{"id":139,"date":"2010-06-16T12:17:16","date_gmt":"2010-06-16T16:17:16","guid":{"rendered":"http:\/\/georgianbayphotographs.ca\/gbay_blog\/?p=139"},"modified":"2010-11-20T10:21:09","modified_gmt":"2010-11-20T15:21:09","slug":"whats-with-that-colour","status":"publish","type":"post","link":"http:\/\/georgianbayphotographs.ca\/?p=139","title":{"rendered":"What\u2019s With That Colour"},"content":{"rendered":"

One of my pet areas of interest is colour reproduction. \u00a0Film has always had its issues, and Digital has its issues as well. \u00a0 Digital seems at times, to have bigger issues. \u00a0Any three colour system of reproduction will have problems reproducing real world colours that don’t match the primaries of the system. \u00a0 The further away the real colour is from a primary the worse the results. \u00a0The reproduced colour will become undersaturated as a mix of colours tries to represent, potentially a single colour of light. \u00a0When a colour nears a reproduction primary the saturation may become over saturated as the other primaries fall away in brightness. \u00a0Giving only a near single colour when viewed. \u00a0We see it all the time when we watch television. \u00a0The Reds are to Orange, the Greens to Yellow. \u00a0 We usually just adapt, but once in awhile the observant will notice that a Fire Truck is the wrong shade of Red, to Orange. \u00a0Colours will be reproduced as shades of the primaries in use. \u00a0These Winter scenes demonstrates the effect of limited available colours and proximity to the system primary. \u00a0I suspect the images also indicate the Blue channel has some sensitivity to Ultraviolet. \"\"<\/a>\"\"<\/a> Digital has a further issue. \u00a0The sensor is very sensitive to Infrared light. \u00a0A simple demonstration, \u00a0an active TV remote pointed at the camera. \u00a0Normal it isn’t visible to human vision, but to a digital camera even the pulses of the command are visible. \u00a0 The LED not appearing as pure Red is an indication that the built in filter colours for the senor also have some leakage in the Infrared. \u00a0The coloured glow from this Infrared LED measures with a large amount of Blue, and Red, with a small amount of Green. \u00a0This skewed sensitivity might well affect reproduction of foliage as plants are famous for reflecting Infrared light. \u00a0This same effect, however is convenient if you wish to do Infrared Photography. \u00a0A special version of a Canon 5D is available without the Infrared filter installed, used mostly for astronomy. \u00a0Some people even purposely remove the filter for the effect.<\/p>\n

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The Macbeth, or GretagMacbeth colour checker, now a product owned by Xrite, has for years been used as a standard for reproduction. \u00a0Simply, a large card with colour swatches painted on that are chosen to represent real world colours. \u00a0The actual values are precisely controlled, so that everyone has the same reference. \u00a0Below are four versions of the card, a computer rendering<\/a>, a scan of an Ektachrome slide, and two digital shots of the card. \u00a0The same one in this case. \u00a0Why use a standard? \u00a0Very simple, if I send a picture of a painting via email and the image contains the Macbeth chart, then who ever receives it will know how the reproduction of the painting has been affected. \u00a0At its simplest a visual check, but readings of the colours can also be used to correct the image for more faithful reproduction.<\/p>\n

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As you can see these images each while similar also have their differences. \u00a0In this case film has a double whammy. \u00a0There is the film’s reproduction faults and then its been scan by a digital film scanner, which is really just another digital camera. \u00a0While the digital scanner will be more tightly controlled, its still another colour process. \u00a0Another issue to consider is that we are viewing these images on monitors, CRT or LCD, which also have their own problems with colour reproduction, but that’s another topic.<\/p>\n

