[meteorite-list] Digital Photography

From: Sterling K. Webb <kelly_at_meteoritecentral.com>
Date: Thu Apr 22 10:02:28 2004
Message-ID: <3C904EA3.FC2C7ADD_at_bhil.com>

Hi, Martin and List,

    Translating digital pixels to film resolution is complicated. The highest
resolution 35mm format lens commercially available, the Carl Zeiss T* Planar,
has a resolution of 63 lines per mm when tested on a standard film resolution
card. Since resolving a "line" needs a theoretical minimum of two pixels, that
would correspond to a digital resolution of 3024 x 4536, or about 13.7 million
pixels, to equal the 35mm film format (24mm x 36mm). That is only the
theoretical minimum, however. In practice, it might take more than 17 million
pixels.
    The five megapixel digital camera is roughly equivalent to having a film
camera that uses an imaginary 20mm format (14mm x 21mm), if there were such a
thing. Sounds a lot like the current APS format to me.
    On the other hand, Ansel Adams' 8 x 10 sheet film cameras produced images
that translate to a minimum digital resolution of 12,600 x 16,000 or about 200
million pixels. I suspect it will be a long time before any direct digital
device matches that!
    There are vast difference in the way grains of photosensitive chemicals
respond to light as compared to the way the bins of a CCD respond, which means
that people will undoubtedly continue to argue about which is "better" long
after the two media have achieved parity of theoretical resolution.
    Most modern monitors have a 0.25mm dot pitch which corresponds to slightly
more than 100 dpi. Even an older 0.28mm dot pitch monitor is 91 dpi. Both image
scales are beyond the power of the best human eye to "resolve" into individual
pixels.
    Truly high quality monitors (starting at around $600 to $800) offer a
control over color rendition that vastly exceeds that of any film technology,
with control of color temperature in one-degree increments and 48-bit cards
provide adjustments in luminosity, saturation and hue up to 600 times finer in
scale than any film or paper offers.
    Virtually all commercial photography, from the medium-grade "pro" up to the
top of the field, combines the two technologies. Images are shot on film (for
the highest resolution) and then digitized and manipulated (for the greatest
control of outcome) for production. Medium format film (120) in modern emulsions
and commercially digitized can easily create an image with more than 200 million
pixels to work with.
    Finding another Ansel Adams is harder, though...

Sterling Webb
-----------------------------------------------------------
Martin Horejsi wrote:

> On 3/13/02 8:04 AM, "Jim Strope" <jim_at_catchafallingstar.com> wrote:
>
> > According to some friends of mine who are very involved in photography,
> > Digital camera resolution will equal that of 35mm when the digitals reach
> > 17megapixels.
>
> Hi Jim and All,
>
> I don't know if the 17 megapixel limit is right or not, and I don't dispute
> it, however there is another side to that limit.
>
> Most people cannot take a picture that is anywhere near the limit of what
> 35mm photography is all about. I used to do high resolution art photography
> with 35mm. I know that sounds like a contradiction, and in a way it was, but
> that's what I did.
>
> To reach the limits of 35mm cameras, one first must have the best equipment.
> Retail, that would probably be Leica. However I used Nikon which I felt was
> definitely in at least second place, but not by much.
>
> Then there is the film issue. One would have to shoot very low EV black and
> white film (maybe ASA 10-12) and use special development procedures to get
> the proper limit of resolution.
>
> Then their is the support issue. Lightweight tripods won't cut it. Nor will
> very fast or very slow shutter speeds. There is an optimum range for max
> resolution.
>
> Then there is F-stop (or F-step as some like to say). Each lens has a
> particular f-stop where it will be sharpest and it is never the max number.
>
> Finally, there is the exposure of the image. Again, few people could ever
> measure a proper exposure without training. However, the excellent matrix
> metering in today's auto cameras makes this less of an issue.
>
> So you can see, there is really much to the theoretical comparison of 35mm
> and digital. When you put all of this through a filter of general use
> photography by the serious consumer, I believe 5 megapixel is actually
> plenty for 99+ percent of all digital use, in fact, it is usually overkill.
>
> Now when you are using only a computer monitor for viewing (ie Internet,
> email), all of this is mostly meaningless because of the limited color
> quality (or at least color control and predictability), and the low
> resolution of monitors (about 72-75 dpi).
>
> Just my two rolls of film.
>
> Cheers,
>
> Martin
Received on Thu 14 Mar 2002 02:17:56 AM PST