Re: Default dpi

On 17/03/08, Henry G Belot wrote:

> Don:
>;
>>; ...I disagree.
>>;
>>; I think we are just beginning to be able to handle realistic
>> resolutions, which will allow you to make a large print on which you
>> can
>> examine fine detail.
>>
>
> Perhaps, but that's a very limited goal. 35mm wasn't the best choice
> for that purpose. When you wanted that sort of detail you started from
>; large-format negatives.

Ideally, yes. But I didn't mention 35mm.

> Most of the time, when "fine detail" is
> important, the appropriate starting point is close-up photography.

Why? What about architectural photography? And how about originals such
as detailed drawings, plans or maps?

All of these need plenty of megapixels.

If you are scanning a 19C engraving, you will lose significant detail at
anything less than 1200 dpi.

> I've come across a couple of low-cost digital microscopes and they
>; were both VGA resolution because the fine detail is already inherent

Optical microscope images are low resolution. For high resolution
optics, look at the lenses that were used in graphic arts for copying
and platemaking.

>; in the image. In photography, terms like "normal," "close-up," and
> "telephoto" are actually defined in terms of where the viewer stands
> with respect to the finished image. "Normal" means that the print
> fills approximately the same arc of vision as a real-life view of the
> same subject would. When the print is large, people will normally hold
>; it farther away than when it's smaller. The actual need to have both
>; in the same print is fairly rare. Specialists in the field tend to
> develop a skewed perspective about this.
>
You are off the point. I am talking about the resolution of detail in a
good quality image, such as might be used for top quality advertising
photography (formerly on 10x8 transparencies, nowadays on digital backs
for studio cameras).

This has nothing to do with the size of the objects being represented.

> The key in this example is that the professionals have developed
> unrealistic expectations because of the way they work with the
> original photography. There will always be people who expect an Ansel
> Adams print to reveal each pebble on a mountainside, but it isn't the
> way most of us operate.

Most people are not photographers to Adams's standard. But at much less
than this standard, you still need 20 Megapixels for a "prosumer"
quality image.

> We stand back and take it in as a whole. Yes,
>; there are times when you might need both perspectives in one picture,
> but digital photography trumped 35mm in the professional world before
> cameras with the monster "resolution"; of today were available.

I haven't yet seen a digital camera that equals Tech Pan on 35mm, let
alone microfilm. But we are getting there.

The quality of image I get from my Epson "professional" scanner scanning
film is barely acceptable - nowhere near what a good enlarging lens will
give in a traditional darkroom. It is completely incapable of crisply
resolving the grain on a medium speed film such as FP4.

> There
> is a need, but it's small compared to the whole and it's more likely
> to be satisfied with digital versions of large-format cameras than
>; with the digital 35mm equivalents. For one thing, it's cheaper than
>; spending $800 for the camera and $10,000 or more for each lens.

Very few lenses cost that much - mainly ultra-long lenses for sports
photography.

> You
> can go in the other direction more economically just as you could with
>; conventional photography. Not nearly as economically as you might in a
> mass market but, even so, the trade-offs are better.
>

All I am saying is that current digital equipment is at last approaching
what we have been used to in analogue. This is mainly because we now
have enough RAM and big enough disks to comfortably handle files of
60Meg and up.

The cameras are IMO at the stage colour film was at in the 1960s - in
the middle of a steady process of improvement, but with some way to go.

In the meantime, Pagestream 4 on Amithlon crashes if I try to save a
Postscript or PDF file with images of around 20 Megapixels. This means I
can't make a print quality PDF, neither directly nor via Ghostscript.

As for PGS 5, that remains a dream here.

Regards
--
Don Cox
doncox%40enterprise.net">doncoxenterprise.net

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.

Don

>> ...35mm wasn't the best choice
>> for that purpose. When you wanted that sort of detail you started from
>;> large-format negatives.
>>;
>
> Ideally, yes. But I didn't mention 35mm.
>

Fair enough, but for most of us digital photography means cameras based
on 35mm design goals.

