[Fwd: Re: When will digital photography replace regular photography?]

Dan Connolly (connolly@w3.org)
Sat, 14 Mar 1998 14:43:26 -0600

This is a multi-part message in MIME format.

Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

Some interesting physics and economics on the topic...

(I'm sending it to fork mostly for archival purposes.)

Anybody here know how to turn film negatives into bits
quickly and easily?

Any opinions on the Kodak Photo Network?

Altavista gives just a few hits; mostly negative impressions.


Dan Connolly


Path: jumpnet.com!news-fw-22.sprintlink.net!!news-fw-12.sprintlink.net!!news-west.sprintlink.net!news-peer.sprintlink.net!news.sprintlink.net!Sprint!newsfeed.internetmci.com!!news.adnc.com!not-for-mail From: "Gregory Benjamin" <gregben@adnc.com> Newsgroups: rec.photo.digital Subject: Re: When will digital photography replace regular photography? Date: Fri, 13 Mar 1998 20:52:37 -0800 Organization: Laserlab, Inc. Message-ID: <6ed2ci$dud$1@hops.adnc.com> References: <35096A9B.41C6@acm.org> NNTP-Posting-Host: X-Newsreader: Microsoft Outlook Express 4.72.2106.4 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.2106.4 Xref: jumpnet.com rec.photo.digital:65470

This is by far the most informed, clear discussion I've seen yet on this topic. Thank you!

A. Nowatzyk wrote in message <35096A9B.41C6@acm.org>... >Besides cost, ease of use, turn-around time, etc. there are at least two >measurable characteristics to compare these technologies: spatial >resolution and dynamic range. > >Spatial resolution is the number of points per unit distance that the >film >or digital imager can resolve. It is measured in dots per inch (dpi) or >line pairs per milimeter (lp/mm). 1 lp/mm = 50.8 dpi. It is not uncommon >for a CCD or CMOS imager to have photodetectors on a 7 to 5 micrometer >grid, making it a 100 lp/mm device. Given that chips with deep >sub-micron >feature sizes are in production, digital imagers with higher spatial >resolution are possible, but the reduced photodetector size also means a >smaller signal to noise ratio and/or lower sensitivity due to a higher >ratio of light insensitive support electronics to active detector area. >Expensive imagers can use chips that have the detectors on one side and >the read-out electronic on the other side of a thinned chip, but this is >not a technology for volume production in the near future. > >Good film and quality optics are both in the 100+ lp/mm range. However >there are special films with resolutions of up to 3000 lp/mm (for >example >films developed for holographic purposes). Also, CCD imagers that match >the area of 35mm film (say 4800x7200 pixel) are not yet economical. >Besides for high quality photography, 35mm film is usually insufficient >(6x6cm and 4"x5" cameras serve these needs). Hence digital photography >has >still a long way ahead before it can match the resolution of regular >photography. > >Dynamic range describes the number of levels of gray (or RGB) that one >pixel can have. It is measured in db or sometimes density. If an imager >can >distinguish between N (linear) levels of intensity, then it has a >dynamic >range of 20*log10(N) db. Density expresses how much light will p ass >through the film. If T is the fraction of light that is transmitted >through a pixel, then the density is said to be log10(1/T). This means >if >a digital imager can distinguish between N shades of gray (or RGB), the >darkest region corresponds to a transmissivity of T = 1/N, therefore the >density is log10(N). If a CCD imager uses 8bits per pixel, it has a >dynamic range of 48db or it can deal with a density of 2.4. The dynamic >range is limited by the noise floor of the sensor. In a CCD, the leakage >current, various cross-coupling effects, injected electric noise from >the >drive electronics and the finite charge accumulation capacity, etc. >limit >the S/N ratio. A good CCD imager at room temperature can resolve about >12 >bits (72db). For each 20 deg of cooling, the S/N ration is doubled, >adding >one bit of resolution or about 3db of dynamic range. A good, cooled CCD >imager (for example ones used in astronomy) can resolve about 18 bits >(108db). Because CCD sensors are very good light integrators (i.e. can >deal with long exposures) and have good quantum efficiency (i.e. high >probability that an incoming photon produces charge that is accumulated >in the sensor), they have essentially replaced film for astronomical >applications. > >The dynamic range of film is limited by several non-linearities (such as >Schwarzschild effect) and noise from the finite grain size. Good film is >about equivalent to 16bits / pixel (48bit for color). A drum scanner can >extract this information because it uses an intense light source and a >PMT >detector to deal with high densities. However special films, for example >films for X-ray imaging (thick emulsions on both sides of the carrier) >can >exceed 22bits. Photographic paper on the other hand has a much smaller >dynamic range, this is why folks like Ansel Adams spend so much time in >the darkroom trying to compress the vast dynamic range of the negative >in >an aesthetically pleasing way. The upshot of this is that a digital >camera >with 8bit quantization is over two orders of magnitude inferior to film: >exposure control is much more critical and loss of detail is inevitable >if >the scene has uneven lightening (both bright and dark areas). In >principle, digital photography can match the dynamic range of film with >a >cooled CCD imager, high quality electronics and a 16bit (for B&W, >3x16bit >for color) ADC. Unfortunately, that also means almost 200 Mbytes for >each >35mm equivalent picture (before compression). In practice, a digital >camera that rivals 35mm film quality isn't exactly around the corner :-(


