(Note: Be sure to look at
my FlashPix reference images,
which are presented on a separate page so that those who haven't yet
loaded the plug-in aren't annoyed by dialog boxes)
I wrote this document in July of 1997. Since then, some of the
information has become obsolete. Notably, Hewlett-Packard has stopped
distributing software in a simple manner (they do have some software but
I haven't figured out what it does and they say that it will expire
after 45 days). If you just want a PhotoShop plug-in, visit
http://livepicture.com
FlashPix is an imaging format that lets you publish extremely high
resolution images over the Internet. Readers of your site, however,
wait only for the bits that they need.
For example, suppose that you are publishing a 4000x6000 ProPhotoCD
scan. Uncompressed, this is a 72 MB file. After typical JPEGing, you'd
still have a 7 MB file. This would take at least 20 minutes to download
via a 56 KB modem. And if your reader wants to make a high-quality
print at home, that's how long he will wait for the bits. But if the
reader is viewing the image on a 1000x768 pixel display, he will never
wait for more than 1000x768 pixels to download.
There are some other interesting things about FlashPix from a Web
publisher's point of view, but I've written about them already in my scanning guide and my book on Web publishing. This document
concentrates on the mechanics of getting a Flash image onto your Web
site.
The Short Answer
Get a Kodak PhotoCD or some other high quality, high-resolution scan
made
Visit
http://image.hp.com and
download the plug-in for Adobe PhotoShop (Mac or PC)
Load the high resolution scan into a computer where PhotoShop has
enough memory to hold the entire image, plus some. I have successfully
converted regular 2000x3000 pixel PhotoCDs on a Windows NT 4.0 machine
with 64 MB. The plug-in failed (silently) when converting the 72 MB Pro
scans on this machine. The same software converted the larger image
without a hitch on a Windows NT 4.0 machine with 256 MB of RAM.
The plug-in will not tell you if it fails. Test your FlashPix
immediately by downloading the Netscape Navigator plug-in from
http://image.hp.com. Then tell Netscape
to "open the foobar.fpx" that you just created. If you can successfully
work with the image that way, then you know that the server software
will ultimately be able to read it.
Visit
http://image.hp.com
and
download the CGI scripts for HP-UX or Windows NT (http://www.kodak.com
is eventually going to have some server software for other operating
systems but they didn't have anything to download last I checked). Install the CGI scripts on
your Web server.
Add some hyperlinks to the pages where you'd like FlashPix to
appear. You can make an in-line IMG hyperlink directly to a
full-browser FlashPix with
(as of November 1997, the plug-in situation was in a state of flux so
I'm just serving these in-line Java images)
The Long Answer
Now that you can let readers zoom way in on your images, you have to
think a lot more about your original image quality and the way that you
are scanning images.
High-Resolution Photography
Almost any image looks good if you don't enlarge it too much. That's
the secret of the latest digital cameras and disposable cameras: most
people never see the image larger than 4x6". If they enlarged it to
16x20" and then stuck their nose up against it, they'd be very
disappointed. But they don't because it would take a week and $50 in
lab fees. With FlashPix, you're enabling people to view images at
effective enlargements even larger than 16x20". In a couple of minutes.
For free. And they probably won't change their viewing position since
they are sitting in a chair in front of the computer monitor.
The good news is that modern film is very very good. You can get 100
lines/mm resolution out of almost any film these days. lines/mm in the
analog world means that you can resolve a pattern of alternating black
and white lines, with N black lines/mm (only the black lines are
counted). Using a caveman conversion to digital, that's 200 pixels/mm
(one for the black line, one for the white).
The bad news is that, even if you had a lens capable of resolving 100
lines/mm, by the time you convolved its response with the response of
some 100 line/mm film, you'd have only about 70 lines/mm in your
picture.
The worse news is that you probably won't be able to find a lens capable
of resolving 100 lines/mm. 50 is more typical of a prime (non-zoom)
Nikon or Canon 35mm lens.
The even worse news is that lens resolution falls off in the corners and
edges of the frame, the precise areas where a curious viewer is likely
to be poking around.
I could spend a lot of time filling in the technical details that I've
elided above, e.g., that resolution numbers vary by factors of 2 or 3
depending on the contrast of the target. But we've all got Web sites
maintained so I'll keep it short and concentrate on bottom line advice.
Kodak Was Right
When Kodak limited regular PhotoCD to 2000x3000 pixels, they weren't
cheating you out of the rest of your bits. Unless you have a
tripod-mounted prime lens with Royal Gold 25 film, a 35mm negative does
not contain much pictorially useful information beyond 2000x3000 pixels.
With most equipment, you're lucky to get 50 reasonably
contrasty lines/mm over the standard 24x36mm frame of a 35mm
camera. That corresponds to 2400x3600 pixels. Of course, you're still
somewhat better off with a higher resolution scan because at least then
the convolution with the response of the scanning system doesn't further
degrade the resolution you captured on film. But going to a 4000x6000
pixel ProPhotoCD scan for a 35mm original probably won't open up the
dramatic vistas for which you'd hoped.
Conventional Wisdom is Wrong
With modern films, super electronic bodies, and millions of dollars of
TV advertising behind them, it would seem that the 35mm SLR is the right
camera for almost everything. That's probably true if what you want to
do is take aesthetically pleasing pictures and blow them up to modest
sizes and not view those modest enlargements from too close. I'm as
fond of my Canon EOS system as the next
photographer, but if I want to really impress someone with a deeply
zoomable FlashPix, it isn't the right technology.
