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- Depth of Field
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| Depth of Field | |
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| Topic Started: Sep 19 2007, 01:56 PM (434 Views) | |
| kman627 | Sep 19 2007, 01:56 PM Post #1 |
Film Junkie
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Depth of Field Depth of field is one of the most important aspects of photography. It’s an interesting concept because it is a place where the physics of light converge with creativity. For an engineering nerd like me, it’s incredibly interesting and it should be for everyone who considers themselves a photographer. So what is depth of field? There are many definitions out there, but I prefer the following: The apparent sharpness of a photograph considering the distance between the nearest and farthest elements that appear to maintain acceptable sharpness and clarity. Simple enough right? Here’s a great photo that shows you exactly what I’m saying:  Notice the area that’s in focus? This is the focal plane. If the person taking this photograph were to move their focus ring in and out, this plane would move forward and backwards. Click on this link for a flash animation of what I’m talking about: http://www.photocourse.com/itext/criticalf...iticalfocus.swf Where depth of field truly comes into play is not the location of this plane, but how big it is. The photo above is an example of Shallow Depth of Field . If you were to do one of the three things I’ll explain later, you could increase the size of this plane, thus giving you a Large Depth of Field *I’m trying not to be too terribly technical, but to stay completely and scientifically accurate, the area that appears to be in focus is not truly defines as in focus, it’s defines as being sharp within what’s called the Circle of Confusion. To keep it simple and understandable, I’ll refer to it as “Focused” Although, technically, it is “Perceived as sharp by the eye” If you’re not quite grasping exactly what depth of field is, look no further than your eye. Take a small object and pick it up. Close on eye and move the object about six inches from your eye and focus on it. You’ll notice that while the object is sharp and in focus, the area in the background is not. Now keep the object at six inches from your eye and remain focused on it. Take another object or your finger and place it in between the object and your eye. You’ll notice the now the first object is still in focus, but now the background object and the foreground object you’ve just introduced are blurred and out of focus. This is shallow depth of field. Your eye uses the same principles as a lens and uses depth of field in the exact same way. Just for a little useless knowledge, your eye has a maximum aperture of approximately f/2.1 and a minimum of roughly f/8. Its focal length is around 17-24mm, about the same of a wide angle lens. As far as sensitivity, at night your eye has about an ISO 800 equivalency and in bright sunlight an amazing ISO 1! Okay, enough useless facts. But it is pretty interesting huh? So now you know what depth of field is. So what’s the next? How do you as a photographer control depth of field and why would you want to? I’ll answer the second question first. You want to be able to understand and control depth of field for several reasons. 1. Keeping things sharp – This comes into play with even the most simple of family snapshots. For example, if you’ve got a group of people standing in two rows, you want to make sure you can get all of these people in focus and not just the first row. Understanding how to use depth of field will allow you to do this. 2. Another example would be a landscape photograph. You want to ensure that the entire image is sharp and in focus. Again, you would do this by using depth of field. 3. Creative control – Sometimes you come across a subject that is not too interesting or there might be something that distracts from the message your image is trying to convey. But utilizing shallow depth of field, you can isolate a smaller portion of your critical plane of focus. But remember, just because something is not sharp and in focus doesn’t mean it won’t affect your photograph. The out of focus area of “Bokeh” (Japanese word for blur or fool, depending on translation) is a very important part of an image and its creative being should always be taken into consideration. 4. There are several other reasons to adjust depth of field and it will be a matter of your creative process and aesthetic desires to determine when and how to use what aspects of it. So now that you know why you might want to know this, let’s talk about the three factors that affect depth of field. Factor #1: The first factor I’ll discuss is Aperture. The aperture of a lens actually serves two distinct functions. The aperture is responsible for controlling the amount of light that is being projected onto the film/sensor plane. The other element that controls the amount of light entering is the shutter. However, the function of the Aperture that we’re interested in is its ability to control depth of field. I could go into deep technical explanations of why this happens, but it’s not important. What’s important is that you know how to use it. So you must absolutely know the following: The smaller the aperture, the larger the depth of field. Likewise, the larger the aperture, the smaller or shallower, the depth of field. This is VERY important. For example, an aperture of f/22 will have large depth of field. Likewise, an aperture of f/1.4 will have shallow depth of field. f/8 is typically regarded as the middle of these two, giving you acceptable sharpness (or size of the area that appears focused) as well as some distinction in sharpness between the fore, middle, and background. Remember that everything dealing with aperture will always be backwards from what would make sense. I.e. Larger number f/stop, the smaller the aperture and visa versa. Also, the smaller the aperture, the greater the depth of field. Confusing yes, but once you understand this it will become second nature.  Factor #2 Focal length The second factor affecting depth of field is the focal length of the lens being used. The wider the angle of view of the lens, the greater the depth of field. For example, a 17mm lens (in the 35mm format) will have a considerable depth of field. Even at large apertures, the lens will still render a large amount of depth. Inversely, a 300mm lens will have less or shallower depth of field than the 17mm lens if the two are set to the same aperture. This is the reason one would typically use a wide angle lens for a landscape and a long telephoto lens for a portrait. The wide angle will give great sharpness across the entire image, and the longer lens will isolate the subject in the portrait. Typically, the standard portrait lens is the 85mm (again in 35mm format) and why 85mm lenses typically will come standard with large 1.8 or 1.4 apertures. So to sum it up, short lens (roughly 10mm-35mm) will have large depth of field even at larger apertures and a long lens (roughly 85mm-300mm) will have shallow depth of field, even at smaller apertures. Factor #3 Distance from