Sony A100 to A700

[A complimentary Cc of this posting was sent to
Alfred Molon
], who wrote in article :
In article , Fred McKenzie
says...

At present, my 10 megapixel APS sensor's images are approaching the
resolution of lenses designed for 35mm cameras, but they aren't there
yet.

Depends on how you define resolution. In any case the MTF of DSLR lenses
is quite low at the sensor resolution (at least for what concerns 10MP
or more sensors), so already now the lens is the limiting element. We
need much sharper lenses.

Even kit lenses *at their best settings* outperforms 10-12MP
half-frame sensors. (What one needs is to have MTF about 50% on the
most area of the sensor, at the frequency about 70% of Nyquist [the
latter number assumes Bayer sensors]. Just look at dpreview graphs.)

And well-below-$1000 wide-range QUALITY zooms start to appear, which
are getting "close" to such performance even when wide-open...

Hope this helps,
Ilya

[A complimentary Cc of this posting was sent to
Chris Malcolm
], who wrote in article :
No change is required. Digital sensors have already exceeded the
resolution of the best films, and there is still enough development
life left in current technologies to push the boundaries up to at
least the point I'm proposing. That's not just my personal
opinion. Some of today's sensor manufacturer's have quite explicitly
stated that's where their current development programmes are aimed
at. We won't know until independent people assess the resulting
cameras whether that point will be reached with 24MP or 40MP in a 35mm
full frame size of sensor, but there seems general agreement that it's
somewhere in that region, and that in a year or few cameras with such
sensors will appear.

It is more or less clear that with today's technology of rangefinder
lenses, a fixed-focal-length lens can saturate a 100MP full-frame sensor.
E.g., I wrote some calculations in

http://groups.google.com/group/rec.p...9cdc6b94acef9c

Eventually, when we get sensors with higher QE (higher than the
riduculous 15% we have now), FF sensors will have a potential to
become equivalents of LF cameras (unless these LF cameras are used are
used "wide-open", with something like f/24).

Hope this helps,
Ilya

Chris Malcolm wrote:

What I'm pointing out is that at around the same times as that new
range of DSLRs appears there will be a technology convergence
permitting the development of a new kind of camera design which by
omitting the reflex mirror will allow better image quality at lower
prices in exchangeable lens cameras of DSLR size.

Where is the big savings? The digital lenses tend to be telecentric and
rangefinder wide angle lenses don't work so well on digital from what
I've read. Eliminating the mirror & pentaprism is significant I guess,
and makes the cameras smaller. I would be interested in that if new OLED
or some such EVFs become good enough but they really would have to come
a long way.

Such technological
discontinuities are a golden windows of opportunity for a well funded
innovative camera maker to move into that new market ahead of the big
established players who have the largest investment in the current
marketplace.

I suspect that at least Sony has its sights set firmly on that goal.



--
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam

[A complimentary Cc of this posting was sent to
Paul Furman
], who wrote in article :
Chris Malcolm wrote:

What I'm pointing out is that at around the same times as that new
range of DSLRs appears there will be a technology convergence
permitting the development of a new kind of camera design which by
omitting the reflex mirror will allow better image quality at lower
prices in exchangeable lens cameras of DSLR size.

Where is the big savings? The digital lenses tend to be telecentric and
rangefinder wide angle lenses don't work so well on digital from what
I've read. Eliminating the mirror & pentaprism is significant I guess,
and makes the cameras smaller. I would be interested in that if new OLED
or some such EVFs become good enough but they really would have to come
a long way.

1mega-singlet (=VGA) EVFs are known to be less convenient than optical
ones, but not RIDICULOUSLY less convenient. When you take into
account the possibility of instant 2x/4x magnification, they are
reported to come much closer in usability.

So I expect that 2 mega-singlet EVF (about 1024x768) resolution would
be a decent replacement for an optical viewfinder. TODAY, there are
1280x1024x3 eyeglass-like displays commercially available; I expect
them to outperform optical displays (even without taking into account
instant magnification).

Hope this helps,
Ilya

Alfred Molon wrote:
In article , Chris Malcolm says...

The second point is that it is easier and cheaper to design high
resolution lenses if you can get the back of the lens closer to the
sensor than the mirror allows. The only reason we still need the
mirror is to get the optical viewfinder, and the only reason we need
the optical viewfinder is because EVF isn't yet as good as a good
optical viewfinder. But like sensor resolution, that too is simply a
matter of waiting for the technology to get there at an affordable
price. Just as with the sensor resolution improvement, there's no
inherent physical barrier to making EVFs as good as optical
viewfinders, it's just a case of waiting for the well-established
technological development bandwagon to to get there. The only question
is how long we'll have to wait. We need higher resolution small
internal LCDs, and faster processors capable of translating the larger
amount of sensor "pixels" into the larger display at a fast enough
speed.

I'm being told that to have a fast phase detection focusing system
(typical of DSLRs) you need a mirror. Without mirror, as people here
say, you can only have a contrast detection AF.

Interesting point. If the extra speed of phase detection is simply due
to its knowing in which direction to move to improve the focus, then
there are a number of smart things you could do to contrast detection
to improve its speed which at the moment nobody has bothered to do.

Then there's the point that the mirror doesn't have to be an angled
plane. It could be a lot of slats like a venetian blind. Nasty slat
alignment problems, but that wouldn't matter for the purposes of a
phase detection focusing system.

