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Problems with bolex

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#1 Troy m

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Posted 24 February 2015 - 07:17 PM

Hello, I recently bought a bolex 16mm film camera. Runs well. However, everything in the viewfinder is very very dark, even with quite a bit of light and aperture fully open. Is there anyway to fix this?

Also, I got a 25mm to 100mm zoom lens for it. Almost impossible to focus because viewfinders so dark. Besides that, even when zoomed out all the way, things appear closer than they should. I have to stand at the other end of the room just to get a medium cu shot.

Any ideas? Thanks.
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#2 Simon Wyss

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Posted 25 February 2015 - 01:40 AM

Seems you have an H-8 with a lens for 16-mm. film on it.


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#3 Troy m

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Posted 25 February 2015 - 02:00 AM

Seems you have an H-8 with a lens for 16-mm. film on it.


It says h16 on the camera. What would you recommend doing?

I did run a roll of 16mm film, but have to get it processed and telecine do though.
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#4 Simon Wyss

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Posted 25 February 2015 - 06:09 AM

When you read H16 on a plate then the camera is a 1963-built or younger. It might be an H-16 Reflex. They have a filter slot and I presume you have an ND gel filter in there. An H-16 M has no filter slot.

 

A 25 through 100 mm zoom lens doesn’t give you a wide angle view. 25 mm is normal focal length. Perhaps you have a filter at the lens front. The viewfinder darkens when you close the iris. Brightness is not comparable to a mirror reflex system.

 

Please load up an image of the equipment. That way we can help much better and faster.


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#5 Mark Dunn

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Posted 25 February 2015 - 06:16 AM

If anything a 25 is a bit long on 16mm. It only has half the angle of view of the classic 50mm. normal lens on 35mm. still format.

You wouldn't want to go on set with nothing shorter than a 25


Edited by Mark Dunn, 25 February 2015 - 06:20 AM.

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#6 Troy m

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Posted 26 February 2015 - 01:05 AM

Here are two pics of my camera. I tried putting more but it kept saying the files too large.

 

Let me know if there are any certain "angles" of the camera that might be more helpful.

 

Also, what lens is considered normal and would work well with this bolex?

 

It says "H16 Reflex" on this camera.

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#7 aapo lettinen

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Posted 26 February 2015 - 01:30 AM

that looks like H16RX0, exactly the same model I have. 

Your viewfinder shutter seems to be on (the small silver lever on the viewfinder assembly just over the frame counter) , have you tried to move it back and forth? the shooting position is the lever down, facing backwards. 

It this does not help you should check the prism assembly: rotate the turret so that the prism is exposed. remove the filter frame and then carefully flip the prism to the side (be careful because the prism frame is spring loaded and can hit the side of the turret with force) 

 

please take a picture of the prism assembly when turned on the side so we can see the ground glass on the top of the prism.

you can also try to see through the viewfinder when the prism is on place but the take-up lens is removed and see if the image is now any brighter


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#8 aapo lettinen

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Posted 26 February 2015 - 01:33 AM

there seems to be holding screws on place on the other c-ports of the turret, so you have to remove them first before you can rotate the turret, maybe it's best to remove the lens also.

 

your rubber eyecup seems to be missing btw, you should get one for preventing light leaks through the viewfinder


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#9 aapo lettinen

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Posted 26 February 2015 - 01:46 AM

the kern 18-86 is a very basic zoom lens for this camera, quite ok lens but little soft and heavy and has square bokeh and a bit too much CA.

the kern primes are very good with the bolex, if you don't specifically need zoom lens i'd recommend getting at least two primes, at least the 25/1.4RX and something from 10 to 16mm range.

If you plan to shoot a lot of fiction with it, it might be better to get some lenses which are easier to use with follow focus, for example Nikon AI-S lenses with c-mount adapter   :)


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#10 aapo lettinen

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Posted 26 February 2015 - 05:56 AM

the viewfinder optics: 

h16reflex_2.jpg

(image from http://www.bolexcoll.../h16reflex.html  )

 

There isn't much which could be causing the perceived low brightness other than the possible filter, something wrong with the ground glass or something in the light path which dims the image, maybe dust or other stuff on the optical parts. Bolex viewfinders are quite dim in general though (about 20% of the light going to viewfinder compared to nearly 100% of a standby mirror reflex camera)


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#11 Dennis Couzin

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Posted 26 February 2015 - 10:48 AM

If you plan to shoot a lot of fiction with it, it might be better to get some lenses which are easier to use with follow focus, for example Nikon AI-S lenses with c-mount adapter 

 

Take care when choosing non-RX lenses for the Bolex RX camera.  Bolex disseminated a rule-of-thumb: lenses up to 50 mm should be RX; lenses longer than 50 mm need not be RX.  The rule-of-thumb was FALSE.  I first challenged it in 1976-78, and returned to the matter (with more optics under my belt) in 1987.  Others have confirmed my findings, most recently this by Dom Jaeger.

 

Unfortunately, as Bolexes become collectors' items, the original Bolex literature becomes holy text. 

 

When buying old RX lenses, beware that either the focus mount grease chosen by Kern, or some lubrication around the iris, tends over time to transfer to the two lens surfaces facing the iris.  Cleaning those two surfaces requires minimal disassembly of the lens. 

