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Focal plane vs. leaf shutters in MF SLRs



 
 
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  #21  
Old April 3rd 04, 10:38 PM
Winfried Buechsenschuetz
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Default Focal plane vs. leaf shutters in MF SLRs

"Bandicoot" wrote in message ...

No. Roland is correct - logic should tell you that, rally, apart from
anything else. The only cameras that get away with leaf shutters in the
bodies (Pentax Auto110, for example) do so by having specially designed
lenses that effectively have a node where the shutter is.


Maybe this is the case with the Auto110. Actually there have been
quite a couple of cameras with standard design lenses and leaf
shutters on the body. In the 50s and early 60s there were quite a few
rangefinder cameras with shutters in the body but the lenses did not
have a special design. Some cheap rangefinders like the Konica C35
have behind-the-lens shutters, and their lenses are standard Tessar
designs where both nodal planes are INSIDE the lens. The Vito B camera
made by Voigtlaender in the 50s also has a behind-the-lens shutter,
and the lens is the same Skopar (Tessar) design as used on many other
cameras of that brand.

That is correct - though lightness is also a factor, and some see having a
shutter in each lens as a reliability issue: if one breaks at least you can
go on using the other lenses.


But that's not the main reason behind it. The first reason is that
placing the shutter in the nodal plane is the best place concerning
vignetting etc, as already mentioned. Another reason is that you would
need quite a big leaf shutter to be able to mount powerful lenses with
longer focal length. On most leaf shutter cameras with interchangeable
lenses, the range was restricted to f/4 135mm lenses or so - no longer
and no more powerful lenses. If you compare a 135mm lens for a Kowa
leaf shutter SLR to a 135mm focal plane lens design you can easily see
which compromises the designers had to make to get the light through
the (rather small) shutter opening. In the nodal plane, the cone of
light rays has the smallest diameter, and a shutter placed in the
nodal plane can be much smaller (and requires much less compromises in
lens design) than a leaf shutter on the body.

Winfried
  #22  
Old April 3rd 04, 11:51 PM
Martin Francis
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Default Focal plane vs. leaf shutters in MF SLRs

"Bandicoot" wrote in message
...
"Martin Francis" m wrote

in
message ...
[snip]

Personally i'd aim for a camera whose shutter is moved by
faeries on rocket boots.


Didn't Black Sabbath write a song about that?


Black *who*?

:-)

--
- Martin Francis

"People Say I'm Insane Because I Am Frowning All The Time"
- George Burns


  #23  
Old April 4th 04, 12:12 AM
Q.G. de Bakker
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Default Focal plane vs. leaf shutters in MF SLRs

Wilt W wrote:

Kerr-cell type electronic shutters don't move at all. Capable of
fantastically fast speeds too.
With (slow) liquid crystal technology where it is today, i can't help but
wonder why we haven't seen any developments in that direction.

How about 'Because the light has to go THRU the device, and that itself
degrades the image. And it provides additional surfaces on which dust
collects. Digital SLR suffer from the need to keep the CCD clean of dust,

so
imagine how a light-shutter would affect things, too!


Light goes many solid objects, having dust collecting surfaces already.
Modern lenses are not short of those.
Dust directly in front of, or even on the sensitive layer/sensor poses
problems of an rather different magnitude than those caused by dust on lens
elements. After all, a Kerr-cell type shutter can be positioned inside the
lens. It could even be integrated into the optical design of the lens.

The liquids used in the Kerr-cells i know off are all slightly coloured (and
highly toxic), and that is a problem. But then, that's what i was hoping
advances in the field of liquid crystal "technology" would have solved by
now. After all, typical liquid crystal displays in use today are very clear,
colourless and highly transparent, c.q. very dense. If only they where fast
enough...


  #24  
Old April 4th 04, 01:40 AM
Bob Monaghan
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Default Focal plane vs. leaf shutters in MF SLRs


yes, I have had similar experience with the short releases too ;-( I have
a rather long release now, and an even longer (25 ft IIRC) air pressure
release (yeech), and a series of radio remote solenoid based releases etc.
Like you, I also discovered that the self-timer is just about the best,
esp. if you use MLU beforehand ;-)

I keep wanting to study this more, using a dual axis accelerometer, but
the modern surface mount devices are so tiny (5 mm square with 8 contacts)
that they are very hard to mount. I mean, my small grounded soldering iron
is about 5mm across, great for soldering the chip contacts to each other!
;-) I keep looking for a board with windows interface they briefly made
for the ADXl series devices that would be nifty for studies of camera
vibration in 2 axes (up/down, left/right). One will turn up - eventually!

