I have always used a Photoshop plugin (Focus Magic) for sharpening, by turning off all raw sharpening and applying FM to the tiff immediately after rendering from raw. Having said that, I am now in the process of exploring PWP's Advanced Sharpen, so a couple questions.
I am wondering why the dialogue box has a preview window, especially with 1) the ability to have a before/after image and 2) the preview can't be zoomed in like the before/after can be (unless it is there and I just can't figure out how to do it). I would be happy using just a preview window if it could be zoomed in.
I am confused on the operation of the Halo limiting sliders (I presume this is the same thing as Maximum Overshoot/Undershoot in the literature?). I am assuming one set is for controlling dark halos and the other set controls light halos but I am not sure which does which as they all seem to impact the others. For example, the bottom right white slider will move the bottom left white slider if it bumps into it but it will also move the top right black slider as well, so I am not sure of the interplay between all four. The help and download documents are not really explicit in this area.
Thanks,
Marv
Advanced Sharpen
Moderator: jsachs
Re: Advanced Sharpen
The preview is to speed up the operation which, if applied to the entire image, can be quite slow depending on the settings. To see a full image preview that you can zoom and scroll, click the Running Man icon just above the preview to update the output image.
You seem to be confusing the Halo Limit sliders with the histogram below it. There is just one black and one white halo limit slider.
The histogram serves the same general function as the Threshold slider in Unsharp Mask, namely to let you avoid sharpening small details which are mostly noise while still sharpening more prominent edges.
Personally, I use Bilateral Sharpen most of the time instead of Advanced Sharpen. It does a good job of halo suppression and has a lot fewer settings to mess with.
You seem to be confusing the Halo Limit sliders with the histogram below it. There is just one black and one white halo limit slider.
The histogram serves the same general function as the Threshold slider in Unsharp Mask, namely to let you avoid sharpening small details which are mostly noise while still sharpening more prominent edges.
Personally, I use Bilateral Sharpen most of the time instead of Advanced Sharpen. It does a good job of halo suppression and has a lot fewer settings to mess with.
Jonathan Sachs
Digital Light & Color
Digital Light & Color
Re: Advanced Sharpen
Marv if you just click on different parts of the image the preview window updates to show that area and I am assuming its at 1:1 where sharpening should be viewed ...generally if you could see significant sharpening on the full after preview it is probably over sharpened....this is how several image editors work when applying either denoise or sharpening, ie at 1:1 to present the right zoom and in a smaller preview for processing speed...
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Marpel
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Re: Advanced Sharpen
Jonathan and priort,
Thanks for the replies. Couple points.
I asked about the preview and zooming in past 1:1 because, although I understand that sharpening is best viewed at 1:1, as I am trying to see exactly what the settings are doing, it assists me a bit better to really zoom in and look at what is happening and how the light/dark areas change as the sliders are moved, especially with haloing. Once I get to understand this stuff better, having the preview at only 1:1 would be OK, so not a big worry.
Regarding confusing Halo Limit sliders with the Histogram, I likely am. In the Help document attached to the A/S dialogue, under the heading Sharpening > Histogram, there is the last sentence which states "Lowering the upper limits helps reduce halos" which led me to believe that the Halo Limit slider was not the only control for this purpose. I presumed after that slider was adjusted, the histogram pointers on the far right side had some use as well and, as previously mentioned, when I moved those pointers to the left end (because they seemed to serve no purpose way over there on the right), they bumped into the other two pointers, so I was curious on how they actually worked.
Marv
Thanks for the replies. Couple points.
I asked about the preview and zooming in past 1:1 because, although I understand that sharpening is best viewed at 1:1, as I am trying to see exactly what the settings are doing, it assists me a bit better to really zoom in and look at what is happening and how the light/dark areas change as the sliders are moved, especially with haloing. Once I get to understand this stuff better, having the preview at only 1:1 would be OK, so not a big worry.
