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Leitz infrared dedicated lens
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PostPosted: Wed Jun 03, 2020 5:26 pm    Post subject: Leitz infrared dedicated lens Reply with quote
I've got a Leitz Wetzlar lens, certainly constructed for night vision military use. It looks like this (a photo provided by the seller)



An simple outer ring in aluminium instead of focusing helicoid, fixed aperture. It looks quite a lot as a projection lens. And I had an idea that I may easily put it to a custom adapter or to bellows, with some duct tape, and to have a great Leitz IR glass to play with.

But I don't arrive to get the lens' flange distance. I tried to put it to various distances, from pushed up to the sensor, and up to 50 cm with extension rings and bellows together. The result is the same, an evenly lit red square as the resulting shot.

There is no way neither to see a light circle on white paper, with sun or a flash bulb. There is just no circle, visibly because of the thickness of the red glass. The latter is attached dead at the lens bottom, so it is not a filter, but a concave rear element. This is how it looks like (the seller's image)



I wonder if you have any experience with a similar night vision lens. Is it still possible to use it in any way?


PostPosted: Wed Jun 03, 2020 5:39 pm    Post subject: Reply with quote
I'd have guessed the filter can be removed, not a lens element.


PostPosted: Wed Jun 03, 2020 6:24 pm    Post subject: Reply with quote
I can only have access to the bottom by the top, after unscrewing the upper retaining ring and dismantling all the elements. I may try to disassemble the lens and to see what it is in its rear end.

But what is seen without any dismantling, the rear red element is concave, so looks more like a lens.


PostPosted: Wed Jun 03, 2020 10:04 pm    Post subject: Reply with quote
I saw some lens work my friend Marco Cavina has done, and I remember having seen an IR lens where that red filter glass had lens form. So if you remove it the lens may not work well. But anyway it will not be corrected for visible light, so expect crappy images with horrible CA anyway..

And it rear focal length was very short, basically in contact with the rear glass - no wonder you don't see anything...

Here it is...


(c) Marco Cavina


PostPosted: Thu Jun 04, 2020 6:47 am    Post subject: Reply with quote
Thank you, Klaus, for your valuable input! So much precious glass inside and so little chance to get smth good out of it. I'll try later to take off the red glass and to see what it gives.


PostPosted: Thu Jun 04, 2020 7:13 am    Post subject: Reply with quote
alex ph wrote:
Thank you, Klaus, for your valuable input! So much precious glass inside and so little chance to get smth good out of it. I'll try later to take off the red glass and to see what it gives.


Most welcome! I have an amplification system which has a similar lens in front, will try and see if that works. It is rather deep IR around 1000nm...


PostPosted: Thu Jun 04, 2020 3:16 pm    Post subject: Reply with quote
Please share your results!

From my side, I haven't managed to unscrew the upper retaining ring of the lens, even after some drops of WD40 applied and much effort with a lens spanner. There are two thin slots on the outer barrel, equal to those which the retaining ring has. But I see no sense in it. Maybe it is made for unscrewing the whole lens from a bigger device? Anyway, it seems to be dead stuck in my copy.

I found out that being reversed the lens gives some image. That lets see how much light it lets through, which is finally not negligible. Besides, it seems to have a pretty wide angle. Here is how the reverse freelensing looks like on Sony Nex.



While the upright lens position brings no objects shapes at all. Probably because of what Klaus says about the flange distance to be too short.

If you have some additional ideas and hints, please don't hesitate to put them forward.


PostPosted: Fri Jun 05, 2020 7:34 am    Post subject: Reply with quote
Well, at least you got some sort of result....

I have one coming, let's see what I can do with it. Guess I will put it on my amplification system...


PostPosted: Fri Jun 05, 2020 8:23 am    Post subject: Reply with quote
I didn't ask you before, but that's a good moment: how does your amplification system look like?


PostPosted: Fri Jun 05, 2020 10:03 am    Post subject: Reply with quote
...

