Film & Digital Times Issues 36-38 - Imago

Sensor Sensibility
“Check the Gate.”
Even after endless takes of the same scene, in which a director
numbingly has actors repeat the same lines, the AD’s exhortation
to move on is not “Check the script.”
The AD asks the AC to remove the lens, peer inside the film camera
cavity, and declare that all is well. Or not. If there’s a speck of dust
anywhere in the picture area, the dreaded words ring out, “Hair
in the gate,” and with a groan, the scene is usually repeated again.
Digital cameras aren’t much different. You should check the gate
as carefully and as often. Sometimes you can see smudges or
specks on a good monitor. But not always. Therefore, whenever
you change lenses, be careful about dirt or dust flying into the lens
cavity. Watch out on windy days. Check the sensor the way you
checked the gate on film cameras: with a lighted magnifier.
An excellent magnifier is included in the LensPen SensorKlear
Loupe Kit. It focuses, the light is LED, and there’s an opening on
the side with access to clean the sensor. (www.lenspen.com)
Digital sensors are protected by an expensive, coated cover
glass and low-pass filter pack. This is what we’ll be cleaning,
and it should not be the untouchable, forbidden territory we’ve
been warned about. It’s a piece of glass very much like coated
lens elements or mirror shutters we’ve cleaned before. We’re
not touching the individual photosites of the sensor—they are
mercifully protected by this cover glass.
Cleaning the cover glass of sensors is delicate business, and there
lurks great potential for great damage. It’s still best to leave this
to skilled camera technicians. If you’re not comfortable with it,
don’t do it. If the World’s Worst Assistant is working on your job,
keep him away. But, more likely, you’re shooting on the Skeleton
Coast of Namibia. The wind is howling, the salt spray and sand
are flying, and something’s on the sensor from the previous lens
change. You’re 1,100 miles away from Jannie van Wyk at Media
Film Services in Cape Town. Are you feeling lucky?
While there are as many opinions on cover glass filter cleaning as
a New York cabbie’s opinions on the best route crosstown, I have
several favorites. Remember, these are personal opinions. Test it
on an inexpensive stand-in sensor first. It goes like this, in steps.
1. Use the illuminated magnifier to determine what kind of
schmutz is on the cover glass. It’s usually either dry or sticky.
2. Peter Meurrens, VP Operations of Parkside Optical (makers
of SensorKlear) says, “About 75% of the time a simple use of
the hand blower solves the problem. It is quick and you do not
actually touch the sensor surface. By holding the camera upside
down, gravity and vortex swirl of the blower in the chamber takes
the dust outside. Anything remaining after use of the blower is, by
definition, stickier dust.”
3. For stickier dust, use a LensPen. LensPens have been the
winners of the Camera Cleaning Olympics held periodically and
unofficially since 2000. They come in many shapes —our favorite
is the new SensorKlear-II. It has a right-angle probe fitted with
a small mushroom-shaped micro-fiber tip that contains carbon
black to “wick” contaminants away from surfaces like lenses and
cover glasses. Meurrens explains, “The function of the LensPen
SensorKlear-II is to make the sticky dust particle stop sticking.
Most of the sticky dust is held in place by static electricity or by
a small bit of moisture caused by humidity. The SensorKlear-II
Cleaning Pad has 3 corners—used for getting into the 90° corner
of the sensor surface. It also has 3 sides; I like to use these edges
to lightly ‘kick’ the sticky dust particle by approaching it from the
side. The dust particle will either stick to the cleaning pad and I
take it out and blow it away, or the dust particle will move, i.e., stop
sticking. I do not use the flat surface of the Cleaning Pad as I do
not want to push the dust particle down onto the sensor surface.”
4. After removing sticky dust with the SensorKlear-II, use the hand
blower to blow dust off the cleaning tip. One SensorKlear-II can last
up to 200 cleanings, but at $24 each, it’s an inexpensive replacement
to begin fresh with each job. What will severely shorten the useful
life of the Cleaning Tip is to clean the messy residue left on the
sensor surface by other products. For that, use Pancro.
5. Pancro Lens Cleaning Fluid has been the perennial runner-up
in the Camera Cleaning Olympics, and a longtime favorite for
lenses, mirror shutters and eyepieces. Use Pancro if the speck on
your sensor is salt spray, a stubborn stain, or gooey residue that
requires a liquid solvent. Use sparingly. You don’t want the fluid
to leak around the cover glass and onto the sensor’s photosites.
(www.pancro.com) Apply Panchro with ITW Texwipe TX762
Swabs. These are lint-free swabs for cleaning microscopes. (www.
texwipe.com and www.soscleanroom.com)
Dec 2010
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