Subtle Changes
Contents
1. LXP42 ctut gimp 30 75 03 6 36 pm Page 72 D TutorialGIMP e puppy layer lighinr than sponding tel ist thi te cerry harsh edges E Af p ssible inthe Color Less ehini Gl inn is probally veinek betrer fiar a Your tastes rite beck mba pikirna tliat Aig isl a la Subtle Changes Michael J Hammel introduces the photo editing capabilities of this great art application _ ae nderexposed images can occur because of poor lighting or by improper film processing Fixing the mistakes isn t as hard as Scanner Support you might think using a few basic tools of The GIMP Where to get your drivers There are many problems in photography that are difficult SANE www mostang com sane to solve with the mechanics of the shoot but easy to fix with digital XSANE www xsane org imaging software Problems like underexposed portions of an image Vuescan www hamrick com washed out colour from poor processing or poor lighting and redeye Image Scan www epkowa co jp english index_e html can all be addressed with minimal effort using tools like The GIMP Quitelnsane http quiteinsane sourceforge net index shtml This month s tutorial looks at all three of these common problems AED At ETRE eT PETTUS Gus Linux USB Project www linux usb org and how you can fix them with only a few minutes of work 72 LXF42 JULY 2003 www linuxformat co uk Lil LXF42 tut_gim2. 30 75 03 6 37 pm Page 73 D TutorialGIMP CONTRAST LEVELS AND CURVES washing the colour back in Washed out images are often the result of using the wrong speed film overexposing the shot which means using too much light or because of poor film processing In all three cases much of the information available to you is still ore ve na ays p T i LJ We start with an image with a fair amount of detail hidden by our poor choice of film The image content may be a bit on the boring side but lets see if we can pull some colour and a bit of detail back out kiaat Laven tot Channa Value os inpute 0 gt oar 4 rss EJ One option here would be to manually adjust the Levels once again this time moving the center point slider beneath the gradient bar under the histogram off to the right The picture shows the image adjusted in this way This reduces the white range and increases the black range effectively bringing out more colour in the image by making it darker Unfortunately though this process is less than perfect A better tool to use here is the Color Correction plug in H Now come the most subtle changes of all we want to improve the colour of the sky and tents using the Hue Saturation tool We re going to increase the saturation levels of three colour channels the Red Cyan and Magenta These were chosen through a little trial and error but adjusting these will bring out the blue in the sky
3. _O Reset of ee ee ee o iia ce J One final adjustment to the Brightness Contrast of the image to bring out a little more detail in the jet engines and we ve quickly and easily turned this faded and unremarkable photo into something respectable gt gt LXF42 JULY 2003 73 LXF42 tut_gim 30 5 03 6 37 pm Page 74 D TutorialGIMP d BRINGING OUT LOST DETAILS tweaking poorly exposed images The last tutorial added a snap of colour to a poorly exposed image but a closer look shows some detail is still not visible How can we pull real detail from a poorly exposed image By using the image data itself to brighten the areas that are too dark that s how Experiment with photos of your own to get a feel for it Our original image shows a dancing fool on the plains of Texas cows and oil wells not included Standing in the shade of an outdoor shelter ona bright day left him and the shelter underexposed But there is detail in those shadows We start by duplicating the background layer ni d T Ss EE Ss 74 LxF42 JULY 2003 After cleaning up the mask just a bit more around the raised arm by air brushing it white so it would be lightened the same amount as the rest the body we changed the layer blend mode to Screen And that s it A close up here shows how the detail in the final version compares to the same are in the original The blur in the final image can be adjust
4. and tents from Cyan adjustment the Red in the tent and cone from the Magenta and Red adjustments and the green and yellow in the grass from the Red adjustment www linuxformat co uk in the image it just needs to be scanned at a high resolution and then post processed using The GIMP This tutorial goes step by step through fixing one image shot with the wrong speed film F4 The Levels tool is our first stop in correcting this image This dialog shows us through the histogram at the top that the darkest pixel is not truly black and the lightest is not truly white To fix this we ll spread the range of colours so the darkest becomes black and the lightest becomes white To do this just press on the Auto button The picture shows the Levels dialog and the histogram before the adjustment is made and the image after it has been Auto corrected The result is good but we can improve on this cea T The Color Correction Plug in available from the GIMP Registry provides a more detailed histogram in its Levels page Here we see that there is a slight skew of the histogram towards the right more pixels with heavier white content than black We can adjust this by choosing one of the peaks to the right we chose the first peak to add more black to the image The result is not as dark as the manually adjust Levels version but more vivid than the Auto adjusted image It s better but we still want more colour _
