Low noise: why not small sensor with fast lense?

There are two ways to reduce noise in low light shooting. The most obvious
is to make the pixel bigger, thus making the whole sensor bigger at same
resolution. Another way is to reduce the ISO and make the lense faster. E.g.
Instead of shooting at ISO 100 F4, shoot at ISO 25 at F1.0.

Currently available cameras with low noise indeed have larger sensor (mostly
DSLR). But there is no camera with small sensor and very fast lense to
achieve low noise. Why?

Some may say fast lense are costly. But keep in mind this fast lense has a
small image circle, so it is not necessarily more expensive than a slower
lense with a larger image circle.

In article <n8Idj.1685$Xe5.742@trndny09>, peter says...
> There are two ways to reduce noise in low light shooting. The most obvious
> is to make the pixel bigger, thus making the whole sensor bigger at same
> resolution. Another way is to reduce the ISO and make the lense faster. E.g.
> Instead of shooting at ISO 100 F4, shoot at ISO 25 at F1.0.
>
> Currently available cameras with low noise indeed have larger sensor (mostly
> DSLR). But there is no camera with small sensor and very fast lense to
> achieve low noise. Why?
>
> Some may say fast lense are costly. But keep in mind this fast lense has a
> small image circle, so it is not necessarily more expensive than a slower
> lense with a larger image circle.

The now discontinued Olympus C4040 and C5050 have lenses with start at
F1.8. Most older prosumer cameras have lenses which started at below
F2.4. You might get one of these cameras.
--

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

On Sun, 30 Dec 2007 07:53:55 GMT, "peter" <nospam@nospam.com> wrote in
<n8Idj.1685$Xe5.742@trndny09>:

>There are two ways to reduce noise in low light shooting. The most obvious
>is to make the pixel bigger, thus making the whole sensor bigger at same
>resolution. Another way is to reduce the ISO and make the lense faster. E.g.
>Instead of shooting at ISO 100 F4, shoot at ISO 25 at F1.0.
>
>Currently available cameras with low noise indeed have larger sensor (mostly
>DSLR). But there is no camera with small sensor and very fast lense to
>achieve low noise. Why?

Probably because the market is too sensitive to price, size and weight.

>Some may say fast lense are costly. But keep in mind this fast lense has a
>small image circle, so it is not necessarily more expensive than a slower
>lense with a larger image circle.

But still much more expensive, larger and heavier than a slower lens,
and it's much harder to do a fast zoom lens than a slower zoom lens.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)

On Dec 29, 9:53*pm, "peter" <nos...@nospam.com> wrote:
> There are two ways to reduce noise in low light shooting. The most obvious
> is to make the pixel bigger, thus making the whole sensor bigger at same
> resolution. Another way is to reduce the ISO and make the lense faster. E.g.
> Instead of shooting at ISO 100 F4, shoot at ISO 25 at F1.0.
>
> Currently available cameras with low noise indeed have larger sensor (mostly
> DSLR). But there is no camera with small sensor and very fast lense to
> achieve low noise. Why?
>
> Some may say fast lense are costly. But keep in mind this fast lense has a
> small image circle, so it is not necessarily more expensive than a slower
> lense with a larger image circle.

People who are buying small compact cameras tend to be looking for
cheap cameras and most people don't understand about lens speed, just
zoom range and megapixels.

The Sony F828 did have a fairly fast lens, f/2 at the wide angle end
and f/2.8 at the long. This helped make up for the fact that you
really needed to shoot at iso 64 with the F828.


Scott

In article <n8Idj.1685$Xe5.742@trndny09>, peter <nospam@nospam.com> wrote:
>There are two ways to reduce noise in low light shooting. The most obvious
>is to make the pixel bigger, thus making the whole sensor bigger at same
>resolution. Another way is to reduce the ISO and make the lense faster. E.g.
>Instead of shooting at ISO 100 F4, shoot at ISO 25 at F1.0.
>
>Currently available cameras with low noise indeed have larger sensor (mostly
>DSLR). But there is no camera with small sensor and very fast lense to
>achieve low noise. Why?

There was one - the Olympus E10 and E20 - and they're available at a
reasonable price on ebay; they have a small sensor, a pretty low ISO,
and a 2.0-2.4 zoom lens which reviewers considered comparable to
Canon's best - certainly I had much less trouble taking really sharp
photos with my E10 than I have with my D100 and 18-200VR.

Tom

On Dec 30, 1:53 am, "peter" <nos...@nospam.com> wrote:
> There are two ways to reduce noise in low light shooting. The most obvious
> is to make the pixel bigger, thus making the whole sensor bigger at same
> resolution. Another way is to reduce the ISO and make the lense faster. E.g.
> Instead of shooting at ISO 100 F4, shoot at ISO 25 at F1.0.
>
> Currently available cameras with low noise indeed have larger sensor (mostly
> DSLR). But there is no camera with small sensor and very fast lense to
> achieve low noise. Why?
>
> Some may say fast lense are costly. But keep in mind this fast lense has a
> small image circle, so it is not necessarily more expensive than a slower
> lense with a larger image circle.

The image format circle has to match your sensor, regardless of the
speed of the lens. In addition to being heavy and expensive, even the
best lenses do not give that good a sharpness at the very low f/
numbers. If you stop them down to improve sharpness you are back to
the same thing as a slower lens.

I've designed very fast lenses, but thankfully that project did not
need very good image sharpness. Thank goodness. Fast lenses are
*****es to design, and need a LOT of elements to correct to even a
halfway decent sharpness. And all those elements hurt flare and ghost
performance.

Single focal length fast lenses are hard enough. If you want a zoom,
you will REALLY pay for sharpness.

