Filmo 70DR Critical Focuser Alignment/Adjustment?

Alex Freeman · June 22

Hey everyone, I shoot with a Filmo 70DL that I absolutely love, and picked up a DR as a second body. Unfortunately, after buying it on eBay the shipper just wrapped the camera in bubble wrap and shipped it as a ball of packaging resulting in a some dented lens threads and a jammed film speed selector. I was able to fix the film speed selector by popping it back in place and now the camera (amazingly) runs just fine (testament to the durability of this thing). However, I noticed when checking out the camera that when I focus a lens through the critical focuser the distances on the lens barrel were reading a little short. As a test I focused the same lens on my DL critical focuser, and when I transfer the lens over to the DR, it is not in focus through the viewer. As a further confirmation, I placed a piece of scotch tape over the DR film gate. I used to focuser to get the lens image sharp, and when I spin the turret to the taking position, the image appeared blurry on the tape. This to me says that the focuser is the issue, at least until I can film test the camera or get it on a collimator to check the film plane focus. I'd like to adjust the focuser as I think it's probably the most useful part of the Filmo to me.

The only thing I can find about this mechanism says it must be adjusted by Bell and Howell technicians, does anyone here know what this adjustment entails? Internally, it looks like the focuser has a flathead screw slot, might this be the point of adjustment?

Simon Wyss · June 22

As you can see on this photo of an older model the critical focuser tube is held down by a buckle (correct expression?) under two screws. It may have been pounded inwards.

The axial groove nut or ring in the tube holds down a lens that enlarges the view. Be careful when trying to loosen it, most often lacquered in and made from brass.

Alex Freeman · June 22

Thank you Simon, I was hoping you would see this haha. Ok thank you for the photo (by the way I'd call it a "bracket" to refer to the part holding the focuser tube) Ok so, if the part got pounded inwards, would I need to move it all slightly outward? I'm guessing the tube houses a lens and ground glass that has now been pushed in. I'll have to take the front off of mine to get a better look at it, but do I need to loosen the bracket so I can move the entire tube?

Simon Wyss · June 23

The prism is polished. You have this little ground glass in a tube. With a lens of which you know it depicts infinity in focus you can adjust that tube during assembly. If things don’t want to come apart, put everything in a solvent to soften the lacquer. If have found that naphta or a light oil is taken up by the lacquer overnight, over two days. Then you attack with ethanol, acetone, petroleum, benzine.

Alex Freeman · June 23

Ok I got mine open. Thank you for the disassembly photo! Do you know if there is a way I can adjust infinity without full disassembly?

Studying your photos and looking at the one in front of me, if I understand correctly, the threaded piece with the large flathead screw, can screwing this is or out move the angled bracket that holds the prism? And therefore set the distance between the ground glass and the prism, which sets infinity focus to be the same as the film plane? I dont have a spanner small enough to remove the optics from the tube but am hoping the flathead can be the correct adjustment point?

Simon Wyss · June 24

The GG bushing has an outer thread, it goes deepest into the threaded tube. By threading it forth or back you set at flange focal distance equal.

The tube has an inner wall with hole. The prism is held against that wall by pressure from the slotted cap, an intermediary disc, and a rubber piece cut at angle 45 degrees.

The circular opening that lets fall light into the prism must be centered on the optical axis. So there is one correct position for the assembly which you should achieve first. Then you adjust the GG bushing and then the lenses to the eye.

Alex Freeman · June 24

Ok, thank you Simon! So the slotted cap is just pressure fitting the prism, doesn't matter if I adjust it or not. Looks like I need to find a way to unscrew the optic and to get to, and then adjust, the ground glass depth. But first I need to find a tiny tool that will let me unscrew the optic and adjust the ground glass position, my lens wrench wont go small enough unfortunately.

Alex Freeman · June 24

Well this is unfortunate.. looks like someone might have tried to get in here before me. There isnt much left of the slots to be able to unthread here, looks pretty beat up compared to the parts on my other Filmo

Simon Wyss · June 25

Pity. That’s what uninformed, uninterested wrestlers leave behind.

Decision whether to look for a replacement assembly or to take this to someone who can twist out the ring slowly with an endmill cutter or a fitting screwdriver. Chemical preparation as described is indicated. You have lacquer in the tube thread the whole length.

Alex Freeman · June 26

Dug a little deeper, decided to remove the focuser and try disassembling from the other end. Here's a photo showing what I got: The silver tube (you can just see the ground glass in there on the other side of the wall) then the prism, followed by whats left of the rubber/cork-like part that holds the prism in place (it broke apart as I pulled it out) then the brass disc, and then the slotted end cap. I'll try taking the tube to Duall camera and see if they have any small tools to be able to free up damaged outer optic holder. The optics and ground glass in this focuser are very clear, the image is a bit sharper than the one in my 70DL, so maybe if I can get them out i'll reuse the parts in the DL's focuser. I'll update the thread with progress but for now I'll probably pause it. I may try to take the 70DR's geared turret and viewfinder ring, and swap it over to my DL as the viewfinder auto rotating is a nice feature. I've also gotten pretty good at removing the front part of the Filmo having removed and reinstalled it a bunch at this point. Thank you Simon for all the help!