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ArtKramr 10-07-2003 06:36 PM

MP's vs Effective MP's?
 
What is the difference. MP's sound fine. Effective MP's sounds like stuff made
up by an ad copywriter.

Arthur Kramer
344th BG 494th BS
England, France, Belgium, Holland, Germany
Visit my WW II B-26 website at:
http://www.coastcomp.com/artkramer


Jim Townsend 10-07-2003 08:10 PM

Re: MP's vs Effective MP's?
 
ArtKramr wrote:

> What is the difference. MP's sound fine. Effective MP's sounds like stuff
> made up by an ad copywriter.
>


Actually effective megapixels is surprisingly.. Truth in advertising.

Lenses are round and sensors are square. Focusing a round image on a squre
sensor results in the corners being missed. Imagine putting a penny on a
postage stamp and how it works should be clear.

A sensor may be able to produce 5.2 megapixels, but the fact that the corners
don't see any image cuts that down a bit.. They have to crop a bit to
eliminate vignetting. (Darkness in the corners).

So a 5.2 megapixel sensor will only rusult in only 5 effective megapixels.



David J. Littleboy 10-07-2003 08:59 PM

Re: MP's vs Effective MP's?
 

"ArtKramr" <artkramr@aol.com> wrote:

> What is the difference. MP's sound fine. Effective MP's sounds like stuff

made
> up by an ad copywriter.


It's a (slight) mistranslation of a technical term that would sound just as
dizzy if a better translation were available. It's the number of pixels that
actually measure light in the the sensor. However, not all of those are used
for imaging. Since it's a bigger number than the "recording pixels", the
twits in the advertizing department prefer it. Said twits really much prefer
the total number of pixels, which includes a lot of pixels that aren't used
at all, but that blatant false advertising got silly, so everyone agreed to
state the effective pixel count.

David J. Littleboy
Tokyo, Japan



Rafe B. 10-08-2003 12:03 AM

Re: MP's vs Effective MP's?
 
On 07 Oct 2003 18:36:41 GMT, artkramr@aol.com (ArtKramr) wrote:

>What is the difference. MP's sound fine. Effective MP's sounds like stuff made
>up by an ad copywriter.



There are layers upon layers of misrepresentation when
it comes to pixel counts in digicams.

The most blatant is calling a sensor "six megapixels"
when in fact it's got six million sensing elements distributed
among three colors. But this misrepresentation runs
across the board (Ie., not specific to Brand X or Brand Y.)

Another layer of misrepresentation is the whole "effective
pixels" game. The idea is that Brand X pixels are somehow
better or worth more than the other guys, so Brand X invents
a multiplication factor with which to fudge the numbers.

IIRC, Fuji was one of the first to play this game when they
first released their "super CCD" with the hexagonal photo
sites.

It's gotten to be a lot like power ratings in audio gear.


rafe b.
http://www.terrapinphoto.com

Crownfield 10-08-2003 02:55 AM

Re: MP's vs Effective MP's?
 
Jim Townsend wrote:
>
> ArtKramr wrote:
>
> > What is the difference. MP's sound fine. Effective MP's sounds like stuff
> > made up by an ad copywriter.
> >

>
> Actually effective megapixels is surprisingly.. Truth in advertising.
>
> Lenses are round and sensors are square. Focusing a round image on a squre
> sensor results in the corners being missed. Imagine putting a penny on a
> postage stamp and how it works should be clear.
>
> A sensor may be able to produce 5.2 megapixels, but the fact that the corners
> don't see any image cuts that down a bit.. They have to crop a bit to
> eliminate vignetting. (Darkness in the corners).
>
> So a 5.2 megapixel sensor will only rusult in only 5 effective megapixels.


so my s2 pro,
using normal nikon lenses, which make a great 24x36 mm image,
falling on a 15.57x23 mm sensor will not cover the corners?

think again.

MikeWhy 10-08-2003 04:35 AM

Re: MP's vs Effective MP's?
 
"Crownfield" <Crownfield@cox.net> wrote in message
news:3F837C99.D2A@cox.net...
> so my s2 pro,
> using normal nikon lenses, which make a great 24x36 mm image,
> falling on a 15.57x23 mm sensor will not cover the corners?
>
> think again.


Well... Zuiko says they won't. Or at least mumbled something about light
drop-off in the corners from the sensor self-shadowing. ;-)



Crownfield 10-08-2003 04:43 AM

Re: MP's vs Effective MP's?
 
MikeWhy wrote:
>
> "Crownfield" <Crownfield@cox.net> wrote in message
> news:3F837C99.D2A@cox.net...
> > so my s2 pro,
> > using normal nikon lenses, which make a great 24x36 mm image,
> > falling on a 15.57x23 mm sensor will not cover the corners?
> >
> > think again.

