Photography at NPL- tips and tricks

Tips for good stack series:

Use brush to gently dust off any dirt on specimen. Finish with the hand-pumped air blower. Stubborn lint, especially visible on whitened specimens, can be plucked off with tweezers.

Set the high point a little above what you think it should be, and set the low point a little below the lowest point.

Tall specimens with variable thickness and specimens with sections that 'overhang' are difficult to shoot without introducing stack errors. In these cases, it is best to increase the F stop and take small steps. This allows for a broader focus slice, increasing the chance that in-focus pixels will overlap and the 'fuzz' will be stripped away.

Positions

A good rule-of-thumb is to take about 3 views per specimen, although this number will vary with individual differences.  In general, it is good to take dorsal (top), ventral (bottom), and lateral (side) views, and any others that will capture important detail.  For example, if photographing an echinoid, take the standard dorsal, ventral, and lateral views. In this example, you should also take a fourth view of the aboral end (opposite of the oral end).

Photography

Any given drawer will most likely have specimens with a range of sizes, colors, and shapes.  You can minimize the number of lens and exposure changes if you group the specimens by size and color before photographing.

The limiting factor when you are photographing small specimens with lens extenders is vibration of the camera body. Moving to the microscope may be a better option for small specimens.

Lighting:

When possible, the strongest light should hit the NW section of the specimen. Do not sacrifice image quality to follow this.

With 3 lights on, try rotating the specimen to see which angle provides maximum detail.

Lights can be shaded with paper to decrease 'hot spots' (areas where the light hits too strongly, resulting in white, featureless areas)

Rotate the polarizing filter to find an optimal position for reducing glare on shiny specimens. Watching the histogram can help determine this- look for the highs points to flatten a bit.

Include at least the black and white squares of the color chart.