Note: Descriptions are shown in the official language in which they were submitted.
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REFERENCE CARD
The present invention concerns a reference card to be
used as a reference object concerning the light reflection and
colour balance in photography, especially a grey card, which
has neutral grey colour and reflects a predetermined amount of
light.
Grey cards are used in photography for taking light
measurement and exposure setting of the camera, and in after
treatment of the picture, the grey card can be used as a
reference when producing a picture with the right colour
balance. Briefly the method comprises the steps to measure the
reflecting incoming light on the grey card by means of a light
meter, the grey card normally reflecting 18 % of the incoming
light, and to adjust the exposure setting of the camera
according to the measured value. Thereafter, the object is
photographed with the settings of the camera appropriate for
the occasion, whereby the photo is stored on a film or in an
electronic memory according the used camera technique. When
producing the picture it is known that the grey card is
properly exposed, whereby this information gives data for
copying or for digital production of the whole picture.
Previously known grey cards are made of rigid carton with
a neutral grey side, which reflects 18 % of the incoming light
and a white side, which reflects substantially 90 % of the
incoming light and are sold in one smaller and one bigger
size, about 130 cm= and 520 cmz, respectively, at a relatively
high price. The grey cards are sensitive to light and
gradually change colour. After some time the colour value has
changed too much so the grey colour is not neutral any longer
and the grey card cannot be used for the balancing of grey and
colours any longer.
Another problem is that the grey cards are large and
ungainly to transport together with the camera equipment and
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occupy a large area of the photo so that a large portion of
the original photo must be cut away. Additionally, they are
difficult to place at the object to be photographed. Mostly
large clips are required or you have to try to lean the grey
card against something, at the same time it is not allowed to
be in an angle towards the wrong direction.
The aim of the present invention is to set aside the
above mentioned problems.
This aim is fulfilled by means of a reference card
according to the preamble which is characterized in that the
back of the reference card is provided with a releasable
adhesive and a number of reference cards are assembled in a
pad, on a sheet or attached to a strip, which is stored in a
rolled-up position so that the reference cards are pratected
from light by each other.
The advantage with this reference card is that it is easy
to bring, easy to attach where it is preferably positioned and
also easy to remove and reattach at another position and reuse
it as long as the colour stays unchanged. Since the reference
cards are attached one upon the other as in a pad, attached to
sheets or attached to a strip, which is stored in a rolled-up
position they protect each other from having a change in
colour due to exposure of light. Only the top one in the pad
will be exposed to light. The sheets are preferably stored
with the reference card sides opposing each other or folded so
the reference cards thereof are protected from light.
According to one embodiment, the reference card is
flexible, which has the advantage that the reference card may
be folded and, for example, attached in an inclined position
from the surface.
According to another embodiment the front of the
reference card is provided with a field, which facilitates the
setting of the focus when photographing objects without sharp
contours and which additionally, when photographing using
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multishot technique (for example three shot technique where
one red, one blue and one green picture is assembled on top of
each other) may be used for centering of the taken pictures
(three in case of three shot technique, four in case of four
shot technique) so that they exactly coincide.
According to a further embodiment, the reference card is
provided with a grey scale, which has the same neutral grey
colour as its basis as the rest of the reference card but is
mixed with white and black, respectively, and which extends
from white, 0 % black mixed in, to black, 100 % black mixed
in, via a number of grey fields with varying mixes of white
and black, respectively. The grey scale is, for example, used
as a reference for the contrast and to set the white- and
blackpoint of the motif.
According to another embodiment, the reference card is
provided with a colour scale with reference colours.
Preferably the pad, the sheets or the roll of reference
cards are stored in a Light tight box and the size of the
reference card is smaller than 300 cmz prefereably smaller
than-130 cm= and most preferably smaller than 70 cmZ. Also
very small reference cards may be made with an area surface of
about 1-3 cm2. Such card may advantageously be provided with a
white and a black field to give the possibility to set the
white and black point of the motif.
Preferred embodiments will now be described in more
detail in connection with the drawings, in which:
Fig. 1 shows a pad of reference cards according to the
present invention.
Fig. 2 shows an enlarged reference card according to the
preferred embodiment of the present invention.
Fig. 3 shows a roll of reference cards according to the
present invention.
Fig. 4 shows a number of sheets with a number of attached
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reference cards according to the present invention.
