From: Bates on
On Jul 15, 9:22 am, John P Sheehy <j...(a)no.kom> wrote:
> I've made a direct comparison of RAW data per unit of area in the deep
> shadows of ISO 100 between the FZ50 (1.97 micron) and the 400D (5.7
> micron). Exposure is the same, same Av (f/4.5), same Tv (1/100), same real
> focal length (22mm), both shot at "ISO 100" pushed to ISO 13,500. Large
> crop is 100% for FZ50 (0.4MP), and small crop is 100% for 400D (0.05MP),
> and the other two are the other camera scaled to the 100% crop of each. As
> I already knew, the bigger pixels of the DSLR are inferior compared to the
> higher pixel density of the small sensor camera:
>
> http://www.pbase.com/jps_photo/image/100092629
>
> --
> John Sheehy

It's an interesting test but it there are too many other variables
involved here which are causing problems. For one (and I'm not saying
you have the equipment, resources or money to do this test), if you
want to really only compare the effect of pixel density which is what
your subject line states, then I would think the better test is to
line up a 350D and 400D and a 450D - all of which have the exact same
sensor size, but differ in pixel density only (http://www.dpreview.com/
reviews/compare_post.asp?method=sidebyside&cameras=canon_eos400d
%2Ccanon_eos450d
%2Ccanon_eos350d&camuser=canon_eos400d&camuser=canon_eos450d&camuser=canon_eos350d&show=all).
Then you can use the exact same lens etc....compare the exact same
sensor size, and only worry about pixel density.

Bates....
From: Rich on
On Jul 15, 10:50 pm, John Sheehy <J...(a)no.komm> wrote:
> "Richard" <rander3...(a)gmail.com> wrote innews:udCdnfTLKrdVyuDVnZ2dnUVZ8tLinZ2d(a)giganews.com:
>
> > Notice that I can buy a lens from a scientific supplier that specifies
> > exactly what lp/mm (like 100 maybe?) I'll get with say 5um pixels, but
> > NONE of the consumer mfgs will provide that kind of data for their
> > lenses? It can only be derived by testing.
>
> I've used lenses I own on 8 and 10 MP APS DSLRs with stacks of TCs of 2.8x,
> and 4x, and gotten detail that was fragile enough to get lost downsampling
> to 70%. This means that these lenses should enjoy 8x to 16x the pixel
> density, without the TCs.

I've heard the claims from some mfgs. What their lenses will support
in-terms of resolution. But they never provide enough specifics for
it to make any real sense.
Good lenses (diffraction-limited with resolution based on wide open
apertures) should support about at least 20x their aperture in focal
length (for a 50mm wide lens, 1000mm), at which point resolution
potential of the lens should be reached. I can pretty much guarantee
that very few camera lenses would meet this test. Most would see
image "break down" before reaching that focal ratio because they are
FAR from being diffraction-limited.
From: Rich on
On Jul 15, 11:11 pm, John Sheehy <J...(a)no.komm> wrote:
> Jufí <b0w...(a)h0me.c0m> wrote innews:Zhbfk.265$av4.11(a)trnddc04:
>
> > John, nothing you've posted here is correct. If you want, I'll shoot
> > pix using my G9 and 5D at ISO 1600, and post the 100% crops.
> > Resolution of the sensors is very close, only the size of the pixels
> > is very different. It will shot that smaller pixels simply cannot
> > compete with larger pixels. Unless I'm totally missing your point
> > here...
>
> Yes, you are totally missing the point here. The demonstration is of PIXEL
> DENSITY; not SENSOR SIZE; not PIXEL SIZE.

E.g. an Olympus 4/3rds sensor is only 18mm x 13mm in size. It can
have 10 megapixels. Another camera (Nikon, etc) can have a 23mm x
17mm sized sensor and 10 megapixels. Given the same lens focal
length, the Olympus sensor has a higher pixel density because it has
concentrated as many pixels into a smaller area than the APS-sized
sensor. This means with a specific lens focal length, the Olympus
image will be higher resolution for any specific part of the image.
But, the Olympus sensor covers a narrower area than the APS sensor.
From: ASAAR on
On Wed, 16 Jul 2008 21:54:02 +0900, David J. Littleboy wrote:

>> Uh, OK. So why not compare cameras with the same size sensors but
>> different numbers of pixels?
>
> That would make it too easy. Which would you rather have: a D70 or a D300?

That's also too easy since a G9 and 5D were mentioned. Switch a
'0' and you can have the D30 while I'll take the D700 that's left.

From: Jufì on

"David J. Littleboy" <davidjl(a)gol.com> wrote in message
news:19Gdner-fK_xcuDVnZ2dnUVZ_qfinZ2d(a)giganews.com...
>
> "Jufi" <bowser(a)work.com> wrote:
>> "John Sheehy" <JPS(a)no.komm> wrote in message
>> news:Xns9ADCEBDB1EE43jpsnokomm(a)199.45.49.11...
>>> Juf� <b0wser(a)h0me.c0m> wrote in news:Zhbfk.265$av4.11(a)trnddc04:
>>>
>>>> John, nothing you've posted here is correct. If you want, I'll shoot
>>>> pix using my G9 and 5D at ISO 1600, and post the 100% crops.
>>>> Resolution of the sensors is very close, only the size of the pixels
>>>> is very different. It will shot that smaller pixels simply cannot
>>>> compete with larger pixels. Unless I'm totally missing your point
>>>> here...
>>>
>>> Yes, you are totally missing the point here. The demonstration is of
>>> PIXEL
>>> DENSITY; not SENSOR SIZE; not PIXEL SIZE.
>>
>> Uh, OK. So why not compare cameras with the same size sensors but
>> different numbers of pixels?
>
> That would make it too easy. Which would you rather have: a D70 or a D300?

I guess I just don't get the point of his comparison. Why bother to compare
the results of two cameras that have virtually nothing in common when you
can compare sensors of the same size with different pixel counts? And how do
you account for the diminishing returns as you approach very small pixel
sizes? I just don't see the point of this excercise at all, regardless of
what someone's intrepertation of the results may be. Unless you're designing
and building your own sensors, then you need to select a commercial product,
and why not just compare available products?

maybe it's me...