Before discussing the right technology, it is worth taking a moment to
think about how to get the most out of a standard 35mm SLR system. Here
are some tips:
leave the zoom lenses at home; they are nice toys but none are as
high resolution as a 50/1.8 or similar prime lens
set the camera on a tripod and use mirror
lock-up or pre-fire to minimize vibration
avoid the lens's minimum aperture (e.g., f/22 for a typical 50mm
lens). At this aperture, you get lots of depth of field but are
beginning to lose resolution due to diffraction. Optimum image quality
from most lenses will be obtained at f/8 or f/11 though you can go
smaller if you need the depth of field for pictorial reasons.
use Royal Gold 25 color negative film, the new ISO 100 APS-derived
films (Kodak Royal Gold 100, Fuji Reala), or slide film that is ISO 100
or slower. (See my film page for more.)
The Right Stuff to Begin With
You need a large-format original. A large format camera uses sheet film
in sizes of 4x5", 5x7", and 8x10" (a few films are made in 11x14" sheets
as well). I've written a bit about view cameras in What Camera Should I Buy?.
Suffice it to say that the are not especially convenient to use. You
would be lucky to get one good image/hour working with a view camera.
Loading film is a hassle also, unless you are using a 4x5" camera and
buy Fuji Quickload or Kodak Readyload film. Finally, scanning will be
extremely expensive unless you use 4x5", the maximum size original that
will fit into a Kodak ProPhotoCD scanner.
On the plus side, view cameras are easy to rent and relatively cheap to
buy. The latest and greatest view camera lenses are reasonably high
resolution. Surprisingly, they aren't as good in terms of lines/mm as a
Canon or Nikon lens, but they don't need to be. You aren't enlarging as
much.
Caveat: you must verify your view camera's alignment with a Zig-Align
tool (available from zigalign@compuserve.com for
about $50). This is a marvelously simple pair of mirrors. One of them
fits into the camera back like a film holder. The other mirror fits on
the lens board and has a small hole in the middle. If you throw a
penlight into the bellows and look through the mirror on the lensboard,
you'll see a infinite regression of concentric circles when the mirrors
are perfectly parallel. If you don't align your view camera, especially
a wooden one, you'll probably get enough unsharpness from focus
variation that you'd have been better off using a rigid medium format
camera (e.g., Hasselblad).
ISO 100 film is fine in a view camera. I am extremely lazy so I like to
use Kodak Pro-100 Readyload. It is a color negative film, so it
tolerates minor exposure errors well and never gets too dense for a CCD
scanner like the one used to make Kodak ProPhotoCDs. If you use the
Kodak Readyload back, exposures are reliable (though I've created quite
a few "black bear in a cave" pictures trying to use Kodak Readyloads,
mostly in the Polaroid 545 holder which allegedly works but not for me).
A good film for landscapes is Fuji Velvia, ISO 50, available in Fuji
Quickload. Bracket your exposures, though, because Velvia doesn't have
too much scale (ability to represent a lot of shades from black to
white). Many people prefer Velvia slightly overexposed (especially if
you are scanning with a CCD) so bracketing +1/2 and +1 f-stops from the
meter's recommendation might be wise.
The Semi-Right Stuff to Begin With
If you aren't willing or able to lug around a view camera, you can get
at least one extra level of zoomability with a medium format camera.
The most commonly rentable medium format camera is the Hasselblad, which
exposes 6x6cm images on 120 film. I wrote a review of the Rollei 6008, which is a similar camera. You
might also want to check the photo.net review of
the Mamiya 6, a simpler alternative (the Mamiya 7 is also a nice
camera that takes 6x7cm negatives).
The highest resolution color film in 120 is Ektar 25 (PHR-120), the same
film sold as "Royal Gold 25" for 35mm cameras. It is a color negative
film and therefore scans very nicely to PhotoCD. For landscapes, I
would consider this or possibly Fuji Velvia. For photographing people,
I like the subdued palette of Fuji NPS.
Scanning
The cheapest and easiest way to get a good high resolution scan is to go
to one of my favorite PhotoCD labs and
say "please make me a ProPhotoCD". That gets you 4000x6000 pixels for
$15-25. Another approach is to go to a drum scanning house and say
"please make me the highest resolution file that you can." I had a
couple of 590 MB files produced this way. They cost almost $1000 each
at Graphics Express in Boston. I wasn't very happy with the file gamma
and thought that the image had been overly sharpened (drum scanners have
built-in hardware to do unsharp masking). Moreover, it is tough to find
a combination of hardware and software that can convert the full 590 MB
files into FlashPix. My latest approach is getting 600 MB files made at
The
Photo Lab, a drum scanning house that is also a ProPhotoCD shop and
therefore more experienced with the needs of Web publishers. They are
giving me 600 MB files with little or not sharpening for about $300
each. You'll want to look at my FlashPix reference images
to decide if the extra bucks are worth it over ProPhotoCD.
Text and pictures copyright 1991-1997 Philip Greenspun.
philg@mit.edu
You need a large-format original. A large format camera uses sheet film
in sizes of 4x5", 5x7", and 8x10" (a few films are made in 11x14" sheets
as well). I've written a bit about view cameras in What Camera Should I Buy?.
Suffice it to say that the are not especially convenient to use. You
would be lucky to get one good image/hour working with a view camera.
Loading film is a hassle also, unless you are using a 4x5" camera and
buy Fuji Quickload or Kodak Readyload film. Finally, scanning will be
extremely expensive unless you use 4x5", the maximum size original that
will fit into a Kodak ProPhotoCD scanner.
