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RX and non RX lenses


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#1 Brandon Rubesh

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Posted 01 April 2007 - 03:01 PM

Hello, I hav a bolex REX 4 and was looking on ebay for some cheap but reasonable options for lenses when I came across a set of angeniuex lenses that claim to be "non RX" lenses. What kind of difference does this actually make? If the gate and ground glass is the same on RX and non RX bolex cameras then it should be fine right?

Any information appreciated.
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#2 Nick Mulder

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Posted 01 April 2007 - 03:06 PM

If the gate and ground glass is the same on RX and non RX bolex cameras then it should be fine right?
Any information appreciated.

Yup, they would be fine, except they aint the same (how the GG works that is) - in fact that is specifically what determines the difference between an RX and a parallax Bolex...

Do a search here - its another topic that has been beaten to death in at least 5 previous threads :)

Edited by Nick Mulder, 01 April 2007 - 03:08 PM.

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#3 boy yniguez

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Posted 16 April 2007 - 07:10 AM

Hello, I hav a bolex REX 4 and was looking on ebay for some cheap but reasonable options for lenses when I came across a set of angeniuex lenses that claim to be "non RX" lenses. What kind of difference does this actually make? If the gate and ground glass is the same on RX and non RX bolex cameras then it should be fine right?

Any information appreciated.

RX pertains to the reflex viewing achieved via pellicle or prism which diverts some of the light to the eyepiece and the rest to the film gate (sorry i don't remember the percentages). RX lenses would mean therefore that the f-stops were calibrated to give a corresponding correct exposure to the film such that an f4 setting on the lens delivers an f4 amount of light to the film yet still allowing some light to go to your eyepiece.
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#4 Leo Anthony Vale

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Posted 16 April 2007 - 03:00 PM

RX pertains to the reflex viewing achieved via pellicle or prism which diverts some of the light to the eyepiece and the rest to the film gate (sorry i don't remember the percentages). RX lenses would mean therefore that the f-stops were calibrated to give a corresponding correct exposure to the film such that an f4 setting on the lens delivers an f4 amount of light to the film yet still allowing some light to go to your eyepiece.


Not that old canard again!!!
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#5 Nick Mulder

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Posted 16 April 2007 - 03:05 PM

RX pertains to the reflex viewing achieved via pellicle or prism which diverts some of the light to the eyepiece and the rest to the film gate (sorry i don't remember the percentages). RX lenses would mean therefore that the f-stops were calibrated to give a corresponding correct exposure to the film such that an f4 setting on the lens delivers an f4 amount of light to the film yet still allowing some light to go to your eyepiece.


No,

This may sound logical - but it is not the reality, RX lens f-stops are f-stops - not re-calibrated pseudo-T-stops (B-stops ?? :rolleyes:)...

The RX refers to the collimation of the lens itself so that the 'widening' of the rays by the prism is corrected to focus on the film plane (and ground glass) - the prism takes %17 of the light and Bolex countered this by offering its own light meter which was indeed re-calibrated, you see them on eBay every now and again...

Without the light meter you have to multiply your exposure time (in seconds) by 0.83 to get the effective speed that you would put in your standard meter...

If you are working in the 'fps' mode of thinking then multiply this by 1.2 to get the effective speed

1/1.2 = 0.83 100 - 17 = 83 see what I mean ?

In both methods you will also need to account for the adj shutter afterwards...

There is a lot of slightly underexposed bolex footage out there.
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#6 boy yniguez

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Posted 24 April 2007 - 04:22 PM

No,

This may sound logical - but it is not the reality, RX lens f-stops are f-stops - not re-calibrated pseudo-T-stops (B-stops ?? :rolleyes:)...

The RX refers to the collimation of the lens itself so that the 'widening' of the rays by the prism is corrected to focus on the film plane (and ground glass) - the prism takes %17 of the light and Bolex countered this by offering its own light meter which was indeed re-calibrated, you see them on eBay every now and again...

Without the light meter you have to multiply your exposure time (in seconds) by 0.83 to get the effective speed that you would put in your standard meter...

If you are working in the 'fps' mode of thinking then multiply this by 1.2 to get the effective speed

1/1.2 = 0.83 100 - 17 = 83 see what I mean ?

In both methods you will also need to account for the adj shutter afterwards...


i stand corrected! thank you!
for more info check out http://www.city-net....olex/truth.html.

boy y
There is a lot of slightly underexposed bolex footage out there.


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#7 Bryan Darling

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Posted 24 April 2007 - 08:29 PM

Schneider made some great RX lenses for the Bolex. Do a search for Schneider RX on ebay. They made a full set of primes starting at 10mm and going into a 150mm I believe. I have their 10, 16, 25, & 75. It's great glass and the prices are wonderful because most people only want the Switar primes.
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