Bolex H16 Rex prism

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The_kodak_kid
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Bolex H16 Rex prism

Post by The_kodak_kid » Mon Apr 16, 2018 1:13 pm

I touched the prism. How bad is this??

Pj
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Re: Bolex H16 Rex prism

Post by Pj » Mon Apr 16, 2018 5:54 pm

I have done this many times, when cleaning, to clean off any smudges that I've made I use acetone liquid.
Pav

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Re: Bolex H16 Rex prism

Post by The_kodak_kid » Thu Apr 26, 2018 11:11 am

Pj wrote:
Mon Apr 16, 2018 5:54 pm
I have done this many times, when cleaning, to clean off any smudges that I've made I use acetone liquid.
Pav
Thank you for letting me know. I read an article online that keep repeating “don’t touch the prism” I actually lost sleep over it hahah :-ss

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Re: Bolex H16 Rex prism

Post by doug » Thu Apr 26, 2018 11:18 am

I've got an H16RX with age marks on the prism's surface. I did think of getting it changed as the camera is first class otherwise, but after thorough testing I found there was really no difference in the filmed results. I'd think any lens cleaner should work fine on yours, so sleep well !
Doug
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Re: Bolex H16 Rex prism

Post by slashmaster » Sat May 12, 2018 8:39 pm

A lens cleaning kit will take care of this problem and is something you should have for any camera or projector. By the way, a none reflex camera almost always gives a better image and it would probably be relatively easy to convert one of these to one.

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Re: Bolex H16 Rex prism

Post by doug » Sun May 13, 2018 11:16 am

slashmaster wrote:
Sat May 12, 2018 8:39 pm
A lens cleaning kit will take care of this problem and is something you should have for any camera or projector. By the way, a none reflex camera almost always gives a better image and it would probably be relatively easy to convert one of these to one.
Good grief. Is that so ? I always thought the prism doesn't interfere with the picture quality, excepting the 1/3 stop light-loss.
Doug
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Re: Bolex H16 Rex prism

Post by slashmaster » Sun May 13, 2018 7:33 pm

doug wrote:
Sun May 13, 2018 11:16 am
slashmaster wrote:
Sat May 12, 2018 8:39 pm
A lens cleaning kit will take care of this problem and is something you should have for any camera or projector. By the way, a none reflex camera almost always gives a better image and it would probably be relatively easy to convert one of these to one.
Good grief. Is that so ? I always thought the prism doesn't interfere with the picture quality, excepting the 1/3 stop light-loss.
Oh yes. Any piece of dust on the front of the prism or back of it hurts the image. Any flaw that was in the prism from the factory hurts the image, light that comes from where you look into the viewfinder hurts the image. I won't use 16mm cameras or reg 8 cameras that have a prism just because of this. Super 8 cameras that don't have the prism are more difficult to find so still find myself using ones with prisms.

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Re: Bolex H16 Rex prism

Post by The_kodak_kid » Wed May 16, 2018 12:32 pm

slashmaster wrote:
Sat May 12, 2018 8:39 pm
A lens cleaning kit will take care of this problem and is something you should have for any camera or projector. By the way, a none reflex camera almost always gives a better image and it would probably be relatively easy to convert one of these to one.
I do have a box of Brillianize, that’s alcohol and ammonia free, you think that would be safe?

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Re: Bolex H16 Rex prism

Post by The_kodak_kid » Wed May 16, 2018 12:34 pm

slashmaster wrote:
Sat May 12, 2018 8:39 pm
A lens cleaning kit will take care of this problem and is something you should have for any camera or projector. By the way, a none reflex camera almost always gives a better image and it would probably be relatively easy to convert one of these to one.
Convert it by removing the prism? You think it’d be that easy, doc?

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Re: Bolex H16 Rex prism

Post by Phil_F_NM » Wed May 16, 2018 6:51 pm

Why would one want to remove the prism of an H16 reflex? This would change the lens registration to 20.76mm and nothing would focus properly. Also, if I recall correctly, depending upon the age of the reflex camera, you would have no benefits of having a Bolex. No reflex viewing and no variable shutter which could easily be had in a non-reflex model. So removing the prism turns the Bolex into a non-focusing Filmo.
It just seems crazy to take a reflex camera and turn it into a non-reflex camera then have to move the lens turret back in order to get the flange to focal plane correct. Like doing dental work but going in to fill a tooth through an entirely different body cavity.
Please, correct me if I'm wrong but these are indeed issues that would arise if the prism were removed.
Phil Forrest


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Re: Bolex H16 Rex prism

Post by slashmaster » Thu May 17, 2018 8:33 am

Phil_F_NM wrote:
Wed May 16, 2018 6:51 pm
Why would one want to remove the prism of an H16 reflex? This would change the lens registration to 20.76mm and nothing would focus properly. Also, if I recall correctly, depending upon the age of the reflex camera, you would have no benefits of having a Bolex. No reflex viewing and no variable shutter which could easily be had in a non-reflex model. So removing the prism turns the Bolex into a non-focusing Filmo.
It just seems crazy to take a reflex camera and turn it into a non-reflex camera then have to move the lens turret back in order to get the flange to focal plane correct. Like doing dental work but going in to fill a tooth through an entirely different body cavity.
Please, correct me if I'm wrong but these are indeed issues that would arise if the prism were removed.
Phil Forrest
You couldn't just remove the prism, You'd have to have a thinner front cover to bring the lenses closer to the film of course. Otherwise it would be way out of focus. But the whole front nose of a non reflex looks like it would fit a reflex.

