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Focal plane vs. leaf shutters in MF SLRs



 
 
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  #41  
Old May 12th 04, 02:19 AM
Bob Monaghan
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Default Focal plane vs. leaf shutters in MF SLRs


true enough, but for many MF cameras, such as the rollei 6000 series SLRs,
the top leaf shutter lens speed for the PQS lenses is up to 1/1000th
second, partly due to some innovative designs. Then again, lots of the
larger older focal plane shutters were also rarely as fast as marked at
their top speed, often 2/3rds of a stop slower ;-( But the bigger issue
with MF focal plane shutters is the flash synch speed vs. top speed, since
most of the pro action shooters seem to have migrated to 35mm AF systems
;-)

grins bobm
--
************************************************** *********************
* Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 *
********************Standard Disclaimers Apply*************************
  #42  
Old May 12th 04, 07:42 AM
Lassi Hippeläinen
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Default convertible lens RF? Focal plane vs. leaf shutters in MF SLRs

jjs wrote:

wrote in message
...

Why hasn't this approach been used more frequently in 35mm as well? [...]


Funny this should come up. One of my student workers just now returned my
Contaflex, which as you know is an SLR that with a Prontor leaf shutuer and
X,M synchro, and of course it has interchangable lenses. It remains one of
my favorite miniature cameras with the 30mm lens.

Why wasn't it used more? For one, it's expensive and entails rather strident
limitations. To make this Contax system work there is one common lens behind
the shutter and all the lenses use it as the rear element. I can post some
pictures of the lens system if you like.


The Contaflex is complex, because it is an SLR. There are very many
things happening almost simultaneously when you release the shutter.
Primary shutter closes, aperture steps down, mirror goes up, secondary
shutter opens, primary shutter opens, ... and all again in reverse
order. No wonder it was the most expensive camera in the world when it
was first released.

One of the reasons why a TLR would be better architecture is its
simplicity. Having two lenses isn't a big issue, if you only change the
front group. It would be cheaper than Mamiya C series, which changes
whole lenses and the shutter. (Rollei, are you listening? Zeiss knows
how to design those lenses...)

-- Lassi
  #43  
Old May 12th 04, 06:54 PM
Gordon Moat
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Default convertible lens RF? Focal plane vs. leaf shutters in MF SLRs

Bob Monaghan wrote:

yes, I should clarify that I am NOT saying that my proposed convertible
lens Med Fmt camera would require the highest performance levels possible
requiring equaling leitz or contaflex or mamiya 7II optics. ;-)


Though that is possible by adapting some large format lenses to medium
format. Unfortunately, there is little cost savings in doing that. The only
ready made bodies that could handle something like that would be the ALPA,
Silvestri, and perhaps the Cambo Wide, none of which are low cost despite
their simplicity of construction.



Rather, I would like a decent MF camera where you have low cost (as three
lenses for little more than cost of one leaf shutter with swappable front
elements) and light weight (three lenses weighing little more than one), a
RF for low weight and ruggedness with lower costs than a mirror and prism
SLR, perhaps even a folding RF (cf. old folders, fuji..) design for
compactness for travel.


The Bronica RF645 is somewhat light in comparison with most other 645
cameras. The older Fuji 690 with changeable lenses was not terribly heavy
(compared to some 6x7 SLRs), but slightly bulky. Neither of those choices is
expensive in comparison to similar SLR cameras, and both are well bellow the
cost of a Mamiya 7 II.



There have been convertible lenses in LF for ages, and there have been
examples of this design approach (as with the cited Contaflex, Kodak
Retina..) which worked quite well.


Some of the newer LF convertible lenses could be put into a focusing mount,
and then adapted to a body without too much trouble. One issue beyond the
lens cost is that focusing mounts are not inexpensive.

Given that most of the lens cost is in
the shutter, iris, and mounting mechanics, a design which eliminates these
costs by substituting interchangeable lens fronts for different focal
lengths seems pretty direct design for a low cost low weight camera
option. I understand exotic lenses would be problematic, but I am just
looking for the relatively modest standard lens trio (50/80/150mm) in MF.


