Hasselblad leaf shutter problem

[archphoto]

Measuring it should not be a great problem: just take-out the retardment and measure I gues.....
(measuring opening and closing times)

 

[Anscojohn]

Measuring it should not be a great problem: just take-out the retardment and measure I gues.....
(measuring opening and closing times)

*******
Or a density test. If exposure were strictly linear, the density of a grey card should be one zone different at 1/250 f/16 compared to 1/500 f/16, assuming a perfect-running shutter, of course.

 

[Philippe-Georges]

Philippe,

If you let them set the fastest speed of your H-lenses to 1/350, you're more than 1 full stop off.

Between 1/250 and a little more than 1/400 — close to 1/500 —, 1/350 is more a 1/2 than a full stop.
But in reality, it is a bit faster than 1/350, the mechanism is actually made to go faster and after a while it is fastening op a tiny little bit and is stabilising then. Do not ask me why, "...and frankly my dear I do not give a damn...", but this is what the technician told me and I trust hem because he's good in it.
BTW, he is the one who advised me to set the speed slower for about 1/2 a stop, ilm is flexibel enough ...
Better to be sure about 1/350 than to doubt about 1/500, and I hardly shoot that fast.
When high speed is needed, take (rent, borrow) a focal plane shutter camera, that is why it is made for.

Philippe

 

[Ed Sukach]

Well... considering the mass of the shutter blade elements, and the spring power available to overcome that mass ...

I've GOT to avoid falling into a trap here: trying to argue without one shred of objective data. Myself, I'd be more confident in the Hasselblad/ Prontor/ Compur/ Engeering organizations.

One question: If you tech IS able to "set" your 1/500th shutter speed to 1/350th ... why would you not have him/her set it to 1/500th?

 

[Ed Sukach]

...
When high speed is needed, take (rent, borrow) a focal plane shutter camera, that is why it is made for.

Depends on the specific "need".

Full flash synchronization at ALL shutter speeds is more important to me in studio work.
Yeh ... I KNOW about the "long duration" flash units. Pitifully weak at any given point on the "swept" film.

 

[Philippe-Georges]

Well... considering the mass of the shutter blade elements, and the spring power available to overcome that mass ...

I've GOT to avoid falling into a trap here: trying to argue without one shred of objective data. Myself, I'd be more confident in the Hasselblad/ Prontor/ Compur/ Engeering organizations.

One question: If you tech IS able to "set" your 1/500th shutter speed to 1/350th ... why would you not have him/her set it to 1/500th?

Well actually no, the genuine 1/500 is not possible, in real life situations at least, in ideal situations (laboratorium?) this is not a problem (what else?).
To be sure, I called this technician (retired Hasselblad-factory trained and a friend) and he states that the real maximum speed for a well used Synchro-Compur, and after a CLA, is somewhere between 1/400 and 1/425 (on his shutter tester).
He can not guarantee that this speed might deviate and will lower to perhaps less than 1/400, particularly in the cold and after a long period of rest or intense use. That's why he prefers 1/350, this is stressing the shutter mechanism a lot less and deviates to a much lesser degree. Consistency is somewhat reassuring.
He told me that the Prontors are less prone to that kind of problem.
BTW, shutter speed in general is not always the same, fire a (Compur-) shutter set at the extreme speeds (1 sec. ore 1/500 sec.) a dozen times, the timing will never be the same, in the middle (1/30, 1/60, 1/125), there it will be more consistent.

But, who really cares about 1/500, 1/400 or 1/350 of a second, life is...

Philippe

 

[BrianShaw]

I've GOT to avoid falling into a trap here: trying to argue without one shred of objective data. Myself, I'd be more confident in the Hasselblad/ Prontor/ Compur/ Engeering organizations.

Leaf shutter efficiency data seems to be hard to find. I agree, though, that confidence in the compur/Prontor/etc shutter engineers is a good posture to take. For most practical purposes we're talking nits, after all.

Here is something that purports to be data-like:

http://books.google.com/books?id=e5...&hl=en&sa=X&oi=book_result&resnum=3&ct=result

 

[Q.G.]

Between 1/250 and a little more than 1/400 — close to 1/500 —, 1/350 is more a 1/2 than a full stop. [...]

The native fastest speed of the Hasselblad "H-lenses" is 1/800.
1/350 is 1.2 stops slower...

But i know.
You were talking about Compurs and Prontors in V-system lenses, with "H" not standing for "H-System", but for "Hasselblad".

