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Re: Death of the slapping mirror

 
 
Bruce
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      08-24-2010
Alfred Molon <(E-Mail Removed)> wrote:

>New Sony Alpha 55 with semitransparent non-moving mirror, only 30% light
>loss but always on fast phase-AF, EVF.
>No more issues with noise and vibrations caused by a slapping mirror,
>phase AF available when shooting video.
>
>Quite an interesting innovation, I wonder if other manufacturers will
>choose the same path. The advantage over an EVIL design is the phase-AF.



A pellicle mirror is **DEFINITELY NOT** an "innovation".

Canon used it in their 1960s Pellix and again in the Canon EOS RT,
plus the 10 frames/sec Canon EOS 1n HS. Nikon also flirted with
pellicle mirror versions of some of the F series 35mm SLRs.

All were low volume experiments that were discontinued due to weak
sales. I predict the same fate for the Sony Alpha 33 and 55.

 
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Bruce
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      08-24-2010
Allen <(E-Mail Removed)> wrote:
>Bruce wrote:
>> Alfred Molon <(E-Mail Removed)> wrote:
>>
>>> New Sony Alpha 55 with semitransparent non-moving mirror, only 30% light
>>> loss but always on fast phase-AF, EVF.
>>> No more issues with noise and vibrations caused by a slapping mirror,
>>> phase AF available when shooting video.
>>>
>>> Quite an interesting innovation, I wonder if other manufacturers will
>>> choose the same path. The advantage over an EVIL design is the phase-AF.

>>
>>
>> A pellicle mirror is **DEFINITELY NOT** an "innovation".
>>
>> Canon used it in their 1960s Pellix and again in the Canon EOS RT,
>> plus the 10 frames/sec Canon EOS 1n HS. Nikon also flirted with
>> pellicle mirror versions of some of the F series 35mm SLRs.
>>
>> All were low volume experiments that were discontinued due to weak
>> sales. I predict the same fate for the Sony Alpha 33 and 55.
>>

>Thank you, Bruce. I was trying to remember the details of that almost
>50-year-old device, but my memory failed me. But considering the patent
>laws nowadays, though, I wouldn't be surprised if Sony files for and
>gets a dozen patents on it.



It doesn't matter how many patents Sony has.

It won't sell.

 
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dj_nme
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      08-26-2010
George Kerby wrote:
>
>
> On 8/24/10 11:25 AM, in article http://www.velocityreviews.com/forums/(E-Mail Removed),
> "Bruce" <(E-Mail Removed)> wrote:
>
>> Alfred Molon <(E-Mail Removed)> wrote:
>>
>>> New Sony Alpha 55 with semitransparent non-moving mirror, only 30% light
>>> loss but always on fast phase-AF, EVF.
>>> No more issues with noise and vibrations caused by a slapping mirror,
>>> phase AF available when shooting video.
>>>
>>> Quite an interesting innovation, I wonder if other manufacturers will
>>> choose the same path. The advantage over an EVIL design is the phase-AF.

>>
>> A pellicle mirror is **DEFINITELY NOT** an "innovation".
>>
>> Canon used it in their 1960s Pellix and again in the Canon EOS RT,
>> plus the 10 frames/sec Canon EOS 1n HS. Nikon also flirted with
>> pellicle mirror versions of some of the F series 35mm SLRs.
>>
>> All were low volume experiments that were discontinued due to weak
>> sales. I predict the same fate for the Sony Alpha 33 and 55.
>>

> Thank you, sir.
>


These EVIL/hybrid cameras (lack of optical reflex viewfinder
disqualifies them from being SLR cameras) made by Sony seem to be better
suited to video.
It might be the student and small-time movie makers that help them
survive in the marketplace.
Who really knows?
From a video-camera perspective, the Sony A33 and A55 both look like a
pretty good deal: interchangeable lenses and large sensor, presumably
with an "entry level" sized "DSLR" price-tag rather than a pro-video
camera "ultra luxury" price.
 
