John Betts - Fine Minerals > Home Page > Educational Articles |
by John H. Betts, All Rights Reserved
Digital cameras come with many other features. While these features may come in handy for other applications, they are not important for mineral photography. These features include zoom lens, digital zoom, interpolated high resolution, special effects modes, and red-eye reduction. While having an optical zoom lens on the camera may seem important, for mineral photography all images will be composed by moving the camera closer to and farther away from the subject. Digital zoom enlarges the image digitally without changing the optics. Digital zoom leads to image degradation and is not advisable to use, even if the camera comes equipped with the feature.
At the time this article was written, both Sony and Nikon offer the best digital cameras that meet the criteria for digital mineral photography.
In addition to the camera, there is other equipment needed. Some of the same equipment used in conventional photography will suffice. A sturdy tripod is very important because camera movement is the enemy of a sharp photograph. Tripods have improved greatly in the last 20 years. It might be worth upgrading to a better tripod with more convenient features.
The same backgrounds, reflectors, diffusers as conventional photography will be needed. This author prefers photographing on black glass or Plexiglas because of the relative ease of keeping clean and its moderate resistance to scratches. An assortment of small Mylar reflectors, mirrors, and diffusers are used to create controlled reflections off crystal faces to define the crystal shape.
Probably as important as camera selection is lighting. Digital cameras have built in white balance to compensate for the color temperature of the light source. It is relatively easy to compensate the color for a specimen illuminated under incandescent light, something not easily accomplished with conventional photography. However it is important to use a full spectrum light source. For example, a 60 watt incandescent bulb has very little blue/purple in the spectrum of the light it outputs. A mineral specimen with dark blue (i.e. azurite) on a black matrix illuminated under incandescent light will render both colors as black. No amount of photo manipulation on the computer will ever differentiate the two colors. By using a full spectrum light source that problem can be minimized.
Also the light sources should be small, adjustable/moveable lights that produce a broad illumination without strong hot spots, either by use of frosted bulbs or additional diffuser. This is required to control the reflections off individual crystal surfaces, without harsh hot spots - very important in mineral photography.
The one light source that meets all of these needs is the new SoLux halogen bulbs. This is a new technology lamp based on MR-16, 50 watt halogen bulbs, but with proprietary technology to produce a full spectrum light output. SoLux has been so successful, they have been adopted by several museums as the standard light source for their paintings and exhibits. SoLux bulbs are available in several different color temperatures. The Solux bulb best for photography is the 4700° version which is the equivalent to daylight at 10:00 A.M. and very close to 5000° Noon daylight. (35-mm photographers can use an 80D filter to convert SoLux illumination to conventional daylight film.) For digital photography, Solux bulbs are perfect, yielding accurate rendition of difficult to photograph minerals like dioptase and azurite. They are 12 volt bulbs and fit in any light fixture that can accept an MR-16. Solux also manufacturers a task light to hold Solux bulbs with highly adjustable swivel arm that works well in photography, display or even illuminating specimens under a microscope. I use the widest angle bulb (flood) which has a spread over 30 degrees. But any of the Solux bulbs will work.
It is a mistaken assumption that a photograph can be used "straight" or not retouched. Even in conventional 35-mm photography color balance, exposure adjustments, and contrast control are manipulated to produce a satisfactory image by the photo processor.
Image exposure (lightness and darkness) is the most commonly manipulated variable. Digital camera built-in exposure meters try to balance the image exposure to produce a medium value. This works well when the subject is a medium value - like skin tones. But if you are photographing a dark mineral like azurite, the camera will lighten the exposure in an attempt to yield a medium value, making the image overexposed. If you are shooting a bright white subject like okenite, the camera will attempt to darken the exposure to yield a medium value, making the image underexposed.
Similar problems occur with color balance. Digital cameras have an automatic "white level" control to achieve normal color balance. This works well with a normal subject. But if the subject is a specimen of etched green prehnite with no brilliant highlights, the camera will not see any white highlight pixels in the image and think color correction is necessary. The camera in this instance will shift the color from green towards white (usually by adding red/pink/magenta) and fail to accurately capture the green prehnite.
Lastly, images need to be adjusted because digital sensors may artificially enhance one particular color. This is common with 35-mm slide films too, Kodachrome has exaggerated reds, Fujichrome has exaggerated green, Ektachrome has subdued neutrals, etc. So the image may need adjusting to accurately represent the subject. The author’s camera overly saturates reds, probably because camera manufacturers artificially enhance the reds to produce better skin tones.
Image retouching varies from simple to extreme. Following are some typical operations:
Simple |
Moderate |
Radical |
Crop image and adjust for any tilt |
Retouch dust or lint on subject |
Combine multiple exposures |
Adjust lightness/darkness |
Cleanup background |
Add airbrushed background |
Color correction |
Remove digital artifacts |
Sharpen focus |
Retouching can improve an image only to a limited extent. The beginning image, before adjustments and retouching, must still have a good pose, sharp focus, good exposure, and descriptive shadows and reflections. These cannot be faked or added at a later time.