 

[Jon Shiu]

There is some info on effective shutter speed in the Calumet Shutter Tester instructions. See page 6-7:
http://www.kenleegallery.com/html/shuttertester/manual.html

Jon

 

[Anscojohn]

You all, it seems to me, are missing the basic point. It is not a problem of "poor" design by those snow-bound Swedes: rather, it is basic geometry. nor is it a problem of shutter efficiency overcoming inertia, etc. Ahthough those factors do obtain.
I know the Hasselblad engineers are geniuses. But they cannot alter the basic aspects of the geometry of plane surfaces. Let's look at it this way: the "problem" is inherent--ineluctably inherent--in the incontrovertible fact that the leaf shutter---a hole---is uncovering another "hole":--the aperture. It does not take a rocket engineer to understand this simple concept. In the original Hasselblad shutter, the aperture "hole" was swept by a moving curtain; not by another "hole." I am sure that Victor's boys and girls at the design desks were more than willing to make the trade off of that exposure "problem" at small apertures and fast shutter speeds with leaf shutters in order to get rid of the cranky focal plane shutters of the original 1600 and 1000 fs.
I know it must gall some perfectionists to know that for all the $$$$ they spent on "Blads and Rolleiflexes, this phenomenon must obtain. We poor peasants who shoot focal plane shutter 6x6s can merely be smug. Or, if we happen to be using a Yashica, an Autocord, my Dad's Argoflex, or even a Rolleicord, we have the same "problem" only for much less outlay of cash. Ngh, ngh! (vbg)

 

[BrianShaw]

John, you need to study up on "shutter efficiency." It has nothing to do with overcoming inertia. It has to do with a hole uncovering another hole, as you say. Suggest you look at the google book link I posted earlier (you need to back up to the "previous page" for the discussion of leaf shutters), or even better read Ansel Adams "The Camera" in which he describes shutter efficiency.

Shutter efficiency and the resulting "relative exposure" resulting from the phenomenon has been an issue since the development of the first leaf shutter. It has nothing to do with "ego" of Hassy, Rollei or even Yashika owners and users. I hope your tongue was in your cheek when you typed that.

p.s. it will also help if you start believing that shutter timing does NOT start when the shutter is fully open.

 

[Q.G.]

Indeed. Brian is absolutely right in all he wrote.

Another thing is that, though it may appear to be, it is not a big practical problem.
That is not to say that it is not a real phenomenon. It certainly is.
But also really not that big a deal.

The deviation of the actual speed from what it should be is small.
We know when it happens, so can adjust for it.
And it is not that often that you are shooting the fastest speed at small enough apertures for this to be a problem to begin with.

And when you consider that leaf shutters have been in use for many years, in many different cameras/lenses, and are still being sold and used new, it really cannot be that big a problem. Else we wouldn't have put up with it for so long, nor still put up with it today, would we?

 

[Anscojohn]

John, you need to study up on "shutter efficiency." It has nothing to do with overcoming inertia. It has to do with a hole uncovering another hole, as you say. Suggest you look at the google book link I posted earlier (you need to back up to the "previous page" for the discussion of leaf shutters), or even better read Ansel Adams "The Camera" in which he describes shutter efficiency.
*****
This thread began with problems with a cold-crank Compur shutter and has gotten muddled. My attempt in my last post was to attempt to point out that it is basic geometry which is the bete noir is this, such as it is. And although I am a poor benighted former history major with no scientific training, common sense (and least my own, I think) tells me that if there is a given amount of inertial "drag" of an opening shutter, and that self-same shutter is opening with the same geometry as the aperture, then the smaller the aperture, the greater the percentage of effect (however slight) the smaller the aperture being "uncovered." I would suggest to anyone wishing to try this out, that they would find that the exposure of a leaf shutter given at, say an actual shutter speed of 1/500 sec at f/22, will not be precisely linear with the exposure given by the same shutter at an actual shutter speed of 1/250 at f/22.
Now we all know that, for various reasons, many shutters at the higher speeds are not dead on accurate--which is, I think, what Phillippe is talking about. But that is a different issue, is it not?