 

Concerning the dim viewfinder, the diagram of the optics shows internal reflections off three 45° prism faces.  Those purposely uncoated faces must be scrupulously clean to avoid reflection failure.  Many years outgassing of the camera's paint and lubricants might cloud them.  


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#12 Robert Hart

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Posted 16 April 2017 - 11:58 AM

The splitter optic, from memory, takes away about 1.5 stops but I could be wrong. It has been a long time. The groundglass itself will take another 1.5 stops of brightness from your eye view. So darkness in the viewfinder image is its normal state. The lenses specifically for use with the RX camera have apparently been re-marked so that the aperture settings are "as if" there is no splitter brightness penalty for a given light meter reading. The lenses are also collimated to this specific camera type and will be off if used on another non-reflex type. They will focus but the witness marks on the barrel of the lens will be wrong. 

If using lenses not specially calibrated for the RX camera, you then need to add another 1 to 1.5 stops of exposure to your light meter's recommended aperture setting and focus with the groundglass viewfinder, not the witness marks which will be wrong. A common practice in this circumstance was to set the light meter "as if" the ISO of the film was 1 to 1.5 stops slower and then use it normally without having to remember to count back stops on the aperture setting. It was too easy to muck up and go 1.5 stops the wrong direction in haste and end up three stops wrong.

A necessary normal practice when using these cameras is to open your lens aperture wide for both viewfinder brightness and the shallowest depth-of field which pretty much guarantees a sharp focus at a tighter aperture. You set focus, then reset your aperture to correct exposure, then frame as best you can with the groundglass finder or revert to the much easier parallax side-finder which should be in your kit and attached to the left-side door. Forgetting to reset the aperture after a focus trim is the common trap which will bite you.

There is an adjustment knob on the parallax finder to adjust the correct offset for distance from subject. 


Edited by Robert Hart, 16 April 2017 - 12:05 PM.

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#13 Dom Jaeger

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Posted 16 April 2017 - 04:57 PM

So many threads like this where the original poster never returns to say whether the problem was solved. I wonder if it was just the viewfinder closing lever being in the closed position like Aapo said?

Robert, the Bolex prism only diverts about a third of a stop of light to the viewfinder.
Regarding Rx lenses, about which there is much confusion: they aren't collimated differently, they are computed to negate the optical aberrations introduced by the prism, mainly spherical aberration. So it's part of their optical design, you can't adjust their back-focus to make them normal again.
The f/stop markings refer to the lens only, like all other lenses. There is no correction for the prism light loss in Rx lenses.
Sorry for the corrections, just trying to keep some of these common misconceptions from confusing newcomers to the Bolex.
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#14 Robert Hart

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Posted 17 April 2017 - 01:07 AM

Dom. Thank you indeed for the correction and my apologies to other readers for misinforming you. Age does not necessarily weary us but the brains sometimes addle.

The light loss "seemed" to be the case with my specimen back in 1980s and I think now I have confused my recollections with also using the tungsten balanced reversal film I was supplied with for the news work and having to use a colour correction filter for which exposure had to be adjusted.

My camera may have some of the light-stealing characters induced by surface contamination of the splitter optics described in an earlier post. I certainly did not then nor have since opened it up to check. I should dig it out of storage and have a look.

Advice which was given to me at the time was that the lenses for RX had been adjusted so that the focus and aperture marks behaved as if there was no light loss. This was word-of-mouth and not a document so it is a fair bet I was misinformed way back then.

Groundglass textures are a curious thing. They do steal light but apparently not in a linear fashion related to the lens aperture setting.


Edited by Robert Hart, 17 April 2017 - 01:10 AM.

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#15 Simon Wyss

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Posted 18 April 2017 - 01:15 AM

Beware of speaking about light loss with C-mount lenses for Paillard-Bolex H Reflex. The scale rings bear marks that stand for the f/something relation, a purely arithmetic thing. F is focal length, 25 mm for example. F/4 says 25 mm against a quarter of that length as iris aperture diameter, 6,25 mm. It says nothing about the true light transmission of the lens. T stops do. With an H-16 Reflex or an H-8 Reflex you deal with abstract values until you want to expose really exactly. That would call for one developer formula, available repeatedly, constant processing parameters, you know, pH, freshness of the bath, temperature, agitation, time, constant lighting of one test chart, iris always closed in the same direction to eliminate backlash, measurements of the light in a rigid setup, densitometry of the processed strips. It is possible to install a measuring cell behind the camera aperture for checking light transmission but then you still must compare the photo cell’s spectral sensitivity to the film.

 

You should even take a lens’ state into consideration because it can have a thin film of grease on the glass surfaces or something. The reflex double prism of these cameras must be impeccably clean. It is not so easy to clean optical elements. In case of doubt give object in question to a trained specialist. I have replaced damaged prisms with H-16 Reflex cameras, adjusted and collimated them. I do lens repair.

 

What concerns the ground glass, which actually isn’t a distinct element but the surface of the upper prism etched, you mention an important point. The matt surface must also be clean and that is a technician’s job again. Do keep in mind that Paillard made an amateur product that cannot be compared to professional gear. You can pimp your PB up, though. I have just given a total overhaul to a Bell & Howell Filmo 8 Aristocrat plus some D-mount lenses. The matt surface of the focusing element, a plano-convex lens, needed chemical washing. Now it’s bright again. No professional uses instruments that sat around for 30 years without having them refreshed thoroughly.


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