In other words while you do need a DSLR-type mirror for fast focus
with today's technology, I'm not convinced clever engineers won't be
able to think up another way of getting fast focus.

--
Chris Malcolm DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

Chris Malcolm wrote:
[]
Interesting point. If the extra speed of phase detection is simply due
to its knowing in which direction to move to improve the focus, then
there are a number of smart things you could do to contrast detection
to improve its speed which at the moment nobody has bothered to do.

Chris,

It knows not only in which direction to move, but the amount to move as
well. It can almost be open-loop. (I have been told here that it /is/
open loop, at least when not in continuous focus mode).

Cheers,
David

In article , Ilya Zakharevich says...

Even kit lenses *at their best settings* outperforms 10-12MP
half-frame sensors. (What one needs is to have MTF about 50% on the
most area of the sensor, at the frequency about 70% of Nyquist [the
latter number assumes Bayer sensors]. Just look at dpreview graphs.)

And well-below-$1000 wide-range QUALITY zooms start to appear, which
are getting "close" to such performance even when wide-open...

A 10MP 3:2 sensor has about 2600 lines.

The Sony 18-70mm f/3.5-5.6 DT kit lens has been reviewed by photozone:
http://tinyurl.com/3rqwtf

The MTF50 value reaches at best 2200 lines (centre, F5.6, 18mm).
Otherwise it's between 1400 and 2000 lines. In other words, this kit
lens is not good enough for a 10MP sensor. By the way, these MTF50
values are for MTF at just 50%.

The better CZ16-80 lens has been tested by photozone as well:
http://tinyurl.com/478wvz

It tops out at 2300 lines (MTF50 value) and has an overall better
performance. Still 2300 lines is less than the 2600 lines which are
needed by a 10MP sensor and at 2300 lines the MTF reaches a maximum of
just 50%.

Other lenses by other manufacturers, even high quality primes, don't get
much better than 2300 lines at 50% MTF (can't remember having seen
anything better than 2350-2400 lines). In other words, today's DLRSs
with 10MP or more outperform even the best lenses.
--

Alfred Molon
------------------------------
Olympus 50X0, 8080, E3X0, E4X0, E5X0 and E3 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site

[A complimentary Cc of this posting was sent to
Alfred Molon
], who wrote in article :
A 10MP 3:2 sensor has about 2600 lines.

70% of this is about 1800 lines. The information above 70% of MTF is
mostly lost in the sensor anyway.

The Sony 18-70mm f/3.5-5.6 DT kit lens has been reviewed by photozone:
http://tinyurl.com/3rqwtf

AFAICS from dpreview graphs, Sony kit lens is slightly worse than
Canikon ones.

The MTF50 value reaches at best 2200 lines (centre, F5.6, 18mm).

And this is much better than what is needed to "overload" the sensor.

Otherwise it's between 1400 and 2000 lines.

So, I assume, for many (settings?) it is 1800 or better.

In other words, this kit lens is not good enough for a 10MP sensor.

In other words, this kit lens can overload the sensor in many settings.

Hope this helps,
Ilya

In article , Ilya Zakharevich says...

In other words, this kit lens can overload the sensor in many settings.

I'm not sure 70% of the sensor line count is sufficient. But I'm not
deep enough in the math to be able to discuss this further.
In any case, if the sensor were full colour, you'd want to have an ideal
lens with 100% MTF until the line count of the sensor (and an ideal AA
filter with a rectangle response until Nyquist).
With a Bayer sensor you do the colour interpolation, and the situation
is different.

By the way, these are MTF50 numbers and having a higher MTF (ideally
100%) would be preferable.

Besides most if not all reviews of the Sony Alpha 350 (14MP, approx.
3000 lines) point out that the Sony 18-70 lens is a limiting factor and
state that a better lens is desperately needed.
--

Alfred Molon
------------------------------
Olympus 50X0, 8080, E3X0, E4X0, E5X0 and E3 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site

Alfred Molon wrote:
In article , Ilya Zakharevich says...

In other words, this kit lens can overload the sensor in many settings.

I'm not sure 70% of the sensor line count is sufficient. But I'm not
deep enough in the math to be able to discuss this further.
In any case, if the sensor were full colour, you'd want to have an ideal
lens with 100% MTF until the line count of the sensor (and an ideal AA
filter with a rectangle response until Nyquist).
With a Bayer sensor you do the colour interpolation, and the situation
is different.

By the way, these are MTF50 numbers and having a higher MTF (ideally
100%) would be preferable.

Besides most if not all reviews of the Sony Alpha 350 (14MP, approx.
3000 lines) point out that the Sony 18-70 lens is a limiting factor and
state that a better lens is desperately needed.

That 18-70 Sony lens apparently isn't a good performer. IIRC DPReview
didn't think much of it either on 10+ mp dslrs (a700?)
I don't know what the alternatives for Sony are like, but some aps-c
format consumer zooms for other brands are easily "up to the
requirements" of 12mp aps-c sensors. The camera makers will keep
making new higher pixel count aps-c dslrs, and probably newer sharper
lenses to match for some time yet. I don't know what the Nikkor 16-85
will be like, but they need to justify the high price somehow g. At
10-15mp, these dslrs are still equivalent pixel density to only about
2-3mp compact cameras, and for compact cameras, increased megapixels
only became mainly pointless (IMO) once they hit over about 5-6 megapixels.