Bronica EC mirror's bumpers

wakks · Jun 10, 2021

Hello from France,

My Bronica EC got problems with his mirror's bumpers :/ (picture link) i'll try to find solutions, 3D printed plans, spare parts, ideas etc. if anyone can help

https://flic.kr/p/2m4Df12

thanks !

reddesert · Jun 10, 2021

Here are some links related to this issue:
https://www.photrio.com/forum/threads/bronica-ec-possible-gummy-mirror-bumper-repair.117578/
http://35mm-compact.com/forum/viewtopic.php?f=13&t=53005&p=813010 (in French)

I had a similar issue and made a temporary fix by putting one wrap of electrical tape around the post and then a small rubber O-ring from an eyeglass repair kit over that. I haven't got around to doing anything more to it. The post on, I think, the viewer's left side of the mirror box sets the resting position of the mirror, so it affects the focus, and you have to test whatever bumper you use to assure correct focus. Your picture is of the post on the viewer's right side, which may be a shock absorber and not set the mirror position (but you should inspect the post on the viewer's left as well).

wakks · Jun 10, 2021

hey,
I know the 2 websites, but the first one finally said : "I checked the focus at infinity, and it was off, so in retrospect this didn't work. D'oh!"
For the 2d link administrators doesn't validate my subscription, so I can't speak to author

Both sides of my bronica's bumper are broken/wrong, i know that one of them isn't "useful", the link of the picture i've sent is the actual side who affects focus :

the "useless" side :

reddesert · Jun 10, 2021

I'm not near the camera at the moment so I can't check, but my memory is that the post on the side you're calling "useless" doesn't move and is the side that the mirror rests on, so you need to experiment with the size of the bumper (I used an o-ring) to get the focus correct. I think the post on the other side is spring loaded and moves under finger pressure - it's the shock absorber.

Basically your choices are to find an experienced camera repair person to fix it, or to experiment with it yourself until the focus is correct. The person in the earlier Photrio thread seems to have given up before figuring out whether it was the mirror or focusing screen that caused his problem.

wakks · Jun 10, 2021

hummm good, you point that I work on the wrong side since the beginning, thanks for that !
This guy had measured the side i called "useless" (which is finally the useful side ) 6mm for diameter :
https://www.flickr.com/photos/149070754@N07/albums/72157718508661519

wakks · Jun 10, 2021

oh i'm stupid i've checked the focusing screen and his metal frame, foam etc... but don't remember which side is up the bright or mate ?

reddesert · Jun 11, 2021

Nice pictures in that flickr link. The focusing screen goes matte side down (toward the lens).

The Bronica S2 and EC both have issues with foam involved in locating the mirror and focusing screen into place that can degrade and alter the position of the focus. But the issues are different - the S2 has foam under the mirror pressing it up into place, and I think foam on top of the focusing screen pressing it down into place. The EC is a little easier to deal with because it has a user-interchangeable focusing screen.

wakks · Jun 11, 2021

i follow the fix of the guys on flickr (6mm "spacer") but whatever the side of focusing screen i can't reach infinity :/ :

It's just a test, but the moral of the story : it doesn't works /.
1 : with "matte" side & matte center focus circle toward lens, i turn to infinity the focusing ring at maximum, and it's blurry :

2 : with the "shiny" side & "matte" center focus circle toward lens, i get infinity approx 8-9 meters, infinity is 1 or 2 meters earlier according to numbers on lens focusing ring

itsdoable · Jun 11, 2021

For reference, here are the mirror stops for the EC-TL.

Left side with the adjustable stop for the lower mirror.

Right side:

Any time theses are replaced, some adjustment would have to be made to the mirror stop or screen. Focus screen matte side down towards the mirror.

wakks · Jun 12, 2021

Thanks, but do you have measurements, diameter of the right ? size of left piece ? i guess/hope there is no difference (for this 2 pieces) from EC (mine) and EC-TL ?

so this side is top ?

and this one toward lens/down :

itsdoable · Jun 12, 2021

The rubber mirror bumper on the Right sdie looks similar, it's ~6mm like the Flickr site said, but you can't really measure accurately, and regardless, you need to adjust the focus when you replace these parts. The mirror position is set by the Right spring loaded stop for both mirrors (on the EC-TL).

