Pentax 6x7

[flavio81]

Also, some frames were blurry due to camera shake. .

I told you! I told everybody here... for years...

Of all the 120 cameras I have used, this is the most difficult to load by a long way. The fresh spool has to be 'just right' for the 'dog' to engage with the cutout in the spool.

Yes, this is another problem with the P67, i hated to load rolls on it. While the same operation was very quick on the RB67. Not to mention the Mamiya C330, incredibly quick to load on a hurry.

I have this love-hate relationship with the P67, i still regret having sold mine, because once you nail a sharp shot, those Pentax lenses are supreme. And it really looks and feels like an extremely reliable machine, something you woulnd't mind carrying to the end of the world.

 

[abruzzi]

I haven't found loading too difficult, maybe a little more tricky than my Bronicas, but for a while getting the spools out was a royal PIA. Then someone told me the trick, and it hasn't been difficult since (don't try to pull the top of the spool out, insted, push the bottom of the spool down, which pivots to top out.) The hardest to load by leagues has been the Fuji GA645Zi.

 

[DREW WILEY]

Flavio - back to the shutter issue, about all I can say at this point is that just a few days ago I developed a roll in which exactly one frame out of a sequence (on all on tripod) was accidentally exposed without the mirror being locked up (around 1/8 sec exposures), and it is the ONLY frame exhibiting a bit of shake in the image. And that has been the case all through the years.

When it comes to loading a P67, well, there's nothing quite like pulling a glove off in near zero temperatures and fumbling around with a spool of film with stiff fingers. It's not the easiest camera to load. But I find it somewhat faster when the camera is mounted on a tripod and working with the camera in upright position rather than lying lens-down on a surface. Loading 120 films in my Fuji rangefinders is much much easier. But it's really not that big a problem. Spending another 30 seconds on a particularly klutzy day isn't the end of the world, photographically.

And speaking of the end of the world shooting application, and the need for equipment dependability in extreme conditions, what first attracted my attention to the P67 was Shirakawa's famous work in the Himalayas using this system, and that was back before the improved versions of the body and lenses we use.

 

[Neil Grant]

...the test films are drying and I can already see a potential problem. One film has blank frame half way through the roll. I don't think it was operator error and the lens doesn't have a cap. Can the shutter develop capping issues, or can a poor battery cause this? What about the shutter release? Do you have to be decisive with it like a C 330?

 

[flavio81]

...the test films are drying and I can already see a potential problem. One film has blank frame half way through the roll. I don't think it was operator error and the lens doesn't have a cap. Can the shutter develop capping issues, or can a poor battery cause this? What about the shutter release? Do you have to be decisive with it like a C 330?

The shutter release is as smooth as it can be. And no, you don't need to be "decisive" (i know what you mean -- if you press the shutter button almost fully on the C330 and then decide not to take the picture, the machine sometimes might think the film is already exposed.)

 

[flavio81]

Flavio - back to the shutter issue, about all I can say at this point is that just a few days ago I developed a roll in which exactly one frame out of a sequence (on all on tripod) was accidentally exposed without the mirror being locked up (around 1/8 sec exposures), and it is the ONLY frame exhibiting a bit of shake in the image. And that has been the case all through the years.

Hi Drew,

Revisiting this thread because I need to rectiffy myself. I confess: I was wrong and writing BS.

I since have bought back the Pentax 67 i sold. And i had much more time to evaluate the shake issues. I was wrong in saying the shutter was the culprit of shake. The shutter is remarkably gentle, at least on the curtain opening phase (i can't really give an opinion on the curtain closure because it is invariably followed by the mirror coming down). The culprit is the mirror.

It seems my P67 had a very serious shake problem because:

#1 - The foam around the pentaprism was completely degraded. Thus, the pentaprism had slack and became like a "pendulum" free to shake whenever the camera was shaken. Which of course would make any vibration a serious problem. I've since replaced the foam.

#2 - As mentioned by other forumers, technique has a lot to do. Yes, a left hand grip helps, but even more important is a RIGHT hand grip. I've since bought a 3D-printed right hand grip and it makes the camera far, far easier to hold. I've done some informal testing and I found that when I grip the camera at the left and right side of the body, and press the eyepiece against my forehead, mirror shock seems to be canceled out. Of course this would be even easier to do with the wooden handle.

