It is characteristic of the depth mapping process to show us this transition zone and that is why the Dmap output is usually where the halo is most prominent. It faithfully reproduces the background appendage through the out of focus foreground one. Because of the way we are positioned there are some parts of the more distant appendage that are never imaged without the defocused foreground appendage being directly in the way - and that is exactly what our camera captures. But the near appendage has not disappeared - it is still in the foreground, only now it is out of focus, and appears as a soft, enlarged, indistinct version of the leg. As the stack progresses we soon get to the appendage in the relative background and it also starts to fall into focus. ZS has no trouble selecting the sharp parts of the images and forming a well demarcated composite of the appendage closest to us. Think of it like this, when the appendage closest to the camera is in sharp focus, the one in the distance is a soft blur because it is still out of focus. The halo that we see is actually real, a part of the image that has been faithfully reproduced in the images before stacking. Understanding of this difference will inform much of what we must do to avoid or remove halo, but first we should understand what we are looking at in the first cropped image. The majority are of one particular type and these “lost detail” halos are going to be the primary focus of this discussion. Some of these changes are virtually impossible to prevent, but can be significantly improved with some of the measures I will describe later. So the term halo can mean several different things depending on the context. Halo has become something of a catchall term for any haziness, softening, loss of contrast, or indistinct detail seen around foreground (usually) elements in the final photograph. Improvement is usually gradual, as the photographer becomes more familiar with the tools, more intentional in selecting settings, and more deliberate in planning a halo-limiting workflow for each individual focus stacking project. It is not quick or simple, it involves a lot of steps, and requires a fair amount of judgement. With the help of a few examples I will walk you through my own technique for avoiding and/or correcting halo in my focus stacked images. Getting rid of halo artifact starts before the first shot is taken and is not complete even after the final image has been saved from the stacking program. It requires a good understanding of the cause, and a strong working knowledge of the various tools available in your stacking software. The cause is multifactorial, so the cure must also be multimodal, and it is. And this should not come as a surprise to anyone who has been focus stacking at magnification for any amount of time. Ask ten macro photographers what spoils more of their pictures than anything else, and eleven of them will give you some variation on the theme, “halo”.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |