Jump to content

Bolex H16 REX , using other lenses


Derek Heeps

Recommended Posts

As per my other thread , I recently obtained an H16 REX with the Kern-Paillard 18-86mm F2.5 Vario-Switar zoom lens .

It seems a very nice lens and my main initial thought is that it may be a bit limited at the wide end ; obviously depending on what I’m going to shoot .

I know there are various C-mount adaptors to other systems , so my main interest would be to look for a Pentax K adaptor since I’ve been shooting Pentax since the mid seventies and have built up a reasonable selection of glass , although use with the Bolex would likely be only with my SMC-M lenses from the film era , sadly since my DA Limited lenses require electronic control of aperture from the camera body .

It also occurs to me that I have some ENG video lenses that might work ; in particular the Canon YJ12x6.5B4 which is a 6.5mm-78mm zoom ( with 2x multiplier ) hence quite a bit wider at the wide end and longer with the multiplier in.

I used this lens on my Sony DSR500WSP which had 3x 2/3” native 16:9 sensors ; I need to check , but I’m guessing a 2/3” sensor must be a similar size to a 16mm frame , so the image circle ought to cover the 16mm frame . This lens ( like most ENG lenses ) has manual focus , zoom and aperture rings .

The big question would be whether anyone makes C-mount to B4 adaptors ? I can always try IronGlass since they made me a 2/3” to 1/3” adaptor to allow me to use the lens on my JVC GY-HD251 which is a 1/3” camcorder.

There is also the question of weight of this lens , but it is not all that much longer or heavier than the Kern lens .

 

I will also need to consider how to expose correctly. I do still have my old Weston Master V light meter from days shooting still film and I recall it has scales for cine .

The question here is whether the indicated aperture on the lens ( for example a 35mm film lens set to , say , f5.6 , won’t actually be f5.6 on a 16mm frame ? ) I’m thinking that only using part of the circle there will be a ‘stopping down’ factor ? Again I’m pretty hazy on this , but if memory serves , each f stop represents half the light getting through , so if I compare the area of a 16mm frame to that of a 35mm one , that should give me the conversion factor ?

Same with the video lens , but if the two frame sizes are similar it might be negligible.

Last thought , I may have asked this over on my other thread , can’t recall , but the H16 REX has a gelatin filter holder which slots in between the lens and the shutter . It occurred to me that it would be quite easy to fashion a 16:9 crop mask to slot in there so as to shoot a 16:9 crop within the 16mm frame . Has anyone done this ?

While very easy to crop to 16:9 during telecine , it might be nice to be able to project at 16:9 straight off the film ? 

Link to comment
Share on other sites

  • Premium Member
33 minutes ago, Derek Heeps said:

The big question would be whether anyone makes C-mount to B4 adaptors ? I can always try IronGlass since they made me a 2/3” to 1/3” adaptor to allow me to use the lens on my JVC GY-HD251 which is a 1/3” camcorder.

There is also the question of weight of this lens , but it is not all that much longer or heavier than the Kern lens .

You can always use a B4 to EOS adapter first and then combine it with EOS to C-mount adapter. I have done that in the past with a pretty heavy Fujinon B4 zoom and Bolex RX. 

You will need support anyway if the lens is long enough even if it's not super heavy. I recommend making something out of those standard cheap 15mm rod parts you can find for dslr use. use riser blocks and simple adjustable lens support parts to get proper additional support for the lens

Link to comment
Share on other sites

  • Premium Member
9 minutes ago, aapo lettinen said:

You can always use a B4 to EOS adapter first and then combine it with EOS to C-mount adapter. I have done that in the past with a pretty heavy Fujinon B4 zoom and Bolex RX. 

You will need support anyway if the lens is long enough even if it's not super heavy. I recommend making something out of those standard cheap 15mm rod parts you can find for dslr use. use riser blocks and simple adjustable lens support parts to get proper additional support for the lens

found the photo of it!  the black adapter is the EOS to C-mount adapter and the one with red locking ring is the B4 to EOS adapter. You get an idea how to support the system as well

50692329551_2d9b7dfc61_h.jpg

  • Upvote 1
Link to comment
Share on other sites

Yep , that looks pretty good , and I already have 15mm rods for my matte box , so support would be easy enough .

I was also thinking the video lens would be easier to handhold since I could use the handgrip , and cobble up some sort of shoulder pad , maybe from an old video camera . 
 

