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Confused about sensor size.

 
 
Steve Franklin
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      08-15-2005, 09:22 AM
Hi all..

In regard to the full frame / 1.5x sensor I'm genuinely confused about a few
things.

1. The Nikon D2H is listed as a having 4.1 Million effective pixels. I know
I am missing something here. Why the low pixel count? how do we draw
comparisons between that and say the D70?

2. Full frame v 1.5x - What is the technical restrictions that caused this
to exist in the first place? Is it just to sell more lenses? Why not go
straight for a full frame? Are they likely to increase the pixel count
within the smaller sensor size or progress to the full frame?

3. As things progress, do you think that it's likely that sensors could even
increase in size beyond 35mm? E.g without film as a restriction, why not
make the sensor in between 35mm and say 645?


Thanks
Steve


 
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frederick
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      08-15-2005, 09:50 AM
Steve Franklin wrote:
> Hi all..
>
> In regard to the full frame / 1.5x sensor I'm genuinely confused about a few
> things.
>
> 1. The Nikon D2H is listed as a having 4.1 Million effective pixels. I know
> I am missing something here. Why the low pixel count? how do we draw
> comparisons between that and say the D70?
>

Check the frame rate. Do you think newspapers care more about how many
pixels are in the frame, or whether the photgrapher got the killer shot?
> 2. Full frame v 1.5x - What is the technical restrictions that caused this
> to exist in the first place?

Price.
> Is it just to sell more lenses?

No - but it is a cunning plot.
> Why not go
> straight for a full frame?

Price. Kodak did, and couldn't make a viable business of it.
> Are they likely to increase the pixel count
> within the smaller sensor size

Yes - they surely will. They can get 50mp in a small sensor at the same
pixel density as a $300 point and shoot has now.
> or progress to the full frame?

Yes, Canon already does. Nikon might too - but then again they might not.
> 3. As things progress, do you think that it's likely that sensors could even
> increase in size beyond 35mm? E.g without film as a restriction, why not
> make the sensor in between 35mm and say 645?
>

Yes - Google "Mamiya ZD"
>
> Thanks
> Steve
>
>

 
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Mike Warren
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      08-15-2005, 10:04 AM
Steve Franklin wrote:
> 1. The Nikon D2H is listed as a having 4.1 Million effective pixels.
> I know I am missing something here. Why the low pixel count? how do
> we draw comparisons between that and say the D70?


One problem manufacturers face is getting the data from the sensor
to the memory card. The D2H has compromised pixel count for speed.

> 2. Full frame v 1.5x - What is the technical restrictions that caused
> this to exist in the first place? Is it just to sell more lenses? Why
> not go straight for a full frame? Are they likely to increase the
> pixel count within the smaller sensor size or progress to the full
> frame?


The larger a sensor is the more expensive it is to make. This is not linear
however. For a given wafer size there will be imperfections These
imperfections are very small but make the sensor they appear on unusable.
For example, if you can fit 20 sensors on a wafer when manufacturing and
the wafer has 3 defects you still get 17 good sensors. If you can only fit
12 sensors on the wafer and get 3 defects you end up with only 9 sensors.
A higher failed percentage.

Hmm, not sure I explained that well.

-Mike




 
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David J Taylor
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      08-15-2005, 10:16 AM
Steve Franklin wrote:
[]
> 3. As things progress, do you think that it's likely that sensors
> could even increase in size beyond 35mm? E.g without film as a
> restriction, why not make the sensor in between 35mm and say 645?


Steve, my own feeling is that adequate quality can be had from a sensor
half the dimensions of the 35mm frame - so 18 x 13.5mm - and that might
allow a greater capability for a given size and weight, with a lower price
to boot. However, not many professionals think this way. With the large
investment in 35mm lenses, I don't see a larger sensor becoming the norm.

