SLR v P&S

In article ,
MC wrote:

Depends on the size of sensor. If two cameras have the same number of
pixels you will find that you will obtain better quality images from a
camera with the larger sensor. P+S cameras usually use far smaller sensors
than dSLRs and have to fit more pixels into a smaller area. This causes
compromised image quality in the P+S. Sensors in mobile phones, for
example, are tiny in comparison to dSLR sensors and the images produced from
those are normally terrible. The number of pixels just means that you can
produce an image of a certain size. This does not, however, necessarily mean
an image of quality.

Is that really true? I hear it over and over, but it
seems to me the issue is not sensor size directly, rather
it's the number of photons per photosite. dSLRs want
big sensors, it seems to me, because they want to be able
to use lenses that were designed to spread the photons over
a 43.26mm disk to accommodate 35mm film. If the sensors
are small, many of the photons will hit outside the sensor
area and be wasted.

Again, it seems to me that if you want good low light
performance, it comes down to, like in telescopes, a large
aperture. And, of course, you want the optics to put the
photons on the sensor rather than the focal plane outside
the sensor area.

Nobody makes a P&S camera with a big objective lens, but
that's all it would take to make the small P&S sensors
perform like full-frame dSLRs. I.e., I don't think there's
anything intrinsic about dSLRs or big sensors having good
low light characteristics. It's more money (for big optics)
than dSLR vs. P&S.

--alan

"AlanL" wrote in message
...
In article ,
MC wrote:

Depends on the size of sensor. If two cameras have the same number of
pixels you will find that you will obtain better quality images from a
camera with the larger sensor. P+S cameras usually use far smaller
sensors
than dSLRs and have to fit more pixels into a smaller area. This causes
compromised image quality in the P+S. Sensors in mobile phones, for
example, are tiny in comparison to dSLR sensors and the images produced
from
those are normally terrible. The number of pixels just means that you can
produce an image of a certain size. This does not, however, necessarily
mean
an image of quality.

Is that really true? I hear it over and over, but it
seems to me the issue is not sensor size directly, rather
it's the number of photons per photosite. dSLRs want
big sensors, it seems to me, because they want to be able
to use lenses that were designed to spread the photons over
a 43.26mm disk to accommodate 35mm film. If the sensors
are small, many of the photons will hit outside the sensor
area and be wasted.


It doesn't really matter what the reason is for using a certain size of
sensor, squeezing the same amount of pixels onto a small sensor in favour of
a big one will (at present technology levels) will cause slightly inferior
image quality from the smaller sensor.

MC

In article ,
MC wrote:

It doesn't really matter what the reason is for using a certain size of
sensor, squeezing the same amount of pixels onto a small sensor in favour of
a big one will (at present technology levels) will cause slightly inferior
image quality from the smaller sensor.

Why does smaller pixel make a inferior image
and how much is 'slightly' ?

--alan

AlanL wrote:
In article ,
MC wrote:
It doesn't really matter what the reason is for using a certain size of
sensor, squeezing the same amount of pixels onto a small sensor in favour of
a big one will (at present technology levels) will cause slightly inferior
image quality from the smaller sensor.

Why does smaller pixel make a inferior image
and how much is 'slightly' ?

--alan

Smaller pixel size means less active area to detect the image and
therefore greater amplification required to achieve the same
sensitivity, both causing greater noise (or "digital grain") to show up
in photos.
That's what causes the red/green/blue speckles in shadow areas.

Doug Jewell wrote:
Bob Williams wrote:
Pete D wrote:
"Bob Williams" wrote in message
...
Don Stauffer wrote:
YDOD wrote:
I would expect a picture taken with a digital SLR to have better
resolution and contrast than the same picture taken with a P&S.
Are there any web sites which show exactly how much difference
there is between the two types of cameras and also explain what
the average P&S photographer is giving up on on his typical family
and holiday snapshots.

Why would you expect that? I have a five mp DSLR, I see P&S
cameras with ten mp. That is a lot more pixels to make up.

With scenes shot from longer distances, I cannot think of any
reason there would be an inherent technical reason why resolution
and contrast should depend on what kind of viewfinding and focusing
mechanisms a camera has.

Now, with macro work, that is something else. Seeing the actual
lens focus through an SLR does have advantages.
OTOH, getting a 1:1 Macro shot with a DSLR may require a special
Macro lens or an auxiliary lens attachment. Whereas this task is a
piece of cake for a P&S cameras with an EVF.
Bob Williams

Or it might not.

I said, MAY require to hedge my bet.
But I don't know of any "Standard" DSLR lens that can capture 1:1
Macro images without some accessory lens.
Bob Williams

True... but I don't know of any P&S that can achieve 1:1 Macro either.
True 1:1 macro would be an image about 6mm wide with their tiny sensors.
If you consider 1:1 to be "35mm equivalent 1:1" ie - a frame width of
36mm at minimum focus, then things are a little better.

It's a matter of definitions, I guess.
You are correct in that a P&S camera cannot capture an image equal to
the sensor's size. (With the possible exception of the old Nikon Coolpix
9xx series".)
OTOH, If I wanted to make 1:1 copies of a slide collection (24x36mm, one
could easily do so with most P&S cameras, but NOT with a DSLR using a
standard lens.
Bob

My Pentax K10 with the 18-55 Lens has a frame width of 55mm at minimum
focus, while my Canon 450D with 18-55IS has a frame width of 51mm at
minimum focus. To compare this with 35mm film that is 1.52:1 & 1.41:1
respectively.