So , your B4 lens covers the 16mm frame without vingetting ? 

Link to comment
Share on other sites

  • Premium Member
3 hours ago, Derek Heeps said:

The big question would be whether anyone makes C-mount to B4 adaptors ? 

Have you tried googling "C mount to B4 adapter"?

Looks to be a number of manufacturers making them.

Be aware that B4 lenses are specifically designed for 3 chip CCD cameras, which use a beam splitter behind the lens to separate colours. Good quality adapters contain compensating optics and are quite expensive. A purely mechanical adapter is much cheaper but the image may have excessive spherical aberration, especially at wide open apertures. The reflex prism in a Bolex may offset that to some extent though, since it's a similar issue as the 3 chip beam splitter. Lenses for reflex Bolexes were also designed specifically to compensate for the aberrations introduced by the prism (at least up to 50mm). Those lenses were made by Kern, Schneider, Som Berthiot and Angenieux and are generally labelled "RX".

 

3 hours ago, Derek Heeps said:

I know there are various C-mount adaptors to other systems , so my main interest would be to look for a Pentax K adaptor since I’ve been shooting Pentax since the mid seventies and have built up a reasonable selection of glass..

A quick google search for "Pentax K to C mount adapter" shows plenty of options.

In terms of specifically using these adapters on a reflex Bolex, just make sure the adapter C mount base is small enough to fit on the Bolex turret, as there is a maximum diameter before an adapter fouls on the turret handle and other bits.

As mentioned before, the Bolex reflex prism will introduce aberrations on normal lenses under 50mm at apertures wider than about f/3.5, but how noticeable the aberrations are is variable (it actually depends on the exit pupil depth of the individual lens). 

 

4 hours ago, Derek Heeps said:

The question here is whether the indicated aperture on the lens ( for example a 35mm film lens set to , say , f5.6 , won’t actually be f5.6 on a 16mm frame ? ) I’m thinking that only using part of the circle there will be a ‘stopping down’ factor ? Again I’m pretty hazy on this , but if memory serves , each f stop represents half the light getting through , so if I compare the area of a 16mm frame to that of a 35mm one , that should give me the conversion factor ?

F stops are the same no matter the format size. A 35mm lens set to f/5.6 will illuminate everything within its image circle just as brightly as a 16mm lens set to f/5.6. If you think about it, it makes sense since if you simply crop a 35mm lens image down to a 16mm size it doesn't get any more or less bright. The only time that changes is when you use something like a speed booster, which condenses the image, or a focal range extender, which expands it (and the stop increase or loss should be advertised). 

 

4 hours ago, Derek Heeps said:

Last thought , I may have asked this over on my other thread , can’t recall , but the H16 REX has a gelatin filter holder which slots in between the lens and the shutter . It occurred to me that it would be quite easy to fashion a 16:9 crop mask to slot in there so as to shoot a 16:9 crop within the 16mm frame . Has anyone done this ?

While very easy to crop to 16:9 during telecine , it might be nice to be able to project at 16:9 straight off the film ? 

For reversal projection you could also use a projector mask. But if you don't mind permanently cropping the image you could crop in camera. If you use the filter holder, it won't be a very sharp edged crop, as it sits quite a way out from the film plane, and it may vary depending on how angled the cone of light is coming out the back of a particular lens. But no harm in experimenting with it. 

In your other thread you mentioned not having an eyepiece for your reflex viewfinder. That's a pretty important part of  the camera, so you need to either find the missing eyepiece or replace it. Or use the second camera that was on offer. Later models had better viewfinders, so if the other camera is a later model I'd definitely use that unless the condition is significantly worse.

Link to comment
Share on other sites

Thanks for all the info .

I was only thinking of using the B4 lens and my K mount lenses because I have them already .

I did a search on eBay , which drew a blank , but yes I will google for them .

Re the eyepiece , I think I’ll need to find one elsewhere - the cameras lay in a cupboard for my 20 years there and were never touched ( I don’t think they were used after 1972 , that being the date of the last incident in our archive that was filmed on 16mm ) until our studio was recently cleared out to be converted into office space and the contents shifted into a store ( which we are losing ) by caretakers ( who didn’t seem to take much care ) , besides the other Bolex being nowhere near the one I got , of particular annoyance is that the pantographs and much of the rail system from our Bowens hi glide system appears to have been thrown in a skip ! 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...