5. cturers drivers and are being used by many Mac OS X users now as well www linuxprinting org foomatic2 9 Foomatic is the glue between print spoolers and printer drivers www linuxprinting org This is the place to start to find out whether there is a driver available for your particular printer URLS Online GIMP Resources The GIMP www gimp org GIMP Registry hundreds of plugins http registry gimp org index jsp Graphics Muse Tools CD www graphics muse com gfxmuse gfxmuse html Tutorials and other useful links www graphics muse com cgi gmcat pi id 11 NEXT MONTH Cleaning up your old photos isn t all the difficult with The GIMP as long as you know how to isolate the damaged portions Next month we ll look at creating selections using various G MP selection tools including the often overlooked Quick Mask LXF42 JULY 2003 75
6. e resulting image while suffering from poor content is at least clearer and filled with more detail We could apply the steps from this month s first tutorial to bring out the colours if we really wanted though here it might be safer to keep from bringing out too much detail in our dancer LXF42 tut_gimp Probably the most common touchup for amateur photographers is the removal of redeye the effect where pupils glow red when reflecting flash off the back of TutorialGIMP the eye Removing this effect is fairly simple though its not the colour removal where you ll get tripped up its in making a proper selection Our original image isn t terrible but those red eyes a definitely distracting A close up shows that the red area actually bleeds a little in this photo possibly due to poor scanning or even poor film development If this were a truly good photograph we might be able to get a quick selection of the pupils using just the Fuzzy select tool But this photo is not that great and we need a little trick to isolate those pupils First duplicate the layer so we don t corrupt the original layer Next invert the colours Image gt Colors gt Invert in the duplicate layer This lets us see the regions of interest a little better In the Layers and Channels dialog choose the Channels page All three channels should be active Click on the Red and Blue channels to deselect them leaving jus
7. ed even more by reducing the blur used in the layer mask With the duplicate layer active its layer name is white on blue in the Layers and Channels dialog use Edit gt Copy to save a copy of the layer Add a layer mask right click on the layer name in the Layers and Channels dialog to get the Layers menu to the duplicate layer The layer mask will start out white Click on the new layer mask to make it active and then paste a copy of the layer by using Edit gt Paste or Ctrl V Anchor the floating layer into the mask With the mask still active select Image gt Colors gt Invert to produce a negative mask Adjust the Curves for the mask to isolate the area under the shelter and our dancing fool You might have to manually touch up the mask using the airbrush or paintbrush Once you re satisfied with the mask blur it slightly 10 pixels were used here but we came back later and tightened up that blur by adjusting the Curves yet again www linuxformat co uk The duplicate layer will be desaturated Image gt Colors gt Desaturate first This layer will be added actually Screened to the original to brighten the image Desaturating it assures that we add even amounts to each colour channel Next blur this layer just a bit We do this so the Screening process doesn t create harsh edges in the final image The amount to blur depends on the image content but in this case we only blurred about 8 pixels Th
8. t the green channel Now choose the Fuzzy Select tool from the GIMP Toolbox Click inside the pupils The selection you get may not be that good you might have to adjust the Threshold level in the Fuzzy Select s Tool Options dialog double click on that Fuzzy Select icon to get this dialog We had to manually add the center points of the eye after our Fuzzy Select by holding the Shift key down while doing an Elliptical selection Once you have the selection feather it lightly perhaps 3 pixels or so Delete the duplicate layer we don t need it anymore Make the Red channel active in the Channels page of the Layers and Channels dialog but turn off the Green and Red Channels Then choose Image gt Colors gt Desaturate That will remove the red from the eyes www linuxformat co uk Treeware Books on The GIMP Grokking The GIMP Carey Bunks New Riders ISBN 0 7357 0924 6 GUM GIMP User Manual Kylander and Kylander Coriolis ISBN 1 5761 0520 2 also online at www gimp org GIMP for Web Professionals Hammel Prentice Hall ISBN 0 1301 9114 0 Printer resources For your GIMP masterpieces Www cups org CUPS provides networked printing support and a spooling interface http gimp print sourceforge net GIMP Print goes way beyond just a GIMP print plug in It s a full featured set of drivers for many printers Its drivers are so well done they are considered better than some of the original manufa
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