SLR Medium format cameras with an instant-return mirror

[itsdoable]

Not at all. The definition in the given wiki link is quite correct. When your thumb (or the built-in motor) is required to reset the mirror then this cannot be considered an instant-return mirror any longer.

The Camerapedia definition does not specify that the motor or spring is required to return the mirror, just that the end of the shutter cycle triggers the mirror return, which is what happens on all the motor driven cameras (except maybe the Hasselblad EL's, which requires you to release the shutter button to trigger the mirror return).

 

[itsdoable]

...My own viewpoint is that an instant return mirror is one of the least useful features to be found on SLR cameras...
...but I would be interested to know what other people think about this issue.

I prefer to leave my camera shutters untesioned/unwound. I have a thing about keeping spring loaded things tensioned unnecessarily. Plus some of these old cameras do not have a shutter button lock.

The other thing that I like is to be able to change the lens when the camera is uncocked for the same reason above. The only cameras where this is an issue is Hasselblad V's.

But that does not stop me from using Hasselblads, or Pentacon-6's etc... It's just a preference.

 

[Sirius Glass]

I prefer to leave my camera shutters untesioned/unwound. I have a thing about keeping spring loaded things tensioned unnecessarily. Plus some of these old cameras do not have a shutter button lock.

The other thing that I like is to be able to change the lens when the camera is uncocked for the same reason above. The only cameras where this is an issue is Hasselblad V's.

But that does not stop me from using Hasselblads, or Pentacon-6's etc... It's just a preference.

However Hasselblads were specifically designed to be stored with the shutters cocked. The lens springs are supposed to be tensioned.

 

[itsdoable]

However Hasselblads were specifically designed to be stored with the shutters cocked. The lens springs are supposed to be tensioned.

I realize Hasselblad advertised that, but that was out of design necessity - and they made sure the springs were of high enough quality to last a long time. But that doesn't change the fact that an untesnioned Compur main spring lasted longer than a tensioned one. And they did upgrade their main springs on the CFi lenses to make them last even longer. It's just my old school/engineering background that makes me store my cameras and lenses untensioned when possible.

 

[68degrees]

Here we go again with the nasty fake news spread by RF people who are just plain jealous of SLR owners. Get over it and buy an slr.

sounds more like a TLR than a RF. Non moving mirror, leaf shutter, bright and sharp viewfinder. ... IDK

 

[Brett Rogers]

Is there a list of such MF cameras?

Hasselblad driving by electric motors

This is not the instant-return mirror feature I'm asking about.

A lot of helpful people have tried to assist. Perhaps you might put yourself out enough to elaborate on exactly what you are asking about, and why. Less aggravating for everybody that way.

 

[Brett Rogers]

I realize Hasselblad advertised that, but that was out of design necessity - and they made sure the springs were of high enough quality to last a long time. But that doesn't change the fact that an untesnioned Compur main spring lasted longer than a tensioned one. And they did upgrade their main springs on the CFi lenses to make them last even longer. It's just my old school/engineering background that makes me store my cameras and lenses untensioned when possible.

Sorry, I missed that fact. You must have cited a reference, study, metallurgical paper, etc. Didn't see it. I did see you express an opinion (above). I'm not saying you are necessarily wrong. Simply that your opinion doesn't meet my own understanding of what the word "fact" means. It is an interesting topic. If you can provide some solid reference about cocked v uncocked I'd be grateful.
Cheers
Brett

 

[Ben Hutcherson]

This was mentioned already but not added to the list-

The Bronica EC and EC-TL have that weird split mirror that is instant return by any definition you use.

I'll also add that I know there's disagreement as to whether a motor driven body like a 500EL/M is truly "instant return" but I know that mine seems to black out for an eternity relative to the focal plane MF SLRs I've used-of the list compiled so far I've used the Bronica S2a, EC-TL, and Pentax 645. I run my EL/M off a single 9V battery, and while it's certainly a lot faster than a hand-cranked Hasselblad(I still use the latter a lot more than I do the motor driven body), it's not a speed demon in any respect.

 

[mshchem]

Here we go again with the nasty fake news spread by RF people who are just plain jealous of SLR owners. Get over it and buy an slr.

So, I ponder why. of every camera I've ever used, my Hasselblads have the most convenient easy to use mirror pre-release button? I agree with you. But at least with a 'blad it's easy to take the mirror out of the equation.
I have a winder for my 503cw, I don't really like how it looks on the camera, but it comes in handy now and then.
P.S. if you want mirror lock up watch out for the "Si" Bronicas the last versions, ETRSi and SQAI have plastic levers for the mirror lock and multiple exposure. Twice I've had the plastic levers break. Design flaw in a molded plastic part. I ordered a scrap body for parts.
I have sold all but one SQ-Ai, I've kept it for the wide 24x54 35mm back. I have 2 Hasselblad bodies 501cm and the 503cw. No electronic stuff. CLA every few years and they last forever.

