Practical opinions on the RX Lens

Post by **twotoneska** » Thu Dec 20, 2007 5:23 am

I've read a lot online about how you can't use regular C-mount lenses on a RX Bolex. I've also read that you can, so long as your stopped down below f4 (or, maybe above f4, I can't remember).

Anyways, does anyone here use regular C-mount lenses on RX cameras? and, if so, what are the problems that you face, if any?

Post by **sciolist** » Thu Dec 20, 2007 6:47 pm

See http://www.city-net.com/~fodder/bolex/truth.html for a full explanation of Bolex reflex camera optical specifications.

Post by **twotoneska** » Thu Dec 20, 2007 6:58 pm

I've seen that article, but it's really more technical information than I can process. What I'm really trying to do is find someone to give me there first hand experiences in plain english.

Post by **sciolist** » Thu Dec 20, 2007 7:07 pm

In the article cited, the author states the "RX RULE: STANDARD C-MOUNT LENSES WILL WORK WELL THROUGH THE BOLEX PRISM PROVIDED THAT THEY ARE STOPPED-DOWN PAST ABOUT F/3.2".

You didn't state whether your interest is in the H16 RX or H8 RX, but this rule applies only to the H16 RX, and the RX formulation is only an issue on an H16 RX with lenses shorter than 50mm. If you're using lenses longer than 50mm, any C-mount lens ought to work properly at all apertures.

Post by **twotoneska** » Thu Dec 20, 2007 11:52 pm

As I said before, I read the article. What I was looking for is someone to give some practical advice on the matter. Something like - "Yes, I've used regular C-mounts and I've had this or that problem", or "I haven't had any problems", or "I use regular C-mounts, but I make sure not to do whatever".

Telling someone that gravity causes things to fall to the ground doesn't mean that the person you said that too suddenly understands everything about gravity. I was looking for any PERSONAL problems or solutions that people have come up with in using the standard lenses on the RX mount camera, beyond just being stopped down below f3.2.

I'll try to be more clear next time.

Post by **Jean Poirier** » Fri Dec 21, 2007 6:25 am

My two cents. Working with a Bolex Rex modified for double super 8. The best results were with a 16 mm rx zoom lens. All my films with regular c mount lenses or 35 mm Olympus slr lenses with a c mount adapter were always slightly out of focus. I would try to to stick with rx lenses. Jean

Post by **sciolist** » Fri Dec 21, 2007 4:35 pm

twotoneska wrote:As I said before, I read the article.

What you said was "I've seen that article, but it's really more technical information than I can process." I imagined a reply in general terms might be helpful to you; I'm sorry you felt otherwise.

Post by **twotoneska** » Sat Dec 22, 2007 5:03 am

Jean, Thank you for the response. That was exactly the kind of first hand advice/experience I was looking for.

Sciolist, we're obviously arguing semantics at this point. I apologize for phrasing the question incorrectly. I'll try to do a better job next time.

Post by **ECNtoo** » Sat Dec 22, 2007 8:28 am

It is probably out of focus because the backfocus distance between the bolex H8 and regular c mount cameras by about 3.2mm. That will throw the focus out at infinity by a lot. This example can be seen in reverse by putting the H8 lenses on a Beaulieu. They will not focus properly. A spacer is needed.

Post by **morales72** » Sat Dec 22, 2007 11:54 am

My two cents. I had two DS8 converted Bolex H8, REX and REX-4. The first one came with a Som Berthiot P58/97 100mm 1:3,5 lens that didn't say anything about H8RX like the rest of lenses I have (Switars, Pan cinor zoom) and worked properly. I didn't sell it with the camera cause it wasn't precisely in mont condition. I had very few uses for it though. Hope this helps.

Cheers,

Morales.

Post by **sciolist** » Sat Dec 22, 2007 2:41 pm

Flange focus distances for the various Bolex H series cameras are: H8 non-reflex 12.29mm, H8 RX 15.305mm, H16 non-reflex 17.52mm, and H16 RX 20.76mm. If a lens designed for use on an H16 RX camera gave the best results on the DS8 conversion Jean mentions, then the converted camera was probably an H16 RX (Jaakko Kurhi converted an H16 RX4 to DS8 for me in the 1970s). Lenses can be recollimated for use with cameras for which they weren't originally designed. I have an AngÃƒÂ©nieux 8x8B lens typically fitted to Beaulieu 4008 ZM cameras that's been adjusted to work on my Bolex H8 RX4 DS8. I've also fitted Nikon 35mm SLR lenses to my H8 RX4 R8 and DS8 cameras using a Nikon F-C adapter and gotten extremely sharp images. Unless all of the variables affecting the performance of a given lens on a given camera are identified, information about performance seems to me to be anecdotal and of limited use.