David


 
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Mr. Mark
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      08-15-2005, 02:30 PM
> The larger a sensor is the more expensive it is to make. This is not
linear
> however. For a given wafer size there will be imperfections These
> imperfections are very small but make the sensor they appear on unusable.
> For example, if you can fit 20 sensors on a wafer when manufacturing and
> the wafer has 3 defects you still get 17 good sensors. If you can only fit
> 12 sensors on the wafer and get 3 defects you end up with only 9 sensors.
> A higher failed percentage.
>
> Hmm, not sure I explained that well.


Actually it's the first time I've had a clear image in my head of why the
extra cost. Should have been obvious since I've been in IT for 15 years,
but I must have had my head burried in the sand.

Thank you.

--
Mark

Photos, Ideas & Opinions
http://www.marklauter.com


 
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Mr. Mark
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      08-15-2005, 02:31 PM
> Steve, my own feeling is that adequate quality can be had from a sensor
> half the dimensions of the 35mm frame - so 18 x 13.5mm - and that might
> allow a greater capability for a given size and weight, with a lower price
> to boot. However, not many professionals think this way. With the large
> investment in 35mm lenses, I don't see a larger sensor becoming the norm.


Makes sense, but at least they could go square format.

--
Mark

Photos, Ideas & Opinions
http://www.marklauter.com


 
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wilt
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      08-15-2005, 02:57 PM
>adequate quality can be had from a sensor
>half the dimensions of the 35mm frame - so 18 x 13.5mm - and that might
>allow a greater capability for a given size and weight, with a lower price
>to boot.


Two points, in reaction to the above statement...

1. Smaller sensors are inherently more prone to noise than sensors with
larger pixels, so the noise issue needs to be addressed for this to
become practical (unless 'adequate' is good enough!)
2. Smaller formats require lenses with higher resolution specs (again,
unless 'adequate' is good enough!) This is demonstrated in history by
lenses for Large Format (and Medium Format) vs. 35mm lens format.

--Wilt

 
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David J Taylor
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      08-15-2005, 03:41 PM
wilt wrote:
>> adequate quality can be had from a sensor
>> half the dimensions of the 35mm frame - so 18 x 13.5mm - and that
>> might allow a greater capability for a given size and weight, with a
>> lower price to boot.

>
> Two points, in reaction to the above statement...
>
> 1. Smaller sensors are inherently more prone to noise than sensors
> with larger pixels, so the noise issue needs to be addressed for this
> to become practical (unless 'adequate' is good enough!)
> 2. Smaller formats require lenses with higher resolution specs (again,
> unless 'adequate' is good enough!) This is demonstrated in history by
> lenses for Large Format (and Medium Format) vs. 35mm lens format.
>
> --Wilt


1 - agreed, it depends on how adequate is defined. For many
circumstances, the smaller sensors are adequate in respect of noise. For
some low-light use they may not be.

2 - I don't see this as a major issue - there are already many point and
shoot lenses for even smaller sensors with resolutions similar to 35mm
lenses (resolution measured in terms of cycles per picture width). The
image field they need to provide is proportionately less.

David


 
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Robbie
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      08-16-2005, 12:52 AM
On Mon, 15 Aug 2005 19:22:45 +1000, "Steve Franklin" <(E-Mail Removed)> wrote:

>Hi all..
>
>In regard to the full frame / 1.5x sensor I'm genuinely confused about a few
>things.


That's a good sign... means your thinking...

>1. The Nikon D2H is listed as a having 4.1 Million effective pixels. I know
>I am missing something here. Why the low pixel count? how do we draw
>comparisons between that and say the D70?


Depends on the final use... you don't need a big pixel count for press
photography, and you gain speed I guess... But that's an old, antique camera...


>2. Full frame v 1.5x - What is the technical restrictions that caused this
>to exist in the first place?


That's easy... sensors are one size, 35mm film is another... Right now, the
sensor is smaller than the film, so you have to crop the standard lens
projection.

> Is it just to sell more lenses?


I don't see this selling more lenses... it actually gives a benefit to the long
shooter... he could have less lenses!

> Why not go
>straight for a full frame?


