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Angenieux 10mm no focusing ring


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A fixed focus lens is designed for ease of use, to be able to just point and shoot. The idea is that the depth of field is deep enough to cover almost everything in front of you. This is usually achieved by either a very short focal length or a slow aperture (or like on old instamatics simply a cheap lens that doesn't resolve too well). The lens will have its back-focus set for best resolution at around the hyperfocal distance, to maximise the depth of field.

It depends on where you draw a line between what's acceptably in focus and what's not  (which is a factor of viewing magnification and the system resolution capacity), but using a standard 16mm Circle of Confusion figure the depth of field of a 10mm lens at f/1.8 focused to 12 ft is going to be roughly 6 ft to infinity. If you were viewing your footage on a youtube video on your phone after a cheap scan you would get much more depth of field because it would all look soft!

If the lens back-focus or camera flange depth is not set very accurately, the point of sharpest focus (and depth of field buffer either side) will shift, either towards infinity or close focus. So if you shoot a test and find the lens only focuses on close objects, then the lens is sitting too far away from the film plane. (If you deliberately wanted a fixed focus C mount lens to focus closer, you could therefore unscrew it a little.)

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Dear Simon, Dom,

thank you for your reply! This is indeed interesting, because I plan to use this lens with the Admira, a camera which is not TTL, but which is equipped with a Galilean viewfinder. I plan to use this lens and the Openar 20 mm, which is included with the camera itself. I will not use the 80 mm, because it would be too imprecise to focuse, compose, etc...

I plan to use this setup when I will go again in the Nairobi´s slums to make a documentation. 16mm will be a complement to still phoptography. There, speed of action is needed. 

Before the documentation I will shot test film (I have already a spool of Foma R100, which I can self develop in the Lomo tank). 

In particular I have to check what Dom is saying in the last part of his message: to be sure that the lens is focusing correctly (lens should not be too far from the film plane). I can try to do that also with a small focusing screen. I am working on the Admira, which is open now, to clean and lubrificate it. That is needed after years of sleeping.

Do you think I am on the proper way?

 

 

 

 

 

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Dom, actually I am still not really sure about what to do, in the end... 

I have a Beaulieu 4008 ZM2, which has been serviced in May this year by an expert here in Germany, and the Angenieux lens fits it too ( I have the Schneider zoom too, but I don´t like it too much because it is cumbersome).

Therefore I could in principle also use the Super 8, instead of 16mm: I would have a TTL camera with the possibility to compose and focus the scene with higher precision.

But 16mm means double film surface, better system which press the film in the camera (in Super 8 it is plastic, provided by the S8 cassette, in 16mm is metallic which provides better film planarity...).

On the other hand the Beaulieu 4008 is the top in S8, while the Meopta Admira 16A1 16mm is not an Arriflex (which I cannot afford).

To take everything would be a bit complicated (I need to add a Rolleiflex a Fuji GA645 and ~100 film roll in the 120 format, exposure meter...).

It is true that I don´t take all the equipment with me every day, but that I select a certain equipment each day, according to the situation which I think I will find, and I leave the rest of the equipment at the base where I sleep. 

Do you have a suggestion for me?

 

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  • 4 weeks later...

I used that lens years back. To fix perfectly focus  you have to screw  very well the lens  in camera first. Then if you look in the base of the lens ( close to mount) you will find 3 little screws. Unloct them and rotate the lens till you will find perfect focus for your need. Then refix those little screws. That is all

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