quantum photography

[gcol]

A smoked glass filter should be o.k., just dont use an orange or red one, unless you use a specialist infrared film. Now there's a thought.... using a coloured light source, and/or a coloured filter to reduce the spectrum bandwidth could reduce chromatic aberation and increase detail rendering, I guess.

 

I seem to remember that one of the reasons for complex and expensive multi-element modern lenses is to compensate for the internal "spread" of different frequencies. Perhaps a laserlight source through a diffuser might be one way to go, perhaps using an uncoated lens with fewer elements. Probably cheaper and more accurate, too.

 

But it was all a long time ago, memory fades, and technology moves on. When in doubt, back to basics?

 

If you are considering single colour, equivalent to black and white, you could do worse than go back to the old pre-digital and pre-colour texts. The Edwardians produced superb quality photographic images with "old fashioned" equipment that is nigh on impossible to match today. A skill/artform in danger of being lost, perhaps like piano tuning!

[Jacques]

I think a good way to go would be to use neutral color filter on the light source. You can have the specifications on the one you use to know how much light is going throught. A dimer on a ligth bulb is not very linear and the color change... An iris on the source can be good if you add an unpolished glass in front (to keep constant the geoometry of the light source), but you won't get a very big range. I also tought of white led that can be controlled electronicaly, but I am not sure how linear it can be. Hope that help

[gcol]

A white led is, I thought not a pure light source, being actually an assembly of three different coloured led's. Perhaps red led's and infrared film?

[Norman Albers]

One of you guys is going to have to accept this mission. My last major foray into photography was Physics 301 lab where I made a lovely hologram of my Venus de Milo statue, then spent an inordinate amount of time appreciating it from different angles. Babe. This in 1969.

[Klaynos]

A white led is, I thought not a pure light source, being actually an assembly of three different coloured led's. Perhaps red led's and infrared film?

 

It's in no way a smooth emission spectrum.

[Norman Albers]

Spectrum is not so important as making sure it does not change as you run dim light. No, I don't know diddly about film. Here's question: what is the atomic thickness of the iodide (is it still iodide?).

[Klaynos]

Norman you are correct as long as the spectrum changes the same amount across the whole range when the intensity is droped its shape is unimportant.

 

BUT that's quite difficult to achieve and there's little else changing in the experiment and I can think of very little with a time dependence.

[Norman Albers]

I await contact with the Steve S. to hear how he changed light intensity.

[scalbers]

Perhaps film grain can change as a function of light intensity and exposure time? Usually low light levels result in less apparent exposure on the film (so called reciprocity failure). Perhaps high intensities can promote a sort of leakage or clumping among film grains? At lower light levels this hypothesized leakage (or halation) could be suppressed by reciprocity failure.

 

It might help to try this experiment with both film and digital media. The medium may have more to do with this than inherent quantum effects.

[swansont]

This is a guess, but one effect that can be present in the high light-level scenario is two or more photons striking an area in a short period of time. In some kinds of detectors there is a dead-time after an event, but I wonder if there is the opposite in this case - a spillover, as it were, so that multiple photons at once (or in rapid succession) expose a larger area than two photons separated by a sufficient amount of time.

[Norman Albers]

My McGraw-Hill Dict. of Terms tells me "halation" is a halo on the photo image of a bright object caused by light reflected from the back of the film or plate. Swansont, you would lose contrast detail if the higher intensity field could not be processed because of dead-time.

[swansont]

Swansont, you would lose contrast detail if the higher intensity field could not be processed because of dead-time.

 

And if you'll reread my post you might note that I wasn't proposing that this was occurring. I was thinking more along the lines of e.g. a two-photon ionization causing a much larger reaction than a single photon.

[Norman Albers]

I guess the idea of dead-time refers to CCD's and not to film atoms. Yes I see your thinking, Swansont. I wish I knew what we are talking about: are they tiny crystals of many atoms each? I will get in over my head and quote from the QED text I barely understand. They discuss two-photon processes and conclude, "It is not the photons which interfere but rather the transition amplitudes, and these amplitudes can involve many photons." Is this our realm?