# Depth of Field Effect using Lens Blur Filter (Photoshop Tut)



## goobimama (Jul 25, 2005)

This tutorial is about the Depth of Field effect in Photoshop. Since Photoshop does not have any AI, it cannot distinguish the 3D aspect in a 2D image. So, it becomes difficult to get a realistic depth of field with normal blurring such as using the Gaussian Blur. Hereâ€™s a tutorial on achieving realistic depth of field (at least to me) using Alpha Channels. What it does is it creates varying levels of blurring giving it a more natural blurring. 

The tutorial may get complicated and I donâ€™t know if Iâ€™ve used the appropriate words, so if anyone canâ€™t figure it out, lemme know.

Step 1: Open your image. For the trial round, open up an image such that it has two levels of depth, just so that you get the proper idea. The one I have is of my brother playing in the battle of the bands held two years ago. He looks much better than thatâ€¦though not as good as me.

Step 2: Go to Window > Channels if you donâ€™t have your channels palette open. Then, click on the â€œCreate New Channelâ€? button in the lower right corner of the Channels Palette. This will create a new channel â€œAlpha 1â€? and will fill the screen with black. Rename the Alpha 1 to â€œMainâ€?. 

*img339.imageshack.us/img339/3376/blur09gg.jpg

Step 3: Next, click on the right of â€œRGBâ€? channel (As shown by arrow). Then, trace the Main part of the image with the brush tool. Painting â€œWhiteâ€? shows, and painting â€œBlackâ€? hides. The document will have a Red film over it and while you paint white the original will show.

*img339.imageshack.us/img339/3623/blur11jy.jpg

Step 4: After tracing the main focal part of the image, you have to select the sub focal part. Click on the new Channel icon in the Channels Palette. This will create a new Alpha Channel. Rename it to â€œSubâ€?. Then, while still on â€œSubâ€? channel, Ctrl+Click on â€œMainâ€? channel. Then press Shift+F5 to bring up the fill window. Fill it with white. This will avoid retracing the main focal part.

Now trace the sub part of the image (in my tutorial, the second guitarist).

*img339.imageshack.us/img339/4318/blur23ei.jpg

Step 5: Now, create a new Alpha Channel and rename it â€œFinalâ€?. While still on â€œFinalâ€? Channel, Ctrl+Click on the â€œSubâ€? Channel. This will bring out a selection. Press Shift+F5 and fill it with 50% Gray.

*img339.imageshack.us/img339/6306/blur37sn.jpg

Step 5: While still on â€œFinalâ€? channel, Ctrl+Click on â€œMainâ€? Channel. Then press shift+F5 and fill it with â€œWhiteâ€?.

Step 7: Now, in your layers palette, click on Background Layer and then go to Filter > Blur > Lens Blur. In this dialog box you only have to make sure â€œFinalâ€? is selected in the Source of the Depth Map. In my case, Final = Alpha 3.

*img339.imageshack.us/img339/4301/blur47fy.jpg

Move the Radius slider to whatever amount of Blur you want and the rest of the settings are individual preferences. (I added a little bit of â€˜noiseâ€™)

If your main image is blurred while the background is sharp, just click on the main subject of the image. Sometimes, Photoshop takes the Black part to be as the sharp partâ€¦

*img339.imageshack.us/img339/3600/blur52oz.jpg

Hit OK and Voila! Notice that the second guitarist is only half blurred while the background is fully blurred. 

Tips:
- If you want to have less blur for the â€œsubâ€? image, then instead of selecting 50% Gray in Step 5, select Color and then use a lighter gray.
- While tracing the image, use a softness for the brush or it might give you very sharp and unrealistic edges. Use a high amount of softness when tracing the hair part.
- You can have more than two levels of blur, just work on the principles that Black hides, while white shows (shows = blurs). So just give them varying amounts of blur.

* I have blurred a few of the options and stuff in some of the images to reduce file size. 

All comments appreciated.


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## abhishekkulkarni (Jul 26, 2005)

Well I think somethings wrong Goobi.....  

Bcoz I cannot see any image in the Tut..  

I guess the problem is solved.............


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