Alan Browne wrote:
>
> I just noticed that dpreview have finally added a pixel density metric
> which could save some time when comparing cameras.
>
> However they express it as pixels / cm^2.
>
> I just wrote them a spot of feedback recommending that they do it as
> pixel pitch in lp/mm which is more consistent with lens performance
> measurements.
>
> (Even if they did it as pixel pitch in pixels/mm, it would be easier to
> imagine the meaning than pixels/cm^2
Yep!
Pixels/cm^2 is kind of counter intuitive.
A 10MP P/S camera will sport a higher number than than a 10 MP Canon XTi.
The unwashed masses are accustomed to thinking that higher numbers mean
better performance.
IMHO, what dpreview should do is state the pixel pitch (as you
indicated) or something like square microns / pixel which is a more
direct measure of light gathering power and S/N ratio.
Bob Williams
Bob Williams wrote:
> Alan Browne wrote:
>>
>> I just noticed that dpreview have finally added a pixel density
>> metric which could save some time when comparing cameras.
>>
>> However they express it as pixels / cm^2.
>>
>> I just wrote them a spot of feedback recommending that they do it as
>> pixel pitch in lp/mm which is more consistent with lens performance
>> measurements.
>>
>> (Even if they did it as pixel pitch in pixels/mm, it would be easier
>> to imagine the meaning than pixels/cm^2
>
> Yep!
> Pixels/cm^2 is kind of counter intuitive.
> A 10MP P/S camera will sport a higher number than than a 10 MP Canon
> XTi. The unwashed masses are accustomed to thinking that higher
> numbers mean better performance.
> IMHO, what dpreview should do is state the pixel pitch (as you
> indicated) or something like square microns / pixel which is a more
> direct measure of light gathering power and S/N ratio.
> Bob Williams
Agreed, although do you want actual pixel area, or "effective
light-gathering" pixel area? In terms of showing resolution, I think that
a linear rather than an area measure would better match human perception.
Bob Williams <mytbobnospam@cox.net> wrote:
>Alan Browne wrote:
>>
>> I just noticed that dpreview have finally added a pixel density metric
>> which could save some time when comparing cameras.
>
>Pixels/cm^2 is kind of counter intuitive.
Sorry, I don't see the point. Number of items divided by area seems to
be the correct unti for density.
>A 10MP P/S camera will sport a higher number than than a 10 MP Canon XTi.
>The unwashed masses are accustomed to thinking that higher numbers mean
>better performance.
Then they are greatly mistaken. BTW, your 'rule' doesn't apply for many
things:
- F-stop: most people would consider 1.4 to be better than 4 (yes, I
know it's actually f/1.4, but that origin has long been lost).
- weight: most people would prefer a lighter camera
- size: most people would prefer a smaller camera
- price: most people would prefer a lower price
- fuel consumption: I hope nobody would argue that 12 l/100km is better
than 8l/100km
- travel time: most people would prefer traveling 2 hours instead of 6
- ....
David J Taylor wrote:
> Bob Williams wrote:
>> Alan Browne wrote:
>>> I just noticed that dpreview have finally added a pixel density
>>> metric which could save some time when comparing cameras.
>>>
>>> However they express it as pixels / cm^2.
>>>
>>> I just wrote them a spot of feedback recommending that they do it as
>>> pixel pitch in lp/mm which is more consistent with lens performance
>>> measurements.
>>>
>>> (Even if they did it as pixel pitch in pixels/mm, it would be easier
>>> to imagine the meaning than pixels/cm^2
>> Yep!
>> Pixels/cm^2 is kind of counter intuitive.
>> A 10MP P/S camera will sport a higher number than than a 10 MP Canon
>> XTi. The unwashed masses are accustomed to thinking that higher
>> numbers mean better performance.
>> IMHO, what dpreview should do is state the pixel pitch (as you
>> indicated) or something like square microns / pixel which is a more
>> direct measure of light gathering power and S/N ratio.
>> Bob Williams
>
> Agreed, although do you want actual pixel area, or "effective
> light-gathering" pixel area? In terms of showing resolution, I think that
> a linear rather than an area measure would better match human perception.
>
> David
Certainly, "effective light gathering area" would be ideal but that info
would have to come from the manufacturer because it would entail info
not readily available to a reviewer. It is not something that dpreview
could calculate from the known area of the sensor and the number of
pixels on it.