There are many software packages available for editing the images after they have been captured by the camera or scanner. Many come bundled with the camera or scanner and are all about equal. The industry standard is Adobe Photoshop. All other software is attempting to emulate Photoshop and make it easier for novice users. If you are creating a large quantity of images, it pays to invest in Photoshop and learn to use it.
It is possible to avoid paying the full cost of the latest version of Photoshop if you have an older version of Photoshop that came bundled with a scanner or other peripheral (this was very common a few years ago). You can purchase the latest "upgrade" version of Photoshop at a fraction of the regular retail price. Also, Adobe makes an introductory version called Photoshop LE that is an excellent way to get started and learn the basic tools without paying full price for Photoshop.
Commonly, very few commands in Photoshop are actually used when regularly editing images: cropping, adjusting exposure, retouching flaws, re-sizing. However, Photoshop also has productivity features built in that make it much more convenient. One convenience is it retains the history of the last 20 changes and can selectively go back and undo any changes you have made along the way. Photoshop also allows recording any sequence of actions to be saved and used on other images, for example resizing images to create the small preview images known as "thumbnail" views.
Best of all, Photoshop allows batch processing of multiple images. This is a real time saver if you need to perform the same command on many images, for example resizing images to a particular size or adding a company logo to the image. Using Photoshop’s batch command it is possible to perform a command or series of commands to a group of images without any user interaction. Simply select the images to process and the commands to perform, and let Photoshop do the work while you get a cup of coffee.
There are two parts to creating digital mineral photographs: capturing the image with the camera and processing the image on the computer with image editing software. Capturing the image is much the same as conventional photography. Image editing is where much of the work is done.
Before starting a session, you will need to set up your camera. This is done once, when first using the camera, then never has to be done again.
For almost all applications the camera should be set to save images in JPEG format, which is short for Joint Photographic Experts Group. This is a method of saving the image pixels by compressing the data. Some cameras also allow the selecting high resolution (large file size) or low resolution (small file size) allowing more images to be stored in the camera. For mineral photography select the highest resolution option.
Newer digital cameras may have a digital zoom feature, that magnifies the image electronically (independent of zoom optics) to create the illusion of a telephoto image. In fact, the camera is enlarging the same basic pixel data and image quality is not actually improved. Set the camera to turn off the digital zoom.
Some cameras have a high resolution interpolation feature that takes a standard pixel count and expands it to a higher resolution. For example, a standard camera resolution (native resolution) may be 1024 x 786 pixels, but with interpolated enhancement the camera will boost the pixel count to 1280 x 1024 pixels. This feature is solely for marketing and advertising purposes, to boost the pixel count and does not actually enhance the picture quality. Set the camera to disable this feature.
Finally, turn off the built in flash and set the camera to the macro mode. Now everything is set to go.
The basic steps are as follows:
1. Clean the visible area - Eliminating any dust now will save time spent retouching later. Carefully clean all visible dust on the backdrop or lint on the specimen.
2. Pose the specimen - No amount of image editing can adjust for a poorly posed specimen. Support the specimen securely on a stand or use non-staining putty. Posing the specimen to conceal the support reduces time and effort later spent retouching the image. One advantage of a digital camera is the convenient LCD viewfinder that facilitates rotating the specimen while simultaneously previewing the image.
3. Adjust the camera angle to capture the image - Though it is possible to handhold the camera, it is definitely not advisable. Camera motion is the single biggest contributor to blurry images. Set the camera on a sturdy tripod and compose the image by adjusting the tripod. It is best to fill the image as completely as possible with the mineral specimen. Digital cameras have an LCD screen as the viewfinder. This provides the exact view the camera is seeing similar to conventional SLR camera.
4. Adjust the lights and add reflectors for reflections and shadows - Reflections off crystal faces and shadows cannot be added later during image editing. Arrange the lights to describe the form, and crystal luster of the specimen. This usually involves primary and secondary reflections, but is a matter of personal taste to the photographer. See Jeff Scovil’s book for further discussion on how illuminate a specimen for photography.
5. Adjust the exposure - Using the LCD viewfinder, preview the image to adjust the lightness and darkness using the cameras exposure control. It is important to try to get the exposure as close as possible at this time to capture all the information in the image. If the exposure is too dark the shadows will merge into a big, dark mass. Similarly, the highlights will wash out if overexposed. Fortunately previewing and adjustment is easy with the LCD viewfinder. Be aware that the image on the LCD viewfinder can vary as viewing angle changes. This may lead to the mistaken belief that exposure is correct. It is best to make sure you are looking straight at the viewfinder screen to avoid this problem.
6. Pre-focus or manually focus - The shutter release is a two-stage switch. Depressing the shutter release halfway will focus the camera. Depressing the shutter release fully will capture the image and record it. The user should closely inspect the image after focusing the camera. If the image is not properly focused then switching to manual focus may be necessary.
7. Make exposure - Finally, depress the shutter release fully. The camera will capture the image and record it to the memory. An image 1024 x 768 pixels will vary in size from 50k to 280k bytes of memory depending on the image detail. An image with lots of small detail, like drusy crystals, will create a larger file than an image with soft contours and little detail, such as botryoidal malachite.
© John H. Betts - All Rights
Reserved
Please support our sponsor
© John H. Betts - All Rights Reserved