 

[baachitraka]

Pentacon six - CLA with mirror pre-release.

 

[Sirius Glass]

I realize Hasselblad advertised that, but that was out of design necessity - and they made sure the springs were of high enough quality to last a long time. But that doesn't change the fact that an untesnioned Compur main spring lasted longer than a tensioned one. And they did upgrade their main springs on the CFi lenses to make them last even longer. It's just my old school/engineering background that makes me store my cameras and lenses untensioned when possible.

Not only are the advertised to be stored cocked, they were designed to be stored cocked. I would rather trust knowledgeable people than take advise based on what someone had for breakfast.

 

[Sirius Glass]

A lot of helpful people have tried to assist. Perhaps you might put yourself out enough to elaborate on exactly what you are asking about, and why. Less aggravating for everybody that way.

+1

 

[itsdoable]

Sorry, I missed that fact. You must have cited a reference, study, metallurgical paper, etc. Didn't see it. I did see you express an opinion (above). I'm not saying you are necessarily wrong. Simply that your opinion doesn't meet my own understanding of what the word "fact" means. It is an interesting topic. If you can provide some solid reference about cocked v uncocked I'd be grateful.
Cheers
Brett

Not only are the advertised to be stored cocked, they were designed to be stored cocked. I would rather trust knowledgeable people than take advise based on what someone had for breakfast.

I figured that I'd get some grief form that statement after I posted it. It's getting off topic, but it's been 3 page, and we've already wandered off topic on mirror per-release... but I'll try to be brief.

I am not going to provide any reference documents because I no longer have them, it was back in the paper days. You can do your own research.

From an engineering stand point, tensioned springs are under higher stress than untensioned. The Compur and Prontor springs are 4 turns, and they get tension over 270 deg. That is significant, and the strain is beyond the fatigue limit, which is why they eventually fail. Standard engineering practice is to leave springs untensioned, which makes them last longer.

Hasselblad and Zeiss introduce the upgraded Nivarox main spring to increase the lifetime on their CFi lenses. In an interview article (back then), they talked about the change, and the "engineer" mentioned that untenstioned springs last longer (which is standard engineering knowledge on springs that exceed the fatigue limit).

But as I said before, that does not mean you should keep your Hasselblad equipment untensioned. The product's "designed life time before service" was calculated in a tensioned state, which is why they used a quality spring. As Sirius said, they were "designed to be stored cocked". However, the product is likely to last longer than the "designed life before service" if you take some simple engineering care when stored. Some of that equipment is 50 year out, likely beyond the design life.

I will give an analogy - aluminium has no fatigue limit - Zero! That means it will break if you cycle it under stress enough times. So how do all those aluminium stress structures survive? (Planes, bikes, car suspensions, etc...). The product is designed to survive X number of load cycles, which exceeds the number you expect for the life of the equipment. In other words, it lasts your/its lifetime. The Prontor main springs are designed to last X number of cycles - I don't have the # of cycles because Zeiss did not publish that (at least not when I looked, but its just like the shutter cycles quoted on SLRs, which are partly based on the calculated lifetime of their main spring). Strain (tension on the spring) and load cycles are well understood in materials engineering, so I prefer to store all my precision spring loaded equipment untensioned. That does not mean you have to. Because Hasselblad's design and quality (and service) on their V series was so good that a lot of the equipment is still functional.

PS: I had french toast for breakfast...

 

[alanrockwood]

I figured that I'd get some grief form that statement after I posted it. It's getting off topic, but it's been 3 page, and we've already wandered off topic on mirror per-release... but I'll try to be brief.

I am not going to provide any reference documents because I no longer have them, it was back in the paper days. You can do your own research.

From an engineering stand point, tensioned springs are under higher stress than untensioned. The Compur and Prontor springs are 4 turns, and they get tension over 270 deg. That is significant, and the strain is beyond the fatigue limit, which is why they eventually fail. Standard engineering practice is to leave springs untensioned, which makes them last longer.

Hasselblad and Zeiss introduce the upgraded Nivarox main spring to increase the lifetime on their CFi lenses. In an interview article (back then), they talked about the change, and the "engineer" mentioned that untenstioned springs last longer (which is standard engineering knowledge on springs that exceed the fatigue limit).

