"Ed Anson" <EdAnson@comcast.net> wrote in message news:3F1A1653.70300@comcast.net...

> David Ruether wrote:

> > "Ed Anson" <EdAnson@comcast.net> wrote in message news:3F18A45E.7070407@comcast.net...


> >>But the lens was an explicit part of the OP's question.


> > > Then please quote it, if you have it -


> Sorry. I just assumed that you had read it. Perhaps that explains why

> you don't understand what I'm saying.  Here it is. The entire original

> question from the OP, "zing":


I did read it, but the thread developed as it went...


> > I just don't get it. If you have two sensors with the same number of

> > pixels, but one is smaller than the other, why would the larger one

> > give better low light performance? I would think the lens system takes

> > care of it that all incoming light reaches the sensor. Then as I see

> > it, all that matters is how many pixels the sensor has, the size of

> > the sensor should be irrelevant. Right?


To this should be added the title the OP chose to head this,

"Why would a large sensor give better low light performance?",

which is repeated in the first sentence of the post... And, he is right

in that the sensitivity loss due to using a smaller sensor can be made

up for by opening the lens aperture to compensate (until you run

out of apertures, where the CCD sensitivity differences would then

become important...;-) The answer to the question is then: "The

lens can compensate for the sensitivity loss due to the sensor being

smaller until the widest aperture is used. If the widest relative

apertures are the same in two cameras, one with a smaller sensor,

one with larger (with all other relevant conditions being equal, such

as pixel-count, CCD type, signal-processing, etc.), then the

larger-sensor camera will shoot successfully in a lower light level.

Changing the lens of the camera with the smaller sensor to one

with a faster maximum relative aperture may help compensate for

the sensor sensitivity loss, as may switching the CCD type, 

increasing gain, reducing the CCD pixel count, replacing the

CCD with a larger one, etc., but this "muddies" the issue of sensor

size vs. low-light range. And, BTW, there are other advantages

(and some disadvantages) to using a bigger CCD, etc. to affect

sensitivity..." But, the simple answer that really does suffice is

the one given repeatedly by me and others: "The larger CCD

is more sensitive than the smaller, all else (relevant) being



> David, if the question were about the comparitive sensitivity of the

> sensor per se (under constant light intensity) you would be absolutely

> correct in everything you say. I never disputed that. Unfortunately,

> that's not the question as I read it.


Yes - but if a poster throws two variables into the equation, it is

worth pointing out that fixing one of them makes it more likely

that the other can be better evaluated...;-)


> I don't see the OP disputing that the smaller sensor would give a weaker

> signal under equal light intensity. Instead, he seems to be suggesting

> that the lens would reasonably be adjusted to deliver the same amount of

> light to each pixel regardless of its size. [Of course, the same amount

> of light spread over a smaller area requires higher intensity.]


We are coming into agreement on the answers, but perhaps still not

how to "frame" them...;-)


> I answered his question in a separate posting, which I suppose you also

> missed. Well, it's getting late and I'm tired of this, so I'm not going

> to repeat it.


I did read it, and it was a good one....;-)


 David Ruether



 Hey, take a gander at www.visitithaca.com, too...!