>> Most of the time, when "fine detail" is
>> important, the appropriate starting point is close-up photography.
>>
>
> Why? What about architectural photography? And how about originals such
>; as detailed drawings, plans or maps?
>

Ideally this calls for detailed rebuttal inasmuch as you're lumping a
lot of stuff together. For example, today "detailed drawings" usually
originate in the digital domain. So do maps and many plans. I used to
know a lot of architects and they did most of their stuff in 35mm, even
for publication. All of it can be lumped into my vague references to
exceptions where our current equipment may fall short of ideal because
we need to have both the broad canvas and the fine detail in the same
image. And it's very hard to get to that. My Park Association sought the
original architectural drawings of the Park when it was designed 120
years ago and received a page-size Xerox. We did eventually get a
full-size copy, but I can't really use it in my computer and when we
recently shared it with a consultant, he Xeroxed it down and gave us
back the original. So the Xerox is what I've scanned and doctored. And
it serves /our/ main purpose. Even if I scanned the original, on our web
site it would all look the same. In a PageStream document it would get
shrunk (losing resolution accordingly) and look roughly the same as
well. The practical value of the full-size original is of interest or
utility to only a very specialized audience and for specific purposes.
Where detail and the overview are needed at the same time there seem to
be adequate tools and, by and large, they depend less on megapixels in
the camera than on having the original source and different tools for
capturing it.

> ...I am talking about the resolution of detail in a
> good quality image, such as might be used for top quality advertising
> photography (formerly on 10x8 transparencies, nowadays on digital backs
> for studio cameras).
>

There's a professional photographer less than a block from here in the
same block as me who doesn't even have a sign on his building because
everyone in the city knows who he is and where to find him. He has one
large format digital camera and one camera back. He told me he uses them
no more than three or four-times a year. The rest is 35mm digital.
Admittedly part of that is the type of advertising photography he
specializes in. But he would tell you that the need in any kind of
advertising photography is mainly in the eyes of the beholders. By the
time it reaches print, the advantage has generally long-since become
meaningless.

> The quality of image I get from my Epson "professional" scanner scanning
> film is barely acceptable - nowhere near what a good enlarging lens will
>; give in a traditional darkroom.

I don't doubt it one bit. It fits with my experience. But, it strikes me
as apples and oranges. Scanners, "professional" or otherwise, are
designed around market needs. If the market was clawing for that kind of
resolution in a scanner, scanners would already be different animals
than they are, and they're not meant to be enlarging lenses in a
traditional darkroom. Even one-to-one on small images they don't give
back what you started from---and resolution is the least of the issues
there. For the type of thing under discussion they'll do in pinch. Mine
happens to do a bang-up job on the 35mm slides and negatives I've made
over my lifetime---the specs for specialized film scanners aren't a lot
better. Prints out of my Epson printer look better than the prints I got
back from the photo shops and PXs along the way. But then, I'm not
projecting originals anymore and, in that sense, my expectations have
been reduced in favor of more convenient formats.

> ...It is completely incapable of crisply
> resolving the grain on a medium speed film such as FP4.
>;

Which may, or may not, be a resolution issue in the scanner. I don't
know. But, the skewed perspective issue from my original post comes into
play. How many people really want to see that grain? With classic movies
on DVD, many get upset when they can see grain. Others crave it as
recreating the "art" of the filmmakers---as if the filmmakers didn't
usually look at it as a compromise. If we're trying to preserve
originals of any type for posterity as we receive them then , yes, we
absolutely want whatever was there---and perhaps that's your case.
Copying it for the pleasure of the general audience is a different
matter and the line between the two is one the community has to walk all
the time. But if we want to preserve the Mona Lisa does that mean
scouring away ages of dust and contamination and, perhaps, repainting
sections with modern materials, or is it preserving the compromised
original we have, or is to some sort of digital cleanup on a present-day
copy? Mona Lisa aside, however you slice these matters, throwing more
megapixels at them isn't necessarily the answer. Resolution is only one
part of the problems.

> ...The cameras are IMO at the stage colour film was at in the 1960s - in
> the middle of a steady process of improvement, but with some way to go.
>

Gosh, I hope it's better than that by far. In its heyday film resolution
doubled every ten years, or something like that. The better lenses on
digital SLRs are already at or near their resolution limits. Going even
further pushes us well beyond markets where these toys are affordable.
The needed improvements are in areas like digital camera noise, gamma,
and, perhaps, colorimetry. Personally, I don't see "affordable"; tools in
the cards for a long time.

> ...In the meantime, Pagestream 4 on Amithlon crashes if I try to save a
> Postscript or PDF file with images of around 20 Megapixels. This means I
> can't make a print quality PDF, neither directly nor via Ghostscript.
>

Are you creating posters? If not, what's the resolution of the originals
contributing to your PDFs anyway? As Deron pointed out recently,
reducing an image by 50% in PageStream halves the available resolution
in the output. Unless I was copying some image from the Internet, I
can't think of single image in a PageStream document I've created that
wasn't reduced on the page in one way or another. And I don't care. The
resolution was always appropriate to the use.

HB

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