Longshadow Loc: Audubon, PA, United States

Amazing how simple that is, eh?

Retina Loc: Near Charleston,SC

Like most things digital, cell phones and cameras, even round dial electronic clocks or any circuit that uses a crystal and a divider to set frequencies have both analog and digital circuits. Of course, we use the term digital to refer to how an image is converted, stored, and manipulated in the form of bits organized into bytes. It is interesting, at least to some, that our senses are also partially digital. Neural depolarization is like a bit: it's there or not. How often these bits arrive in the brain is an analog factor. Even a camera sensor, like a retina, is partially analog requiring a 1-bit A/D conversion. The ear is also a partly digital transducer, using an acoustic transformer between the ear drum and the inner ear to drive the A/D converter. Humans were not the first to employ digital circuitry in processing light and sound. So one answer to how analog photography is defined refers to how the smallest element of an image is represented and stored. Analog photography does not use bytes to represent the light intensity of a pixel, or three values, one for each primary color.

larryepage Loc: North Texas area

I've read most of the responses. They pretty much all completely miss the distinction between analog and digital systems. It's quite interesting that they hopelessly overcomplicate what that difference is.

An analog system simply uses an electrical voltage to represent some chosen parameter. 1 volt reprenents one value, 2 volts represents a different value, 1.5 volts represents a third value between the other two. The relationship between the two is often linear (2 volts represents twice as much of something as 1 volt), but it doesn't have to be. It can be logarithmic or maybe even something else.

A digital system uses a digital value to represent those parameters with binary bits...signals that are either "on" or "off." A value of 0001 might reprenent the first value above, and the value of 0010 would represent the second one. A big problem with early digital syatems is that in an arrangement like this, there is no way to handle the third example...there typically is no simple way to represent 1.5.

There have been many enhancements, but that is the difference.

A big question is whether film was ever really analog, since it was made up of discrete grains that were either activated by exposure to light or not. The more activated grains, the darker the negative.

Retina Loc: Near Charleston,SC

You could go all the way to quantum physics, but I would stop well short of directly manipulating the number and size of grains the way we do with pixels. Who wants to be called a grain peeper?

jackpinoh Loc: Kettering, OH 45419

Analog photograpy generally refers to film photography where the exposure of the film is actually a non-discrete process (you can't exactly quantify the number of photons that contribute to the exposure). The image is totally dependent on the number of photons captured in the grain structure of the chemical coating on the film. The image captured on the film and print is never quantified with 0's and 1's (digits) anywhere in the image capture, development and printing process. That is why film cameras are called analog cameras. (Painting and sculpture are other analog processes. So is getting a suntan.)

A digital camera focal plane also captures photons in a non-discrete process. The number of photons collected at each photo cell on the sensor during the exposure results in a voltage which is converted to a discrete binary number (a series of 0's and 1's [digits]) by an analog-to-digital circuit. The 0's and 1's from all of the sensor photo sites represent the image and are stored on the camera memory card as series of digits (the RAW format). That is why cameras with focal planes are called digital cameras. The camera digital processor creates a digital JPEG image that can be displayed on the viewfinder or LCD. The image is usually downloaded from the camera in digital format to a digital computer where it can be processed by digital software into a different digital image, sent to the printer as a stream of digits, and output onto paper as a series of discrete pulses of discrete sources of ink. Everything after the analog-to-digital circuits is digital.

Longshadow Loc: Audubon, PA, United States

Ain't that the truth!

No matter how simple a problem seems at first,
it becomes increasingly more complex upon further investigation.

Tote1940 Loc: Dallas

Would Chemical photography be a better term?
Also monochrome rather than B&W

selmslie Loc: Fernandina Beach, FL, USA

There is a simple way. Add another bit on the right to represent 0 or ½. In binary math that is the equivalent of multiplying everything by 2.

Yes, a film grain (actually part of a cluster of discrete crystals) is either developed and remains in the emulsion or it isn't and it gets removed by the fixer. In that sense it is digital.

Tote1940 Loc: Dallas

My first a VHF transceiver mounted on car or boat ( slide mount) hand held mike several channels You hailed a live operator who dialed for you One person talked at a time
Still better than carrying a cup full of quarters and knowing every pay phone around
The joys of taking calls in beeper era

selmslie Loc: Fernandina Beach, FL, USA

deleted

Retina Loc: Near Charleston,SC

I agree. Analog photography does not mean much except when comparing to digital.

So maybe Judge Jackson should have replied "Usually it refers to an adult who is not male".

Seriously, the revolutionary thing about digital photography is that images can be transmitted, stored, and copied over countless generations and distances without degradation. This idea has been around since alphabets, but not with respect to the massive amounts of data it takes to store images on the scale that required high resolution film in the past. Now we take this accuracy for granted when it is really quite new.

larryepage Loc: North Texas area

Scaling is a different problem that just confuses the issue. If you look at the internals of digital scales, one of the critical specifications is the number of "counts"...which represents the total number of different weights it can report. It's the resolution. In your example, adding the extra bit allows represent 1/2 of whatever we are are representing. But then what about the user who is interested in differences of 1/4? Then there is the question of how often samples are taken (how often measurements are made). Analog systems measure continuously. Digital systems take samples some prescribed number of times per second. This has come to be not such a big deal today. It was a very big deal in earlier days, even though "things" were much slower then.

selmslie Loc: Fernandina Beach, FL, USA

Adding another bit takes care of the 1/4 value. You can add as many bits as you wish and each additional bit will increase the precision.

But this clearly has a penalty. If you increase the value of the right-most bit you are also either increasing the total number of bits or reducing the maximum value that can be represented.

An analog signal faces the same issue. If you can measure voltage up to a range of 10 volts you can be more precise than whole integer values (only 10 discrete values) by adding digits after the decimal.

Analog measurements eventually run out of precision. You will run out of precision before you run out of digits.

larryepage Loc: North Texas area

That wasn't the thinking back when 8 bits was a lot.

The whole question of precision is a very interesting one. People every day insist on measuring things to 5 decimal places which can only be controlled to the nearest tenth. My current favorites are all the sporting events where events are "timed" to the nearest thousandth of a second.

selmslie Loc: Fernandina Beach, FL, USA

Even when winning by a nose was good enough it needed a photograph to confirm it.