Medium format versus digital sharpness

Recently, Ken Hart <kwhart RemoveThis @fullnet.com> posted:
>
> [...] But
> I'm asking about the potential. Can a digital image sensor
> potentially capture more detail per square area than a piece of film?
>
One of the problems that I have with this kind of discussion is the
terminology. I have the impression that we are not all using terms such as
"detail" in the same way.

However, your question about _potential_ rather than real-world examples
is problematic for other reasons. For digital technology, the number of
sensor sites per square area is in constant flux. The 12MP sensor of today
is no larger, and in many cases smaller than the 8MP sensor of a few years
ago. So, the _potential_ of digital sensor technology is so far
unrealized. OTOH, film is a mature technology, where recent improvements
are not so much in the area of increased resolution or detail, but in
better performance at higher ISO ratings. The resolution of currently
available films is below such films as discontinued Panatomic-X and
Kodachrome 25 from decades ago. However, films such as TMax and Portra 400
far outperform ISO 160 films of that period.

Another consideration is that while there is a higher count of film grains
per square area than sensor sites in today's digital sensors, not all of
those grains contribute to the captured image (for various reasons) while
most of the digital sensor sites do. Add to that losses of resolution and
detail when printing optically or by scanning the film, and the final
image is considerably more limited than the number of grains per square
area might suggest.

Perhaps the best way to establish equivalence is to compare the final
printed image rather than trying to find a mathematical solution. And, IMO
that's going to be a pretty subjective determination for some time, yet.

Neil

Ken Hart wrote:
> "David J. Littleboy" <davidjl.DeleteThis@gol.com> wrote in message
> news:VcadnZ5lgs_NuK7anZ2dnUVZ_uKpnZ2d@giganews.com...
>> "Ken Hart" <kwhart.DeleteThis@fullnet.com> wrote:
>>>> There's nothing wrong with your math.
>>>>
>>>> The problem is with the meaning of "roughly equal to 32-36 Mpixels."
>>>>
>>>> In real life, 12MP dSLR images simply look way better than 35mm. In
>>>> prints. Every time.
>>>>
>>>> It's not even close.
>>>>
>>>> So what does it mean to say 35mm is "roughly equal to 32-36 Mpixels"?
>>>>
>>>> I don't know. It seems to be complete nonsense.
>>>>
>>>> What does it mean to you?
>>>>
>>> What I understand it to mean is that a 35mm frame contains 32-36
>>> Mega-'grains'. If the quantity of pixels is an indication of the amount
>>> of picture information that can be captured by a dSLR, then the quantity
>>> of grains should be an indication of the amount of picture information
>>> that can be captured on film. Of course, I'm not considering other
>>> factors: lens quality (either shooting or printing), subject matter, etc.
>> But in real life, if you look at the images, 35mm (ISO 100, decent lens)
>> produces prints that are slightly better than those produced by 6MP
>> cameras, about the same as those produced by 8MP cameras, and really bad
>> compared to prints produced by 12MP cameras.
>>
>>> If one is to compare the 'potential' quality of the method of image
>>> capture (film or digital sensor), you would have to compare the
>>> individual light sensing elements-- pixels or grains.
>> The geometry of how they form images is completely different, so that
>> doesn't make sense.
>>
> This is where my brain falls down and goes boom. I realize that there is a
> difference in how the image is formed: light strikes film grain, causes
> latent change, yada, yada, or light strikes image sensor, causes an
> electrical charge, yada, yada.... But whether it be grains of silver or
> silicon pixels, all the little 'bits' add up to make a photo. And if one
> system has more "little bits" than another, that one should be able to
> capture more detail, potentially, right?
>
>>> Comparing the final print seems to me to be a subjective method that
>>> introduces too many other factors.
>> Hmm. I thought the object of photography was to make photographs. Silly
>> me. It's really to brag how many photosensitive elements were used.
>>
>> One learns something new every day.
>>
> OK, you scored big points with that line! I've got to go next door to the
> fire station and have them use the jaws of life to get my head out of where
> the sun don't shine! Of course the object of photography is to make
> photographs (perhaps even 'create a work of art'!). But I'm asking about the
> potential. Can a digital image sensor potentially capture more detail per
> square area than a piece of film?

For any normal film the answer is digital can capture way more detail /
sq inch. A 1/2.5 inch sensor that has 8MP has about 14,000 pixels /
inch. Whereas the image may not be real share at the pixels level on
these sensors a good camera is far sharper then film scanned at even
4000 ppi, an example can be seen here.
http://www.dpreview.com/reviews/panasonicfz18/page11.asp

A full 35mm frame at that pixel density would have about 280 MP, of
course not many lenses could use a fraction of that resolution.

If you put that many pixels per inch on a 4x5 inch sensor you would have
a bit over 4 billion pixels.

There are reason why making your pixels that small is not a good idea,
much lower noise and better dynamic range can be had with larger pixels.

So take the case of my 1.6 crop factor cameras, they have very close to
4000 ppi, and capture far more detail per pixel then a 4000 ppi film scan.

As a way to detect photons film is incredibly inefficient, the only real
advantage is that you can use a huge area of film fairly cheaply where
as the same area for digit sensor would cost a fortune.

Scott