Regarding confusing Halo Limit sliders with the Histogram, I likely am. In the Help document attached to the A/S dialogue, under the heading Sharpening > Histogram, there is the last sentence which states "Lowering the upper limits helps reduce halos" which led me to believe that the Halo Limit slider was not the only control for this purpose. I presumed after that slider was adjusted, the histogram pointers on the far right side had some use as well and, as previously mentioned, when I moved those pointers to the left end (because they seemed to serve no purpose way over there on the right), they bumped into the other two pointers, so I was curious on how they actually worked.
Marv
Re: Advanced Sharpen
I think this is what you are referring to:
"The histogram display just below the Sharpen Amount slider lets you perform selective sharpening by including only those neighbor pixels in the computations that differ by more or less than a given threshold amount from the pixel you are sharpening. Raising the lower limits helps prevent amplifying fine texture or noise. Lowering the upper limits helps reduce halos."
The histogram is created by looking at each pixel in the input image and computing how much it differs from its neighboring pixels. This difference is a number -- if the difference is small, the pixel is surround by mostly similar pixels and represents an area of relatively smooth texture. If the difference is large, the pixel is near an edge of in an area with a lot of strong texture. The histogram is a frequency distribution of the differences, with zero at the left, so smooth areas show up on the left and rough areas on the right. The number of pixels in the input image with a given difference determines the height of the histogram at the corresponding difference level. Where the bar under the histogram is white, pixels with that difference will contribute to the sharpening. Where the bar is black, pixels with that difference will be ignored. Where it is gray, pixels will make a partial contribution. By moving the 4 markers you can select the range of differences that will be sharpened and how abrupt is the cutoff.
To avoid amplifying noise in the input image, exclude pixels with small differences. To avoid oversharpening pixels near edges of in areas of rough texture, you would try to exclude pixels with large differences. If you exclude too much, you won't get much sharpening -- too little and you get artifacts.
By contrast, the Halo Limit sliders simply compare the input image to the sharpened image. If the sharpened image is brighter than the white halo limit, the difference is clipped to the white halo limit. If the sharpened image is darker than the black halo limit, the difference is clipped to the black halo limit. These halo limits work the same way for all the sharpening transformations, but the histogram is unique to Advanced Sharpen.
"The histogram display just below the Sharpen Amount slider lets you perform selective sharpening by including only those neighbor pixels in the computations that differ by more or less than a given threshold amount from the pixel you are sharpening. Raising the lower limits helps prevent amplifying fine texture or noise. Lowering the upper limits helps reduce halos."
The histogram is created by looking at each pixel in the input image and computing how much it differs from its neighboring pixels. This difference is a number -- if the difference is small, the pixel is surround by mostly similar pixels and represents an area of relatively smooth texture. If the difference is large, the pixel is near an edge of in an area with a lot of strong texture. The histogram is a frequency distribution of the differences, with zero at the left, so smooth areas show up on the left and rough areas on the right. The number of pixels in the input image with a given difference determines the height of the histogram at the corresponding difference level. Where the bar under the histogram is white, pixels with that difference will contribute to the sharpening. Where the bar is black, pixels with that difference will be ignored. Where it is gray, pixels will make a partial contribution. By moving the 4 markers you can select the range of differences that will be sharpened and how abrupt is the cutoff.
To avoid amplifying noise in the input image, exclude pixels with small differences. To avoid oversharpening pixels near edges of in areas of rough texture, you would try to exclude pixels with large differences. If you exclude too much, you won't get much sharpening -- too little and you get artifacts.
By contrast, the Halo Limit sliders simply compare the input image to the sharpened image. If the sharpened image is brighter than the white halo limit, the difference is clipped to the white halo limit. If the sharpened image is darker than the black halo limit, the difference is clipped to the black halo limit. These halo limits work the same way for all the sharpening transformations, but the histogram is unique to Advanced Sharpen.
Jonathan Sachs
Digital Light & Color
Digital Light & Color