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I have been following the numerous topics on how many pixels we will get to
with interest but I have a question which doesn't quite fit in.

It just occured to me that you could obtain the same pictures by using a
slightly larger sensor and moving it further from the lens.

Which in itself would allow larger sensors per pixel or more sensors of the
same size (effectively giving a higher resolution image).

Is my logic correct? I realise there isn't much room to move the sensor
further from the lens but there is some.

Thanks in advance,

John

On Mon, 4 Sep 2006 17:21:29 +0100, John Ortt wrote:

> I have been following the numerous topics on how many pixels we will get to
> with interest but I have a question which doesn't quite fit in.
>
> It just occured to me that you could obtain the same pictures by using a
> slightly larger sensor and moving it further from the lens.
>
> Which in itself would allow larger sensors per pixel or more sensors of the
> same size (effectively giving a higher resolution image).
>
> Is my logic correct? I realise there isn't much room to move the sensor
> further from the lens but there is some.

You wouldn't have to move the enlarged sensor even one millimeter.
Just mount the lens on an extension tube. You'll probably have to
redesign the lens though, as you might not care much for its new
focusing ability.

John Ortt wrote:
> I have been following the numerous topics on how many pixels we will get to
> with interest but I have a question which doesn't quite fit in.
>
> It just occured to me that you could obtain the same pictures by using a
> slightly larger sensor and moving it further from the lens.
>
> Which in itself would allow larger sensors per pixel or more sensors of the
> same size (effectively giving a higher resolution image).
>
> Is my logic correct? I realise there isn't much room to move the sensor
> further from the lens but there is some.
>
> Thanks in advance,
>
> John

The distance from the lens to the sensor is determined by the FL of the
lens and the distance to the subject. Moving the lens further away is
the same as defocusing it.

Scott

"ASAAR" <> wrote in message
news:...
> On Mon, 4 Sep 2006 17:21:29 +0100, John Ortt wrote:
>
>> I have been following the numerous topics on how many pixels we will get
>> to
>> with interest but I have a question which doesn't quite fit in.
>>
>> It just occured to me that you could obtain the same pictures by using a
>> slightly larger sensor and moving it further from the lens.
>>
>> Which in itself would allow larger sensors per pixel or more sensors of
>> the
>> same size (effectively giving a higher resolution image).
>>
>> Is my logic correct? I realise there isn't much room to move the sensor
>> further from the lens but there is some.
>
> You wouldn't have to move the enlarged sensor even one millimeter.
> Just mount the lens on an extension tube. You'll probably have to
> redesign the lens though, as you might not care much for its new
> focusing ability.
>
In addition, using an extension tube results in not being able to reach
infinity.
Jim

"John Ortt" <> schreef in bericht
news:44fc4fb2$...
>I have been following the numerous topics on how many pixels we will get to
>with interest but I have a question which doesn't quite fit in.
>
> It just occured to me that you could obtain the same pictures by using a
> slightly larger sensor and moving it further from the lens.

The problem is not that a larger sensor
can not be places in a camera.
The problem is that a larger sensor is more
expensive to produce.

Sensors of different sizes are produced,
the smaller ones are cheaper and make the
total construction of the camera smaller.
Most camera's nowadays are build around
the sensor. The sensor determines what
lenssystems can be used and from there the
formfactor of the camera.

But for rollfilm camera's the larger sensor
was not a problem either. Sensors of the
size of 'the standard' 35 mm format are
expensive to produce. So even for
DSLR's most sensors are produced
smaller. For DSLR's it is even an
disadvantage, because the distance to
the lensflange is 'predetermined' so the
camera can not become a lot smaller.
(Actually DSLR's are not smal compared
to some non-af slr's from 20 years ago).

ben



>
> Which in itself would allow larger sensors per pixel or more sensors of
> the same size (effectively giving a higher resolution image).
>
> Is my logic correct? I realise there isn't much room to move the sensor
> further from the lens but there is some.
>
> Thanks in advance,
>
> John
>

On Mon, 4 Sep 2006 17:21:29 +0100, John Ortt, <> wrote:
> I have been following the numerous topics on how many pixels we will get to
> with interest but I have a question which doesn't quite fit in.
>
> It just occured to me that you could obtain the same pictures by using a
> slightly larger sensor and moving it further from the lens.
>
> Which in itself would allow larger sensors per pixel or more sensors of the
> same size (effectively giving a higher resolution image).
>
> Is my logic correct? I realise there isn't much room to move the sensor
> further from the lens but there is some.

