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A Crash Course in DOF, editing vs. viewer


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   When it comes to photography and photo editing in general, depth of field and bokeh are frequently discussed topics - but I haven't really seen it being spoken of all that much within SL photography, and it's evident by watching people's photos that the range from not using it at all, to using it wrongly, to using it skillfully, produces a huge difference of quality in photos taken. Now I'm hardly a master of it, in fact I tend to be pretty lazy with it as I figure people seldom scrutinize my shots in full resolution anyway - but it's still something that I think that any aspiring photographer in SL should be aware of, and learn to use.

   There are a few different ways of approaching it. There is of course a DOF effect in the viewers that can be played around with using various sliders, but how well this functions varies greatly from viewer to viewer. For example, I've found that DOF in Firestorm works terribly with alphas, whereas Black Dragon Viewer does a much greater job of it - personally I can't be bothered to swap viewer when I want to do a shoot, I'm a Firestorm fanboy and only on very rare occasion use BDW when I need more than one feature from it (i.e. the poser to adjust poses made by others that don't fit my avatar - but then I make my own poses for the majority of my shots, so I seldom need it).

   But before we go into how it works in too much detail, I figure it might be prudent to talk about what the heck DOF and bokeh means. So:

   Depth of Field: is a matter of where the camera's focus is. A simple experiment you can do is to just hold up a finger a little bit in front of your face, and look at the finger - notice how things behind the finger get 'blurry'? Now hold your finger still, and look at something else behind it, and notice how your finger becomes blurry instead. This is often used in movies to shift focus within the same frame, for example when you have two people in different depths of the shot talking, focus can be shifted between the two to make you focus on one or the other, without moving the camera at all. Cameras however don't work like the human eye, and many cameras will simply capture whatever is in front of the lens in complete, crispy detail - which can look unnatural to look at, since we're used to only have crisp detail on things at the same depths of things we look at. 

   Bokeh: is a term specific to applying blur in photography; it's the 'quality' of the blur. Say you've got three depths to your picture; your subject, the subject's immediate surroundings, and something further down in the backdrop. How blurry something is depends on how far away from the focus it is, so a hill in the distance should be more blurred than the payphone two meters behind your subject.

   Now, the ways we can apply a DOF effect to our photos in Second Life can basically be summed up as two main approaches: using the viewer tools to produce a depth of field, or creating a DOF effect in a photo editor (i.e. Gimp or, if you're a silly person, Photoshop). I'm not going to go into too much detail of the viewer tools as I frankly never liked using them much; I find it both easier and prettier to just edit the shot than to try getting the viewer tool to look realistic - but if you want to know more about it, there absolutely are tutorials and wikis with more information on them.

   My preferred method is simple, and since I personally prefer shooting with a backdrop rather than a 'scene', I only have to worry about one focus and one depth, most of the time. The procedure is as simple as creating a copy of your layer, apply a blur, create a layer mask on the blurred layer and use a brush to remove the blur from the areas you want in focus - I usually do a gradient where I only actually use a 100% opacity brush with black on the face of my subject, then I make it dark gray, set it to darken only, and work my way out from the face, going into brighter shades of gray the further away from the focal point I go.

   If you're in a more complicated scene though, with several layers of depth, this approach would get a bit tedious to work with. That's when we're going to use a depth map.


   Here's the snapshot tool in Firestorm set up to take a shot.


   And here, I've set the camera to instead capture the depth. The further away something is, the brighter it is. Now all I need to do is to use the depth map as my mask for my blur layer, and the intensity of the blur will vary depending on how far away things are. You can also just use your brush to fine tune things here, especially alphas may require some attention (hairs, mainly). 

   First, let's see how the picture looks without any blur:


   And what happens if we just blur the whole thing?


   And finally, blurred by using the depth map as our layer mask for the blurred layer:


   With this mask, you can also adjust the darkness (darker = less blur, lighter = more blur), you can increase the contrast to increase the DOF factor, and use the paint brush to pick out specific areas (the subject here wasn't 100% black, which is fine, but I did want that one spot of focus which I put in Neph's face with a brush to make that the center of the focus). You can also change focus with a bit of trickery by 'rebuilding' the depth map, selecting by colour, and adjusting any part of it you want to be in focus (i.e. I could have made the light pole behind her be the central focus, and make her more blurred instead). 

   So anyway. There it is. Mind, the resolution of these images are pretty low, as the forums only allow 4.88 MB of attachments and I didn't want to upload them on Flickr. The higher the resolution, the more it'll stand out (but I've also come to find that doing 6,144 x 4,608 shots just means no one's ever actually going to see them at 100% zoom, which means they'll be compressed for most people anyway).

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There is Bokeh and Shallow Depth of Field. Both are typically blurred backgrounds as Orwar correctly describes them. But, bokeh is extremely shallow DOF. To the point that bright spots appear as circles of light. A good set of examples can be seen in this 'How To' video for RL cameras. Bokeh Effect. When someone is talking about Bokeh they usually have the circular spots in mind.

The Firestorm viewer will create bokeh, the circular bright spots. This is my outdoor Christmas tree with the DOF focal length set to 1.0.


Some image editing tools (PS) provide a means to change the aperture shape, which controls the shape of the bokeh one makes in the image editor. I haven't seen a way to do that in SL viewers.

In Firestorm park you cursor over the control's label in PhotoTools to get a description of what the control does.


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