I imagine there is some manufacturing reason to make sensors a certain size,
factoring materials price and other things...

> Are they likely to increase the pixel count
>within the smaller sensor size or progress to the full frame?


Smaller is noisier... and full frame sensors are here in the bigger cameras...
who knows, they may make sensors larger to get more bits of range.

>3. As things progress, do you think that it's likely that sensors could even
>increase in size beyond 35mm?


Why not? You'll probably have an I-MAX sensor in 10 years!!


> E.g without film as a restriction, why not
>make the sensor in between 35mm and say 645?


Film is a big consideration right now, everything equates to 35mm... but 20
years from now it will be like asking your kid if he has seen the 8-track of
Rare Earth around the house...

>Thanks
>Steve
>


 
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Gisle Hannemyr
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      08-16-2005, 06:27 AM
"Steve Franklin" <(E-Mail Removed)> writes:

> 1. The Nikon D2H is listed as a having 4.1 Million effective
> pixels. I know I am missing something here. Why the low pixel
> count? how do we draw comparisons between that and say the D70?


The D2h is made for photojournalists and 4 Mpx is plenty for
newprint. The low pixel count allowed Nikon to design a camera
with a higher frame rate. The D70, by comparison, is an all-round
camera made for the amateur market. Many amateurs seem to think that
megapixels is the only thing that matters in a digital camera, so
cameras made for that segment tend to emphasise megapixels.

> 2. Full frame v 1.5x - What is the technical restrictions that
> caused this to exist in the first place?


The silicon wafer technique used to make sensor have a success
rate (known in the industry as "yield") that sinks to very low
levels if the chip becomes large. This make large sensors
more expensive and more difficult to mass produce.

> Is it just to sell more lenses?


No, there are real technical and cost restrictions behind the
1.5x/1.6x crop.

> Why not go straight for a full frame?


Contax and Kodak did, and failed. Canon has a professional full frame
camera that is quite successful, but the latest model (EOS 1Ds Mk II)
will cost you $8000 for the body alone. At the end of this month
Canon will, if the rumour is true, announce the EOS 5D, a "prosumer"
full frame body with a price tag around $3500. If the specs and price
are true, this will be a breakthrough for full frame.

> Are they likely to increase the pixel count within the
> smaller sensor size or progress to the full frame?


Both.

With current wafer technology, it costs much less to increase pixel
count in a small sensor than to increase the sensor size, so we'll
continue to see increased pixel counts in cameras at the lower, and
mid-end of market - and even in some high end cameras made for certain
segments of the professional market, such as wildlife and sports.
(Many wildlife and sports photographers regard the "crop" as a free
teleconverter.)

But there is a demand for full frame. The EOS 5D (if you beleve it
is real - I do) indicates that progress is being made with yield and
prices are coming down as a result. Canon seems to be way ahead of
anyone else in this game at the moment. Kodak has the technology, but
they can not match Canon's high-ISO noise levels, and as a result,
there are no takers. Eventually, however, we will see full frame from
more manufacturers than Canon. The most likely candidate is of course
Nikon, but maybe also Pentax and Sony-Konica-Minolta will enter
the full frame arena when full frame sensor technology becomes more
widely avialable.

> 3. As things progress, do you think that it's likely that sensors
> could even increase in size beyond 35mm? E.g without film as a
> restriction, why not make the sensor in between 35mm and say 645?


These exists. They are just not on display at Walmart or Costco.
The Phase One P25 digital back for Hasselblad et al is one
example. With a sensors that measures 48.9 x 36.7 mm, it sports a
1.1x crop compared to 645. The price? Well, if you have to ask,
you can't afford one - but for you: Special price is $29999.95.
Body and lens not included.)
--
- gisle hannemyr [ gisle{at}hannemyr.no - http://folk.uio.no/gisle/ ]
------------------------------------------------------------------------
Kodak DCS460, Canon Powershot G5, Olympus 2020Z
------------------------------------------------------------------------
 
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