# Building my own lens Mine's Bigger than Yours



## Mt Spokane Photography (Nov 8, 2016)

I wanted a large aperture lens, so my first task was to find out how large of a front element I could find. This one is about 14 inches across, and actually consists of two elements. 

Great Start eh, and only $200.

I will post more info about it when I get time, it has quite a history.


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## IglooEater (Nov 8, 2016)

Haha, pretty sweet!! Looking forward to your updates. What focal length are you looking to make? Good luck!


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## Mikehit (Nov 8, 2016)

Lens? That is a bass cone from a speaker with some glass in front of it!
For a more 'focussed' sound no doubt.


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## AlanF (Nov 8, 2016)

IglooEater said:


> Haha, pretty sweet!! Looking forward to your updates. What focal length are you looking to make? Good luck!



If it's a 50mm, then if would be f/0.14. Hate to think what the field curvature and depth of field would be.


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## rs (Nov 8, 2016)

Assuming you can make the aperture match that front element diameter, a 400/1.1 would be quite nice. What was it part of before?


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## Alex_M (Nov 8, 2016)

part of this, likely? 8)



rs said:


> Assuming you can make the aperture match that front element diameter, a 400/1.1 would be quite nice. *What was it part of before?*


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## DominoDude (Nov 8, 2016)

The colour kind of gives it away. I'd bet it has been part of some military equipment.
It might have been part of a door peephole at NORAD operations center. :


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## Khufu (Nov 8, 2016)

Cooool... have you tried holding it near a wall at a dark end of a room to see what its as-is focal length/flange distance is, and how large the projected image is?! Go do aaaall the tests and report back to us, trooper!


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## Mikehit (Nov 8, 2016)

I'd return it if I were you. It is obviously crippled by a poor focus mechanism.


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## Maximilian (Nov 9, 2016)

Mt Spokane Photography said:


> I wanted a large aperture lens, so my first task was to find out how large of a front element I could find.
> ...


If I were to choose something for this task and I wasn't fixated on glass I'd go the mirror optics way 
But $200 is a though price.

Enjoy and post your progress


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## AlanF (Nov 9, 2016)

rs said:


> Assuming you can make the aperture match that front element diameter, a 400/1.1 would be quite nice. What was it part of before?



Solved the puzzle. 14" diameter is the minimum size of the front element for a 1000mm f/2.8.


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