Is that for 645 or 6x6? Seems that those would match that, though cropping a
larger frame could get you nearly the same (like cropped Mamiya 7 images).
The issue I see with the 150 mm is often a desire for head shots. If a medium
format rangefinder offered a goggles and extension tube arrangement, like the
newer Leica 90 mm f4 Macro for their M rangefinder, then tight head shots
would be possible. Is this not what fuels your choices in focal lengths?



If some of the MF fuji zoom lenses had a longer zoom range, this might not
be such an issue. But it looks like fuji is getting out of that business
;-(


Seems that most people who deride rangefinder cameras always point out longer
focal length lenses. However, I think these same people would be better off
sticking with an SLR. There have been goggled lenses in the past for Leica 35
mm rangefinders, but I wonder why no medium format rangefinders made use of
those solutions. Could it be that there is no market, or that the
construction of the optics is too difficult?

Ciao!

Gordon Moat
A G Studio
http://www.allgstudio.com

  #44  
Old May 13th 04, 01:47 AM
Bob Monaghan
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Default Omega 120 surprise convertible lens RF? Focal vs. leaf


yes, the fuji G/BL 6x9cm rangefinders were very nice, but are now quite
old and hard to keep repaired, though the optics are very nice indeed per
reports, and being in Texas, having a "Texas Leica" like that would be fun
;-) But the kit is large, being 6x9cm after all, and rather a lot to
travel with. I just missed buying a 3 lens kit on photo.net some years ago
;-(

The 150mm value was selected as a favored range of portrait types, a
common enough photo activity, and because it is within the range of easy
RF design, and also likely to be moderately compact as an addon lens front
to an existing lens and leaf shutter base in my proposed compact travel
camera design ;-)

The typical trio of lenses 50/80/150mm in 6x6cm is equiv to the popular
35mm RF lens trio of most photojournalists and general shooters, and as
I've shown, closely mimic the sales of SLR lenses in MF (e.g., hassy etc.)
in popularity and frequency of sales and hence ownership ;-)

I admit to being quite mystified as to why the RF folder designs haven't
been copied with a more modern setup (other than by polaroid, yes? ;=)
It is especially frustrating to have a nearly 100 year old folder which
also features a ground glass insert for focusing and front lens standards
which can be shifted up/down and swung around its axis, all for a consumer
"postcard" camera ;-)

Gordon does make some interesting points lenses etc., I hadn't really
thought about making a camera with different bellows and lens standard
lengths and so on to accommodate existing view camera lenses, partly
because of high costs as noted and partly due to mechanics. But there
isn't any reason that we couldn't have a sort of camera back, perhaps with
a dark slide, and slap on different camera bellows and lenses on some sort
of railing, perhaps with an adjustable standard which could be extended
out?

The problem here is that different view camera lenses are designed to
work at different distances via bellows from the film. My proposed
interchangeable front lens element optics eliminate that requirement by
keeping the lens fixed (perhaps rigidly?), while only the front lens
elements are interchanged/

Perhaps what we really need is a wide angle camera, in which the basic
lens is good enough to permit crops as Gordon suggested up to near normal
lens range. Then an afocal adapter such as a small telescope chosen to
produce minimal vignetting and magnification as needed for portraiture
work?

I have an interesting 4X aux telephoto afocal adapter that mounts via a
filter thread to bayonet adapter onto TLRs etc. So an 80mm lens * 4X =
320mm, providing a good deal of magnification in a short (~6") tube. You
can look thru the adapter as a low power telescope, and focus on the
subject. Then snap the adapter on the camera lens and shoot. The main
problem here is the relatively slow (small) lens size limits you to
daylight with rather fast film, and some vignetting and corner softness as
you might expect ;-) But a faster 3X adapter on a basic 55mm wide angle
lens would be pretty useful? It might also be an interesting option for
one of the fuji zoom variants to extend the zoom into more telephoto
ranges?