#2.2 - If you grip the camera in the 'conventional' technique, that is, right hand grips the camera body, left hand cradles the lens, then bad news: this lets the mirror shake the camera.

So far i've seem to overcome the mirror shake issues, on the last rolls i've shot all blur i find seems to have been caused by subject movement only.

By the way, the mirror "up" force is provided by spring drive, and the force might be able to be adjusted. I've not dared to disassemble my P67 that far enough (to remove the sprocket that houses said spring). But if this is true, in theory it could be calibrated for minimum shock. The service manual doesn't mention any spring force adjustment, though. But it could be possible.

 

[markbau]

..the back is very difficult to open - there just seems to be remnants of sealing material left. Will the camera leak light in this condition? Maybe I should postpone the film test until I've redone the seals. The camera wasn't as noisy as I'd expected, nor did it seem to vibrate all that much.

I have two 67 bodies. One of them that I purchased new I dropped about a week after buying it. The back seemed shot but the light trap is so well designed that 25 years later it hasn't been repaired and is still perfectly light tight. Unlike the Blads and the Mamiya's the 67 is a tank. My 2 bodies have been through the wars and still perform flawlessly. Of course the lenses are legendary!

 

[markbau]

...the camera (6x7 MLU) is undergoing 'field tests' for focus accuracy. Initial tests showed light tightness, proper frame spacing and wafer thin dof with it's 105mm lens. Also, some frames were blurry due to camera shake. Of all the 120 cameras I have used, this is the most difficult to load by a long way. The fresh spool has to be 'just right' for the 'dog' to engage with the cutout in the spool.

I've loaded hundreds, maybe a 1000 rolls into Pentax 67's and I agree, I still have trouble getting the new roll to seat properly most times. I'm glad I'm not the only one to have trouble in this regard.

 

[DREW WILEY]

I agree that ease of loading film is not one of the P67's strong points. It's helps to have the camera in shooting position atop a tripod, shaded of course.

Old sticky light seals are fairly easy and inexpensive to clean up and replace yourself if you are patient. That's likely to be the most frequent problem with older bodies.

 

[itsdoable]

... By the way, the mirror "up" force is provided by spring drive, and the force might be able to be adjusted. I've not dared to disassemble my P67 that far enough (to remove the sprocket that houses said spring). But if this is true, in theory it could be calibrated for minimum shock. The service manual doesn't mention any spring force adjustment, though....

The mirror on the P67 is driven by a rotary cam, which approaches tangential when it reaches both end of the mirror travel - thus the cam naturally slows the mirror down before it reaches it's stop point at either end. There is also the foam absorbers that the mirror presses into when its up. However, the rotation of the cam has a bumper when it comes to a stop, that is probably a significant source of shock, especially with aged bumpers.


PS: I don't have the P67 now, but when I did (back when it was current and in production), I would sometimes shoot available light, hand held (without the grips) down to 1/30 sec with a pretty good hit rate. I was always surprised at that.

 

[flavio81]

The mirror on the P67 is driven by a rotary cam, which approaches tangential when it reaches both end of the mirror travel - thus the cam naturally slows the mirror down before it reaches it's stop point at either end. There is also the foam absorbers that the mirror presses into when its up. However, the rotation of the cam has a bumper when it comes to a stop, that is probably a significant source of shock, especially with aged bumpers.

Hi, i'm a camera tech here and I service P67 cameras too. Which bumper are you referring to in the bold part?

The only thing that resembles a bumper that i've seen for the cam rotation arm is the leaf spring that is beneath the mirror and that somehow should cushion the last degrees of rotation of the cam (when the mirror is almost up).

Perhaps there is another bumper i'm not aware of...

 

[flavio81]

Hi, i'm a camera tech here and I service P67 cameras too. Which bumper are you referring to in the bold part?

The only thing that resembles a bumper that i've seen for the cam rotation arm is the leaf spring that is beneath the mirror and that somehow should cushion the last degrees of rotation of the cam (when the mirror is almost up).

Perhaps there is another bumper i'm not aware of...

I just added a bumper on the swing arm, inspired by your comment @itsdoable

You can see it here, it's the small foam bumper on the pic.

