Industrial Fellow, Department Of Mechanical Engineering
University Of Bath, Bath, BA2 7AY, UK
Phone: +44 (1225) 826465
Fax: +44 (1225) 826928
Anyone who has taken photographs using flash photography will be aware of the
phenomenon known as ‘red-eye' - Figure 1 illustrates a typical example.
Although there are several well known ‘solutions' to the red-eye problem,
the phenomenon has by no means completely disappeared.
Figure 1: Red-Eye Phenomenon
This article sets out to do three things; firstly it provides a tutorial
example on use of the TRIZ Contradiction Matrix and how it can be used to
(re-)generate existing and some new solutions to the red-eye problem, secondly
it follows-up an earlier article on ‘Contradiction Chains' (Reference 1) in
order to illustrate the importance of looking to repeatedly seek out and ‘remove'
contradictions, and thirdly, it seeks to follow up on last months article
examining the gap between TRIZ ‘generic' and ‘specific' solutions
(Reference 2) by demonstrating a process to generate new anti red-eye conceptual
solutions using the Contradiction tools.
Problem Definition - The Mechanics of Red-Eye
Red-eye is a flash photography phenonmenon. It is caused by light reflected
off the subject's retina. Research has shown that if the angle of reflection is
less than 2.5 degree, red eye will occur - Figure 2.
Figure 2: Red-Eye Phenomenon
There are several known means to remove the red-eye problem. The basic
mechanism for overcoming the effect is to ensure that the angle of reflection
will be larger than 2.5 degrees. This can be achieved by moving closer to the
subject, or by increasing the distance between flash and lens. Another well
known means to achieve the 2.5 degrees or better requirement is to encourage the
subject's iris to reduce in size (typically the pupil opening will be large
prior to the photograph being taken as there will be little light around (hence
the need for flash! - Ideality would tell us of course that ultimately the
red-eye problem will disappear because the need for flash will disappear)). The
size of the pupil is mainly governed relative to the amount of light present.
Effective use of the TRIZ Contradiction Matrix demands a sound definition of
the contradictions present. It is usually advantageous to conduct this
definition in a number of separate stages (as previously described in Reference
2 for example);
- define the elements of the design that are required to be improved
- map these into the terms of the 39 parameters of the Matrix
- identify the solution directions that will help remove the problem
- identify which of these elements is in contradiction with the feature
to be improved
- map these into the terms of the 39 parameters of the Matrix to get
pairs of improving-worsening features.
From this red-eye example, we might follow these stages as follows:-
Elements to be improved - red-eye
Mapping ‘red-eye' on the Matrix - ‘Object
Affected Harmful Factor'
- reduce distance between subject and camera
- increase separation between flash and lens
- change the amount of light
Identify whether these are in contradiction:
distance - reducing distance between camera and subject means the shot has
to be re-framed and not as much of the subject can be included; so distance is
something that gets worse as red-eye is improved
separation - increased separation means the camera and lens may no longer
be able to be mounted together, or there may be synchronisation problems, or
the flash may generate unwanted shadows; so this too may be seen as a
worsening feature in contradiction with red-eye improvement
amount of light - increasing the amount of flash light present would tend
to worsen red-eye and so is not seen here as a useful solution direction. On
the other hand, reducing the amount of light would improve red-eye, but we can't
do this because if we do, there will no longer be sufficient light to make the
photograph. Hence the amount of light is in contradiction with our desire to
Map these onto the Matrix -
distance ® ‘Length'
(‘of Moving Object' - because there is
relative movement between camera and subject)
separation ® ‘Length'
again, although this time we might chose to use ‘stationary
object' because there is currently no relative movement between lens
and flash unit.
amount of light ® ‘Illumination
In total, then, these contradictions give us a number of Inventive Principle
versus Length of Moving
- 17, 1, 39, 4
Object Affected versus Length of Stationary
- 1, 18
Object Affected versus Illumination Intensity
- 1, 19, 32, 13
We may immediately see the relevance of these Inventive Principle solution
triggers to some well established remedies to the red-eye problem.
Figure 3: Anti-Red-Eye Pens
Inventive Principles 32, Colour Changes, is perhaps not so useful, but does
suggest use of black and white photography, or points towards the plethora of
after-the-event remedies like anti-red-eye pens for touching up photographs
(Figure 3) or, for digital photography, anti-red-eye features in photo
manipulation software. There are also one or two patented solutions where the
‘colour change' is remedied by software processing within the camera when
the photograph is being taken (undoubtedly clever, and an eefective transition
from a mechanical to a field based solution to the problem).