Path: jumpnet.com!news.eng.convex.com!news.ecn.uoknor.edu!feed2.news.erols.com!erols!cpk-news-hub1.bbnplanet.com!news.bbnplanet.com!news.mindspring.com!not-for-mail From: bobad@mindspring.com (Bob Adkins) Newsgroups: rec.photo.digital Subject: Re: When will digital photography replace regular photography? Date: Sat, 14 Mar 1998 05:28:20 GMT Organization: MindSpring Enterprises Message-ID: <35151571.37890236@news.mindspring.com> References: <35096A9B.41C6@acm.org> Reply-To: bobad@1998mindspring.com NNTP-Posting-Host: pool-207-205-150-205.chia.grid.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Server-Date: 14 Mar 1998 05:28:18 GMT X-Newsreader: Forte Agent 1.5/32.452 X-No-Archive: yes Xref: jumpnet.com rec.photo.digital:65463

"On Fri, 13 Mar 1998 09:19:23 -0800,"A. Nowatzyk" <agn@acm.org> wrote: "

>35mm equivalent picture (before compression). In practice, a digital >camera that rivals 35mm film quality isn't exactly around the corner :-(


"When will digital photography replace regular photography"?

Never! At least not *totally*.

There will always be a few hobbyists, tinkerers, and nostalgia seekers, but in such a minority as to be a very tiny fraction of the market, IMO.

The original question is a bit hard to answer without causing a lot of misunderstanding! Let's re-phrase it a little:

"When will digital still photography replace regular photography as the most common medium in regular use?"

The answer is, within a few short years.....I bet less than 5!

Let's ask that question in yet another way that will help us understand what's happening in photography right now:

"When will digital still photography replace film photography as the sales leader"?

Very soon! I'll bet In a year so!

The average 35mm user does not demand the quality of an astronomer or even an Ansel Adams. The average 35mm user is highly attracted to any gizmo that will make his picture taking more fun, interesting, convenient, and economical while yielding reliable, *acceptable quality. This will drive digital R&D very hard for a few years at least.

You are correct about digital photo quality rivaling 35mm film quality not being right around the corner. "So what?" says the masses, which are only snap shot takers anyway. "So what?" says the manufacturers, who are happily selling millions of digitals that meet their customer's needs.

Digital quality will eventually catch film, but when it does, most of us won't even hear about it....it won't make headlines. Why? Because film photo quality potential is far better than the masses need or want anyway. That's just the way it is. Most people simply aren't as picky as we are.

"Disclaimer: Although I take full responsibility for writing the above, I do not necessarily agree with it."

Bob ICQ# 657746

"From the Heart of Cajun Country"

To remove spam block from address, remove the 1998

SPAM Bait: rhundt@fcc.gov jquello@fcc.gov sness@fcc.gov rchong@fcc.gov