The focus screen side on the EC-TL is obvious, probably because people had this issue?

The screen adjustments are the 4 slotted screw that the screen sits on:

wakks · Jun 12, 2021

For the moment that doesn't matter anymore, a test with tracing paper (instead of the film) on infinity showed me that the lens has problems, and i think i'm not able to fix that myself

with lens on infinity (according to my read on the lens ring) :

i reach a good/sharp focus between 3-5 meters (when i read lens ring) :

moto-uno · Jun 12, 2021

If that lens had previously been apart , it's quite possible it was reassembled with the helix ( the correct word ? ) threaded in from the
wrong start thread . Not that I've ever done that . Peter

itsdoable · Jun 12, 2021

Keep in mind, the helicoid and the lens are separate parts on the EC's (except for the longer telephotos). You'll have to figure out which one is out of spec (or has been incorrectly reassembled).

wakks · Jun 12, 2021

I know, but despite everything I don't think I can fix it myself

moto-uno · Jun 13, 2021

You know I said that a few years ago when I got a Kowa Super 66 . And a mere 123 hours later I actually had a completely functional camera .
If you have a few tools and a shocking amount of patience , you can take no small pleasure in your accomplishment . I had absolutely no
experience in this task . After all , what do you have to loose if it doesn't work now ? Peter

reddesert · Jun 18, 2021

Back in the same place as my EC, I measured my makeshift round mirror stop (photographer's right side), and it's roughly 8mm diameter but it's a little compressible. The focus scale distance, focus on the groundglass, and focus with a GG placed on the film rails all seem to be in agreement. It should be pretty clear how to get the GG in place. There is a metal frame on the upper side. The foam is on top of the GG pressing it down onto a hard stop, so the foam doesn't set the GG position, but if it rots the GG could become loose.

@itsdoable does that piece on photographer's left side really set the resting position of the mirrors? On mine it's covered in some crusty-looking foam. The lower mirror is a bit out of place, which is annoying but only an issue with certain lenses. It doesn't seem like the lower mirror should touch that stop?

@wakks what lens do you have? If you post pictures of the lens someone may be able to to tell if it's mis-assembled. Are you sure you're reading the correct distance scale? Most of the focus helicals have scales for 2 or 4 lenses, and the index mark for the distance is not at 12 o'clock but some place to the left, so I often have to double-check myself when trying to read a distance.

itsdoable · Jun 18, 2021

reddesert said:
@itsdoable does that piece on photographer's left side really set the resting position of the mirrors? On mine it's covered in some crusty-looking foam. The lower mirror is a bit out of place, which is annoying but only an issue with certain lenses. It doesn't seem like the lower mirror should touch that stop?

My pictures of the mirror stops are for the EC-TL (not the EC), and on this camera, the flat sets the main mirror, and the screw set the secondary mirror. The "EC" is obviously different. The rubber ring position is probably adjusted by removing the side panels.

wakks · Jun 27, 2021

@reddesert I've bought a new helical ring, now I've infinity focus with tracing paper placed on film place, but i don't have fixed the mirror's bumpers for now, can't find the "good" measurements etc.

moto-uno · Jun 27, 2021

Great to hear about the helical ring allowing infinity focus , now the other concern about bumpers is hopefully the last
problem to overcome . Peter

wakks · Jun 27, 2021

@moto-uno yes i hope someone's give the good measurements

wakks · Jul 27, 2021

i've tested many 3d printed pieces from 5m to 10mm on both sides without success, is there any tools/electronic ruler small enough to check mirror's 45° ?

choiliefan · Jul 27, 2021

A bevel protractor could probably be made to work, somehow.
Perhaps a 45 degree angle block, a straight edge laid across the lens mount and feeler gages or adjustable parallel between the two?
Must be other ways as well.

wakks · Jul 27, 2021

choiliefan said:
A bevel protractor could probably be made to work, somehow.
Perhaps a 45 degree angle block, a straight edge laid across the lens mount and feeler gages or adjustable parallel between the two?
Must be other ways as well.

Ok about the bevel protractor but for now i can't find a small one that can fit into the body of my EC

choiliefan · Jul 27, 2021

A local machine shop or well-tooled hobbyist could help you with this.
If you can square this away and start manufacturing, there are a lot of EC owners who need these bumpers.

Bronica EC mirror's bumpers

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