This lens has an aperture ring with a locking knob.
To focus, loosen the collar (for this particular lens,
a 2mm hex driver is used), and rotate the entire
body of the lens. Loosen the lens body
(counterclockwise) to focus closer; tighten
(clockwise) to focus farther. Tighten the collar
when complete.
Caution – the lens body is not captive and will fall
if screwed all the way out.
When exposure and aperture settings are complete, the image should be bright and there should be no overdriven (red)
pixels in the area of interest. In many cases, ambient light will not be enough to achieve this without using unacceptably
large exposure times or aperture settings; for these cases, supplemental light will be required.
Too bright – overdriven Too dim Correct brightness
For many moderately sized specimens, a simple task lamp of 50-100 watts will give excellent light levels while providing
diffuse, even illumination. For very small specimens at high magnification, a fiber optic illuminator can be used. For very
large specimens, a 300-500 watt halogen light or a specialized machine vision lighting solution may be required. If the
specimen is reflective or highly curved, specialized solutions or careful positioning may be required to avoid
reflections/highlights on the surface.
WARNING: IF THE LIGHT IS POSITIONED IN FRONT OF AND BELOW THE CAMERAS, OR IF THE SURFACE BEGINS TO HEAT UP
FROM THE LIGHTING, REFRACTIVE HEAT WAVES CAN APPEAR IN YOUR IMAGE. THESE WAVES MAY NOT BE VISIBLE IN A
ZOOMED OUT IMAGE BUT WHEN ZOOMING IN THEY CAN BE SEEN AS A SWIMMING/SHIMMERING EFFECT WHICH CAN
BOTH DEFOCUS AND DISTORT THE IMAGE.
IF HEAT WAVES ARE PRESENT IN YOUR IMAGE THEY CAN EASILY INTRODUCE FALSE STRAINS OF SEVERAL THOUSAND
MICROSTRAIN SO IT IS CRITICAL THAT THEY BE AVOIDED.
HEAT WAVES CAN BE MINIMIZED BY EITHER REPOSITIONING THE LIGHT SOURCE, OR, IF NECESSARY, A SMALL DESK OR
STAND FAN CAN BE SET UP TO BLOW ACROSS THE SCENE. THIS WILL GENERALLY MIX THE AIR WELL ENOUGH TO
COMPLETELY ELIMINATE THE HEAT WAVES.
To Next Page
Loading...
Need help?
General