On Dec 30, 6:49*am, Don Stauffer in Minnesota <stauf...@usfamily.net>
wrote:

> I've designed very fast lenses, but thankfully that project did not
> need very good image sharpness. *Thank goodness. *Fast lenses are
> *****es to design, and need a LOT of elements to correct to even a
> halfway decent sharpness. *And all those elements hurt flare and ghost
> performance.
>
> Single focal length fast lenses are hard enough. If you want a zoom,
> you will REALLY pay for sharpness.

But the OP does have a point, if the image circle is smaller a fast
lens is easier to design. A 20X microsope objective is normally about
a f/1.25 lens, very fast and very sharp, but its image circle is very
small.

And if you get down to a one pixel image circle you can buy a f/1 lens
for somewhere around $2-$3, these go into cheap laser pointers, not
much for imaging however.

Scott

Scott W wrote:
> On Dec 29, 9:53 pm, "peter" <nos...@nospam.com> wrote:
>> There are two ways to reduce noise in low light shooting. The most obvious
>> is to make the pixel bigger, thus making the whole sensor bigger at same
>> resolution. Another way is to reduce the ISO and make the lense faster. E.g.
>> Instead of shooting at ISO 100 F4, shoot at ISO 25 at F1.0.
>>
>> Currently available cameras with low noise indeed have larger sensor (mostly
>> DSLR). But there is no camera with small sensor and very fast lense to
>> achieve low noise. Why?
>>
>> Some may say fast lense are costly. But keep in mind this fast lense has a
>> small image circle, so it is not necessarily more expensive than a slower
>> lense with a larger image circle.
>
> People who are buying small compact cameras tend to be looking for
> cheap cameras and most people don't understand about lens speed, just
> zoom range and megapixels.
>
> The Sony F828 did have a fairly fast lens, f/2 at the wide angle end
> and f/2.8 at the long. This helped make up for the fact that you
> really needed to shoot at iso 64 with the F828.
>
>
> Scott
>
But neither compensated for the size of the camera. Too big for my
purposes.

On Dec 30, 1:17 pm, Scott W <biph...@hotmail.com> wrote:
> On Dec 30, 6:49 am, Don Stauffer in Minnesota <stauf...@usfamily.net>
> wrote:
>
> > I've designed very fast lenses, but thankfully that project did not
> > need very good image sharpness. Thank goodness. Fast lenses are
> > *****es to design, and need a LOT of elements to correct to even a
> > halfway decent sharpness. And all those elements hurt flare and ghost
> > performance.
>
> > Single focal length fast lenses are hard enough. If you want a zoom,
> > you will REALLY pay for sharpness.
>
> But the OP does have a point, if the image circle is smaller a fast
> lens is easier to design. A 20X microsope objective is normally about
> a f/1.25 lens, very fast and very sharp, but its image circle is very
> small.
>
> And if you get down to a one pixel image circle you can buy a f/1 lens
> for somewhere around $2-$3, these go into cheap laser pointers, not
> much for imaging however.
>
> Scott

Depends on ratio of image circle to focal length. Only if the focal
length stays the same is it easier. If the focal length and image
circle BOTH change proportionally, it is NOT easier. Neglecting
physical optics (diffraction), lens designs scale with focal length.
It is just as hard to scale a lens with an image circle a quarter of
the focal length whatever the focal length is.

If we reduce the image format size but not the focal length, we are,
in effect, reducing the field of view (field ange), and THAT is what
makes the lens easier to design. The two biggest lens design problems
are wide angle and high speed.

On Dec 31, 5:03*am, Don Stauffer in Minnesota <stauf...@usfamily.net>
wrote:
> On Dec 30, 1:17 pm, Scott W <biph...@hotmail.com> wrote:
>
>
>
>
>
> > On Dec 30, 6:49 am, Don Stauffer in Minnesota <stauf...@usfamily.net>
> > wrote:
>
> > > I've designed very fast lenses, but thankfully that project did not
> > > need very good image sharpness. *Thank goodness. *Fast lenses are
> > > *****es to design, and need a LOT of elements to correct to even a
> > > halfway decent sharpness. *And all those elements hurt flare and ghost
> > > performance.
>
> > > Single focal length fast lenses are hard enough. If you want a zoom,
> > > you will REALLY pay for sharpness.
>
> > But the OP does have a point, if the image circle is smaller a fast
> > lens is easier to design. *A 20X microsope objective is normally about
> > a f/1.25 lens, very fast and very sharp, but its image circle is very
> > small.
>
> > And if you get down to a one pixel image circle you can buy a f/1 lens
> > for somewhere around $2-$3, these go into cheap laser pointers, not
> > much for imaging however.
>
> > Scott
>
> Depends on ratio of image circle to focal length. Only if the focal
> length stays the same is it easier. If the focal length and image
> circle BOTH change proportionally, it is NOT easier. *Neglecting
> physical optics (diffraction), lens designs scale with focal length.
> It is just as hard to scale a lens with an image circle a quarter of
> the focal length whatever the focal length is.

Yes, that is true.

> If we reduce the image format size but not the focal length, we are,
> in effect, reducing the field of view (field ange), and THAT is what
> makes the lens easier to design. *The two biggest lens design problems
> are wide angle and high speed.

Even if the lens is not high speed a wide angle lens is a pain to
design.
With a fairly long lens spherical aberration dominates and so going to
a higher f/number improves things rapidly.

Wide-angle lenses tend to have a lot of astigmatism, which only goes
down linearly with the size of the aperture, but goes up by the square
of the field size. So going to a slower lens with a wide-angle lens
only helps a bit.

Scott

Scott