My Canon Ixus 70 can achieve a minimum frame width of 40mm, while the
SxIS series can achieve minimum frame width of 20mm - this is 1.1:1 &
0.55:1 respectively, so yes they are getting better magnification than
the stock standard SLR lenses. But there is a catch. The Ixus 70
achieves that magnification when the subject is a mere 3cm from the
lens. On the SxIS series, the subject has to be TOUCHING the lens to get
that level of magnification. Basically it is only useful for backlit
subjects, because the camera will shade any front-lit subject. Add in to
the equation that they do these close ups at their wide angle (more
distortion) and it isn't nearly as useful as it sounds.

For greater magnification (or magnification at a more useful operating
distance), you can do 2 things with an SLR - you can use those cheap
disgusting "close-up" filters, or you can buy a true macro lens. With a
P&S your one option is to use a "close-up" filter - which will probably
require you to purchase an adaptor kit as well.

AlanL wrote:
In article ,
MC wrote:

It doesn't really matter what the reason is for using a certain size
of sensor, squeezing the same amount of pixels onto a small sensor
in favour of a big one will (at present technology levels) will
cause slightly inferior image quality from the smaller sensor.

Why does smaller pixel make a inferior image
and how much is 'slightly' ?

--alan

Read the articles on Roger Clark's Web site:

http://www.clarkvision.com/new_articles.html

such as:

http://www.clarkvision.com/imagedeta...l.size.matter/

http://www.clarkvision.com/imagedeta....size.matter2/

http://www.clarkvision.com/imagedeta...mance.summary/

Cheers,
David

YDOD wrote:
I would expect a picture taken with a digital SLR to have better
resolution and contrast than the same picture taken with a P&S.

Trick question. It can be the opposite but in deceptive ways. In ideal
lighting the P&S will look better because the default settings add more
contrast & sharpening, the DSLR will look dull & soft at default
settings but you can adjust that. Resolution in counted pixels can be
more or less but real image detail with a DSLR will be a lot better in
poor lighting - similar in good lighting.

Are
there any web sites which show exactly how much difference there is
between the two types of cameras and also explain what the average P&S
photographer is giving up on on his typical family and holiday snapshots.

Not off the top of my head but there will be a lot of misleading
comparisons. As I said, with default settings in good light, the P&S
will look better to an untrained eye. If conditions get tough, things go
downhill.

In low light the DSLR will be much much better. That includes indoor
family photos. The larger sensor means it gathers more light. A smaller
sensor will have more noise (graininess) in low light so there will be
noise reduction applied by the camera and that smears detail giving less
resolution.

P&S can have much larger zoom range in a much smaller size for much less
money but usually poorer optics and less wide angle zoom. So for a group
of people gathered for dinner, you probably can't back up far enough to
get the whole group with P&S and the standard DSLR kit lens is wider
(depending on budget for both). You can get much wider lenses for the
DSLR with more money. P&S *are* easier to get moderate closeups with
good light but DSLRs can do a lot more with effort & money. A DSLR kit
zoom will have a piddly amount of long zoom compared to many P&S but you
can put any lens on it up to NASA standards :-) and that will be heavy &
expensive.

DSLRs can be put in auto mode but there are many more ways to go wrong &
get confused. That's why P&S are called point & shoot. One example is
the shallower depth of field so focusing is more critical where P&S have
pretty much everything in focus & it's hard to go wrong. But you will
notice that professional portraits have a shallow depth of field so
there is a dreamy blurred background that doesn't distract contrasted
with nice sharp eyes. P&S portraits are often full of messy twigs &
clutter in the background.

I suggest both. A compact P&S that you can always have in your pocket on
daily trips for spur of the moment stuff (content trumps quality) and an
entry level DSLR for more intentional shots with maybe one tricky lens
to play more if budget allows. If you are up for toting a DSLR start
there, most people find a P&S more useful & don't want the hassle of
more than that. If the light is bad, the flash pops - that can look less
nice but you got a picture because you had your camera with you.

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

all google groups messages filtered due to spam

Paul Furman wrote:
[]
I suggest both. A compact P&S that you can always have in your pocket
on daily trips for spur of the moment stuff (content trumps quality)
and an entry level DSLR for more intentional shots with maybe one
tricky lens to play more if budget allows. If you are up for toting a
DSLR start there, most people find a P&S more useful & don't want the
hassle of more than that. If the light is bad, the flash pops - that
can look less nice but you got a picture because you had your camera
with you.

The P&S can also do movies, and complements the DSLR (which usually don't
do video). Another reason for getting both.

Cheers,
David

AlanL wrote:
In article ,
MC wrote:

It doesn't really matter what the reason is for using a certain size
of sensor, squeezing the same amount of pixels onto a small sensor
in favour of a big one will (at present technology levels) will
cause slightly inferior image quality from the smaller sensor.

Why does smaller pixel make a inferior image

It doesn't, necessarily, except in low light. Then smaller pixels collect
fewer photons and therefore the image has to be amplified more. Greater
amplification produces more "noise" which tends to destroy image quality.


and how much is 'slightly' ?

By what unit of measure? :-)

Some people find noise more objectionable than others. Noise may not be
visible on a small print but very apparent on a large print. There are so
many variables I don't think anyone can answer the question, How much is
"slightly"? But compact cameras with their much smaller sensors will
invariably have more problem with noise than DSLRs, assuming high ISOs have
to be used (i.e., poor light). At low ISO numbers (lots of light available)
there may be little if any visible difference.

Neil Harrington wrote:
[]
It doesn't, necessarily, except in low light. Then smaller pixels
collect fewer photons and therefore the image has to be amplified
more. Greater amplification produces more "noise" which tends to
destroy image quality.

It's not so much a question of amplification, although that does come into
it, but that a small number of photons (such as the number collected by a
smaller sensor) will inherently have a higher noise level, and hence a
poorer signal-to-noise ratio. I.e. the noise is in the photon stream
itself.

http://en.wikipedia.org/wiki/Shot_noise

Cheers,
David