Inventive Principle 1, Segmentation occurs several times and thus should
suggest it is likely to be highly relevant to the problem at hand. The most
obvious interpretation of the trigger is the solution adopted by most
professional photographers; that of segmenting the camera and flash (and, in
fact, also segmenting the flash to utilise several flashes). More practically
from the perspective of the amateur photographer are patents in which the
segmentation between camera and flash occurs more locally - pop-up flashes,
flash units driven away from the camera body using linear motors, and even
velcro-attachable flashes are all available or patented solutions.
Principle 1 might also to suggest the idea of segmenting the light emerging
from the flash, which in turn relates to the next solution trigger:
Inventive Principle 19, Periodic Action, emerging specifically from the
contradiction associated with illumination intensity, offers a direct lead into
the anti-red-eye flash solutions incorporated into the majority of current
integral camera designs. This is the idea of a double (or more) flash action -
in which the first flash prompts the pupil to contract such that when the second
flash is fired to coincide with the taking of the picture, the pupil is usually
small enough to allow the 2.5 degree rule to be satisfied.
So, the Matrix may be seen to be offering clearly appropriate solution
directions for the red-eye problem.
Of course, the method always recommends that we don't just satisfy
ourselves with the first group of solutions that emerge. Our brains tend to
fight this direction particularly if it looks like the emerging solution - e.g.
the now prevalent double flash idea - possesses a high degree of elegance, and
so we usually have to force ourselves to remember that ‘if the solution
exists, it contains contradictions', and to look to tackle the remaining
or emerging contradictions after we have solved the first one - as discussed in
the ‘contradiction chains' article (Reference 1).
In the case of the double-flash idea, any user of this solution will be
clearly aware of other contradictions that have emerged as a result of solving
the red-eye problem. New problems relate to the phenomenon that we tend to find
dilated pupils more attractive than small ones, and, more seriously from a
practical point of view, to the fact that when we press the shutter to take a
photograph, the timing of the double flash means there is a delay of up to a
second between action and the resulting photographic image - in other words we're
not taking the photo we intend to take.
Translating this particular new problem into the terms of the Contradiction
Matrix, we may see the ‘duration of action' as a definite feature we would
like to improve. We could thus repeat the TRIZ process for contradictions
related to this situation.
Rather than doing this, however, we will take another direction as a way of
highlighting another important feature about using the Contradictions part of
TRIZ. This feature we will call ‘solution mapping'.
In many senses, the double-flash idea has been seen as so attractive a
solution in the compact camera market that it has provoked the whole industry
along the same direction (see the large range of highly similar patents in the
area on the patent database). Solution mapping gets us to remember that there
are other solution routes available and to question whether solving the next
round of problems with the double-flash is the right thing to do relative to
travelling along one or more of the other available routes. In other words, it
gets us to question whether the double flash idea is actually an evolutionary
Figure 4: Which Thread Leads To The Treasure?
One way of thinking about the solution map is the tangled string game found
in children's puzzle books (Figure 4). In these puzzles, the reader is asked
to choose from a number of loose ends of string (usually three or four - in real
life, there will be many more!) and to trace the chosen string through the
tangle of other strings to hopefully reach the ‘treasure' at the other end.
All but one of the start points, however, ends up not leading to the treasure,
but to some cul-de-sac with anything but treasure at the end of it. If we extend
the analogy so that ‘treasure' becomes ‘ideal final result', we obtain a
useful image of how systems will evolve - with lots of dead-ends and
cul-de-sacs, but (at least) one route through to IFR.
(We might also note that anyone who spent any time at all playing with these
puzzles during childhood, pretty soon learned it was more effective to start
from the treasure and work back to the start. Back then, it was called ‘cheating';
today it's called an ‘IFR tool'.)
Coming back to the real world again, a partial solution map for the red-eye
problem is illustrated in Figure 5.
Figure 5: Partial Solution Map For ‘Red-Eye' Problem
One of the questions provoked by drawing this type of picture is ‘am I
correct to continue down this path, or should I go back and investigate whether
other paths might offer me a more effective route to ideality - including,
incidentally, solutions from other parts of the TRIZ toolkit above and beyond
those prompted by the Inventive Principles.
It should also be encouraging us to examine how different solution routes
might be combined and distilled.