Also, I think that an area measure gives more useful info about S/N
ratio than the linear measure.
For instance, if Camera A's sensor had pixels that were 2 microns on a
side and Camera B's pixels were 6 microns on a side, one might infer
that Camera B's sensor had a S/N ratio 3X better than Camera A's.
Wheras, in fact, B's S/N ratio is closer to 9X greater than A's.
The areal notation would show clearly that A's area is 4 sq. microns and
B's is 36 sq. microns.
Bob Williams
Bob Williams wrote:
> David J Taylor wrote:
>> Bob Williams wrote:
>>> Alan Browne wrote:
>>>> I just noticed that dpreview have finally added a pixel density
>>>> metric which could save some time when comparing cameras.
>>>>
>>>> However they express it as pixels / cm^2.
>>>>
>>>> I just wrote them a spot of feedback recommending that they do it
>>>> as pixel pitch in lp/mm which is more consistent with lens
>>>> performance measurements.
>>>>
>>>> (Even if they did it as pixel pitch in pixels/mm, it would be
>>>> easier to imagine the meaning than pixels/cm^2
>>> Yep!
>>> Pixels/cm^2 is kind of counter intuitive.
>>> A 10MP P/S camera will sport a higher number than than a 10 MP
>>> Canon XTi. The unwashed masses are accustomed to thinking that
>>> higher numbers mean better performance.
>>> IMHO, what dpreview should do is state the pixel pitch (as you
>>> indicated) or something like square microns / pixel which is a more
>>> direct measure of light gathering power and S/N ratio.
>>> Bob Williams
>>
>> Agreed, although do you want actual pixel area, or "effective
>> light-gathering" pixel area? In terms of showing resolution, I
>> think that a linear rather than an area measure would better match
>> human perception. David
>
>
> Certainly, "effective light gathering area" would be ideal but that
> info would have to come from the manufacturer because it would entail
> info not readily available to a reviewer. It is not something that
> dpreview could calculate from the known area of the sensor and the
> number of pixels on it.
>
> Also, I think that an area measure gives more useful info about S/N
> ratio than the linear measure.
> For instance, if Camera A's sensor had pixels that were 2 microns on a
> side and Camera B's pixels were 6 microns on a side, one might infer
> that Camera B's sensor had a S/N ratio 3X better than Camera A's.
> Wheras, in fact, B's S/N ratio is closer to 9X greater than A's.
> The areal notation would show clearly that A's area is 4 sq. microns
> and B's is 36 sq. microns.
> Bob Williams
Agreed on the information not being available.
Disagree on the sensitivity measure - just think of it in f/stop terms -
half the f/number means four times the light... And in any case, for the
photon-limited noise case, SNR is proportional to the square-root of the
light level.
Jürgen Exner wrote:
> Bob Williams <mytbobnospam@cox.net> wrote:
>> Alan Browne wrote:
>>> I just noticed that dpreview have finally added a pixel density metric
>>> which could save some time when comparing cameras.
>> Pixels/cm^2 is kind of counter intuitive.
>
> Sorry, I don't see the point. Number of items divided by area seems to
> be the correct unti for density.
>
>> A 10MP P/S camera will sport a higher number than than a 10 MP Canon XTi.
>> The unwashed masses are accustomed to thinking that higher numbers mean
>> better performance.
>
> Then they are greatly mistaken. BTW, your 'rule' doesn't apply for many
> things:
> ...
> - fuel consumption: I hope nobody would argue that 12 l/100km is better
> than 8l/100km ...
I recently heard it argued that gallons per mile is a more meaningful
measurement than miles per gallon.
This is about whether people are counting low light performance or
compactness... if you are looking for a compact high res camera, they've
chosen the right metric but if you are looking for low light
performance, you'd want to see the size of the pixel. The total MP count
is already given so it doesn't make much sense to talk about megapixels
in this number.
David J Taylor wrote:
> Bob Williams wrote:
>> David J Taylor wrote:
>>> Bob Williams wrote:
>>>> Alan Browne wrote:
>>>>> I just noticed that dpreview have finally added a pixel density
>>>>> metric which could save some time when comparing cameras.
>>>>>
>>>>> However they express it as pixels / cm^2.
>>>>>
>>>>> I just wrote them a spot of feedback recommending that they do it
>>>>> as pixel pitch in lp/mm which is more consistent with lens
>>>>> performance measurements.