The bronica rf645 is a nice option if 645 is your goal, especially since
the issues with the longer telephoto lens options has put it into disfavor
among many folks looking for a camera with longer lenses than 100mm, and
prices have tumbled by half since the intro making it much more
affordable. But the main weight savings here seem to be on the lenses vs.
Mamiya 7-II, say, and you lose out on 6x6, panoramic 35mm, and 6x7cm.
The B&H price is not only $500-ish less than list, but there is a $450
rebate (rebate on lenses too) dropping the price to $1,150 with 65mm lens.

Interestingly, the omega 120, predecessor to the 6x7cm koni omega line
see http://medfmt.8k.com/mf/koomega120.html and korapid.html pages,
weighed only 40 ounces vs 42.7 ounces for the mamiya 7 (both with normal
lens, both 6x7cm RF). That's 5 ounces more than a minolta SRT101 35mm SLR
and only 1.5 ounces more than a yashicamat 124G TLR! The Omega 120 is the
same weight as the bronica rf645 with 65mm lens(!). Partly, they cheated
by using magnesium on some of the Omega parts to lighten weight.

Still, I find it surprising that today's Mamiya 7 weighs more than a
similar 6x7cm RF from 1954, and that the bronica rf645, a 6x4.5cm with
65mm (lighter?) lens weighs the same as the 6x7cm RF omega 120. Sadly, the
followup rapid omega 6x7cm RF models weighed almost twice as much (77 vs
40 ounces). see http://medfmt.8k.com/mf/weights.html for other weighty
surprises ;-) Even my 6x10cm veriwide is only 34 ounces, and it is very
heavy and ruggedly constructed with 47mm SA ;-)

but Gordon may have the right idea; perhaps something like a 6x9cm RF
miniview (busch..) with various lenses on lens boards would be closest to
the spirit of my proposed design in foldup compactness, cost, capabilities
and so on? ;-)

grins bobm
--
************************************************** *********************
* Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 *
********************Standard Disclaimers Apply*************************
  #45  
Old May 13th 04, 02:55 AM
Gordon Moat
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Posts: n/a
Default Omega 120 surprise convertible lens RF? Focal vs. leaf

Bob Monaghan wrote:

yes, the fuji G/BL 6x9cm rangefinders were very nice, but are now quite
old and hard to keep repaired, though the optics are very nice indeed per
reports, and being in Texas, having a "Texas Leica" like that would be fun
;-) But the kit is large, being 6x9cm after all, and rather a lot to
travel with. I just missed buying a 3 lens kit on photo.net some years ago
;-(


Bummer, really nice cameras. They do seem to rarely come up for sale.



The 150mm value was selected as a favored range of portrait types, a
common enough photo activity, and because it is within the range of easy
RF design, and also likely to be moderately compact as an addon lens front
to an existing lens and leaf shutter base in my proposed compact travel
camera design ;-)


When I think of the add-on 135 mm (85?) for the old Retina cameras, that was
not really very small. There are smaller modern optics that are not add-on,
but complete lenses.



The typical trio of lenses 50/80/150mm in 6x6cm is equiv to the popular
35mm RF lens trio of most photojournalists and general shooters, and as
I've shown, closely mimic the sales of SLR lenses in MF (e.g., hassy etc.)
in popularity and frequency of sales and hence ownership ;-)


I guess that 28/50/90 is close on 35 mm, though taking the longest of those
in consideration, the focusing accuracy on the 35 mm camera is easier to
accommodate. The 150 mm on medium format is still 150 mm, and needs greater
rangefinder base length, or magnification, or both, in order to get
reasonably accurate focus.