With little justification other than the desire to travel down a different
route to see how to make the journey most effectively, and to see what happens
along the way, we will now examine the thus far un-explored ‘Asymmetry'
route (from the above contradiction solution suggestions) out of the red-eye
The translation of the TRIZ generic solutions like ‘Asymmetry' into
specific solutions to the red-eye problem is not always an obvious one.
Reference 2 has discussed the gap between ‘generic' and ‘specific' and
recommended strategies for filling the gap.
We will look now at a 3-stage strategy for generating solutions building on
the Reference 2 recommendations. As in that article, if we are to be successful
we need to be aware of the need to be thinking in space and time throughout the
process of making connections between solution trigger and the problem.
The first of the three stages proposed here involves identification of
resources in the current system upon which the ‘asymmetry' solution route
might be applied. This means looking for things in and around the current system
space that are symmetrical, but it also means looking for asymmetries that we
could make either more or less asymmetrical. We conducted this search as a
systematic brainstorming session structured around the camera plus flash plus
photographer plus subject space system illustrated in Figure 2. Thinking about
time issues, we defined ‘past' as the time before the picture is taken, when
the photographer is framing the picture and the camera is warming up; ‘present'
as the point of pressing the shutter; and ‘future' as the time immediately
after the picture has been taken.
Figure 5 illustrates the un-processed outcome of this first (ten minute)
brainstorm session, done with three willing volunteers equipped with ‘LVT-for-TRIZ'
MagNotes (Reference 3). The brainstorm question was to ‘find things that are
symmetrical'. The volunteers wrote down their ideas - one per Magnote - on the
Figure 5: ‘What Does Asymmetry Mean in the Red-Eye Problem?'
Initial Brainstorm Output
The second stage is a relatively short one in which we seek to distill and
re-inforce the ideas emerging from the first stage. This is most effectively
done by asking the brainstorm participants to ‘cluster' the ideas generated
in the first stage into related groups. The outcome of this (2 minute) stage is
illustrated in Figure 6.
Figure 6: Clustered Brainstorm Output
The third stage of the solution process then involves taking these outputs -
actually now ‘resources' - i.e. they all
represent opportunities to deploy the ‘asymmetry solution - identified in the
first stage in order to examine how the ‘Asymmetry' Inventive Principle can
be used to produce useful solutions. A partial picture of the output from this
session - which was allowed to run for around 30 minutes and generated a new
board of ideas for each of the clusters identified in Figure 5 - is reproduced
in Figure 7. The figure is ‘partial' because we think we generated some
useful and patentable solutions on the other boards and thought it best not to
include them here (readers are encouraged to see if they can find them too!).
The excluded parts composed the output from attempts to link ‘asymmetry' to
the other opportunity clusters from Figure 6. The incompleteness shouldn't be
allowed to detract from the method being demonstrated - which, after all, is the
main point of the article.
If we were doing this for real of course, we would also be looking to distill
good ideas being generated by different generic solutions. For example, we might
make a connection between the use of an asymmetrical flash illumination profile
and the earlier double-flash concept; for again there is a largely untapped
resource in tailoring the flash time history to the problem.
As it was, we ended up with a total of over a hundred Magnote-recorded ideas
from the session on just the Asymmetry trigger.
Figure 7: Partial Picture of ‘Asymmetry' Solution
This article has attempted to describe a reproducible process - or series of
mini-processes - to help use the contradictions part of the TRIZ method. In it,
we have seen that the Contradiction Matrix is a pretty good start point for the
red-eye problem; allowing us to quickly re-generate good solutions to the
More specifically, we have introduced the concept of a ‘solution map',
and hopefully demonstrated its importance in helping us to ensure we see that
there are several solution routes to any problem and that there are times when
we may be travelling down a route that is a cul-de-sac rather than a highway to
increased system ideality.
Related to this, we have again seen the importance of recognising the
existence of ‘contradiction chains' (i.e. pre-flash is a good solution to
the red-eye problem, but it comes at the expense of introducing other
contradictions), and that the road to ideality involves challenging a succession
We have also demonstrated a three-stage (resource
identification, distillation and application) strategy for ensuring the
most effective use of the Inventive Principles (although the same strategy will
be effective with other TRIZ tools too) in filling the gap between ‘generic'
and ‘specific' solutions
- Mann, D.L., ‘Contradiction Chains', TRIZ Journal, January 2000.
- Mann, D.L., ‘The Gap Between ‘Generic' and ‘Specific' Problem
Solutions', TRIZ Journal, June 2001.
- Blake, A., Mann, D.L., ‘Making Knowledge Tangible', TRIZ Journal,