Yes, you can do it, *BUT*... in order to maintain focus over the same
range, you end up with a bigger, bulkier camera. Think along the lines
of a scale model train set, with a slightly larger scale.

Let's say that you move the sensor back an extra 10%. The focal
length is now 1.1 as long. The sensor area is 1.1 x 1.1 = 1.21 its
original value. So a 5 megapixel sensor can go to 6 megapixels of the
same size.

Length, width, and height all increase by 10%. Volume increases to
1.331 the original value. The weight increases by 1/3rd to give you
1/5th more pixels (ouch)... *ASSUMING* that you don't need more
re-inforcing for the body. This is the classic trivia about how an ant
can hold several times its body weight, but if you magnified all the
dimensions to make a 10-foot-long ant (as per various B monster movies),
the ant would collapse under its own weight. In real-life, your camera
will probably be 50% heavier (hand-waving number) to maintain structural
integrity.

And if you go to a lens menufacturer and ask for a longer, thicker,
and wider lens, prices go through the roof.

Now on to my rant about form versus function. 50 years ago, consumer
cameras had two cylinders. Unexposed film unrolled off one cylinder to
a flat area, was exposed, and then rolled onto a second spool. The lens
had to go in front of the area where the film was flat. Wrap that all
up in a metal or plastic body, and you have the sterotypical
lens-in-front-of-a-flat-space-with-cylinders-on-both-sides shape that we
all recognize as a camera. Digital cameras do *NOT* work that way, so
why do we keep the old shape?

The shoulder-mounted video-cam shape makes a lot more sense, at least
for professional (and possibly prosumer) cameras. Start off with a big
long lens. Put a big sensor at the back end. Put buttons on the top
*NEAR THE MIDDLE*, with an EVF and/or LCD sticking out the side. For
brownie points, make the EVF/LCD detachable, with plugs on both sides of
the camera, to accomadate lefties. Add a flash on a stalk that is
hinged at the front to be able to stand up, for separation from the lens
(look Ma, no red-eye). Wrap that all up in a metal/plastic body. Here's
a crude side view (fixed font required to view properly). I show the
stalk in both the popped-up and the folded-down positions. Comments?



* Built-in flash on
* a stalk that is
* hinged at the front.
|
|
|
|
| Control
|______*** buttons
hinge O ^^^^^^^^^
|================================|
] [ |
lens ] [ LCD/EVF | back
] [ |
=================================|
/ \
/ \
Shoulder
mount


--
Walter Dnes; my email address is *ALMOST* like
Delete the "z" to get my real address. If that gets blocked, follow
the instructions at the end of the 550 message.

John Ortt wrote:
> I have been following the numerous topics on how many pixels we will get to
> with interest but I have a question which doesn't quite fit in.
>
> It just occured to me that you could obtain the same pictures by using a
> slightly larger sensor and moving it further from the lens.
>
> Which in itself would allow larger sensors per pixel or more sensors of the
> same size (effectively giving a higher resolution image).
>
> Is my logic correct? I realise there isn't much room to move the sensor
> further from the lens but there is some.
>
> Thanks in advance,
>
> John

But the problem is that silicon sells by square inch or cm. Larger
sensors are more expensive- that is the whole issue. Sensors are
gang-fabricated. A round plate of silicon is processed with a number
of individual sensors produced on each plate. There is a limit to the
size of the plates available, and the processing equipment is limited
to the size of the plate it will take. The total cost to fabricate N
chips from one plate is nearly constant per plate, so the greater N,
the cheaper each chip is. Larger chips means lower N, higher cost.