Shutter efficiency and the resulting "relative exposure" resulting from the phenomenon has been an issue since the development of the first leaf shutter.
****
Yup

It has nothing to do with "ego" of Hassy, Rollei or even Yashika owners and users. I hope your tongue was in your cheek when you typed that.
******
I reckoned that the Ngh, Ngh, and the vbg (very big grin) might have been a giveaway on that point. "Course, you are probably just chagrined that you do not have an Argoflex!!! (VBG)

p.s. it will also help if you start believing that shutter timing does NOT start when the shutter is fully open.

*******
I wonder how that crept in?

 

[Anscojohn]

Indeed. Brian is absolutely right in all he wrote.

Another thing is that, though it may appear to be, it is not a big practical problem.
******
Thank heaven for the latitude of modern films.
That is not to say that it is not a real phenomenon. It certainly is.
But also really not that big a deal.
*****
Quite correct.

The deviation of the actual speed from what it should be is small.
We know when it happens, so can adjust for it.
*****
Yup. And, obviously, spending a coupla thousand bucks for a camera system that requires us to make those kinds of adjustments under those conditions is no big deal, either.

And it is not that often that you are shooting the fastest speed at small enough apertures for this to be a problem to begin with.
*****
Very true. I still have AGFA APX 25 in the freezer, so this is not a big deal with this dinosaur.

And when you consider that leaf shutters have been in use for many years, in many different cameras/lenses, and are still being sold and used new, it really cannot be that big a problem. Else we wouldn't have put up with it for so long, nor still put up with it today, would we?
******
It would be great if someone could give us some numbers.

 

[mikebarger]

OK, who has measured the difference on a negative? I'm guessing no one.

I'll try to remember to shoot two frames at the same EV and different apertures and measure the negs with a Xrite 810 next time I have the Hassy out. Measuring negatives might have saved about 15 posts in this thread.



Mike

 

[Anscojohn]

OK, who has measured the difference on a negative? I'm guessing no one.

****
Yup.

I'll try to remember to shoot two frames at the same EV and different apertures and measure the negs with a Xrite 810 next time I have the Hassy out. Measuring negatives might have saved about 15 posts in this thread.



Mike

*****
Sounds good, Mike. Should I do the same with my Argoflex...... Oops, should it not be same aperture, and 1/250 and 1/500? I know that is a different EV, but with a perfectly timed shutter, the density should be one full stop difference. If it is not, the more we shall know about the "problem." Or not?

 

[mikebarger]

Ohhh. I thought it was large aperture / small aperture would give a different result for the same EV.

EV reading of 12; 500 @ 5.6 and 60 @ 16 w/Tri-x should have the same density on the negative. I thought the comment was because of the difference in opening size there would be up to a stop difference in the negatives.

Did I mis read it?

Mike

 

[Q.G.]

It is both.
There would be a difference between f/22 at 1/500 and f/8 at 1/60.
But, the efficiency being better at slower speeds, you should also try to see the difference between, say, f/22 at 1/500 and f/22 at 1/250 or f/22 at 1/125.

Which is why it is hard to test: the latter test would require being able to control the amount of light precisely, such that different EVs lead to the same exposure.

I test my shutters now and again, on transparancy film (i stull have a stash, which i do not use for anything else - no need for transparencies these days), shooting all speeds at constant EV (actually, i need to shoot two series - one for the slower speeds, one for the faster speeds - with some overlap).

I never noticed a considerable difference. Just noticeable, about 1/2 stop maximum, at most. And that only between all other (fast) speeds and 1/500.


You should run a similar test for your focal plane shutters too, by the way.
Odds are on that the fastest speed isn't quite what it should be.
Not because of a similar efficiency problem, but because the faster the speed, the more the inevitable error margin (in setting up and adjusting the thing) shows itself.

 

[Philippe-Georges]

It is both.
There would be a difference between f/22 at 1/500 and f/8 at 1/60.
But, the efficiency being better at slower speeds, you should also try to see the difference between, say, f/22 at 1/500 and f/22 at 1/250 or f/22 at 1/125.

Which is why it is hard to test: the latter test would require being able to control the amount of light precisely, such that different EVs lead to the same exposure.

I test my shutters now and again, on transparancy film (i stull have a stash, which i do not use for anything else - no need for transparencies these days), shooting all speeds at constant EV (actually, i need to shoot two series - one for the slower speeds, one for the faster speeds - with some overlap).

I never noticed a considerable difference. Just noticeable, about 1/2 stop maximum, at most. And that only between all other (fast) speeds and 1/500.