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dj_nme
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      08-26-2010
Neil Harrington wrote:
> "dj_nme" <(E-Mail Removed)> wrote in message
> news:4c75bad9$0$25361$(E-Mail Removed) u...
>
>
>> These EVIL/hybrid cameras (lack of optical reflex viewfinder disqualifies
>> them from being SLR cameras)

>
> I would say as long as it's got a mirror it's a reflex. What happens to the
> imaging after it leaves the mirror doesn't change that. If you took the
> pentaprism and eyepiece off an SLR and adapted an EVF to the body instead,
> it would still be an SLR.


If the imaging sensor for the viewfinder was located in the same place
as the focusing/matte screen of an ordinary SLR camera, then you perhaps
could "stretch" (I would say "butcher") the term SLR camera to include
this hypothetical camera.
The mirror in the two new Sony Alpha cameras plays no part in the
viewfinder, they have no reflex viewfinder at all and so can't be called
SLR cameras.

Call them EVIL (or hybrid) cameras and you would be accurate with your
description.
 
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dj_nme
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      08-27-2010
Alfred Molon wrote:
> In article <4c766259$0$25356$(E-Mail Removed)> , dj_nme
> says...
>> The mirror in the two new Sony Alpha cameras plays no part in the
>> viewfinder, they have no reflex viewfinder at all and so can't be called
>> SLR cameras.

>
> In fact Sony is calling it an SLT camera.


I am fully aware of this fact.
That's why I was particularly keen to point out that these cameras
aren't SLR cameras.
 
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John A.
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      08-27-2010
On Fri, 27 Aug 2010 16:43:20 +0200, Alfred Molon
<(E-Mail Removed)> wrote:

>In article <4c7775bc$0$25361$(E-Mail Removed)> , dj_nme
>says...
>> That's why I was particularly keen to point out that these cameras
>> aren't SLR cameras.

>
>... which is highly irrelevant.


Ok... do you mean that it's irrelevant that they aren't SLRs, or that
the camera is irrelevant in the slr-systems group?
 
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Bruce
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      08-27-2010
dj_nme <(E-Mail Removed)> wrote:
>Alfred Molon wrote:
>> In article <4c766259$0$25356$(E-Mail Removed)> , dj_nme
>> says...
>>> The mirror in the two new Sony Alpha cameras plays no part in the
>>> viewfinder, they have no reflex viewfinder at all and so can't be called
>>> SLR cameras.

>>
>> In fact Sony is calling it an SLT camera.

>
>I am fully aware of this fact.
>That's why I was particularly keen to point out that these cameras
>aren't SLR cameras.



That's a perfectly valid point. They are basically mirrorless
cameras, but with a mirror that is there purely for focusing. They
might have mirrors, but as far as the viewfinder is concerned, the
mirror has no part to play.

The mirror will, of course, be the most problematic part of the
camera. If it is anything less than spotlessly clean, it will degrade
the image recorded by the sensor.

These so-called "SLT" cameras must be among the most pointless cameras
ever produced. But that's Sony for you.

 
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John A.
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      08-27-2010
On Fri, 27 Aug 2010 20:58:32 +0200, Alfred Molon
<(E-Mail Removed)> wrote:

>In article <(E-Mail Removed)>, John A. says...
>> Ok... do you mean that it's irrelevant that they aren't SLRs, or that
>> the camera is irrelevant in the slr-systems group?

>
>Since the mirror is going to disappear sooner or later,
>rec.photo.digital.SLR-systems will go the way of the dodo.
>OVFs will also disappear from most cameras sooner or later, replaced by
>EVFs.


If they do, I have a feeling it will only be a temporary absence.
 
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Kennedy McEwen
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      08-27-2010
In article <(E-Mail Removed)>, Bruce
<(E-Mail Removed)> writes
>
>The mirror will, of course, be the most problematic part of the
>camera. If it is anything less than spotlessly clean, it will degrade
>the image recorded by the sensor.
>

Much less than the degradation of a less that spotlessly clean sensor
filter stack.

A 10um sized spec of dirt on the filter stack causes dust bunny shadows
on the image, which are small and dense at high f/#s or larger and less
dense with low f/#s. The same sized spec of dust in the middle of the
pellicle mirror would be at least 12mm from the focal plane, so even at
f/16 its effect would be very limited.