But as I said before, that does not mean you should keep your Hasselblad equipment untensioned. The product's "designed life time before service" was calculated in a tensioned state, which is why they used a quality spring. As Sirius said, they were "designed to be stored cocked". However, the product is likely to last longer than the "designed life before service" if you take some simple engineering care when stored. Some of that equipment is 50 year out, likely beyond the design life.

I will give an analogy - aluminium has no fatigue limit - Zero! That means it will break if you cycle it under stress enough times. So how do all those aluminium stress structures survive? (Planes, bikes, car suspensions, etc...). The product is designed to survive X number of load cycles, which exceeds the number you expect for the life of the equipment. In other words, it lasts your/its lifetime. The Prontor main springs are designed to last X number of cycles - I don't have the # of cycles because Zeiss did not publish that (at least not when I looked, but its just like the shutter cycles quoted on SLRs, which are partly based on the calculated lifetime of their main spring). Strain (tension on the spring) and load cycles are well understood in materials engineering, so I prefer to store all my precision spring loaded equipment untensioned. That does not mean you have to. Because Hasselblad's design and quality (and service) on their V series was so good that a lot of the equipment is still functional.

PS: I had french toast for breakfast...

A naive question about limits: Is there a relationship between fatigue limit and elastic limit for a material?

 

[miha]

@itsdoable, thanks. Most interesting!

 

[lxdude]

P.S. if you want mirror lock up watch out for the "Si" Bronicas the last versions, ETRSi and SQAI have plastic levers for the mirror lock and multiple exposure. Twice I've had the plastic levers break. Design flaw in a molded plastic part. I ordered a scrap body for parts.

The metal levers on the earlier ETR series cameras fit perfectly on the ETRSi in place of those accursed plastic levers.

 

[lantau]

I haven't seen the inside of my Rolleiflex SLX cameras but from the sound of operation the winding motor is working independently, driving only the film.

As such the mirror is instant return but entirely independent. Perhaps powered in one direction by an electric actuator and the other by spring. It is supposed to have a pneumatic brake when going up. So to me it would make sense to have it returned electrically and opened by spring with a pneumatic dampener.

The leaf shutter and aperture are driven by linear motors, one each. There is no mechanical coupling from body to lens.

 

[choiliefan]

My Rollei 6006 suffered an electrical problem which caused the mirror to rise and fall rapidly.
It reminded me of a wind-up chattering teeth toy. Had the camera been lighter, it would have chattered its way off the edge of the table.
Marflex fixed the problem by replacing the main board so I'm thinking, as you said, the mirror is electrically activated.
The SLX and 6006 are similar cameras.

 

[mshchem]

The metal levers on the earlier ETR series cameras fit perfectly on the ETRSi in place of those accursed plastic levers.

That's good to know, I have a SQA as is body on it's way I'm going to fix my last SQAi body .

 

[GLS]

Is it so important to have an instant return mirror in medium format anyway? You're never going to be machine gunning with them...

 

[Sirius Glass]

Is it so important to have an instant return mirror in medium format anyway? You're never going to be machine gunning with them...

I have never felt the lack of an instant return mirror has been a problem. It would be nice to have but not at the increased weight of an electric motor drive. I would rather use the weight to carry more lenses with me. I never had a problem with the lack of the gliding mirror system on my Hasselblad 503 CX when I use the 250mm lens, 500mm lens or the 500mm lens with the 2XE.

 

[Dennis-B]

Not only are the advertised to be stored cocked, they were designed to be stored cocked. I would rather trust knowledgeable people than take advise based on what someone had for breakfast.

Having been a photographer, and a pistol shooter for more than 50 years, I've seen a lot of fiction put out about springs in cameras and pistols.

Frankly, it makes no difference if a spring is stored wound, or unwound. The stress is created by the action of coiling/uncoiling. I've used 1911 magazines that have been stored full of ammunition for over 20 years, and they've never failed to function. The same is true for mainsprings, etc.

On cameras, I've found them at garage sales with the shutter cocked, where the owners have said the camera hasn't been touched in ten years, etc. These have been a variety of SLR's, TLR's, and even some old folders. What's been the culprit has mostly been dried lubricant, not the springs.

 

[abruzzi]

Is it so important to have an instant return mirror in medium format anyway? You're never going to be machine gunning with them...

That reminds me of this video with a Pentax 67:



I doubt most of us shoot this way, but...

 

[lxdude]

The metal levers on the earlier ETR series cameras fit perfectly on the ETRSi in place of those accursed plastic levers.

I should add that the metal levers are not directional, so they can be used used in place of both the mirror lockup lever or the multiple exposure lever.

 

[GLS]

I doubt most of us shoot this way, but...

Yeah, and I doubt more than 1/3rd of those were properly in focus