However, the study may be problematic given that some tripods have
resonances with certain weights and lenses, magnifying vibrations,
depending on the tripod leg settings, yes? It would be interesting to see
how much better wood and cork are for dampening vibrations than aluminum
and plastic, but first I've got to score one of these hard to find
vibration testing boards ;-)

grins bobm
--
************************************************** *********************
* Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 *
********************Standard Disclaimers Apply*************************
  #25  
Old April 4th 04, 01:44 AM
Bob Monaghan
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Default Focal plane vs. leaf shutters in MF SLRs

IIRC, a major problem with the Kerr cell was the amount of voltage and
power required at the higher speeds making it unattractive outside of
specialty applications? It is also hard to beat the economy of many
mechanical shutters, and for general photography, they are clearly "good
enough" for most needs and users ;-)

grins bobm
--
************************************************** *********************
* Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 *
********************Standard Disclaimers Apply*************************
  #26  
Old April 4th 04, 02:19 AM
David J. Littleboy
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Default Focal plane vs. leaf shutters in MF SLRs


"Bob Monaghan" wrote:

yes, I have had similar experience with the short releases too ;-( I have
a rather long release now, and an even longer (25 ft IIRC) air pressure
release (yeech), and a series of radio remote solenoid based releases etc.
Like you, I also discovered that the self-timer is just about the best,
esp. if you use MLU beforehand ;-)


One of the things that's right about the Mamiya 645Pro is that it uses an
electronic cable releaseg.

I wonder, though, that maybe a cable release is the wrong idea. On a solid
tripod I'd think that holding the camera with both hands and slowly
squeezing the shutter release could provide added damping of shutter
vibration.

However, the study may be problematic given that some tripods have
resonances with certain weights and lenses, magnifying vibrations,
depending on the tripod leg settings, yes? It would be interesting to see
how much better wood and cork are for dampening vibrations than aluminum
and plastic, but first I've got to score one of these hard to find
vibration testing boards ;-)


Well, there's always the laser-pointer-off-a-mirror-glued-to-a-lens-cap
technique.

David J. Littleboy
Tokyo, Japan


  #27  
Old April 5th 04, 01:24 AM
Bob Monaghan
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Default Focal plane vs. leaf shutters in MF SLRs


yes, the laser pointer trick is one approach, but hard to collect the
data ;-) the real problem with the laser pointer is you don't know when
the shutter is open, and when it is closed. The best compromise is to try
and take a photo of the laser pointer itself on a screen, but the dang
things are too faint to show up well when moving fast on photos ;-)

As an example, on the bronica s2/EC series, there is a terrific noise of
blinds moving over the viewing screen and the mirror bouncing up/down
(split in EC series) and so on. You would swear you couldn't get a sharp
photo with such a cannon ;-) but it works fine, because the noise is
happening mostly after/before the shutter is open and exposing film.

I do like the trick of the water in a container (glued to surplus strobe
foot to fit on most 35mm SLRs..) as a quick way to scope out tripod
resonances at different points with lenses. Fun with physics ;-)

the best compromise so far has been to use a microphone and sound card
with inputs from either light sensor at rear of camera (shutter
open/closed signal) or use strobe synch from PC connector (on some models)
to help key where the shutter is open. But microphone positioning and
response curve factors are a big issue, so you can't really compare
signals directly ;-( In short, an accelerometer is the way to go, but
they are too small for my ham-fisted hands to solder up ;-)

grins bobm
--
************************************************** *********************
* Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 *
********************Standard Disclaimers Apply*************************
  #28  
Old April 5th 04, 05:34 AM
Bandicoot
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Default Focal plane vs. leaf shutters in MF SLRs

"David J. Littleboy" wrote in message
...
[SNIP]

I wonder, though, that maybe a cable release is the wrong idea. On a
solid tripod I'd think that holding the camera with both hands and
slowly squeezing the shutter release could provide added damping
of shutter vibration.


I've been convinced of this for a long time: I reckon to press down on the
camera/lens on the tripod to add damping at any speed down to about 1/4s or
so, and go with the release/timer only for exposures longer than that. All
with MLU if at all possible.

My testing has been qualitative rather than quantitative, but so far I'm
convinced.


Peter


  #29  
Old April 5th 04, 05:37 AM
Bandicoot
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Default Focal plane vs. leaf shutters in MF SLRs


"Martin Francis" m wrote in
message ...
"Bandicoot" wrote in message
...
"Martin Francis" m

wrote
in
message ...
[snip]

Personally i'd aim for a camera whose shutter is moved by
faeries on rocket boots.


Didn't Black Sabbath write a song about that?


Black *who*?

:-)

--
- Martin Francis

"People Say I'm Insane Because I Am Frowning All The Time"
- George Burns


LOL!



Peter

"Fairies Wear Boots"
- Iommi/Butler/Ward/Osborne


  #30  
Old May 10th 04, 04:33 PM
Dean Hoffman
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Default Focal plane vs. leaf shutters in MF SLRs

There have been SLRs with a leaf shutter incorporated into the body. The
Kowa 35mm slrs come to mind. Unfortunately these involved complex linkages
that were prone to failure.

"KM" wrote in message
...
I was cleaning my RZ and began wondering why each lens must incorporate

its
own leaf shutter, then began wondering why we find leaf shutters only in
lenses. I understand why the shutter has to be in the lens for rangefinder
systems (proxmity of wide-angle rear elements to focal plane =

insufficient
space), but why couldn't they be incorporated into SLR bodies?

In current leaf-shutter systems like the Bronica ETR and Mamiya RB/RZ,

doing
so would make the lenses smaller and lighter. In focal-plane systems like
the Pentax 645N, you'd get flash synch at any speed.

I'm sure there's a perfectly good explanation I'm overlooking.What is it?



 




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