At f/16 the light forming each pixel in the centre of the image goes
through a circle of about 0.75mm diameter on the mirror. So that same
10um piece of dirt, which causes objectionable dust bunnies on the
filter at f/16, blocks about 0.02% of the light to the pixel when it is
on the mirror. That's less than 1LSB of the 12-bit signal from each
pixel and less than the peak photon noise itself. In short, except on
highly stacked images, it would be completely invisible.

To have any material effect on the image, dirt on the mirror has to be
enormous compared to the dirt that would be unacceptable on the sensor
filter stack. Dirt particles that size are the easiest to clear either
with blown air or vibrating the pellicle itself.

>These so-called "SLT" cameras must be among the most pointless cameras
>ever produced. But that's Sony for you.
>

No, its just you.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
 
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Wolfgang Weisselberg
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      08-30-2010
Alfred Molon <(E-Mail Removed)> wrote:
> In article <(E-Mail Removed)>, Alan Browne
> says...
>> I also doubt the mirror will disappear as soon as some believe/hope.


> Huge advantage if that mirror goes:
> - no mirror movement vibrations any more (MLU no longer needed)
> - much faster cameras (faster AF, higher frame rate)
> - 100% match between viewfinder/LCD image and what is being recorded
> - more accurate metering if the main sensor is used for metering


Huge advantages if the mirror stays:
- Zero[1] power cost to watch through the viewfinder. All EVIL
viewfinder screens need power to display and most all will need
significant power to light the screen.[2]
- a few cm at lightspeed view lag. EVIL cameras need to read
the data from the sensor, postprocess it and write it to the
viewfinder screen.
- inbuild non-glare function. At night all electronic viewfinders
need lighting, and I haven't yet found one that can be turned
down low enough to not at least damage night vision, much less
one that does that automatically.
During daytime the viewfinder is automatically much brighter,
without needing extra lighting.
- cooler (less noisy) main sensor, as it and the amplifiers and
digitizers can be switched off unless you are actually taking an
image now. Google amplifier glow. EVIL cameras need sensor,
amplifiers and digitizers to run just to show something on
the viewfinder.
- viewfinder quality is only determined by optics, not by how
few dots a viewfinder has. Current viewfinders have around
VGA resolution (ca. 640x480, or ca. 1 Mio dots). That's not
much at all --- even camera makers think so and allow zooming
for manual focussing. (Which is a nice feature.)[3]
- no mirror movement necessary, as soon mirrors will be optionally
risable pellicle mirrors.[4] If you need the 33% of the light
the pellicle mirror eats for the viewfinder, it'll rise like
a current SLR's mirror. Further in the future is the electric
mirror, where a current makes the mirror stop mirroring and
can also act as a shutter.[5]
- much faster AF, since dedicated phase detection AF sensors know
which direction and how far the focus motor needs to be turned.
(Additionally, the sensors are more light sensitive and/or
more detailed than the main sensor can be.[6]) Even today they
are programmed by the lens on how much to offset that result
to reach an overall maximum sharpness (different colours of
light are refracted in different degrees and the AF sensors
sensitivity need not necessarily align with what the eye
sees dominantly).
EVIL cameras need to guess the direction of the focus by try
and error and reach being in focus the same way, step by step.
And the darker it becomes, the worse the focussing capability.
- 100% viewfinders are possible, that's not an EVIL only feature.
- dedicated metering sensors are better than the main sensor for
metering, since they can be purpose built. Of course, if you
insist, use the main sensor: see pellicle mirror.
- Frame rate only depends on the main sensor --- just as with
EVIL cameras. See pellicle mirror. Just keep the shutter
open, if need be.

-Wolfgang

[1] near zero for overlays, as in 'drains the camera slower than
the self discharge of the battery'.
[2] You could use ambient light during the day, but not at night.
[3] For these situations lifeview and back monitors were invented.
[4] It's such a trivial idea, it must be patented by now.
[5] It should be possible to adjust the strength of the mirror,
too.
[6] EVIL cameras need to mostly use the green pixels for sharpness,
loosing 50% of the light to red and blue sensors, light is
stopped by the green filters too --- and the distance to the
next green pixel is SQRT(2) of the pixel spacing.
 
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