[Blindmath] grayscale braille

[Michael Whapples]

I think Richard Baldwin has given a more technical meaning to what contrast 
means. I had sort of taken the more general meaning, how much two differ 
which could be how much colours differ or how much intensity differs.

Michael Whapples

-----Original Message----- 
From: Pranav Lal
Sent: Thursday, March 22, 2012 4:36 PM
To: 'Blind Math list for those interested in mathematics'
Subject: Re: [Blindmath] grayscale braille

Hi Michael,

You are probably right. I have used contrast as a  tool and yes it is
measuring the intensity of color. The vOICe does have a color spectrum
feature but I have not done much work with it since you lose all shape
information when using that feature.

Pranav

-----Original Message-----
From: blindmath-bounces at nfbnet.org [mailto:blindmath-bounces at nfbnet.org] On
Behalf Of Michael Whapples
Sent: Thursday, March 22, 2012 2:40 PM
To: Blind Math list for those interested in mathematics
Subject: Re: [Blindmath] grayscale braille

Contrast might or might not relate to changes in colour, particularly as far

as the voice is concerned if I understand how the voice works.

To explain now, I understand the voice is using a form of grayscale
representation. I know you can apply a particular colour filter, but this
even so is a form of grayscale. I understand the voice only gives you a
level of intensity (IE. how loud the sound is) and in the case of colour
filter mode it is only measuring the intensity of one colour rather than
them all.

The colour filter mode actually makes me think of an early electronic
magnifier system I used. The magnifier system had a black and white camera
in it, so output on the screen was grayscale. However the magnifier system
used LEDs to illuminate the page being viewed, however the manufacturer had
used red LEDs and therefore one was unable to read red text on a white
background as red reflected the red light just as well as the white
background and therefore the gray level used was the same for both. Equally
one could not necessarily see the difference between blue and green when
viewing the grayscale of the magnifier system as both of those would reflect

the red light  equally poorly.

Anyway back to contrast, the intensity is just one dimension where things
may contrast. If the viewer has colour information as well then differences
in that may also be contrasting, but if one has thrown that information away

in creating a grayscale image then changes in colours will not contrast.

I think the contrast of changes in colours is what Richard Baldwin's tool
for enhancing diagrams for the blind is detecting and showing. That is why
you only get outlines of objects in his tool as the boundary is where there
is a colour contrast.

I am not fully sure, but I think some of what you mention on very high
contrast images distorting the image, may be something to do with how it
appears to the viewer. I know some find having the pure white background for

text can be a bit glaring, I think this is to do with the eye recieving so
much light that it is hard to see the small amounts of black. Whether that
is just a problem for how the eye works I don't know.

Whether distortions happen to images on cameras I don't know, however there
are many digital cameras which might try and do some autocorrection and so
might be tricked into doing something which isn't quite right for what the
operator would desire. Images with large amounts of very light stuff and
large areas which are quite dark could be difficult as a short exposure time

may loose detail in the dark sections and a long exposure time may lead to
the bright sections being over exposed.

So may be high contrasts in intensity can give problems.

Michael Whapples

-----Original Message----- 
From: Pranav Lal
Sent: Thursday, March 22, 2012 1:36 AM
To: 'Blind Math list for those interested in mathematics'
Subject: Re: [Blindmath] grayscale braille

Hi all,

I do not know colors perceptually. However, One comparatively rare
circumstance where color in a tactile image may be important is if the blind
person is presenting to a group of sighted persons. I have frequently been
to conferences where people display graphs and talk about the blue line
representing such and such variable. I say this is rare for blind people
since I do not know how many blind people keep tactile diagrams with them
when making such presentations.

When we talk about changes in color, are we talking about contrast? If so,
then I have experienced this with the vOICe. The higher the contrast, the
better I can distinguish objects. However, I remember that too high a
contrast distorted the image but I will have to double check this.

Pranav


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