Lesson #1

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Lesson #1; Depth of Field
Topic Started: May 11 2006, 01:20 PM (210 Views)
kman627	May 11 2006, 01:20 PM Post #1
Unregistered	For our first lesson and assignment, we'll be dealing with depth of field, aka. DOF. Since I don't have much time to write my own lesson for this first week, I'm going to use one already written that covers everything I'd like to go over. Typically these will be posted on Friday mornings, but since it's the first week I'll post it on Thursday so everyone can get comfortable with how this is going to work. So the following is the lesson plan for DOF. It is very simple and to the point. Read through it, and if you have any questions, just post them here on the thread so that everyone can see them and we can get a discussion going regarding the subject. Once you're ready, go to the assignment: http://snapshotforum.com/index.php?showtopic=1958 Good luck!. Lesson 1: When you focus your camera’s lens on a subject, the point focused upon is sharp. Objects in the scene closer or farther than that point appear progressively less sharp as their distance from the focused point increases. Depth of field refers to the area in front of and beyond the point focused upon in which things appear acceptably sharp in a photograph. Depth of field is really an illusion: Again, the point focused upon is sharp; everything in the scene closer to or farther from the camera is less sharp. Depth of field is based on the fact that our eyes can’t differentiate between dead-on sharp and almost-sharp until the lack of sharpness reaches a certain degree. Within depth-of-field limits, objects in the photo will appear sufficiently sharp at normal viewing distances for the print size. Depth of field affects every photograph. So it’s a good idea to put it to work for you, rather than just leave it to chance. You have three controls over depth of field: aperture, focal length, and focusing distance. Smaller apertures increase depth of field, while larger apertures decrease it. Shorter focal lengths increase depth of field, while longer focal lengths decrease it. And greater focusing distances increase depth of field, while shorter focusing distances decrease it. 1. Great Depth of Field Great depth of field is handy when you have several important subjects in a scene, each at a different distance from the camera. It’s also useful when you want to get an entire three-dimensional subject sharp, rather than just a portion of it. To produce the needed depth of field, the best strategy is to stop the lens down. You can also increase depth of field by using a shorter lens focal length, but this will also change the framing of the image. And you can increase depth of field by moving farther from the subject, but this will also change the framing and the perspective. So the best way to increase depth of field generally is to stop the lens down. Note that stopping the lens down will reduce the light transmitted by the lens, and thus require longer exposure times in a given light level. If shutter speeds get too slow, it’s a good idea to mount the camera on a tripod, or use flash. (A good rule of thumb for when to put the camera on a tripod is when shutter speeds drop below the reciprocal of the focal length of the lens: For example, with a 200mm lens, use a tripod when shutter speeds drop below 1/200.) 2. Selective Focus While we’re more often concerned with increasing depth of field, limiting it can also be effective. If you must shoot against a distracting background (i.e., you can’t move the camera or the subject), you can minimize depth of field by shooting with the lens wide open, and thus throw the distracting background so far out of focus that it ceases to be a distraction. Macro photographers often take advantage of extremely limited depth of field at very close focusing distance to concentrate the viewer’s attention on a specific portion of a flower or insect or other small subject, focusing carefully on that area and letting all else go completely out of focus. Remember that three factors affect dof 1. Aperture (smaller aperture i.e. f/22=more depth of field. Wide aperture i.e. f/4.0=less or shallow depth of field) 2. Distance between the subject and the lens 3. The physical length of the lens. Depth-of-Field Tips 1. Small apertures provide more depth of field, wide apertures less 2. Shorter focal lengths provide more depth of field, longer focal lengths less 3. Greater shooting distances provide more depth of field, shorter distances less For more in-depth information, visit http://en.wikipedia.org/wiki/Depth_of_field I look forward to hearing your thoughts, questions, and ideas about dof and how it can be used. Now go to the assignment http://snapshotforum.com/index.php?showtopic=1958 and get to shooting!
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kman627	May 11 2006, 04:18 PM Post #2
Unregistered	Storm brought up the following question: "But one question on assignment 1, I was reading the steps about this assignment, and you were talking about stopping it down some and sutff. My camera has no manual settings, will I still be able to this decently?" The answer is yes. Being that your camera has no manual settings, it is likely that it has a button on it that probably has a picture of mountains or something like that. That will automatically set your camera to it's smallest aperture. If you don't have this option on your camera, you can still do this assignment because your camera is probably optimized to be focused with an infinite depth of field. Another way to accomplish this is to just ensure that there is a good amount of distance between your subject and lens. The term "Stopping Down" refers to making the aperture on your lens smaller. Stopping it down to a smaller size, which will increase depth of field. Does this answer your question?
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minnielee1	May 11 2006, 04:55 PM Post #3
Posts: 1,648 Group: Senior member Member #26 Joined: October 31, 2005	i think it answers mine! i will try the landscape mode and see what happens. i actually dont use that setting much so it will be interesting to see if i get the effect that i need! since i can't manually set the aperature either, hopefully this will do it for me!



kman627	May 11 2006, 04:58 PM Post #4
Unregistered	minnie, Using the landscape mode will work just fine for you and should provide sharp focus across the whole field. I'm looking forward to seeing everyone's work!
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stormluvr1	May 12 2006, 08:34 AM Post #5
having a great time with new friends Posts: 656 Group: Members Member #74 Joined: January 13, 2006	Thanks so much kman. Yes I do have the little mountain symbol, that's what my camera is always in unless I use macro mode. I am gonna try the assignment this weekend.



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