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TOPIC: Horses for Courses

Horses for Courses 2 years 8 months ago #66

Most of the gem/mineral pics I make are of a forensic nature, designed to depict and record as best I can some particular features or characteristics in a specimen. Just occasionally, I go a different way like Angharad, trying in an abstract composition to capture some memory or emotion provoked in me by looking at some specimen.

There was no attempt at composition here. I was simply exploring a cut peridot under the microscope when this double/triple abstract image slid into view. I liked it and snapped it :-)
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Horses for Courses 2 years 6 months ago #71

Duplicate removed

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Last edit: by Owen Lewis.

Horses for Courses 2 years 6 months ago #72

Combining image magnification and control of lighting sometimes produces images through a camera sometimes reveals beauty where the naked eye is unable to find it. It also can find beauty in a cheap specimen where a speciment large enough to be appreciated by the naked eye might be too expensive for the budget of many collectors.

Here's an image of native gold on a small cluster of quartz crystals. The face dimensions of the cluster are approximately 2mm x 1mm.

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Last edit: by Owen Lewis. Reason: Sigh... one last try...

Horses for Courses 2 years 6 months ago #73

Most of us can capture effective images with no more that one set of image producing equipment but I defy anyone to capture good macro or micrograph photo using just one light and light placement relative to the line of view. The two fundamentals for most effective imaging seem to me to be:
1. No camera-shake.
2. Lighting that emphasises what the cameraman wants to show an de-emphasises (hides) what it is unhelpful to show.

Here's an example of a poor quality, very badly polished chiastolite slice lit with a single quartz halogen lamp co-axial to the line of view. Every flaw shouts out it presence. It's the sort of image might discard with a shudder and consign the specimen as 'fish-tank gravel' where the water immersion would make it look a little better at least.



But here's another photo of the same stone, changing only the lighting. The light is now first diffused with a piece of frosted glass and placed behind this translucent stone, so that the light is then transmitted through the specimen rather then bounced off it. Most of the flaws are concealed and those that are not seem to acquire some mysterious interest - to my mind anyway.

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Horses for Courses 2 years 5 months ago #74




The pic above is of a piece of colourless spodumene rough lit by ambient daylight only. The reflected light image shows the surface features of this piece in some detail and a viewer is led to think that the specimen is translucent or even opaque.

Replacing the plain white paper background with a sheet of the same but with black printing on it and adding just a little side-lighting eliminates most of the surface detailing from the resulting image. Now a viewer sees that the specimen is truly water-clear and colourless apart from some minor surface staining.


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Horses for Courses 2 years 5 months ago #75

Haematite in amethyst
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Horses for Courses 2 years 5 months ago #80

Haematite in rock crystal.
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Horses for Courses 2 years 4 months ago #84

Isolating effect from cause. Colouration due to thin film light interference caused by a fracture associated with an inclusion in a tourmaline crystal.


Dancing in the Dark.
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Horses for Courses 2 years 4 months ago #85

Synthetic quartz can show crystal forms that do not seem to occur in quartz that is geologically formed. The following photos are of sections of a 19x2x1.3cm quartz crystal hydrothermally grown on a seed plate cut from a natural crystal. To enhance the appearance of some of the forms present in this colourless crystal the section photographed was illuminated with white light but with the crystal between crossed polarising filters.. When so viewed, there is interference between the <o> and <e> wavetrains of a birefringent, anisotropic crystal, creating a colour effect that helps describe to the viewer the growth forms being imaged.



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Last edit: by Owen Lewis. Reason: Tidy.

Horses for Courses 2 years 4 months ago #86

Continuing a look at the synthetic quartz crystal begun in the previous post.... Still illuminated by transmitted white light with the crystal between crossed polars, the crystal has been re-orientated so that the two widest (2cm) and opposing faces are at 90 degrees to the line of view.

The face nearest the viewer is near perfectly planar and is thus invisible in the following images.The far-side face shows small patterns of growth that render it translucent and the growth patterns are captured by their linear form and with the false-colouration caused by the cross polarised <o> and <e> wave-train interference. For images 1 and 2 below, to ensure that all detail is in sharp focus, a series of nine images were made, each with different points of critical focus on and in the crystal and with slightly over-lapping depths of field. This series of digital images were then combined into one, using image stacking software to produce a single image in which all detail within the field of view is captured sharply. Image 2 is simply an enlarged section of image1.

Image 1.

Image 1. Though the false colours and straight lines of the crystal growth on the far-side face give an interesting image, they also act partially as 'camouflage' preventing the eye from appreciating some significant details present. These can be clearly seen in the cropped and digitally zoomed part of image 1 that is image 2.

Image 2.
- A loose fibre lying on the near-side face (at about the three o'clock position, just over half way out from the image centre, shows clearly where that face must be but, without any such marker, the face is invisible.
- A part of the seed crystal plate on which this specimen was grown can now be seen - though much significant detail is still missing.
- Line and colouration on the far-side face speak eloquently to a lammelar type of growth. What is shown is, of course, a negative image - the reverse of what would be seen by looking directly at the outer face of the air/crystal boundary (i.e. the tops of 'cliffs' are actually the least growth and not the maximum levels of growth).


To communicate the maximum detail of the seed-plate from the images made, the image stack is abandoned and just the one, single image, showing the most sharply focused capture of the seed-plate, is selected as image 3. In this image the two-phase inclusions in the seed-plate can be seen - but little else.

Image 3.


Horses for courses :-)
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