[tabi] technical info for users of the KNFB reader

  • From: "Chip Orange" <Corange@xxxxxxxxxxxxxxx>
  • To: <tabi@xxxxxxxxxxxxx>
  • Date: Tue, 25 Aug 2009 16:25:33 -0400

>

> K-NFB Reading Technology, Inc.

>

>

>

> TECHNICAL ASSISTANCE BULLETIN

>

>

>

> Date: August 19, 2009

>

> SUBJECT: Advisory on use of polarizers

>

>

>

> Installation of polarizers over the camera lens and flash has been a

> specified procedure of K-NFB Reading Technology since the Mobile
Reader

> products were first released in January 2008. The purpose was to
improve

> the quality of images captured by the Nokia N 82, which uses xenon
flash

> technology to illuminate target text. Polarizers minimize glare caused
by

> the flash reflecting back to the camera lens when the text is printed
on

> glossy material, or the image is captured through glass. The glare
would

> otherwise prevent accurate text recognition.

>

>

>

> Polarizers do improve image quality, as confirmed by our direct
observation

> and reports we continue to receive. But only if they are correctly

> installed and maintained in accordance with our specifications.

> Unfortunately, over time normal day-to-day use of the Mobile Reader
often

> results in polarizers being moved or dislodged, such as when the phone
is

> carried and frequently removed from a pocket, purse, or carrying case.

> Misaligned polarizers not only fail to improve images of glossy
surfaces

> but

> also can distort all images, leading to unsatisfactory performance.

>

>

>

> To address this, we have decided to recommend polarizers as an
optional

> rather than a required accessory. End-users may choose to have them

> installed or not based on individual needs, requirements and
preferences.

> The information below is intended to help Mobile Reader distributors
and

> end-users decide whether to recommend polarizers or use them,
respectively.

> Additional assistance to address particular questions or concerns is

> available from K-NFB Reading Technology's technical support service.

>

>

>

> 1. Expected reading requirements

>

> As noted in the Mobile Reader Users Guide, polarizers are particularly

> essential when capturing images of text printed on glossy material or
when

> a

> picture is taken through glass. An alternative to polarizers under
these

> conditions is to switch off the flash, which can be done without

> sacrificing

> image quality provided the lighting in the room or area is moderate or

> better. Another alternative is to use a reading lamp, which can
improve

> the

> brightness of the image and still avoid glare if the light is properly

> situated to avoid reflection from the glossy surface . So switching
the

> flash off while attending to lighting conditions is a suitable
alternative

> to polarizers, unless one needs to read glossy documents very
frequently

> and

> under varying conditions of light.

>

>

>

> 2. Installation and maintenance requirements

>

> In order for polarizers to function as intended, installation must be

> performed in accordance with our specifications. Thereafter great care

> must

> be taken at all times to maintain the precise positioning of each

> polarizer.

> The end user must understand this.

>

>

>

> 3. Camera considerations -

>

> Two supported phones, the Nokia N 82 and the Nokia 6220 classic, are

> equipped with xenon flash, which produces the brightest light possible
but

> also can introduce the most glare. The Nokia N 86, first announced as
a

> supported phone in August 2009, is equipped with a camera which has
been

> optimized for low light images, including an 8 megapixel camera and an

> advanced dual LED flash. Consequently, images of glossy content
captured

> by

> the N 86 used without polarizers tend to show less distortion even
with the

> flash turned on than comparable images taken with the xenon flash of
the N

> 82 or 6220 Classic. Images taken by the N 86 without polarizers and
the

> flash turned off usually compare favorably to images captured by the N
82

> or

> 6220 Classic when polarizers are installed and the xenon flash is
turned

> on,

> provided there is moderate or better light. So there is less need of

> polarizers for the N 86 than there is for the N 82 or 6220 Classic.

>

>

>

> In summary: beginning August 2009, K-NFB Reading Technology will no
longer

> specify pre-installation of polarizers as a product requirement.
Decisions

> on installation and use of polarizers as an optional accessory should
be

> made by distributors and end users based on individual needs and

> capabilities. Polarizers will remain available upon request for all

> supported phone models.

>

> Switching the flash on and off, while attending to lighting
conditions, is

> recommended as the best all around option for end users who do not
express

> a

> significant need to read glossy documents in low or fairly low light
with

> the flash turned on. See the chart on the following page.

>

>

>

> For more information or to order polarizer sets, please contact K-NFB

> Reading Technology by email at: support@xxxxxxxxxxxxxx or by phone at:

> 1-877-547-1500. If ordering polarizers, please specify the quantity
and

> supported phone model. Previously published rates for multiple
polarizer

> sets shipped in quantity to distributors still apply.

>

>

>

> Explanations on the decision to use polarizers follow in both text and

> chart

>

>

>

>

> Our recommendation as to whether polarizers should be installed
depends on

> 2

> questions:

>

>

>

> Do you frequently need to read glossy documents, and under varying
light

> conditions?

>

>

>

> Would you carefully maintain the position of the polarizers on the
camera

> lens and flash?

>

>

>

> If the answer to either of these questions is "No", our recommendation
is

> not to have the polarizers installed. Turn off the flash before
shooting

> glossy surfaces and make sure that there is at least moderate
lighting.

>

>

>

> If the answer to both of the above questions is "Yes", then your
preference

> should determine whether polarizers are installed on the Reader. N82
and

> 6220 Classic phones have a very bright xenon flash, which can produce
a lot

> of glare in an image of a glossy document, whereas the N86 has a
dual-LED

> flash which does not create as much glare. The polarizers will greatly

> diminish the glare which appears in an image of a glossy document, but
you

> can also turn the flash off, which will eliminate the glare and still

> provide good reading performance if there is good ambient lighting.

>

>

>

> If you choose to have the polarizers installed, make sure that the

> polarizers are not rubbed against surfaces or put under stress, as
this can

> cause them to move out of position. If you choose not to install

> polarizers, turn off the flash before shooting glossy surfaces and
make

> sure

> that there is good ambient lighting.

>

>

>

> Best Regards,

>

>

>

> James Gashel

>

> Vice President of Business Development

>

> K-NFB Reading Technology, Inc.

>

> Direct phone: (720) 878-4248

>

> Fax: (781) 263-9999

>

> Skype: james.gashel

>

>

>

> email: jim@xxxxxxxxxxxxxx

>

> http://www.knfbreader.com <http://www.knfbreader.com/> 

>

>

>

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