[garywakeling]

Sigma 15mm f/2.8 on the K-1
So much in the frame... and sharp the way through
So little flare.
A great FF choice.

Pentax K1 SMC 17-28 F Fisheye zoom

It must have been umbrella sale time this month here is my effort



and a friend's car

[tim60]

Pentax K1 SMC 17-28 F Fisheye zoom

It must have been umbrella sale time this month here is my effort



and a friend's car

That grille is unusual. Was it an upmarket model or a year for which there are not many left?

[garywakeling]

That grille is unusual. Was it an upmarket model or a year for which there are not many left?

No , not upmarket just a basic model Holden EH model panel van, naturally the fisheye helps emphasise the grill

[tim60]

No , not upmarket just a basic model Holden EH model panel van, naturally the fisheye helps emphasise the grill

Thanks. I was thinking of my primary school headmaster's Holden Premier (that no self-respecting Premier would actually buy).

[garywakeling]

Landscapes and fisheyes seem to work well, not always looking fishy however handy when you're not quite sure where the subject will appear in the shot!



K1 smc F 17-28 Fisheye @19mm f4

[WPRESTO]

Great capture!

[tim60]

Landscapes and fisheyes seem to work well, not always looking fishy however handy when you're not quite sure where the subject will appear in the shot!



K1 smc F 17-28 Fisheye @19mm f4

Agree with WPresto - great capture, including the eerie colours of a storm.

[garywakeling]

Agree with WPresto - great capture, including the eerie colours of a storm.

Yes I finally understand why so many photos of lightning have a purple tinge, they are purple, which the wide angle of the fisheye has shown me against the yellow of the setting sun or the grey of the clouds.

[WPRESTO]

Yes I finally understand why so many photos of lightning have a purple tinge, they are purple, which the wide angle of the fisheye has shown me against the yellow of the setting sun or the grey of the clouds.

V-A-V the purple color, my head runs along the following thoughts: 1) the color of light is to some extent related to temperature of the source: hotter = shorter wavelength = toward the ultra-violet end of the spectrum; 2) lightning is extremely hot; 3. very short wavelength light (ultraviolet) released by the lightning is lengthened when it passes through and is refracted by water droplets in clouds and becomes visible violet instead of invisible (to humans) ultra-violet.

[garywakeling]

V-A-V the purple color, my head runs along the following thoughts: 1) the color of light is to some extent related to temperature of the source: hotter = shorter wavelength = toward the ultra-violet end of the spectrum; 2) lightning is extremely hot; 3. very short wavelength light (ultraviolet) released by the lightning is lengthened when it passes through and is refracted by water droplets in clouds and becomes visible violet instead of invisible (to humans) ultra-violet.

I had never really thought about it, I do have an infrared converted camera , so I guess I need to look for the next storm to see how the light appears on that, yes the colour temperature would explain it, my high school physics might finally kick in and become useful again

[tim60]

V-A-V the purple color, my head runs along the following thoughts: 1) the color of light is to some extent related to temperature of the source: hotter = shorter wavelength = toward the ultra-violet end of the spectrum; 2) lightning is extremely hot; 3. very short wavelength light (ultraviolet) released by the lightning is lengthened when it passes through and is refracted by water droplets in clouds and becomes visible violet instead of invisible (to humans) ultra-violet.

I suggest an alternative explanation.


Lightning ionises the air - it is a dielectric breakdown discharge through the air.


In the process the electrons are removed from the atoms in the air and then, as they reassemble the light is emitted from the electrons falling through particular energy level steps in the quantum arrangement of electrons around the nucleus.The effect is discharges of light at specific wavelengths (same effect as the pair of yellow colours in Sodium discharge lamps or the UV discharges of mercury in mercury vapour and fluorescent lamps, which are then converted to visible in phosphors. The different elements in the air would each have their own specific colours of discharge, so lightning would illuminate the sky with combinations according tot he relative concentrations in air.


Henry Moseley, EW, killed at Gallipoli, 1915, was a major contributor to this and several other aspects of atomic physics. Remember the story from high school and there is a display related to him at the Museum of Natural History in Broad St, Oxford.

[WPRESTO]

I suggest an alternative explanation.


Lightning ionises the air - it is a dielectric breakdown discharge through the air.


In the process the electrons are removed from the atoms in the air and then, as they reassemble the light is emitted from the electrons falling through particular energy level steps in the quantum arrangement of electrons around the nucleus.The effect is discharges of light at specific wavelengths (same effect as the pair of yellow colours in Sodium discharge lamps or the UV discharges of mercury in mercury vapour and fluorescent lamps, which are then converted to visible in phosphors. The different elements in the air would each have their own specific colours of discharge, so lightning would illuminate the sky with combinations according tot he relative concentrations in air.


Henry Moseley, EW, killed at Gallipoli, 1915, was a major contributor to this and several other aspects of atomic physics. Remember the story from high school and there is a display related to him at the Museum of Natural History in Broad St, Oxford.

Tim60 is entirely correct on this. Did a little quick research (as I should have done before posting) and the blue-violet color of several atmospheric phenomena is related to ionization and de-ionization of nitrogen in particular (atmospheric oxygen when ionized, rather than de-ionizing and emitting photons, is more likely to form bonds with non-ionized O2 to form ozone = O3). The blue light emitted by re-ionizing nitrogen is responsible for the spooky light called St. Elmo's Fire.

[garywakeling]

Wow, now I will have to do much more research , I thought the colour wheel was hard, now to research dielectric breakdown , thanks Tim60

[tim60]

These physical effects have affected photography since ling ago.


Tungsten lights create light by heating a filament, and so it is a colour temperature spectrum that is released.


Fluorescent lights use a mercury discharge and phosphors, and so produce that green colour which is fairly heavily weighted to the specific green colours, but provides a much wider range of colours, so the eye can be fooled to see them as 'kind of white', and a filter can correct.


The mechanism of light production in LEDs is a quantum effect of the atoms, and therefore the extremely colour specific illumination - and therefore the challenges of getting 'natural' looking pictures (either looking 'normal' or looking like you remember from the event) in PP.


BTW: refraction is based on change in light transmission in a material. Materials each propagate light at different speeds, hence the possibility of bending beams by shaped materials. But the materials propagate light at different speed depending on wavelength - hence the dispersion effects that lead to directing different colours to different place through a lens - and image effects such as fringing and blurring. But refraction can only separate colours already in the light, refraction does not change frequency, and so does not remove or introduce colours not in the original light.

[Coiseam]

DA 10-17 at 10 mm, Pentax K-1