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SharpControl 1.1 - Review
SharpControl is a free MS Windows .exe for image sharpening with many advanced functions that is worthy of deeper exploration. The program uses a proprietary sharpening implementation found in an undisclosed commercial medical image processing tool, rather than conventional USM (Van Cittert deconvolution is believed to be used). Version 1.1 can be found here: www.photo-freeware.net/sharpcontrol.php. There is no product home page, although the author offers some basic information in the dpreview.com forums. Although the author produced this utility as a 'toy', the actual sharpening process and results are of commercial quality.
System & File Preparation
Save Open Files - All documents in all open applications should be saved before processing images in SharpControl. The program is offered without any guarantee or warranty (The author notes that the software is not designed for 'mission critical' use).
Supported Image Formats, Colour Modes & Bit Depth - Accepted file formats for the open and save command are JPEG (JFIF) and uncompressed TIFF in RGB mode only. Regular 8 bpc and high bit 16 bpc data input and output are supported.
Paste or Open - Images can be copied through the clipboard and pasted into SharpControl for processing, although there are clipboard memory issues on larger file sizes which prohibit the use of the paste command once inside SharpControl. That being said, large images can be successfully opened, filtered then copied to image editing software via the clipboard. This clipboard memory limitation appears to be one way. Like the open command, SharpControl restricts paste to RGB data only.
Colour Management - SharpControl does not perform ICC colour management and the preview will not be accurate if one is using an RGB working space in Photoshop that is radically different from the current monitor characteristics. Simply ignore the fact that the colour preview is not accurate, as this does not affect the sharpening. As the processed data will be untagged, the original image profile should be assigned to the image in Photoshop (this can be automated via Photoshop droplets when batch processing).
Process Duplicate Files - It is commonly advised that sharpening be performed on a copy of the original document, as sharpening is often applied for a specific reproduction size, output method and viewing distance/conditions. In the case of SharpControl, there are further reasons for working on a duplicate file - as custom meta data such as image resolution headers, ICC profiles and EXIF data will not be included in the file when saving.
SharpControl v1.1: Initial splash screen visible before an image is input for processing.
Processing Speed
High Bit Processing - As SharpControl performs sharpening on the Intensity channel of HSI colour space, the conversion and sharpening process takes place in high bit mode to reduce errors in the conversion between RGB and HSI modes. SharpControl uses 32 bpc high bit mode, this obviously restricts the live preview size and significantly adds to the time taken for final image filtering. Do not expect quick results on medium or large size files (one should remember that this is a freeware offering that the author produced as a 'toy' on the side to his paying job).
Filter Preview
Preview Frame - The main image window contains the preview frame, which can be moved to preview different areas when experimenting with the various sharpening options. The preview frame will display the original image in the upper preview window, with the current live filter settings being updated in the lower preview window.
Sharpening Options
Radius - The halo radius settings can range from 0.10 to 8.33 pixels in preset steps to create a wider sharpening halo. Minimum effective halo width appears to be 0.51 pixels. The radius in SharpControl is similar to the Photoshop radius concept found in USM.
Intensity - The Intensity option can range from 0 to 1000% in strength. With higher Control or Edge values, larger Intensity settings can be used. The intensity option is similar to the Photoshop amount option found in USM.
Control - Control appears to apply light halo reduction, threshold and edge smoothing. Lower settings seem safer than high settings, although the Intensity and Edge values will often determine the appropriate Control settings. Range 0 to 100%.
Edge - The edge option applies an edge mask to the image isolating high frequency areas. Ideally future versions will have a preview toggle for the edge mask operator. Range 0 to 100%.
Iterations - Van Cittert iterative deconvolution filtering should probably be used with caution with lower Intensity settings. Range 1 to 20.
Filter Application
Add - When you are happy with the sharpening preview options, the Add button performs final filtering to the entire image (which may take some time). This operation is recorded in a 'history' list where the original and different filtered states can be compared.
Delete - The Delete button will remove the current selected filtering state from the list.
Sharpening Option Controls & Settings Text File
Arrow Controls - The five sharpening option arrow controls move in preset increments, which may be too coarse for the current image. The Settings Text File option can be used to overcome this issue.
Settings Text File - When exiting SharpControl, a text file is written in the same directory as the SharpControl application. The name of this text file is 'SharpControlSettings.txt'. This file can be opened in a text editor and the settings can be changed to finer increments which are not possible via the GUI arrow controls. Simply overwrite the file as a plain text file. Next time SharpControl is launched, it will use the settings found in this file. To reset SharpControl to the original 'base' setting, simply delete the text file.
Batch Processing
As sharpening is very much an image and output dependent process, batch processing is usually a trade off between results and productivity. Sorting images into folders with similar pixel dimensions and image content is advised. Batch processing in SharpControl has the following features and limitations:
Batch Input - Hit the batch process button on the menu bar. Simply shift select a range of images or control select multiple discontinuous images in the destination folder from within the file open dialog box (only one type of file format can be batched per session).
Batch Output - The batch process will overwrite the destination images.
Batch File Formats - The file format output will match the input file type.
Batch Settings - The batch process will use the current active settings found in the programme interface (the settings text file is ignored once the application is open).
Note that the batch process progress bar may image above and obstruct other programs and operating system windows.
Copy & Save
Copy - Simply select the desired sharpening state from the list and copy the data to the clipboard and paste into Photoshop.
Save - The save command will write an RGB 8 bpc JPEG (JFIF) in high quality mode or an 8 or 16 bpc uncompressed TIFF file. The save dialog box will default to the same format as the input image, however the filename extension must be manually changed if this file format is changed.
Conclusion
SharpControl is an interesting application that shows great promise, particularly so for a freeware offering. This is not a commercial project and it is missing many features relating to file handling and memory optimisation that commercial software users take for granted. Version 1.1 adds new options and workflow enhancements, however the speed improvements were not as significant as hoped for. There are many sharpening techniques which can be applied using native Photoshop tools (such as light halo reduction), and for many situations these methods will suffice. Due to the significant lack of processing speed on larger file sizes, high volume or large format settings may prefer to use SharpControl as a back-up tool for the situations where regular sharpening techniques do not produce the required results. Sharp control can provide excellent acquisition sharpening when combined with Photoshop techniques such as blend if layer option sliders or layer masks.