the first then move the binoculars so that the other occupies exactly the same place and you should see the same reflection.

The coloured reflections are a property of the lens coatings. As these coatings are usually only applied to surface which are exposed to air (in other words, not to surfaces that are bonded) then seperation wouldn't be the cause in this case.

Hope that helps!

Looking into each objective at the time, and rotating the binocular 360 deg, I see the same as before (three reflections on the left prism and four reflections on the right prism).

After you have suggested the separation of glass elements, I got more curious. Since the binocular is used primarily on astronomy I have posted few days before on a different forum (Cloudy Nights -- an astronomy forum that have a section on binoculars). The topic was on the internal reflection -- there I asked if different level of green could be a coating problem because I found on different web sites that "white reflection may indicate some uncoated surface". If you do not mind, I have on that post I have some photographs that show exactly what I see:

link

Since this is my first binocular and I got it less than two months ago I need to know if it all this is normal.
If you could give some advice I would appreciate.

Alex.

I've read your thread on the other forum and looked at your pictures and I think it's possible that you have a case of seperation. Without looking at the binoculars in person I would not say for sure so my advice is to take them back to the shop where you bought them and ask for them to be replaced under warranty.

Sorry I can't help further and good luck!

Thank-you,

Alex.