Look what happens to the 150 mm for the Mamiya 7, in that it is slow and not
very close focus. Now compare that to the older Leica 135 mm f2.8 with
goggles (magnifier), which allowed better focus accuracy. Another comparison
is the newer Leica 90 mm f4.0 Macro, which also uses goggles to aid focus
accuracy. Any way you look at it, to get that 150 mm on a medium format
rangefinder to be similar in framing and close focusing to an SLR, you would
need a device that magnified the viewfinder. Unfortunately, such a device
would add complexity (expense), and bulk. If the rangefinder body was really
designed to accommodate such a long lens, then it would greatly increase the
size of the camera.



I admit to being quite mystified as to why the RF folder designs haven't
been copied with a more modern setup (other than by polaroid, yes? ;=)
It is especially frustrating to have a nearly 100 year old folder which
also features a ground glass insert for focusing and front lens standards
which can be shifted up/down and swung around its axis, all for a consumer
"postcard" camera ;-)


Well, I guess there is the ALPA 12, but no companies make anything similar at
more affordable prices. I guess that leaves the question of whether there is
even a market for affordable medium format rangefinders, though I think Fuji
leaving that market might show there is little interest.


Gordon does make some interesting points lenses etc., I hadn't really
thought about making a camera with different bellows and lens standard
lengths and so on to accommodate existing view camera lenses, partly
because of high costs as noted and partly due to mechanics. But there
isn't any reason that we couldn't have a sort of camera back, perhaps with
a dark slide, and slap on different camera bellows and lenses on some sort
of railing, perhaps with an adjustable standard which could be extended
out?


Okay, the Littmann 45 is one idea, though the choice of lenses is a little
limited. This could be getting more towards the Linhof idea of cams matching
lenses, but then those are not light cameras. The ALPA uses box sections to
mount longer lenses already in focus mounts, and also allows a ground glass
back, though obviously at a price, and without coupled rangefinder.



The problem here is that different view camera lenses are designed to
work at different distances via bellows from the film. My proposed
interchangeable front lens element optics eliminate that requirement by
keeping the lens fixed (perhaps rigidly?), while only the front lens
elements are interchanged/


What I have found is that many large format lenses do not need a long focus
movement, so only a rail arrangement needs to accommodate various focal
lengths. The problem is that the focus travel should match a rangefinder
travel, and provide reasonably accurate distance measurement.

An entirely different direction might be a return to front cell focusing,
like some older folder cameras. As long as the cell changing was easy enough,
it would be a simple solution. Indexing the main mount to the focal length
would be another step, perhaps controlled by a lever, or insert. Weird, but
it could work. Plenty of old folder cameras could be altered to test this.



Perhaps what we really need is a wide angle camera, in which the basic
lens is good enough to permit crops as Gordon suggested up to near normal
lens range. Then an afocal adapter such as a small telescope chosen to
produce minimal vignetting and magnification as needed for portraiture
work?


Seems like the easiest solution, and then only one lens needs to be carried.
This would also seem like a 6x9 camera would provide and ideal solution, even
allowing panorama crops. I have been working out details for a folder camera
conversion that places a large format lens onto a 6x9 body, though obviously
it could not fold anymore without removing the lens. Too many details.



I have an interesting 4X aux telephoto afocal adapter that mounts via a
filter thread to bayonet adapter onto TLRs etc. So an 80mm lens * 4X =
320mm, providing a good deal of magnification in a short (~6") tube. You
can look thru the adapter as a low power telescope, and focus on the
subject. Then snap the adapter on the camera lens and shoot. The main
problem here is the relatively slow (small) lens size limits you to
daylight with rather fast film, and some vignetting and corner softness as
you might expect ;-) But a faster 3X adapter on a basic 55mm wide angle
lens would be pretty useful? It might also be an interesting option for
one of the fuji zoom variants to extend the zoom into more telephoto
ranges?


A faster lens would also be more expensive, ruining the affordable idea.
Finding some large format lenses that worked nice wide open would be nice,
especially if they were 90 mm or shorter.



