TOPIC: Data files and formats. Colour space, compression, etc
Last Update 22 July 2005
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Terry Redman, Chairman of Farnborough CC (SPA) |
The rules
for digital competitions are in our opinion no different to print and slide
competitions, and I attach the relevant section from our Club Handbook which
deals with these rules – only the first 2 pages are relevant. You will note
that because there are now 3 formats of competition (print, slide and
digital) we have restricted members to using an image in one format only per
season. However where there is a difference is in the preparation of images
and we have found that detailed user-friendly guidance is essential if the
competition is to run smoothly. Also attached, therefore, is Appendix 4 to
our Handbook which contains this guidance - it has been written with both the
benefit of our experience and having considered papers produced by other
clubs. It is hoped that these docs will be of help in establishing a set of
standards, if that is what the Sub-committee intends to put in place. Download/View
their image preparation Rules
(pdf, 407KB) |
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Site for Nova Scotia with
detail and screen shots of how to prepare data files for the digital
events. Recommends sRGB space. When assigning the profile the text
recomends perceptual rendering, but screen shots show relative
colorimetric. Compression at JPEG-12
(ie high quality). Requests authors
to use 768 pixels on the longest side always. This means both landscape and portrait formats display similar
area: landscape not allowed to use full width/area. |
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via Roy Moore, Maidstone CC (KCPA), about use of AdobeRGB as the colour space for submitting entries |
There
were two reasons for choosing Adobe RGB 1998 as the standard colour space for
the KCPA Digital Imaging Competition: 1)
Most entrants would be digital workers who print their images; they would, of
course, be using Adobe RGB 1998 as their working colour space and would have
their copies of Photoshop set accordingly. Therefore choosing Adobe RGB 1998
means that they would not have to make a profile change before submitting
their entries. 2)
(The main reason) I was advised by GretagMacbeth that, when calibrating a
projector using their equipment, the limitations of the projector can be
overcome to a considerable extent (precisely how much depends, apparently, on
the particular design of projector). Therefore it is possible to specify a
colour space somewhat bigger than sRGB even though the projector
specification seems to be imply that sRGB is all that is possible. I gathered
from talking to one of their personnel that many projectors can indeed work
to a larger colour space, but that fact is not spelled out in the literature
since business users (by a very long way, the largest group of users) are not
particularly concerned about accurate colour rendition and burdening the
literature with information about colour spaces could possibly have a
negative marketing influence. I
must add that the literature about colour spaces is very large and not
particularly self-consistent; it is not impossible that the information I
received from GretagMacbeth could be contradicted by information from another
source. For example, it is well known that the graphical representation of
profile gamuts depends greatly on which company provides the graphing
program. Compare, for example, representations by Monaco, GretagMacbeth and
Chromix of the same data; or look at the 'out-of gamut' parts of an image as
represented by Photoshop and Chromix. |
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