You should run a similar test for your focal plane shutters too, by the way.
Odds are on that the fastest speed isn't quite what it should be.
Not because of a similar efficiency problem, but because the faster the speed, the more the inevitable error margin (in setting up and adjusting the thing) shows itself.

Many, many years ago, I stopped testing shutters (of any kind).
I do not want to spend anymore time, energy and film, I had more than my share of it.
Now, I trust the guy who's servicing my gear at regular times. When he say's that 1/350 is better, so be it, and I learn to live whit it.
After 28 years of hauling a Hasselblad around (still the same one), it has become like a part of myself, an extension of my hands/eyes (and my poor back). Sometimes, I just feel and hear what's going on inside that damn thing and, unconsciously, I anticipate. This is how it works for me, and I am happy whit it, why should I not? After all, a Hasselblad is just a tool, no more no less, but yet a very good one.

Remember, the use of a hat as a shutter was common practice among our predecessors, and their pictures where wonderful. Now, we 'need' a quarts controlled high speed shutter to satisfy or sighs, but are we making better pictures? Just different ones and that is good to.
And as film is still so flexible (and King's Pyrocat-HD is doing a good job), there is no reason for insomnia...

But, if you want to test, please do go ahead and tell us what you found!

Be happy,

Philippe

 

[Claire Senft]

Lets not get carried away with nostalgia Mr. Leica of the 5 iteration of M. Some of those old time exposures would have been better having been kept under the hat and in some cases it would have been a good idea to save the film and protect the head from sunburn.

 

[Anscojohn]

It is both.
There would be a difference between f/22 at 1/500 and f/8 at 1/60.
But, the efficiency being better at slower speeds, you should also try to see the difference between, say, f/22 at 1/500 and f/22 at 1/250 or f/22 at most. And that only between all other (fast) speeds and 1/500.
******
Envision, for the moment, a shutter that is perfectly timed at 1/250 and 1/500.The point the old timers made was that---with a leaf shutter--- there would be no detectable difference in density between 1/250 at f/22 and 1/500 at f/22--even though we all KNOW there should be one stop difference.

 

[Philippe-Georges]

Lets not get carried away with nostalgia Mr. Leica of the 5 iteration of M. Some of those old time exposures would have been better having been kept under the hat and in some cases it would have been a good idea to save the film and protect the head from sunburn.

Claire,

You are absolutely right!
But nostalgia, just like progress, has its merits, more ore less anyway.
And about exposing with the hat : indirectly, I was somewhat referring to what great and actual photographers like Sally Mann, Quinn Jacobson, Ken Merfeld and the alike, are still doing. Their techniques are inherited from our predecessors, perhaps loaded with a little nostalgia, but what fine and interesting pictures they make!
The good thing is that they are reinterpreting and picking up the threat where others, in the past, have stopped.

Sorry if this was not clear enough.

Yes, let's not be carried away by a futility like a tiny fraction of a second, it isn't worth it!

Philippe

 

[BrianShaw]

I never noticed a considerable difference. Just noticeable, about 1/2 stop maximum, at most. And that only between all other (fast) speeds and 1/500.

That's all the data I need. I concur based on my own personal experience, especially the "maximum, at most" part. While the phenomenon is real, it is well known and not important enough to have generated a lot of data in the past 100 years or so. Important or controversial scientific, technical, and/or engineering "problems" tend to generate data that is published. There is nothing new or proprietary about the shutter efficiency effect. Maybe there is something about it in scientific journals where the effect might make a difference. Frankly, with regard to photography 'shutter efficiency' is more of a discussion item for dilettants (I mean that politely, of course, since I too can be one at times) than practical photographers. If one does find or generate data it would be interesting, though.

 

[BrianShaw]

Don't confuse shutter ACCURACY with shutter EFFICIENCY. But your point remains valid that testing of FP shutters is warranted if one is concerned about teh shutter efficiency issue... there is indeed a shutter efficiency effect with FP shutters too. The physics of the timed opening/closing of a hole across other various sized holes shares certain similarities with the physics of sliding various sized slits across various sized holes... to put it in the fully-acccurate language of a history major.

As Phillipe sez: let's not get carried away...

 

[BrianShaw]

*******
I wonder how that crept in?

You're right, John... that comment shouldn't have referenced you. It should have referenced an earlier post that erroneously stated that shutter timiing begins at the full open position. My boo boo. But it is important to understanding shutter efficiency that shutter timing is measured from full-closed to full-closed, no matter when the retarder inside the shutter starts/stops retatarding.