Night Vision Strange blems in filmless tubes

[gthirteen]

Have a couple of new tubes with good specs overall. One has a couple of transparent blemishes, one looks like a tiny circle, the other a rhombus, and basically the center is clear, you can just see the edge of the shape, of that
Makes any sense.

The other appears to have a traditional blem, but it appears to be on top of a lighter colored blem. It almost looks like a shadow. None of this stuff focuses well with any camera that I have. All are very small.

Anyone seen something like this before?

 

[jwramp]

Tough to say without pictures. Could be foreign debris inside the unit too. Can you try to take a photo of the issue?

 

[sea2summit]

Tough to say without pictures. Could be foreign debris inside the unit too. Can you try to take a photo of the issue?

That^ first thought was finger prints.

 

[zinny]

Do they appear more prominent with the day light filter on?

 

[gthirteen]

They are not bright, if that’s what you’re asking.

Imagine you were looking out a window and there was a small round extra piece of glass attached to either side of the pane. You’d notice it, but it wouldn’t prevent you from seeing through it. That’s the best way I can explain the “clear” blems

 

[zinny]

The daylight filter restricts the aperture increasing the depth of field. If you see more odd shapes with the daylight filter on in the same plane as the other shapes, you may have finger prints or dust on the front of the tube.

 

[gthirteen]

Ah! Thanks. Will check

 

[pucker]

Are they perfectly round?... or possibly hexagonal shaped?

More prominent when gain is maxed out, looking at light colored background?

 

[gthirteen]

Will check. I recall that one was circular, perhaps not perfect but pretty close the other had 4 sides.

 

[pucker]

Could be fixed pattern noise...like faint honeycomb pattern. Pretty normal under high light or bright background.

 

[gthirteen]

No, I see the honeycomb, too. Never bothers me. This is something different.

 

[GBMaryland]

Take the tube, put it behind a piece of white paper with the light on in a room (not crazy bright), and take a picture through the tube with you cell phone.

Post it....