>>>>>
>>>>> (Even if they did it as pixel pitch in pixels/mm, it would be
>>>>> easier to imagine the meaning than pixels/cm^2
>>>> Yep!
>>>> Pixels/cm^2 is kind of counter intuitive.
>>>> A 10MP P/S camera will sport a higher number than than a 10 MP
>>>> Canon XTi. The unwashed masses are accustomed to thinking that
>>>> higher numbers mean better performance.
>>>> IMHO, what dpreview should do is state the pixel pitch (as you
>>>> indicated) or something like square microns / pixel which is a more
>>>> direct measure of light gathering power and S/N ratio.
>>>> Bob Williams
>>> Agreed, although do you want actual pixel area, or "effective
>>> light-gathering" pixel area? In terms of showing resolution, I
>>> think that a linear rather than an area measure would better match
>>> human perception. David
>>
>> Certainly, "effective light gathering area" would be ideal but that
>> info would have to come from the manufacturer because it would entail
>> info not readily available to a reviewer. It is not something that
>> dpreview could calculate from the known area of the sensor and the
>> number of pixels on it.
>>
>> Also, I think that an area measure gives more useful info about S/N
>> ratio than the linear measure.
>> For instance, if Camera A's sensor had pixels that were 2 microns on a
>> side and Camera B's pixels were 6 microns on a side, one might infer
>> that Camera B's sensor had a S/N ratio 3X better than Camera A's.
>> Wheras, in fact, B's S/N ratio is closer to 9X greater than A's.
>> The areal notation would show clearly that A's area is 4 sq. microns
>> and B's is 36 sq. microns.
>> Bob Williams
>
> Agreed on the information not being available.
>
> Disagree on the sensitivity measure - just think of it in f/stop terms -
> half the f/number means four times the light... And in any case, for the
> photon-limited noise case, SNR is proportional to the square-root of the
> light level.
>
> Cheers,
> David
>
>
Right you are, David!
I forgot that S/N ratio was proportional to the square root of the
area......not the area itself. Thanks for the memory jog.
Bob
>>> (Even if they did it as pixel pitch in pixels/mm, it would be easier
>>> to imagine the meaning than pixels/cm^2
>> Yep!
>> Pixels/cm^2 is kind of counter intuitive.
>> A 10MP P/S camera will sport a higher number than than a 10 MP Canon
>> XTi. The unwashed masses are accustomed to thinking that higher
>> numbers mean better performance.
>> IMHO, what dpreview should do is state the pixel pitch (as you
>> indicated) or something like square microns / pixel which is a more
>> direct measure of light gathering power and S/N ratio.
>> Bob Williams
>
> Agreed, although do you want actual pixel area, or "effective
> light-gathering" pixel area? In terms of showing resolution, I think that
> a linear rather than an area measure would better match human perception.
>
> David
>
I don't see the point of the pixel density metric since dpreview already
measures noise and resolution at different ISO settings. That's what
matters. Bigger pixels tend to perform better on those respects, but
it's not a direct measure so why bother when you already have the real
thing?
timeOday wrote:
> David J Taylor wrote:
>
>>>> (Even if they did it as pixel pitch in pixels/mm, it would be easier
>>>> to imagine the meaning than pixels/cm^2
>>> Yep!
>>> Pixels/cm^2 is kind of counter intuitive.
>>> A 10MP P/S camera will sport a higher number than than a 10 MP Canon
>>> XTi. The unwashed masses are accustomed to thinking that higher
>>> numbers mean better performance.
>>> IMHO, what dpreview should do is state the pixel pitch (as you
>>> indicated) or something like square microns / pixel which is a more
>>> direct measure of light gathering power and S/N ratio.
>>> Bob Williams
>> Agreed, although do you want actual pixel area, or "effective
>> light-gathering" pixel area? In terms of showing resolution, I think that
>> a linear rather than an area measure would better match human perception.
>
> I don't see the point of the pixel density metric since dpreview already
> measures noise and resolution at different ISO settings. That's what
> matters. Bigger pixels tend to perform better on those respects, but
> it's not a direct measure so why bother when you already have the real
> thing?
Dpreview only lists ISO and provides jpegs to assess, there's no number
other than highest offered ISO, which is an OK general indication but...
If they calculated SNR, full well saturation or some such from raw
files, that'd be useful but they don't.
dpreview pixel density metric 
Linear Mode
