Photoshop Image Size: What you may never know
: Sunday, January 28th, 2007 (Last Updated: March 4th, 2008)
: freetime
Photoshop Image Size command use for change image dimension by resampling image. If you’r
- downsample (decrease the number of pixels): information is deleted from the image.
- resample up (increase the number of pixels): new pixels are added.
You can specify an interpolation method to determine how pixels are added or deleted. There’re several methods that you can choose in photoshop to re-sampling your image.
- Nearest Neighbor:
for the fast but less precise method. This method is recommended for use with illustrations containing non-anti-aliased edges, to preserve hard edges and produce a smaller file. However, this method can result in jagged effects, which become apparent when distorting or scaling an image or performing multiple manipulations on a selection. - Bilinear:
for a medium-quality method. - Bicubic (default):
for the slow but more precise method, resulting in the smoothest tonal gradations. - Bicubic Smoother:
when you’re enlarging images. - Bicubic Sharper:
for reducing the size of an image. This method maintains the detail in a resampled image. It may, however, over-sharpen some areas of an image. In this case, try using Bicubic.
Below is an example of different interpolation method. I blow up vector shape up by 2000% to see different between each method.
Nearless Neighbor, Bilinear and Bicubic
Bicubic, Bucubic Sharper and Bicubic Smoother
Please click on thumbnail to see image:
You may see in the first set of image, it’s quite obvious to see different between Nearest Neighbor, Bilinear and Bicubic. It’s clearly that Nearest Neighbor is suitable for vector or hard edge image. And bicubic is the best method for all other raster image. I’m yet not found any good to use something in between. Bilinear may save time but for all PC speed to day I think it’s not worth to using it.
For other set. It’s slightly different. At first time I didn’t plan to blow out this much but even in 1000% it really difficult to see different between three Bicubic method (especially when I need to put it on web) . You may notice that at the edge of picture that use Bicubic Sharper and Bicubic Smoother have some error. This’s what you should pay attention when you decide to use this 2 methods. So I still prefer to use regular bicubic to both downsample and resample up anyway.
About Free Transform Command
Free transform is other photoshop command that use to re-size image. By default it use bicubic interpolation method. You can change free transform interpolation method by using Photoshop General Preferences.
- For Windows: menu Edit > Preferences > General
- For Mac: menu Photoshop > Preferences > General
Keep in mind that resampling can result in poorer image quality. Applying the Unsharp Mask filter to a resampled image can help refocus the image’s details.
Mostly if I need to resize image I will try to do it only once or less as possible especially in highly detailed image. And i alway keep my original image in save place and leave it untouched.
Some time I may use free transform tool to resize my image as many as I wish until I satisfy with it’s composition and then I will replace it with original image with only one pass of resample.
See also: Change print size without resampling image
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December 7th, 2007 at 1:24 am
[...] target resolution in one single command. The crop with re-sample image combines the function of the Image Size command (Image » Image Size) with Crop tool. The Crop tool also provide ability to hide the [...]