The IMAtest<\/a>. \u00a0This is a very nice piece of software that compares the know values of the Macbeth chart, and the information in a digital image file containing the same chart. \u00a0The comparison is presented as a colourful graph showing pictorially the deviation from ideal reproduction, percentage errors are also included. \u00a0Many online camera review websites provide these results and other highly technical information for the camera being reviewed. \u00a0Doing a Google for IMAtest and your own model of camera should produce one or more reviews with this comparison graph. \u00a0Many sites will also include sample images and results from their own criteria. \u00a0I find that looking at their own tests less useful as I don’t know what their sample actually looks like.<\/p>\n

I’ve included several samples of cameras of interest below. \u00a0The Canon A650 IS, and the Canon A620 are the two digital cameras I use. \u00a0Also the Pentax K20D, which I contemplated purchasing, but didn’t for other reasons. \u00a0The Canon 5D, which is a, wouldn’t it be nice to have, and a Canon 1000D or Canon Rebel XS. \u00a0The Canon 1000D is their entry level DLSR. \u00a0As a balance I’ve include one of the recent Nikon D5000\u00a0 digital camera. \u00a0These images are from www.imaging-resource.com<\/a>,\u00a0www.digitalcamerainfo.com<\/a>, www.photoreview.com.au<\/a>. \u00a0I find these sites useful and informative, but don’t endorse them.<\/p>\n

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So what do all these pretty graphs mean? \u00a0Well firstly the background colour of each graph is only an indication of the tonal range and not the actual colour. The gray line tracing a rough box represents the colour reproduction of a typical monitor or sRGB colour space. \u00a0The little coloured squares represent where the colour swatches of the Macbeth chart should be reproduced inside the colour space. \u00a0The larger coloured circles represent the actual colour produced by the camera being tested. \u00a0Ideally the circles should be on top of the squares, but as you can see the majority aren’t. \u00a0To get a sense of what is going on, consider that the centre of the graph is no colour or, no saturation or, gray scale. \u00a0As you move out from the centre the colour intensity or saturation of a particular colour increases. \u00a0Eventually becoming a pure or monocromatic colour. \u00a0Most of these graphs share a common colour issue the red squares are reproduced as to pure or saturated a colour. \u00a0If the colour being reproduced isn’t straight out in direction from the centre another problem is present. \u00a0This is colour shifting. \u00a0The circle is now representing a different colour than the original square. \u00a0On some graphs the Reds are grossly more saturated, while only slightly a different shade of Red. \u00a0As you look at each graph look at the shifting and saturation changes of each colour. \u00a0Some cameras are better than others, and price isn’t necessarily an indication of quality. \u00a0Compare Nikon D5000 with the Canon 5D, which is almost twice the price.<\/p>\n

All of these tests can of course be skewed if they not tested under the same camera operating conditions and settings. \u00a0Course some camera won’t have comparable settings. \u00a0I include the last two images to demonstrate this. \u00a0These are both from a Pentax K20D, but different websites. \u00a0Obviously something is amiss.<\/p>\n

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One of my pet areas of interest is colour reproduction. \u00a0Film has always had its issues, and Digital has its issues as well. \u00a0 Digital seems at times, to have bigger issues. \u00a0Any three colour system of reproduction will have … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0},"categories":[5],"tags":[],"_links":{"self":[{"href":"http:\/\/georgianbayphotographs.ca\/index.php?rest_route=\/wp\/v2\/posts\/139"}],"collection":[{"href":"http:\/\/georgianbayphotographs.ca\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/georgianbayphotographs.ca\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/georgianbayphotographs.ca\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/georgianbayphotographs.ca\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=139"}],"version-history":[{"count":27,"href":"http:\/\/georgianbayphotographs.ca\/index.php?rest_route=\/wp\/v2\/posts\/139\/revisions"}],"predecessor-version":[{"id":185,"href":"http:\/\/georgianbayphotographs.ca\/index.php?rest_route=\/wp\/v2\/posts\/139\/revisions\/185"}],"wp:attachment":[{"href":"http:\/\/georgianbayphotographs.ca\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=139"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/georgianbayphotographs.ca\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=139"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/georgianbayphotographs.ca\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=139"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}