Last edited by Blazer0ne on Tue Feb 22, 2022 6:52 pm; edited 1 time in total


PostPosted: Sat Jun 06, 2020 12:04 am    Post subject: Reply with quote
Thank you for your allusion! Now I know at least on way to use it for mood shots.

But it is still unconvenient in real life, as the distance to sensor is small, and I may only can freelensing.


PostPosted: Sat Jun 06, 2020 12:38 am    Post subject: Reply with quote
alex ph wrote:
I didn't ask you before, but that's a good moment: how does your amplification system look like?


You wouldn't want to know, as it is $$$$...


PostPosted: Sat Jun 06, 2020 1:52 am    Post subject: Reply with quote
Can a relay lens system help here?


PostPosted: Sat Jun 06, 2020 10:23 am    Post subject: Reply with quote
kds315* wrote:
alex ph wrote:
I didn't ask you before, but that's a good moment: how does your amplification system look like?


You wouldn't want to know, as it is $$$$...


Oh dear, that sounds serious. In fact, my curiosity considers the concept itself of photo amplification. I can see what it means in audio: a machine letting you make sound louder or modulate its pitch, frequency and other parameters. But in optics the most natural idea that comes to my mind as for amplification is... a photo enlager.

Visualopsins, I thought about somehing similar, in order to extend the flange distance. But I am completely inexpert in optics. How that could look like?


PostPosted: Sat Jun 06, 2020 12:31 pm    Post subject: Reply with quote
No, it is this Alex: https://en.wikipedia.org/wiki/Image_intensifier
using that technology inside: https://en.wikipedia.org/wiki/Microchannel_plate_detector

Most likely what it has been used in was that (night vision device):


(C)Wiki


PostPosted: Mon Jun 08, 2020 12:09 am    Post subject: Reply with quote
Wow, thank you, Klaus! This is a pretty impressive device. The general principle is that the vacuum tube makes the light brighter? Kind of large and costy speedbooster.


PostPosted: Mon Jun 08, 2020 7:45 am    Post subject: Reply with quote
alex ph wrote:
Wow, thank you, Klaus! This is a pretty impressive device. The general principle is that the vacuum tube makes the light brighter? Kind of large and costy speedbooster.


Not really, as it converts invisible light into visible and this then can be recorded using a camera. BUT it only delivers monochrome results (mostly green) and resolution is rather limited and one gets rather grainy images. Looks here, I did some shots using this system:
https://photographyoftheinvisibleworld.blogspot.com/2019/12/reflected-uv-photography-using-amplifed.html



THIS IS NOT THAT LEITZ LENS; BUT A 250mm MIRROR LENS!!!

Last edited by kds315* on Sat Jun 13, 2020 12:05 pm; edited 1 time in total


PostPosted: Tue Jun 09, 2020 4:17 pm    Post subject: Reply with quote
Well, I got that little lens, and it does produce an dark red image, and if I hold it to the light amplification system there is an image too, but it seem that the back focal length indeed is VERY short, so it seems not to have much use...


PostPosted: Wed Jun 10, 2020 10:29 am    Post subject: Reply with quote
Had it in my Spectrometer, it transmits from approx 700nm onwards...


PostPosted: Sat Jun 13, 2020 11:46 am    Post subject: Reply with quote
Thank you, Klaus, for your sample and for the confirmation about the lens.

Haven't you tried the lens reversed on your device?

The sample looks interesting. Not the best IQ for sure, but it has some 8mm film character.


PostPosted: Sat Jun 13, 2020 12:06 pm    Post subject: Reply with quote
alex ph wrote:
Thank you, Klaus, for your sample and for the confirmation about the lens.

Haven't you tried the lens reversed on your device?

The sample looks interesting. Not the best IQ for sure, but it has some 8mm film character.


THE PICTURE ABOVE WAS NOT TAKEN WITH THAT LEITZ LENS!!!

It was just to illustrate how an image using this image amplification device looks like (a 250mm CAT lens was used for that)

Last edited by kds315* on Sat Jun 13, 2020 12:23 pm; edited 1 time in total


PostPosted: Sat Jun 13, 2020 12:10 pm    Post subject: Reply with quote
This is what I understand, no worries!
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