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Author Topic: artifact avoidance  (Read 2764 times)

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« on: November 13, 2007, 20:47 »
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Lately at Istock I seem to always get the inspectors with excellent eyesight who always seem to reject for artifacting the same pics that the other 6 take.  I shoot in RAW with a Canon XTI and post process with Photoshop Elements 5.0.  I was led to believe that after the most recent version of the RAW engine came out, that doing the majority of the adjustments was better in RAW than inside Elements after the conversion.

The only two controls that I am unsure of their effects are clarity and recovery.  Do any of these two have more possibilities in introducing artifacts?  Any work flow suggestions would be appreciated.

Lee


« Reply #1 on: November 13, 2007, 21:26 »
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Apart from in-camera processing (saturation and sharpening, which should be turned down to zero) the major source of artifacts (and noise) is incorrect exposure.

If you are getting a lot of rejections due to artifacts I suggest you spend some time examining how you achieve exposure with your camera (your camera shouldn't be producing these problems).

Learn to 'shoot to the right' and 'shoot to the left'.  Also, carry out some experiments to check that your camera does not habitually over or under expose.  I discovered months ago that my Nikon D200 underexposes by about half a stop.  A good way to check is to take a picture of something white, using your camera's histogram to get the shot exactly at the right side (RGB 255).  Then, have a look at that same picture with the eyedropper tool in photoshop and see what readings you get.  When my Nikon shows 255, photoshop shows it as about 248, confirming that the Nikon is incorrect.

Once you get exposure right you'll have little need to use levels and curves and you'll find that artifacts and noise will magically disappear.

Might not work for you, but worth a try.

« Reply #2 on: November 13, 2007, 23:12 »
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Would that only work if the white object is a true white? What would be a good subject for this.

« Reply #3 on: November 14, 2007, 15:25 »
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Do the rejected images really have artifacting? Because I've had rejections, later reversed by Scout, in which in fact the texture in some element (cloth, rough paper) was mistaken by artifacting.

Sometimes however the culprit was indeed artifacting from editing an underexposed image.

Regards,
Adelaide


 

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