I'm not sure if there should be one there, though.

 

[itsdoable]

Hi, i'm a camera tech here and I service P67 cameras too. Which bumper are you referring to in the bold part?

The only thing that resembles a bumper that i've seen for the cam rotation arm is the leaf spring that is beneath the mirror and that somehow should cushion the last degrees of rotation of the cam (when the mirror is almost up).

Perhaps there is another bumper i'm not aware of...

Flavio, you are probably right, it's been a 1/4 century since I worked on the P6x7 and P67's. I might be mixing it up with the Rollei SL35E, which uses a similar mechanism.

What stops the rotation of the mirror coupler cam after the electromagnet releases it? Just the metal stop inside the mirror box? A thin strip of black rubber would probably work well. There is a spring mirror brake for when the mirror returns.

I'm not sure the big foam block at the edge of the mirror is a good idea, it defeats the pneumatic damping that the mirror has when there is a continuous foam strip - although I suspect it does the same/similar job.

Oddly, the Pentacon Six uses a similar rotarty cam, but it's only used to return the mirror, raising it is a direct spring, along with the natural pneumatic air dapming and foam strips.

 

[flavio81]

Flavio, you are probably right, it's been a 1/4 century since I worked on the P6x7 and P67's. I might be mixing it up with the Rollei SL35E, which uses a similar mechanism.

What stops the rotation of the mirror coupler cam after the electromagnet releases it?

Most likely, some cam in the mechanism, not visible from within the mirror box.

Hey, thank you very much, the foam i've installed made a slight improvement in vibrations, it seems.

 

[flavio81]

Note: D135 is "mirror retaining plate", as is D136

On the "improved" version of the camera (see below), this part is "modified to an elastic type fitted with cushions":

Now, which is this "improved" version of the camera? From what I see, it's still the 6x7 non-MLU model. It's the very early improvements. Source:

Improvements:

This must be a very early improvement, since the "recovery button" is present also on the original 6x7 non-MLU model. Thus these cushions should have been present, at least, on most original 6x7 cameras.

Now, funny enough, my camera is a Pentax 67, the mirror has no retainers (D135,D136). Probably the mirror is glued on.

 

[mtjade2007]

Every time I fired the shutter of my p67-ii the camera would give a slight jolt that I could feel by my hands. That's really scary initially. But I have never had a blurred image (I shoot at 1/60 or above shutter speed). In fact all the images are very very sharp. It reminds me my military target practices when I was in military training. It was a M-1 riffle that I practiced shooting in target shooting ranch. Every time after pulling the trigger the riffle, the legendary M-1, would give a fairly violent jolt. But that never affect the bullet flying to the target.

 

[flavio81]

Every time I fired the shutter of my p67-ii the camera would give a slight jolt that I could feel by my hands. That's really scary initially. But I have never had a blurred image (I shoot at 1/60 or above shutter speed). In fact all the images are very very sharp. It reminds me my military target practices when I was in military training. It was a M-1 riffle that I practiced shooting in target shooting ranch. Every time after pulling the trigger the riffle, the legendary M-1, would give a fairly violent jolt. But that never affect the bullet flying to the target.

The P67II is a very much improved camera, but in any case...

There are two jolts, the one when the mirror comes up, and the other when the mirror comes down. The latter is stronger, but doesn't matter at all. The former is the one to be concerned with.

On the P67 (and all the P67 cameras i've tested so far - three), if you hold the camera with only your right hand, you can see it jolting on mirror up and mirror down movement.

If you hold the camera with both hands at both ends of the body, then you can cancel out the first jolt fully. At least in my experience. A right hand grip makes this easier to do. And then, shooting at lower than 1/60 speeds shouldn't be a problem. So far it seems to work.

 

[flavio81]

The key difference is that it is an electronic camera; on the P67, the common joke is the only electronic bit is the battery check button!

For some odd reason (a yearning for years gone by?) people are gravitating toward the older P67 and even more vintage Pentax 6x7 cameras. For those keen to shell out a fortune for a well-kept, unabused body, the rewards for working carefully and methodically will be thrilling.

The Pentax 67 and 6x7 (all models) are fully electronic cameras, no matter what people believe. I know exactly how the shutter works, it's an electronic shutter, as is the one in the P67II.

Remove the battery on a Pentax 6x7/67 and you won't ever be able to fire a shot, only raise the mirror halfway, nothing more.

The P67II isn't more popular simply because it's MUCH more expensive...

 

[flavio81]

Battery...??
I forgot there was a battery...
Such being the case I cannot remember when or if the battery was ever changed...

Well, that's great news, this means your camera is OK and has no problems with undue battery drain.

The camera only draws current when the mirror is up. So for brief exposures the energy consumption is very little.

 

[mtjade2007]

The P67II is a very much improved camera, but in any case...

There are two jolts, the one when the mirror comes up, and the other when the mirror comes down. The latter is stronger, but doesn't matter at all. The former is the one to be concerned with.

On the P67 (and all the P67 cameras i've tested so far - three), if you hold the camera with only your right hand, you can see it jolting on mirror up and mirror down movement.

If you hold the camera with both hands at both ends of the body, then you can cancel out the first jolt fully. At least in my experience. A right hand grip makes this easier to do. And then, shooting at lower than 1/60 speeds shouldn't be a problem. So far it seems to work.

Yes, there are two jolts and the 2nd one is stronger indeed. Just fire the shutter in B and they can be felt easily The word jolt is more an exaggerated statement. I have completely overcome the concern about it over time. Another way to exaggerate the camera jolt is to hit a tank (such as an M1A2 Abraham tank) with a sledge hammer. You will feel a loud and clear ban but other than that nothing happens.

 

[Neil Grant]

..I have the wooden grip now - but no time to use it. Still, it looks great.

 

[Matteo_Csepeli]

I almost bought a Pentax 6X7 some years back, but I could not see the full viewfinder due to my glasses. Do any other glasses-wearers have this problem or should I revisit this camera? Thanks in advance.

I had the same problem, it only takes some time to make practice... but you can actually look around and see the whole scene, also it's very easy to have focus spot on!

 

[Matteo_Csepeli]

A limited or restricted view will be what you get if there is no rubber eyecup in place on the viewfinder. These are plentifully available. Once fitted, press your glasses to the eyecup and all will be revealed.

A related problem though is a mismatch between the corrective power of eyeglasses versus the dioptric correction in place on the camera's viewfinder. A nearest-value corrective lens for the viewfinder eyepiece is as good as can be done (when and where you can find such corrective lenses!) unless you want to go through the more expensive custom corrective channels like Edmund Optical (edmundoptics.com); they can (but not always) manufacture specific and accurate dioptric

Thank you so much! I will research following your suggestions

 

[flavio81]

The grip has nothing to do with internal camera shake. It just makes it easier to hold in certain circumstances. The mirror slap itself can be a factor except at higher shutter speeds where the shutter curtain opens and closes before the mirror hits the top. That's why there's a mirror lockup feature on all but the oldest models. They knew what they were doing. Of course, mirror lockup requires a tripod too. But it completely solves the "shake" issue.

Hi Drew,

Years have passed and now I actually work (repair) those cameras. I discovered something very interesting...

Some Pentax 6x7 cameras (that ended on my hands) had much gentler mirror "slap".

Well, i've discovered that the mirror actuation force can actually be adjusted (!!). It is not easy to do, but it's doable nevertheless. I thus adjusted one 6x7 of mine for minimal mirror slap. It is remarkably gentle now.

The shutter vibration itself is extremely low (no matter what bs i've said before) and if it's not gentle then the shutter brakes would need adjustment, which would also manifest as other problems such as shutter bounce.

I will be working this year on creating a service document that thoroughly documents everything that the Pentax 6x7 service manual does not mention, and this will include mirror actuation force adjustment.

Finally, i did buy a wooden grip and it does cancel out much of the mirror slap. So, as you said Drew, Pentax "knew what they were doing". The huge wooden grip is a nice accessory, really.

cc: @itsdoable

 

[DREW WILEY]

Thanks for passing that information along. I always use the mirror lock-up feature anyway at speeds 1/60th and slower. Of course, adding more mass to the system, like a wooden grip, a big heavy telephoto, solid attachment to a wooden tripod below, etc, helps control any potential vibrations.