The reference cards 10 according to the invention are
provided with a releasable adhesive on the back. The adhesive
may cover the whole of the back or portions thereof, for
example, as a strip along one of the edges. Thanks to the
adhesive the reference card 10 may be provided in a pad l
where the reference cards placed on top protects_the reference
cards 10 placed underneath from exposure of light, since light
gradually makes the reference cards more and more yellow, i.e.
the neutral grey colour changes into a grey colour where
yellow dominates. See fig. 1. Another possibility is to attach
preferably small reference cards 10 to a strip 7, which is
rolled-up into a roll where the reference cards 20 are
preferably provided on the inside of the strip 7 to be
protected from light by each other and the strip 7. See fig.
3. A further possibility is to attach a number of reference
cards to a sheet 8, Which, for example may be stored as loose
sheets or in a pad, see fig. 4.
The reference card, according to a preferred embodiment,
is flexible so it is bendable or foldable, Whereby the
adhesive attach to the surface and the folded-out portion
faces the camera in an appropriate angle, and therefore are
easier to attach and position in an appropriate place. It may
be torn apart so that a smaller portion is used in close-up
photography or made in very small sizes.
The reference card must be light-tight and may not let
light through, for example, from behind. Preferably the back
is black.
When photographing, for example, large paintings it may
be difficult to set focus, wherefore preferably a white field
2 with a black grid 3 is provided at the front of the
reference card, see fig. 2. Also a black field 4 with white
lines 5, which, for example, forms a target may be provided.
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Of course may such fields have any design, the main thing is
that it is contrasty.
Such fields 2, 4 are a great help when taking digital
photos and then especially when taking digital photos using
5 multishot technique. This technique comprises the steps of
taking a photo of the object a number of times, for example
using three shot technique three times, with the same settings
but with different colour filters, using three shot technique
red, blue and green and then assemble these photos into the
~10 one and same photo. The camera is very sensitive so the
slightest movement of the floor causes easily a displacement
of any of the photos. To be able to see if a displacement has
occurred and thereafter centre the photos, i.e. pixle adjust
the photos, a very contrasty field in the photo with thin
lines, which seldom naturally exists on the object being
photographed, is required. To have at least one field like
this on the reference card facilitates the work enormously.
Preferably also a grey scale 6 provided at the front of
the reference card, which grey scale is based on the same
neutral grey colour as the rest of the reference card. The
grey scale extends from white to black via a number of fields
with different mixes of white and black, respectively. In the
preferred embodiment a grey scale is illustrated which show
the percentage of black mix. The white field has 0 % of black
mixed in, the next field has 5 % of black and in this way the
scale steps up with 5 % per field until 100 % black is
reached. Of course other than shown sizes of the percentage
steps may be used or the numbers may show the percentage of
mix in of white or the numbers may be missed out. The grey
scale helps determining of the contrast and at which
percentage the picture shall be produced. This is important
for obtaining the best results in typing and printing of
pictures. Of course, a colour field may also be.provided on
the front of the reference card if wished (not shown) so that
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a reference maybe achieved for each colour, red, blue, green,
cyanogen, magenta and yellow.
Advantageously the inventive reference card may be used
when scanning reflective images to be able to determine the
grey balance.
One of the advantages of the reference card according to
the present invention is the convenient size. Fig. 2 show the
reference card in its biggest size, about 300 cm=, but
preferably they are not larger than about 130 cm2 and rather
not larger than about 70 cm2. The reference cards may also be
made in very small sizes, preferably between 1-3 cm~ and
preferably without the previously mentioned fields. However
they may advantageously be provieded with a black and a white
field for the determination of the blackpoint and the
whitepoint, respectively. These small reference cards may be
of great use in general photography since such a small field
not always need to be cut away from the picture but gives one
or more reference points. Thanks to the adhesive on the back
they are easily positioned at desired place. The pad 1, the
y 20 strip 7 or the sheets 8 with reference cards is preferably
stored in a light-tight box (not shown). In its smallest size
the box of reference cards may easily be carried in a pocket
without the risk of being creased or damaged.
Since the reference cards, just as film, is a "fresh
article" decaying with time and light sensitive they may be
marked with a date and even marked with a serial number or
emulsion number so that their exact values may be attained
from the producer.
With this preferred embodiment a convenient reference
card, which is easy to work with, last for a long time and
additionally has a lot help and special functions, is
provided.
The reference card according to the invention may be
manufactured of a carrier means of paper, carton or of a
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suitable plastic material and the colour in question may be
applied by means of opaquely covering by spraying or painting.
This method is preferred instead of a printing method, which
may bring up problems at the actual printing in achieving a
fully covering colour layer, the right tint as well as a
reference card with full quality and resistance.