>
> Well... Zuiko says they won't. Or at least mumbled something about light
> drop-off in the corners from the sensor self-shadowing. ;-)


what about the coverage, same lens,
Kodak 14N with 24x36 mm sensor?

MikeWhy 10-08-2003 05:48 AM

Re: MP's vs Effective MP's?
 
"Crownfield" <Crownfield@cox.net> wrote in message
news:3F8395FF.7C85@cox.net...
> MikeWhy wrote:
> >
> > "Crownfield" <Crownfield@cox.net> wrote in message
> > news:3F837C99.D2A@cox.net...
> > > so my s2 pro,
> > > using normal nikon lenses, which make a great 24x36 mm image,
> > > falling on a 15.57x23 mm sensor will not cover the corners?
> > >
> > > think again.

> >
> > Well... Zuiko says they won't. Or at least mumbled something about light
> > drop-off in the corners from the sensor self-shadowing. ;-)

>
> what about the coverage, same lens,
> Kodak 14N with 24x36 mm sensor?


This was in context of their 4/3 system; tiny, puny, insignificant stuff
compared to the Kodak's (or even Hasselblad's) monster. Since I see you
wanting to make a serious discussion of this, self-shadowing probably isn't
an issue until they bring the lens as far into the case as Olympus is doing,
and probably not at the sensor sizes they're talking about otherwise. Not
being an optical engineer, I can only regurge what the popular press has to
say, and I suspect it's mostly hyperbole based on slim but real fact. How
much light fall-off can you tolerate before compensation artifacts become
objectionable? I dunno... hence the emoticon previously. (Ummm... Having
forgotten what the original discussion was, I agree with your statement
above. I look forward to less expensive quality glass that takes advantage
of the smaller coverage.)



Crownfield 10-08-2003 06:12 AM

Re: MP's vs Effective MP's?
 
MikeWhy wrote:
>
> "Crownfield" <Crownfield@cox.net> wrote in message
> news:3F8395FF.7C85@cox.net...
> > MikeWhy wrote:
> > >
> > > "Crownfield" <Crownfield@cox.net> wrote in message
> > > news:3F837C99.D2A@cox.net...
> > > > so my s2 pro,
> > > > using normal nikon lenses, which make a great 24x36 mm image,
> > > > falling on a 15.57x23 mm sensor will not cover the corners?
> > > >
> > > > think again.
> > >
> > > Well... Zuiko says they won't. Or at least mumbled something about light
> > > drop-off in the corners from the sensor self-shadowing. ;-)

> >
> > what about the coverage, same lens,
> > Kodak 14N with 24x36 mm sensor?

>
> This was in context of their 4/3 system; tiny, puny, insignificant stuff
> compared to the Kodak's (or even Hasselblad's) monster. Since I see you
> wanting to make a serious discussion of this, self-shadowing probably isn't
> an issue until they bring the lens as far into the case as Olympus is doing,


it seems that someone who puts a sensor into a camera,
and then can not use the whole sensor
because of design problems is really not good at his job.

could it be that the angle at which the light hits the sensor,
with those lenses, is acute enough to cause some fall off?

this would apply to non film lenses,
and lenses which are designed to have a very small lens to film
distance.

> and probably not at the sensor sizes they're talking about otherwise. Not
> being an optical engineer, I can only regurge what the popular press has to
> say, and I suspect it's mostly hyperbole based on slim but real fact. How
> much light fall-off can you tolerate before compensation artifacts become
> objectionable? I dunno... hence the emoticon previously. (Ummm... Having
> forgotten what the original discussion was, I agree with your statement
> above. I look forward to less expensive quality glass that takes advantage
> of the smaller coverage.)


MikeWhy 10-08-2003 06:27 AM

Re: MP's vs Effective MP's?
 
"Crownfield" <Crownfield@cox.net> wrote in message
news:3F83AAC4.350D@cox.net...
> could it be that the angle at which the light hits the sensor,
> with those lenses, is acute enough to cause some fall off?


That's the gist of it. Film emulsion isn't "rough" enough to be a problem in
the same way. The sensor, however, is at a non-zero depth below the surface
of the chip. Hence, the more acute rays away from the lens axis begins to
self=shadow.

> this would apply to non film lenses,
> and lenses which are designed to have a very small lens to film
> distance.


This is where a better understanding of optics would help. Zuiko says the
light rays in their 4/3 series lenses are closer to parallel, less oblique.
I think I can see how this is possible, but it seems to me you don't get
nothin for nothin. Any way, it's probably as much marketing as it is real
science and fact.



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