Just about Photography

This article is reverse idea from my article before… I suggest you read my previous article before read this article. This article is trying to repair distortion effect, especially for fisheye lens distortion. Fisheye lens has good distortion especially for full frame camera (ex: EOS 5D, EOS 1Ds, Nikon D3), but someone maybe didn’t like the distortion - he just need the 180 degree view angle - in this case repair the image is quite necessary. I will use defisheye as terminology for repairing image from fisheye lens. When you use google to find the way to defisheye image, maybe you will know there are some methods to defisheye the photo. If you use ImageMagick, there are Fred’s ImageMagick Scripts for defisheye the photo, if you interesting you can go to his web. I also checked in flickr, there are discussion of this topic - you can see here. Here, the programs that many people use: Capture NX, Panorama Tools, Fisheye Warp, Hugin, etc. I use photoshop to defisheye the image, generally there are two ways: use plugin or without plugin. Using plugin is much easier, because you just click and you get the result - but you need to find freeware plugin otherwise you need pay money to register the software. Anyway if you like use plugin, I recommend you to use Fisheye Hemi, this program is very good - but it is a shareware (not freeware). Because I don’t have fisheye lens, so I use other people photo to explain my idea to defisheye the image. The original photo can be seen here, I use this photo because Albert Jou is good photographer and the model (小布, read: xiao bu) also beautiful. You can compare the original and the result using fisheye hemi (unregistered version):

Because I am interesting to find an approach how to do this, so I do some experiments. I want to know how fisheye hemi works - if you know you will know how to approach the method. First you need distortion line, by using fisheye hemi unregistered version you will get the result. After that, I make the layer above the result of fisheye hemi and find the way how to make it looked like fisheye hemi effect. As you can see, the distortion line won’t be the same but at least it close to the fisheye hemi effect result.

The trick to do this is easy, you just use Edit->Transform->Warp. By using warp you can move the point looked like picture above. Because I use feeling to move the point, it won’t be perfectly symmetric - anyway it close to the fisheye hemi result. Using Albert Jou photo, you can see the process and the result (sorry for watermark) here:

This method have advantage compare with fisheye hemi because you don’t need any plugin so you can work in any computer (with photoshop CS 2 or CS 3 installed) - I am not say who use the plugin isn’t pro, but I think if you are depend on plugin, you don’t know the process how to do it - so in the other case you will need the other plugin. The other advantage is you can repair the distortion as you feel satisfy with the result - use the plugin you can’t freely change into what you like. Example you are not use fisheye lens, but the image has “a little” distortion and you want to fix it - by plugin it will mis correct the distortion because you just need “a little correction” - using this method maybe better to fix this problem because you can repair the distortion until you feel satisfied.

Anyway I also mention the weakness of this method. Warping the image will cause the pixel bigger - then it will reduce the sharpness of image. Comparing with fisheye hemi effect, sharpness reduce significantly - so you can use Filter->Sharpen->Sharpen to repair this problem. Second problem is you can’t get the perfectly defisheyed image because you use feeling to repair the image - so it won’t be perfectly symmetric.

Finally, you can try what the method/software/plugin do you like - I only can say this “good software without people that know how to use it - it means nothing”. I can give you the other example, still Albert Jou photo - you can compare the original photo and defisheyed photo with my method.

Finally, hope you like this tutorial - any comments, critics, suggestions are welcome.