Mamiya RZ lens - leaf shutter blades apparent in strobe bokeh - hmmm

nick mulder

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Take a look at the attached pic ...

I dont have the details of shutter speed or aperture but a guess would have been around 1/30 (partial ambient exposure) near fully open on the RZ 110mm (2.8 if my memory serves me well) - synched via the a PC cord direct to the lens ...

Flash was a Metz 45CL or CT...

Thing is my theory was that the flash was firing slowly and was catching the shutter in its closing state - something along those lines ...

But thinking back these are bokeh from DC powered xmas tree lights - not specular reflections from the flash.

So leaf shutters, aren't made to expose the complete frame at equal intensity like I thought they would be (like a focal plane would, but with the time issue) - Having never seen one go about its action at a speed I can see, its been hard to speculate on its exact movement

Are all leaf shutters like this ? Or is this one faulty ?

enlightenment appreciated

thanks,
~Nick
 

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Ole

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All leaf shutters are like that. It takes a little time for them to open, and a little time to close.
 

jamie

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hmm...I'm not quite sure that this is normal. Even though leaf shutters take (very little) time to open and close, I wouldn't expect it to be visible like this. Especially not with a 1/30s exposure where the opening and closing of the shutter would only be a unsignificant fracture of the whole exposure time.
 

eddym

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I dunno, but I think it's a cool effect! I wonder if the digiheads could come up with a PS filter to fake it...
 

Nick Zentena

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nick mulder said:
Flash was a Metz 45CL or CT...

Thing is my theory was that the flash was firing slowly and was catching the shutter in its closing state - something along those lines ...
Click to expand...

IIRC full power is something like 1/300th of a second. If you had the shutter at 1/30th I think it should have fired well before the blades closed. No?
 

John Koehrer

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I would guess that it's a sync problem with the shutter.
the way it should work is as follows.
release is pressed & shutter closes & stops down aperture.
Shutter opens for exposure & fires flash when completely open.
Shutter closes.
In this sequence the flash should fire ONLY when the shutter is completely open. If you're getting the image of the shutter blades, the flash is out of sync because the sync switch is out of adjustment. Typically the adjustment is made by achieving access to the switch contacts & reforming(bending) them to change the timing.
Reforming them costs more than bending them.

It could also be switch bounce where the contacts actually close, make a momentary contact, bounce open & close a second time. You can see this if you use an oscilloscope to test the switch.
 

cowanw

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Would the lights not be an independant light source at 1/30 of a second. Having said that I really would not have expected the shutter blade shapes to come out as the shape of the enlarging shutter opening is round or at least polyhedral. Is it possible the shape of the glass of the light bulbs looks like this?
Regards
Bill
 
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nick mulder

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Once I had posted the original question I then realized something ... I did put it in the original post but I couldn't edit the post title ...

But:

But thinking back these are bokeh from DC powered xmas tree lights - not specular reflections from the flash.
Click to expand...

So yes, I agree with the theories for flash but its a bit trickier than that huh (the xmas lights were in an area far enough away not to be illuminated by the flash)

Ole, so leaf shutters work by the fact the movement time is very fast compared to the open time, so they must have a maximum speed before the effect becomes too apparent - in the case of the Seiko shutters in the Mamiya lenses this is 1/400 sec - and the larger shutters 1/125 and so on (more momentum/distance to travel). But I'm pretty sure this was shot on a slower setting - maybe my shutter blades are sticky ? thing is though it is exposing correctly, no under-exposure ...

Still not sure what is going on here - the only possible thing I can think of is that either my memory or gear is faulty and somehow I shot this one frame on 1/400 and this is just the effect of a proper shutter
 
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nick mulder

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cowanw said:
Is it possible the shape of the glass of the light bulbs looks like this?
Regards
Bill
Click to expand...

Hmmm, smart bean Bill! yip, they weren't point sources, they had little plastic shape things on them and it wasn't a wide lens ... I'm keen for other theories though (hope other people enjoy this kind of carry on) - but the coincidence is possible
 

23mjm

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Maybe the lense needs a CLA might be working a little slow!!! The RZ/RB are real work horses of a camera--I think with all the Pros who use them if that was a normal thing you would see it often. Just a thought.
 

cowanw

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If you shot a 1/30 and the shutter opens and shuts faster than 1/400 ( the fastest setting) then the shutter is moving for, say, 1/500 sec and, at the speed of 1/30, the shutter is open for 16/480 sec ie opening for one unit of light and wide open for 16 times that ie 4 stops.
By my math the max shutter effect will be 1/4 of a stop. I should not have thought that would be visible to the degree on your picture.
Is my math wrong?
Of course if it's right it doesn't solve the question at hand?
Regards
Bill
 

Struan Gray

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You'll see the same thing in the background of this image:

(there was a url link here which no longer exists)

As others have said, these are pointlike specular highlights, turned into images of the aperture by being well out-of-focus. Because the leaf shutter takes time to get the blades out of the way, and because the shutter opening is an odd star-ish shape, not a circle, you see the arms of the star as brighter parts of the out-of-focus blob. That is, for a significant portion of the exposure, the shutter *is* the aperture.

In my case, it makes sense: I was shooting at a relatively wide aperture with one of the fastest speeds: exactly where the shutter blades are most likely to spend the most time obscuring the aperture.

The odd thing with your shot is the slow shutter speed. Are you sure you actually got that speed? Your result could be explained if you had a dead or dying battery and the RZ defaulted to the fastest, spring-driven shutter speed (do RZ shutters do this?, I only have LF electronically-timed shutters, and they do). The flash exposure would still be correct since the flash on-time is so short. The background ambient would be underexposed, but the Christmas lights were so over-exposed to begin with, that they still show up.

PS: my shot is with a 150 mm lens on a Kowa 6x6. Probably f4 and 1/250th or so.
 

Philippe-Georges

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If you were shooting outside at Christmas time, well I guess that it could be cold out there? So, if the shutter has been CLA'ed a rather long time ago, the grease in the mechanism lost its viscosity, particularly due to the cold, and slowed down the blades . This is what happened to my Hasselblad, and might be the same with you Mamiya, a good CLA cured it...

Good luck,

Philippe
 
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nick mulder

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Its summer down here near on the subtropics The lens is also exposing fine ... My current theory is that I somehow shot this one pic at 1/400 (i.e. memory at fault) and it is the effect of a working shutter at its limit of usefulness (if this kind of bokeh carry-on in unacceptable)
 
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nick mulder

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well, I reckon if you have a leaf shutter set up some point source lights at different intensities (to find which works best), put em out of focus and shoot your fastest shutter speed ... Theory is that it will happen
 
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