The bronica rf645 is a nice option if 645 is your goal, especially since
the issues with the longer telephoto lens options has put it into disfavor
among many folks looking for a camera with longer lenses than 100mm, and
prices have tumbled by half since the intro making it much more
affordable. But the main weight savings here seem to be on the lenses vs.
Mamiya 7-II, say, and you lose out on 6x6, panoramic 35mm, and 6x7cm.
The B&H price is not only $500-ish less than list, but there is a $450
rebate (rebate on lenses too) dropping the price to $1,150 with 65mm lens.


Check the MTF charts on their 100 mm. I have only seen a few sample images
from one, but it does seem to be one of the all time great lenses. I only
wish Bronica would come out with more lenses, especially super wide choices,
or just something faster.



Interestingly, the omega 120, predecessor to the 6x7cm koni omega line
see http://medfmt.8k.com/mf/koomega120.html and korapid.html pages


Oh sure, that looks inconspicuous. Guys must have owned an AGFA Clack.

,
weighed only 40 ounces vs 42.7 ounces for the mamiya 7 (both with normal
lens, both 6x7cm RF). That's 5 ounces more than a minolta SRT101 35mm SLR
and only 1.5 ounces more than a yashicamat 124G TLR! The Omega 120 is the
same weight as the bronica rf645 with 65mm lens(!). Partly, they cheated
by using magnesium on some of the Omega parts to lighten weight.


The Bronica is also mostly Magnesium, while the Mamiya 7 uses more plastic.
Both look more ergonomic than the Omega.



Still, I find it surprising that today's Mamiya 7 weighs more than a
similar 6x7cm RF from 1954, and that the bronica rf645, a 6x4.5cm with
65mm (lighter?) lens weighs the same as the 6x7cm RF omega 120. Sadly, the
followup rapid omega 6x7cm RF models weighed almost twice as much (77 vs
40 ounces). see http://medfmt.8k.com/mf/weights.html for other weighty
surprises ;-) Even my 6x10cm veriwide is only 34 ounces, and it is very
heavy and ruggedly constructed with 47mm SA ;-)

but Gordon may have the right idea; perhaps something like a 6x9cm RF
miniview (busch..) with various lenses on lens boards would be closest to
the spirit of my proposed design in foldup compactness, cost, capabilities
and so on? ;-)


Even simpler, a single lens on a 6x9. While a good lens might not be cheap,
donor bodies are plentiful and inexpensive. To be really simple, sticking to
an uncoupled, or accessory, rangefinder might work best. Just a little
practice, and you would be surprised how accurate you can be with an
accessory rangefinder, and a distance calibration on a lens.

Ciao!

Gordon Moat
A G Studio
http://www.allgstudio.com

  #49  
Old May 13th 04, 10:05 PM
Jim-Ed Browne
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Default Focal plane vs. leaf shutters in MF SLRs

At the risk of flogging a long-embalmed horse-hey, thirty million
Elvis and MM fans can't be wrong!-I think flash sync for daylight is
an issue best solved by longer-duration flashes, such as perhaps an
updated variant of the old Polaroid Wink-Light, which pulsed an
incandescent bulb with a cap and high-voltage battery. I can't believe
it would be that hard to build one today, perhaps using a triac to
limit the current to the triggering camera. Doesn't anyone have basic
electronic skills anymore?
  #50  
Old May 13th 04, 10:52 PM
jjs
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Posts: n/a
Default Focal plane vs. leaf shutters in MF SLRs


"Jim-Ed Browne" wrote in message
om...
At the risk of flogging a long-embalmed horse-hey, thirty million
Elvis and MM fans can't be wrong!-I think flash sync for daylight is
an issue best solved by longer-duration flashes, such as perhaps an
updated variant of the old Polaroid Wink-Light, which pulsed an
incandescent bulb with a cap and high-voltage battery. I can't believe
it would be that hard to build one today, perhaps using a triac to
limit the current to the triggering camera. Doesn't anyone have basic
electronic skills anymore?


Great, tell the whole world. Now there will be an ebay rush on Wink Lights.

I got several cases of M bulbs, and ain't afraid of using 'em!


 




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