When correcting an image @ x100% using the unsharp mask and then reducing the image size for slide presentation (using the Action Macro) I notice that sharpness is lost. This is contrary to logic since normally sharpness could be expected to diminish as magnification increases. How can the sharpness obtained with the unsharp mask be retained?
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No, the re-sample box is not active. Another aspect is when an image is viewed at say 16%, a road sign appears out of focus. However, when the image is enlarged to say 50% the focus is crystal clear.
Photoshop is designed to save time (read run faster) by not doing a detailed redraw at odd percentages of zoom (such as 16% or 32%). The program does a high quality redraw at even percentages such as 100%, 50% and 25%. That is why you have a ‘blurry’ image at 16% and a clear one at 50%.
First of all if you enlarge or reduce an image (alter its pixel dimentions) the resampling will cause data to be lost. therefore it is always desirable to make sharpening the very last step. In other words if you are resizing your image to make a 300 ppi A4 print, resize first, then sharpen.
If you then require a 72 ppi image for web use, go back to the master file (NOT the A4 300ppi) resize down for web use, then sharpen.
Secondly consider how the image looks on screen. If you view an image at 100% magnification you will see the actual pixels which make up the image. At any other magnification the screen redraw will have to interpolate the information. ( a screen pixel cannot display a fraction of an image pixel.) An fuzziness observed at these other magnifications can be ignored.
Every time you interpolate an image, approximations are made to fit the pixels to the new dimension, and resampling is taking place (true for every image distortion and enlargements/reductions, except for 90 degree rotations and mirrors). Resampling introduces loss of acuteness (sharpness).
Try using the Bicubic Sharper interpolation in Image Size instead of Bicubic when reducing images.
Try using the Bicubic Sharper interpolation in Image Size instead of Bicubic when reducing images.
Unfortunately, while that seems like a good idea, the degree of sharpness can’t be controlled (at least I’ve not found a way), and as often as not the image is over sharpened, or sharpened inappropriately for its intended use. Bicubic Sharper doesn’t take any of the image factors into consideration when used – the entire image is treated globally.
There are numerous sharpening techniques out there and it’s probably a good idea to learn at least a few – those most appropriate to the work one does.
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