God for us to design products, we are the porters of nature!
Digital photography is a very powerfull tool to document a large number of collectible objects like mineral specimens.
Documenting a complete collection with several thousand specimens was in the times of analog photography a expensive project, mostly because of cost of color slides and prints, but also frustrating because of the low speed of the procedure.
Now in 2008 the digital photography provides tools to produce pictures of mineral specimens in a short time while maintaining a reasonable picture quality in all aspects: technical, educative, scientific and in most cases also aesthetic. Many minerals or mineral specimens are not attractive and will never give a good picture but are worth to be photographed for educative and scientific reasons or as an identification aid.
Under optimized conditons, for a trained photographer it is possible to take pictures within a few minutes, from carrying the specimen to the photo setup until a labelled printout of a labelled 10x15 cm test-print. This is valid for specimens in the typical collection size from about 20 mm to 20 cm. Crystals in the micromout size need microscopic (with a stereomicroscope) or macroscopic techniques, large specimen special preparation of the setup. So the following is focused on the 2 to 20 cm range.
Making a picture can divided into several steps:
-Specimen setup onto background and adjusting view direction(s)
-Adjusting view of field and sharpness
-Adjusting illumination, taking a preshot, viewing the preshot
-Optimizing illumination and expousure time
-Taking the shot and transferring to computer
-Optimizing the picture with software, resizing, sharpening, and labelling
-Archiving and eventually printing
To follow the steps above, of course, some equipment is needed, which will be discussed subsequently.
A straight forward way is to use a black (or white) background. Most useful as black background is a piece of black velvet. If specimens are set direct on the background often the structure of the background or dirt is visible, this can avoided if there is some distance between the focus plane and the background. In practice this can be done by using a (metal) socket on which the specimen is mounted with putty, in way that the socket is not visible. An alternative is a glass or plexiglas plate above the background. White background is possible with a sheet of white plexiglas but only perfect if a backlight ist used. It is a good way to illustrate transparency. In most cases some hidden putty helps to adjust view directions. It is a goal of me that no putty , glue, boxes, fingers, hands, scales, cm-cubes etc. are visible. Decent shadows are OK. I personally do not like colored background. But its no big task to replace a black or white background with a more fancy one with photoshop.
Of course this happens with the camera. Any kind of camera is mounted on a (solid) copy stand and a focusing rack. Very heavy and solid Tripods may also used. In principal any kind of digital camera capable for close up photography can used. I started experiments a few years ago with a Nikon Coolpix 950. As soon as digital SLR cameras came in a payable price range I switched to a Canon EOS SLR. For the EOS mount a range of adapters are available so Nikon and Leica-lenses can mounted, but at the end I used a Canon Macro Lens EFS 60 mm. This focal length is good compromise for working distance and close up capabilities. The smallest field of view is ca 21 mm (full format). Until this format (1:1) the depth of field and sharpness is ok for most cases if a f-stop of 11- to 16 is used. But even in this range stacking software can be very useful.
The camera is direct connected to a computer with a Canon EOS utility software running. I use the camera in manual mode and manual ! color balance, f-stop and exposure time are set manually on the computer. Also the focus is set manually by disabling autofocus. The shutter is triggered by a cable control with active mirror pre release. This avoids vibrations from the mirror. Exposure times are mostly between 1/30 to 1/250 sec. with an f-stop of 11 to 16. Because of user demands the DSLR still have a mirror and a shutter which causes vibrations. A high resolution digital camera with a corresponding lens would be a better, but much more expensive equipment but is offered for industrial applications.
Using a Macro lens is essential. A standard (zoom) lens will work for larger objects but not well in the close up range. Good alternatives are macro lenses from analog cameras like the 55 mm Micro Nikkor. This can connected to the EOS mount with an adapter.
By far the most underestimated factor which contributes to quality photographic pictures is light !
Simple illumination can give excellent results in some cases, but fails in most of the difficult situations.
The best lens cannot give good results if color balance is wrong and the contrast is not optimal balanced to the capabilities of the imager and the subsequent viewing media computer screen, fotoprint or printmedia.
Optimal lightning is an iterative process and in many cases, for fine tuning the light, some pre-shots are essential. A setup seen in the view-finder may look well, but the digital imager of the camera cannot handle to high contrast. The high light will over exposure and dark parts will be darker than seen with eye and loss details. On the other hand to low contast will make a unattractive picture.
A key to good balanced light is to use many (4 to 8) light sources in a contast enhancing direction combined with a soft screen. A setup is shown in Picture 1 without and Picture 2 with soft screen in place. I use cheap (10 €) halogen parabol reflector lamps of 20 Watt with bulbs of different beam angel (10 ° and 30 °). Position and effect of each light source needs to be optimized and it needs some training to handle many lamps.
It is very difficult and lenghty to give detailed advice how light is used, the best way is experiment and practice.
If the object is in focus and lights are set a preshot is taken. I most use a f-stop of 11 for smaller objects and up to 22 for larger objects. In critical cases the f-stop is set to 5.6 and a multi-layer picture is made using Helicon focus.
