How can the unsharpness of the strongly curved slides be treated?
After numerous slide-shows, many positives are not fixed evenly any more in the frame but have a clear curve on one side. Those who project their slides with a slide projector on a screen also know the “plop-effect”: a slide that already has a slight curve in the frame, “plops” to the other direction during a longer projection due to the heat caused by the projector lamp and the readjustment of the slide projector for sharpening has to be made. The problem of the sharpening also does exist in the case of filmscanners. Due to the LED lights that do not generate any heat there is indeed no “plop-effect”, but before the scanning, the autofocus has to be adjusted for sharpness on a certain level. In the case of a strongly curved slide, there are parts of the image unsharp as for example at the edge or the centre of the image, depending on the level on which it has been focused. There is only one solution against these unsharpnesses: reframing. A cheap solution is the reframing in glass fra