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Re: Bolex H16 Rex prism

Post by slashmaster » Thu May 17, 2018 8:37 am

The_kodak_kid wrote:
Wed May 16, 2018 12:32 pm
slashmaster wrote:
Sat May 12, 2018 8:39 pm
A lens cleaning kit will take care of this problem and is something you should have for any camera or projector. By the way, a none reflex camera almost always gives a better image and it would probably be relatively easy to convert one of these to one.
I do have a box of Brillianize, that’s alcohol and ammonia free, you think that would be safe?
What are you going to use for wipes? Gotta use proper lens tissue. You can find that in a lens cleaning kit.

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Re: Bolex H16 Rex prism

Post by slashmaster » Thu May 17, 2018 8:42 am

slashmaster wrote:
Thu May 17, 2018 8:33 am
Phil_F_NM wrote:
Wed May 16, 2018 6:51 pm
Why would one want to remove the prism of an H16 reflex? This would change the lens registration to 20.76mm and nothing would focus properly. Also, if I recall correctly, depending upon the age of the reflex camera, you would have no benefits of having a Bolex. No reflex viewing and no variable shutter which could easily be had in a non-reflex model. So removing the prism turns the Bolex into a non-focusing Filmo.
It just seems crazy to take a reflex camera and turn it into a non-reflex camera then have to move the lens turret back in order to get the flange to focal plane correct. Like doing dental work but going in to fill a tooth through an entirely different body cavity.
Please, correct me if I'm wrong but these are indeed issues that would arise if the prism were removed.
Phil Forrest
You couldn't just remove the prism, You'd have to have a thinner front cover to bring the lenses closer to the film of course. Otherwise it would be way out of focus. But the whole front nose of a non reflex looks like it would fit a reflex. I've shot films with both reflex and non reflex cameras and always enjoy the results of a non reflex WAY better. The only exception is maybe filming closeups of tiny seahorses in macro mode. Would be very difficult to get the focus right on that.

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Re: Bolex H16 Rex prism

Post by doug » Thu May 17, 2018 12:05 pm

slashmaster wrote:
Thu May 17, 2018 8:42 am


You couldn't just remove the prism, You'd have to have a thinner front cover to bring the lenses closer to the film of course. Otherwise it would be way out of focus. But the whole front nose of a non reflex looks like it would fit a reflex. I've shot films with both reflex and non reflex cameras and always enjoy the results of a non reflex WAY better. The only exception is maybe filming closeups of tiny seahorses in macro mode. Would be very difficult to get the focus right on that.
I can't really see that prism Bolex's would show inferior definition to non-prism Bolex's. After all, when they first designed the H16RX they surely would have carried out exhaustive tests for comparison. It wouldn't have made sense for Bolex to launch a camera with inferior lens performance, particularly as it was aimed at professionals and semi-professionals. If there was a difference in image quality, Bolex would have surely gone for the mirrors-on-shutter idea. The prism is a piece of high grade optical glass which they must have been confident with.
That said, the non-reflex cameras offer better choice for high quality lenses. Also easier to convert to S16 and U16.
Doug
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Re: Bolex H16 Rex prism

Post by Phil_F_NM » Thu May 17, 2018 1:59 pm

doug wrote:
slashmaster wrote:
Thu May 17, 2018 8:42 am


You couldn't just remove the prism, You'd have to have a thinner front cover to bring the lenses closer to the film of course. Otherwise it would be way out of focus. But the whole front nose of a non reflex looks like it would fit a reflex. I've shot films with both reflex and non reflex cameras and always enjoy the results of a non reflex WAY better. The only exception is maybe filming closeups of tiny seahorses in macro mode. Would be very difficult to get the focus right on that.
I can't really see that prism Bolex's would show inferior definition to non-prism Bolex's. After all, when they first designed the H16RX they surely would have carried out exhaustive tests for comparison. It wouldn't have made sense for Bolex to launch a camera with inferior lens performance, particularly as it was aimed at professionals and semi-professionals. If there was a difference in image quality, Bolex would have surely gone for the mirrors-on-shutter idea. The prism is a piece of high grade optical glass which they must have been confident with.
That said, the non-reflex cameras offer better choice for high quality lenses. Also easier to convert to S16 and U16.
The quality of images through reflex Bolex cameras is certainly outstanding but as far as optical design and physics are concerned, putting anything in the optical path will reduce definition. That reduced quality would probably be on a near microscopic level using a camera with a brand new prism and precisely collimated lenses matched to the camera. The prism itself adds two air-glass surfaces which will increase the propensity for flare and reduced contrast. If a beamsplitter is involved there's another surface that will suffer from aging Canada balsam cement.
All that said, the presence of the prism is probably not significant with regard to image quality in comparison to proper adjustment of the camera, collimation of lenses, etc. Those things would affect image quality much more I think than the presence of a precision optical focusing aid.

Phil Forrest

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