The preshot is direct transferd in a zoombowser ex software ( a software which came withthe camera) and previewed. From that picture light, focus and exposure time is optimized, a second preshot may useful.
If a satisfactory picture is tarsferred to the comuter it is sent to a picture software. Processing a digital picture in a software is a key factor for quality. On the other hand it is time consuming.
If a satisfactory picture is transferred to the comuter it is sent to a picture software. Processing a digital picture in a software is a key factor for quality. On the other hand it is time consuming. So for most cases processing is limited to a automatic optimizing. This mostly improves contrast, gradation and color balance. I do that with Arc soft photo studio 5.5. The picture is transferred from the zoom browser direct into that software. The picture is then automatic optimized by clicking. Often the picture is improved and then improved then further processed. If improvement fails, the original picture is taken for further processing.
The next step is cropping the picture to format. I do that in Irfan-View, also resizing to either to 963 pixels in width or 722 pixels in hight. The simple reason is that this format is suitable for presentations with Powerpoint etc. The resized picture is sharpened. This step is made for best viewing on the computer screen. A version if that picture is saved and the a label is written mostly in one of the corners of the picture.
This label shows minerals, location size and a copyright mark. Last step is saving all pictures. In my picture archive the minerals are saved under the location. The picture can then printed, uploaded to Mindat or used for other purposes.
Some mineral photographers try to use very simple light sources. This can work well in many cases. If the minerals are opaque, coloured, show good contrast and reasonable reflections. But there are situations in which a sophisticated light technique is the key issue. Of course all other technical parts of mineral photography like camera, lens, camera stand, focusing devices, background, processing on computer and possibly multifocus techniques have to be solved to most possible perfection before.
Sophisticated lightning is a combination of of mounting a specimen and creative use of light. Experiments are here a good way to improve rather than slavery copy of the solutions of other photographers. In this sense the following is intended as an example and inspiration to find even better ways of light use. And a comment for those who like to do it fast, simple and with equipment for less than 500 (Euro or Dollar): You need time !
The above picture shows two version of a picture from the same Analcime crystal. It was set with a small roll of putty on clear plastic boxes. Black Velvet under the boxes give a black background. The elevated position of the crystal with 12 individual crystal faces allowed to use light reflections from light positioned at. ca. 120 ° on the optical axis. This was done by direct lightening and using light reflected from the boxes. Light by light was switched on, optimized and in critical situations controlled by a sample shot. This shot is instantly sent to the computer screen and examined. If not to satisfaction it´s again optimized. So 12 shots have been taken to optimize shutter speed and light. Finally the pictures are processed (see above). The positions of the halogen lamps is illustrated in the picture below. Only one light is on to give a better vision.
For some minerals a black background is not the first choice. Dark grey and black minerals will give much better pictures with a light or white background. Also transparent minerals are better shown with light background. But using for example a white paper sheet will often only give a ugly background with shades of grey and multiple shadows. A shadow free white is a bit more difficult than black. Best results are obtained with white acryl-"glass" with some back light, so the background and possible shadows are overexposed and not any more visible. The mineral itself is lightened with soft light from diffuser screens. A example of such picture is shown below.
Background light and main light must be balanced. Again this is best done by some pre shots. There is some equipment on the market to obtain good white background. Here I show the (ab)use of cheep salad bowls. A Sheet of white acryl-"glass" (plexi-glass) is mounted between two white to transparent plastic bowls. At the upper bowl the bottom is cut out, and the lower has a light inside or aluminum foil for reflection. The specimen is set on the plexi-glass and illuminated though the bowls. Its important to adjust the white balance of the camera. This setup works for specimens from about 2 to 8 cm . For larger specimen larger equipment is needed (larger salad bowls?) or another method: the white to black background discussed in a later section.
It is obviously that flat, polished mineral specimens can be well reproduced with a scanner. Agate and other flat and polished objects work fine.
See:
Scans a best done in the 1200 or 2400 dpi range and afterwards resized, color corrected and sharpened.
Some experiments showed that its is also useful for some other specimens which can be put with a flat part on the scanners surface. The scanner I used is a Mustek bearPar 4800TA ProII. I experimented with some samples from my collection. As long as the field of interest on the specimen is flat (+/-) about 5 mm, not to dark and not to lustrous, it works. As there is no control over the lightning, there cannot optimized very much.
Scanning a not complete flat specimen is here demonstrated with a cross section of a zonar Quartz crystal:
A not polished flat specimen:
A scanner is not an ideal tool to make pictures from crystals, but it works well in some cases. The following picture is from a box with Stilbite crystals. The box was covered with a carton , put upside down on the scanner surface and then carton removed. The same was done with a box of polished thomsonite nodules.
Finally a test was done with grains of Olivine. Even with this relatively small objects of only 15 mm the result was useful. The scan was made with 2400 dpi.
Conclusion: A scanner is worth to be considered as a tool to make mineral pictures. Its fast and easy to use. In cases the result is bad, just the >delete< button helps.
to be continued
Any hints to improve the text are welcome
Volker
Volker.Betz(at)Zeolith-Sammlung.de
YueGongAnBei 44051102000467
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