This is the depth of field technique which I promised to write. It is intended for use with Photoshop. I learned this technique using one of the free videos issued every month with the "Digital Photo" magazine. This not a copy of their article which is much better and more comprehensive than this and being a video it is easier to follow.
The following image is the start image. For some reason I can't get two other images to appear so I will add them in susequent posts, If I can!!
1. Open the channels pallet by clicking ‘windows/channels’ and then add a new channel by clicking the Rt. facing arrow at the top of the drop down menu, then click on ‘new channel’. A new channel called Alpha 1 appears.
2. In the new drop down menu which appears select ‘masked areas’, color ‘red’, opacity ‘50%’ and then click OK. At this point the screen turns black.
3. Click the eye icon to the left of the RGB channel. The image reappears covered by a red mask which will protect the image from the blur filter, used later. We can remove different parts of the protective mask by painting white into it. We do this in a graduated manner using the gradient tool. The remaining red areas are those which will be protected from blurring later.
4. We now set up the gradient tool as follows:- Set the foreground and background colors to white and black respectively. Select the linear gradient tool and choose foreground to transparent. Use mode ‘normal’, opacity 100%, tick ‘dither’ and ‘transparency’ and leave reverse unticked.
5. Apply the gradient as follows:- Whist holding the shift key down click on the bottom of the image and drag to just below the largest sunflower. Release the mouse and shift key.
6. Repeat 5 only this time drag from the top of the image to just above the same sunflower. The image should now look like hat in the next post. The red areas will be protected from blurring in proportion to the density of the red mask.
7. We now apply the blur. Click on the RGB channel icon because this is the one we want to blur. Then select filter/blur/lens blur. In the new drop down menu select ‘preview’ and ‘faster’. For ‘source’ choose ‘Alpha 1 ‘. For ‘shape’ choose whatever you think looks best. I Like ‘Octagon’. The radius slider determines the amount of blur. Play with this. The ‘blur focal distance slider’ moves the sharp area up and down the image: leave it at zero, initially anyway. Under noise you can add a small amount if you wish, but no more than 1 or 2. Click OK.
8. Turn off the Alpha1 channel by clicking the eye icon to reveal the finished picture below. Flatten the layers, if you wish, and save the image. The finished image in the next post but one.
PS Any blurred areas which you would prefer to be sharp can be protected during stage 6 as follows:- Select them with one of the lasso tools and apply the usual feathering technique, say 1 or 2 pixels. Then fill with black which will appear red. Then continue through stages 7 and 8. I protected the sunflowers in the middle distance in this way using 70% black for fill.
See next but one post for final image.
Hope this is what you wanted.
John.