subject to lens. For this one we can revert back to the exercise we did at the beginning using your eye. Take that same object, close on eye, and focus on the object at about 6 inches. Now as you move that object away from your eye, you will see that the foreground and background becomes sharper as you move the object farther from your eye. A camera’s lens works exactly the same. The closer the subject is to the camera, the smaller the plane of focus will become. So likewise using a camera, if you take a photograph at the minimum focus distance, it will have shallower depth of field than if you photographed the object at a distance of say 15 feet. Make sense? So now you should have a good understanding of what depth of field it, and most importantly how you as a photographer can control it and use it to your advantage. Using depth of field should become second nature and you should treat it with the same importance as you would composition and exposure. Remember as I said earlier that you need to be cognizant of everything in the frame, not just the part that will fall into the sharp/focused area. Remember that Bokeh has the ability to ruin a photograph if it is unattractive and distracts from the subject you’ve isolated. Also remember that if you’re taking a landscape photo, you don’t want to have something in the foreground that is not sharp and takes away from the overall aesthetics because you didn’t have enough depth of field. So what now? Now it’s time for some exercises. We’ll do the first one and then move on to the second after the first is completed. Exercise #1: Get out there on the internet and find me two photos that you like. They can be from a friend, professional whose work you admire, or anyone else. Just so long as they’re not yours. I want you to find one that shows exceptional use of shallow depth of field, and one that shows great depth of field. Easy enough? Feel free to ask any questions that might have arisen from this lesson and we’ll discuss them. Enjoy. Kyle Here are my two examples for exercise #1 Shallow depth of field:  Drops by Tommy Oshima Large Depth of Field:  Tree by Zamario |
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| genarae | Sep 19 2007, 02:49 PM Post #2 |
GenaRae
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Okay here are my examples. (I hope they are what you want) Shallow DOF  Iris closeup by Ernst Haas Large DOF  poolside gossip by Slim Aarons |
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| kikals | Sep 19 2007, 03:19 PM Post #3 |
Innocent
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I love betterphoto... so I just went on there and looked around... and so Im just gonna post the links... is that ok?? heres the shallow depth http://www.betterphoto.com/gallery/dynoGal...Number=2&camID= and heres large depth... I found a TON of landscape photos and such thats would work, but thought this really showed something being really close and far away and both being in focus... this is the part I need to work on! so thats why I choose this one. http://www.betterphoto.com/gallery/dynoGal...9341&catID=8459 |
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| kman627 | Sep 20 2007, 01:40 PM Post #4 |
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Film Junkie
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Great examples ladies. Gena's second one is a great example of the added depth when using a wide angle lens. |
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| bambam203 | Sep 20 2007, 05:58 PM Post #5 |
BAM
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ok these are local shots done by a lady that lives in our town.....Let me know if these are right or not???? Short http://www.photographybylori.net/pages/gal...ay.php?catID=11 Long http://www.photographybylori.net/pages/gal...D=303&flagger=3 |
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| gretchensteele | Sep 20 2007, 06:55 PM Post #6 |
Admin
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looks right to me...:) |
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| gretchensteele | Sep 20 2007, 07:18 PM Post #7 |
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Admin
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I know..I know..this is cheating.....but do I get any extra credit for out of classroom reading ??? ROFL DOF Example |
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| minnielee1 | Sep 20 2007, 07:50 PM Post #8 |
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http://www.betterphoto.com/gallery/dynoGal...umber=43&camID= Shallow Depth Of Field Large DOF http://www.betterphoto.com/gallery/dynoGal...umber=88&camID= This is fun! I really need to understand this better, so I'm so glad you're teaching this to us kman!! I always think I'm going to read up on things like this, but don't ! it's a lot more motivating when we are working on this together!! Thank you! |
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| kman627 | Sep 21 2007, 03:46 PM Post #9 |
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Film Junkie
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More great examples. Thanks for the additional posting Gretchen. Extra credit! Everyone participating seems to have a good grasp on the first part. So for part two, as I'm sure you've suspected, you should do the same thing, but on your own. One photo that represents shallow, and one that shows large depth. Now don't just go out and find something that works and do it, make it artistic and interesting! |
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| b10131990 | Sep 25 2007, 05:06 PM Post #10 |
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this one is from a wedding this weekend......................gave it a shot
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| gretchensteele | Sep 25 2007, 08:04 PM Post #11 |
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Admin
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Julie that's gorgeous! |
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| genarae | Sep 26 2007, 05:15 PM Post #12 |
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GenaRae
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Shallow DOF:  Large DOF:  Alright, I tried to be artistic, but I just wasn't feelin' in!  Not sure if my large DOF is correct but I tried. Be gentle Kyle!  :sly:
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| bambam203 | Sep 26 2007, 10:00 PM Post #13 |
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BAM
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Short- little tiny frog- that came out of the drain! "Living on the Edge"  Long- Fort De Chartres 
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| b10131990 | Oct 15 2007, 06:40 PM Post #14 |
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did our teacher go on vacation,  or do we have a sub? I want our teach back!!! 
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| genarae | Oct 15 2007, 07:25 PM Post #15 |
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GenaRae
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I agree!!!!!!!!!!!!! come out come out where ever you are!
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