Hasselblad leaf shutter problem

[Q.G.]

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.

The old timers would be wrong though.
There IS a detectable difference. And it mostly is near enough 1 stop in size.

Again, if there would not be, do you suppose all those leaf shutter users are somehow ignorant of the fact, and that's why they were, and still are, using leaf shutters?

It's not a problem.
Really! It isn't!

 

[Q.G.]

Don't confuse shutter ACCURACY with shutter EFFICIENCY.

Don't think that i am!

The point is that focal plane shutter users should not feel 'safe', just because theirs is a focal plane shutter.
I, as a seasoned focal plane shutter user as well as a leaf shutter user, know how often the top speeds of focal plane shutters are more whishfull thinking than reality.

And that is indeed - and as i pointed out - an accuracy thing.

... 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.

Now we are really stretching.
The focal plane shutter efficiency effect due to different sized apertures would be something history has yet to learn about, because it would take devices sensitive enough to detect Higgs-bosons.
Maybe we can get CERN to have a go at measuring it?

 

[Q.G.]

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.

But if you do understand shutter efficiency, you know that timing should not be measured from full-closed to full-closed either.

That's why shutter manufacturers don't. Shuttertimings are set so that the effect they have would equal a 'block wave' exposure of the desired length. I.e.: the fully open time is slightly less than what it should be; the time from full-closed to full-closed is more than it should be; the increasing and dimishing exposure that is produced while the blades are opening and closing is taken into account as well.
In practice, this means that the shutter timing is measured from (and set for) the moment the blades are about half way open to when they are half way closed again.
Some mathematical thing, based on the area below the graph. I don't know maths...

Decent shutter testers do this too: they integrate the total amount of light the open shutter lets through. Not just measure the time from 'first light' to 'lights out'.
That is an electronics thing too. I don't have a clue about electronics either...

 

[Anscojohn]

The old timers would be wrong though.
There IS a detectable difference. And it mostly is near enough 1 stop in size.
******
Numbers, please.

Again, if there would not be, do you suppose all those leaf shutter users are somehow ignorant of the fact, and that's why they were, and still are, using leaf shutters?
******
They are not ignorant of the fact; they just worked around it?

It's not a problem.
Really! It isn't!

*******
It's not a big problem, to be sure. Especially when one works around it.

 

[Q.G.]

Numbers, please.

Again?

They are not ignorant of the fact; they just worked around it?

Not really. They know it is not a problem.

It's not a big problem, to be sure. Especially when one works around it.

Which we do not need to.
Know about it, yes. But there is rarely an occassion we could actually do anything usefull with that knowledge.

 

[BrianShaw]

Some mathematical thing, based on the area below the graph [area below the "curve" in statistical speak]. I don't know maths...

I don't have a clue about electronics either...

Neither is worth getting into... you are correct that I simplified too much. Bad me

Re: shutter efficiency and FP shutters... it exists but is below the threshold of a nit. WAY BELOW! I only mention it becuase there is a continual call for data and explanation of things that are very close to the threshold of a nit.

 

[Thomas Bertilsson]

I've now developed another test roll. First I fired the shutter quite a few times, and then, in room temperature, exposed the roll at the following scheme:

Fr# Apt Time Lens
1 f/4 1/15s 150 Sonnar
2 f/4 1/8s 150 Sonnar
3 f/4 1/30s 150 Sonnar
4 f/11 1/2s 150 Sonnar
5 f/11 1/4s 150 Sonnar
6 f/11 1s 150 Sonnar
7 f/4 1/15s 80 Planar
8 f/4 1/8s 80 Planar
9 f/4 1/30s 80 Planar
10 f/11 1/2s 80 Planar
11 f/11 1/4s 80 Planar
12 f/11 1s 80 Planar

This time the exposures between the two lenses are identical. Some of it may have been evened out by the semi-stand development scheme, but there are still clear differences between the over- and under-exposed frames, so it would have been evident if there were any density differences to speak of.

So this means that the shutter mechanism fires well at room temperature. I'll be using it mostly in room temperature, or there about. I will still go ahead and get a CLA for it, but wonder if it's kosher to continue using it until I can afford it (my water heater busted the other night, and i had to spend $1,200 to replace it), as I don't dig into savings for photography stuff.

- Thomas

 

[Anscojohn]

So this means that the shutter mechanism fires well at room temperature. I'll be using it mostly in room temperature, or there about. I will still go ahead and get a CLA for it, but wonder if it's kosher to continue using it
*****
If it were still dragging at room temperature, I would say use it sparingly or not at all. But my gut tells me that if it was getting sluggish in the cold, there is old lube which is probably not doing what it should be doing at 100% even at room temperatures. I've heard of people putting a lens under a desk lamp for a couple of hours then working a sticky shutter or aperture until it freed up a bit; but I would not recommend that course of action.

 

[edtbjon]

There are two issues here. First, your lens seem to have had an issue with being stored without excersise, from which it seem to recover quite well. From your last post (Very early this morning, at least in Sweden. ) you don't mention if the 150 sounds like it's accurate on 1 sec, but from your report I can deduct it's about the same as your Planar.
Anyhow, it's quite obvious that the lubes have become stiffer over the years. Using the lens in freezing conditions will still put the mechanics under extra stress.
The second part is that the shutter have 2 different "clockworks". One part which is the one that usually needs attention is the slow times, from 1/15 to 1 sec. The second part with the faster times usually works fine even though the slower times have problems. So the faster times are probably OK.

//Björn

 

[Greg Heath]

Kodak shutter teardown

With all the talk of shutters here, I just happened to be replacing the bellows on a Kodak No.1 folder and had the lens/shutter off the camera, so I decided to tear it down and clean it out.

I soaked the shutter for about 2 hours, and then flushed it (naptha), and all that sand and gunk came out of it. Truly amazing the crud in the bottom of the dish. Of all the sand and gunk in the bottom of the tray, each one of those grains could tell a story of a snapped picture from a lost time.
Made me wonder what story a camera could tell, and the adventures it's had during it's lifetime before me, since 1920 or so.

There was even the finger print of the person who probably originally put it together.

I had never taken apart a kodak shutter, and although simple compared to others, I took my time and snapped a digital picture every step of the way in case I needed to reverse my actions.

Now it's working better and hopefully ready for more.

Just to get the bellows back on and then I will have a Medium format camera in my pocket.

Greg