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Bloex focus problem

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#1 bleakley mcdowell

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Posted 05 April 2017 - 07:12 PM

I have a Bolex Rex5 that I'm having a focus problem with. Consistent across several rolls of film the fist 15 frames of film waver in and out of focus before finally settling on a just-out-of-focus image which is holds for the remainder of the shot, almost just a soft focus. It is incredibly noticeable when text in in the image. Is this something one would see if the the pressure plate on the gate was not closed properly? I like to to think I didn't improperly close the pressure plate for several rolls of film, but I suppose anything is possible...


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#2 Dom Jaeger

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Posted 05 April 2017 - 10:18 PM

It does sound like the pressure plate wasn't all the way closed. If it was just a lens or viewfinder focussing error you wouldn't get that focus drifting in and out effect.

 

Has the camera worked OK before?


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#3 Simon Wyss

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Posted 06 April 2017 - 02:25 AM

The lid is so constructed that it can’t be closed and locked when the pressure plate is open.

How many H camera lids show marks from people trying to force it down in spite of the

resistance they sense! And it’s Bolex, not Bloex.


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#4 Jean-Louis Seguin

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Posted 06 April 2017 - 07:03 AM

Run the camera with some dummy film and observe the loop. Does it remain constant or gets smaller after a while?
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#5 Robert Hart

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Posted 13 April 2017 - 03:33 PM

This suggests there may be insufficient pressure from the pressure plate springs but you may be also getting a short loop. My sense is that there are two things happening. A short loop which is being tolerated by the camera may pull the film slightly off the focal plane. More commonly, you will get pulled or vertically smeared frames and noisy operation from this condition

The film's normal state as you have it running is slightly out of focus. Temporary ripples which normally form in the film when it is parked in the transport will lift a "soft" pressure plate as they pass through and change the focus momentarily. In your example, those ripples may be pulling the film into correct focus momentarily. This hints that your lens optical focal plane at infinity may be rearwards of the camera's mechanical focal plane. 

Momentary focal shift on startup is a near-to-normal condition with the CP16 cameras but I have not seen it on a Bolex H16 type.

Let's first assume you may just have a loading problem and your camera is otherwise normal.

Do you use the little chrome scissor-guillotine blade inside the bottom of the camera body to cut the required shape on the head of the film before you push it into the first guide when "autoloading"? ( H16RX5 ). On earlier H16 models, the "autoload" feature may not exist.

Do you "autoload" the film by running the camera continuously at normal shutter speed with the guides in the load position.  The better method is to turn the governor back to its slowest frame rate and progress the film through the loading guides in very short bursts. 

Once you have the film threaded through, there is a pin near the centre which is contacted by the door when it is closed. This normally retracts the guides as the door is replaced to the body but will not set the pressure plate in its correct position. It is highly likely that Tarzan has been at play with your camera at some point and forced the lid on and latched it.

If the inner panel has been warped or the little levers have been bent, it is possible that the door will fasten with no hint that something is not in its correct place. On the inside of the door are donkey traps, little holes into which knurled knobs on the loading guides and pressure plate fit when they are in their correct positions for running film.

If the door "rocks" when you are trying to close it, then it is being held high buy one of the knobs which is not in its correct position.

There are other reasons for the film being out of focus.

The position of the viewfinder groundglass focal plane may have moved out of correct position and may be causing you to incorrectly focus relative to the film focal plane. You need a camera tech to fix this.

If you are using a tape measure and witness marks on the lens barrel for focusing - and using a lens not correctly collimated to a Bolex with a reflex prism viewfinder, the focal will be off. Lenses specific to the reflex Bolex are slightly off-focus when used on a non-reflex Bolex and vice-versa.

To help others here with better skill than I drill down to some problems and solutions can you reply to the following questions.

Does it still have a viewfinder on the top of the body?

What type and brand of lenses do you have on your camera?

Does your camera have a three-lens turret on the front that you have to rotate to choose your lenses?

Do you have the little chrome thumbwheel and retainer on the left lower side of the three lens turret tightened to prevent the turret from falling forward and moving the taking lens out of focus.

With the lens directly in front of the viewfinder covered, can you still see through the top viewfinder?


That will do for starters.


Edited by Robert Hart, 13 April 2017 - 03:39 PM.

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#6 Simon Wyss

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Posted 14 April 2017 - 01:41 AM

On earlier H16 models, the "autoload" feature may not exist.

 

Automatic threading was part of Paillard-Bolex H cameras from the very first on.

 

The idea that a short upper loop may happen is a good one. Let’s wait for Bleakley’s reply.


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