Why I think Kubricks F/.7 Nasa lens is actually a T/1

To explain this further:

50mm f2 example, absolute aperture is 50/2=25mm diameter

2x tele converter, 100mm with 25mm absolute aperture = 100/25=f4 relative aperture, 2 stops of loss over f2
0.5x wide converter, 25mm with 25mm absolute aperture = 25/25=f1 relative aperture, 2 stops of gain over f2

The question is how much light is lost in the new optical elements. It depends on the elements.
 
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For this lens it could be f0.7 without the adapter, f0.5 with the wide angle.

I think a T0.6 with everything in place is possible.
 
Otis Grapsas said:
For this lens it could be f0.7 without the adapter, f0.5 with the wide angle.

I think a T0.6 with everything in place is possible.
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Yes, I've always understood the ir2 law and how it applies to teleconverters regarding light loss... and yes, thus the opposite theory of wide angle converters makes sense theoretically... but is that how it works? I don't know. My real world experience has never shown such. If anything they (wide-angle converters) have all had marginally negligable light loss. Can you point me to a wide angle converter that gains light sensitivity? One that is perhaps available to purchase?

If this is possible, I'd think lens series owners such as Arri Master Primes or Cooke 5/i's could take something like this and turn their 100mm and 75mm lenses into T/1 50mm and 36mm glass. Sign me up. :)

I think it could theoretically gain. Don't think it did. But then again, I have a helluva time keeping up with you Otis... you excel in the technical compared to myself. If I had to choose right here and now, I'd go with your knowledge on the matter.
 
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Ryan Patrick O'Hara said:
Yes, I've always understood the ir2 law and how it applies to teleconverters regarding light loss... and yes, thus the opposite theory of wide angle converters makes sense theoretically... but is that how it works? I don't know. My real world experience has never shown such. If anything they (wide-angle converters) have all had marginally negligable light loss. Can you point me to a wide angle converter that gains light sensitivity? One that is perhaps available to purchase?

If this is possible, I'd think lens series owners such as Arri Master Primes or Cooke 5/i's could take something like this and turn their 100mm and 75mm lenses into T/1 50mm and 36mm glass. Sign me up. :)

I think it could theoretically gain. Don't think it did. But then again, I have a helluva time keeping up with you Otis... you excel in the technical compared to myself. If I had to choose right here and now, I'd go with your knowledge on the matter.
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The principle is simple. You preserve the aperture but you go wider. The original focal length cone ends up in a smaller region through the same physical aperture so you get get more light per film area or pixel.

In astronomy they are quite common. They are called focal reducers. 9x the light, 0.33x the focal length. There is not much loss in the lenses, they are simple designs.

Most good 0.8 adapters do not waste light. There is not much light gain in the 0.8x conversion, and the extra elements eat most of it. On 0.5x and 0.33x the light gain is much larger than the loss in the adapter.

High resolution reducers are very expensive and demanding in design. That's why there are not many for photography. A good 0.67x for 2/3" is about $500, a 0.5x could be $2000 (and I have heard of none!). Cheap ones work fine for low resolution and that's what they use in astronomy (they are $100 or so). Astronomy is not about resolution usually, it's about a huge pixel that can detect what is not visible by a small pixel.

They could make high end focal reducers but I doubt it would cost less than the actual wide lens:)

I never did any research in this field, I just repeat some things I have read on the subject. The early stage of the learning process. First you repeat, then you copy, then your understand, then you create, then you innovate:)
 
Ryan Patrick O'Hara said:
We are not sure what they were using the lens for exactly, do we?

F/stops are simply formulas, not true light transmission values. Since the Nasa lens was rated in an F/stop I assume it would simply be used to take pictures of space, on the moon and of other things simply for documentation, not to be scrutinized for scientific measurements of star distance and etc. The lens f/stop will be relatively accurate to about a 1/2 stop depending on how well it is made, perfectly acceptable for photography work.

I doubt that NASA lens was built to take scientific readings such as gauging star distance based on brightness. If it was, then they had it rated as an F-Stop but must have known the true T-stop or similar transmission value, and had that number somewhere else on paper. Also, the lens is a 50mm... 50mm is hardly something I would use to look at stars! Heck, I barely use it on narrative closeups. :) They would have used telescopes for that.



Never thought of that.... indeed it was probably 35mm photography format, not motion 35mm. Very interesting... That would eliminate any edge falloff of exposure, although at 50mm, it would not have been very much or as bad as a wider angle lens.
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Sure, I just meant that somewhere their is an accurate number for that lens as they would have calculated it before use or manufacture. So someone knows the answer.

Heres a good article: http://www.visual-memory.co.uk/sk/ac/len/page1.htm

"The Zeiss 50mm and 36.5mm, f/0.7 lenses used to film candlelight sequences for "Barry Lyndon" without the addition of artificial light were originally still-camera lenses developed for use by NASA in the Apollo Moon-landing program, and modified by Cinema Products Corp."

Good one here too: http://www.visual-memory.co.uk/sk/2001a/bl/page1.htm

""QUESTION: How many foot-candles (no pun intended) would you say you were using in that case?

ALCOTT: Roughly, three foot-candles was the key. We were forcing the whole picture one stop in development. Incidentally, I found a great advantage in using the Gossen Panalux electronic meter for these sequences, because it goes down to half foot-candle measurements. It's a very good meter for those extreme low-light situations. We were using 70-candle chandeliers, and most of the time I could also use either five-candle or three-candle table candelabra, as well. We actually went for a burnt-out effect, a very high key on the faces themselves.""

"ALCOTT: We used the 5254"

Here too: http://www.nemeng.com/leica/040b.shtml
 
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Jimmy Moss said:
ALCOTT:

"ALCOTT: We used the 5254"

Here too: http://www.nemeng.com/leica/040b.shtml
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That is a great link, I like at the bottom of the page where they discuss the, "...French documentary (aka "Dark Side of the Moon") which claims NASA only let Stanley Kubrick use the Zeiss lens because they owed him a favour for helping fake TV footage of the Apollo XI Moon Landing." Now that sounds like a "Must See"!. So Stanley Kubrick helped fake the moon landings..... Ok, I can see that! :2vrolijk_08:

I have 'Barry Lyndon" coming in from Netflix today, too bad it is only available on DVD. Blu-Ray would be cool. I really want to see another projected version of it though (that is not faded).

Great discussion.
 
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