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Bolex Rx-4 w/ Nikon Lenses


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#1 Mark Heim

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Posted 11 November 2006 - 01:44 AM

Hello All... I recently bought a nikon - cmount adapter for my bolex camera. I have a set of Nikon AI-s Primes that I wanted to use with my bolex rx-4. My question is how would these lenses work with the reflex bolexs? Will I have any focus problems? Should I still use the rule for compensating fstop? (open 2/3 stop). Will I have any problems if I shoot wide open?

Also if I were to use another type of lens, say an angenieux cmount zoom, would I run into any problems there either?

Any thoughts would help.

Cheers
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#2 Leo Anthony Vale

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Posted 11 November 2006 - 02:22 PM

My question is how would these lenses work with the reflex bolexs? Will I have any focus problems? Should I still use the rule for compensating fstop? (open 2/3 stop). Will I have any problems if I shoot wide open?


The "rule for compensating fstop" is an urban legend. see the all too many threads in the archive.

Focus problems? Bolexes don't have the brightest finders.

The longer lenses should be no problem. The shorter lenses ought to be fine below f/2.8.
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#3 Mark Heim

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Posted 11 November 2006 - 03:04 PM

thank you for your response!

I thought because of the beamsplitting prism in the veiwfinder system you lose 20% of the light going to the film plane. I have searched through the archives and that's the conclusion I came up with. Am I wrong?
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#4 Patrick Cooper

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Posted 13 November 2006 - 11:57 PM

Reflex Bolexes use a beam splitter so naturally they would steal a little of the incoming light. All I know is that it is a very small amount - possibly 1/2 or 1/3 of a stop - but I'm not sure how much exactly. I have spoken with an expert on Bolexes and apparently there is a light meter that is designed to be used specifically with Bolex reflex models and even compensates for the light loss. I'm not sure of the name of this meter though.
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#5 Bernhard Zitz

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Posted 14 November 2006 - 10:21 AM

The longer lenses should be no problem. The shorter lenses ought to be fine below f/2.8.


so is it then f2.8 and not f4 like most peoble say? Has anyone here compared a 10mm RX with a 10mm or 9.5mm nonRX by shooting testcharts?


for correct metering be aware that beside the lightloss in the prism the rex4 has only 133 degrees shutter angle, shutterspeed at 24i/sec is 1/65sec

cheers, Bernhard
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#6 Leo Anthony Vale

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Posted 14 November 2006 - 03:51 PM

Reflex Bolexes use a beam splitter so naturally they would steal a little of the incoming light. All I know is that it is a very small amount - possibly 1/2 or 1/3 of a stop - but I'm not sure how much exactly. I have spoken with an expert on Bolexes and apparently there is a light meter that is designed to be used specifically with Bolex reflex models and even compensates for the light loss. I'm not sure of the name of this meter though.


Actual Bolex manuals state one should use a meter setting of 1/80th sec, 1/65 is the actual shutter speed but 1/80 allows for the light loss.

An independant Bolex manual claims Rx lens stops compensate for the light loss, but non-Rx lenses have to be opened up to allow for not having those "T stops". But that claim seems to be due to a misunderstanding of what Rx lenses are compensating for.

Using 1/80 sec on your meter will work with all lenses.
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#7 Glenn Brady

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Posted 14 November 2006 - 03:53 PM

The Bolex-Gossen meter is designed to slip into an accessory shoe on top of the H8/H16 RX camera. It's calibrated to compensate for the light loss in the Bolex reflex prism. These meters appear at eBay regularly and sell for about $50.00 to $75.00.
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#8 Mark Heim

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Posted 14 November 2006 - 04:35 PM

if i was using a more modern meter. Say a sekonic 558 cine... How many stops total do i need to compensate for? 2/3 for the prism right? a 1/3 for the shutter? and then make sure i close wide angle lenses down to at least 2.8? So we are looking at a full stop to make an accurate compensation? Am I doing the math right?
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#9 Glenn Brady

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Posted 14 November 2006 - 05:23 PM

With the variable shutter is in the fully open position, the 'adapted' exposure times for the H16 RX are 1/40 at 12f/s, 1/55 at 16f/s, 1/60 at 18f/s, 1/80 at 24f/s, 1/110 at 32f/s, 1/160 at 48f/s. and 1/220 at 64f/s. Single-frame exposure with speed control knob set between 18-64f/s is 1/40.

Edited by Glenn Brady, 14 November 2006 - 05:24 PM.

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