 Stephen |
Why Would Anyone Ever Shoot Wide Open? What's the purpose of shooting pictures with a larger opening like f/8 when there is a sunset, instead of f/22?
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Jeff S. Kennedy |
Well let me start by saying that I find most sunset pictures boring and cliche. The few that are interesting have something more to them than a sunset. Usually there is some center of interest besides the sunset. For example, an interesting sillouette or something of interest in the foreground. What does this have to do with your question? Well, most lenses are the sharpest at somewhere around f8. Once you stop the lens down to f22 lenses have a tendency to get a little soft. If there is an object in your sunset shot it is going to be much crisper at f8 that f22. My final piece of unsolicited advice which I give to people who want to take sunset pictures is this. Turn around and see what all that lovely sunset light is falling on. Its usually more interesting than the sunset. After all you don't take pictures of your other light sources like your flash. You take pictures of what their light is illuminating.
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Stephen |
Can I ask you something else, how is a photograph more crisp at f/8 than at f/22 if f/22 is going to give you more depth of field?
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Jeff S. Kennedy |
F8 doesn't give you more DOF. When you focus on an object you have a critical focus spot and DOF. The critical focus spot is the sharpest point of focus. You DOF is sharp but still not as sharp as the critical focus spot. F22 gives you a larger DOF but the critical focus point is not as sharp as it would be at f8. So unless you need the DOF provided by f22 you are better off with a wider aperture (ie f8,f11,f16 etc.).
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Jiyang Chen |
When you shoot into the sun, a larger aperture will give you a more clear picture of the general shape and the roundness of the sun. If you use a small aperture, the sun will appear blinding with streaks to it (like using a star filter). I'm not sure if it's right, but this is just what I read about.
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John A. Lind |
In addition to what Jeff has written: 1. First, I agree with Jeff that sunset (and sunrise) photographs need to have something very special about them. When you view a competitive photo show and see the tonnage of them submitted (along with mountain lake mirror landscape photos), there must be something that makes it stand out from the rest of the technically perfectly executed sunsets and sunrises. 2. Painting is additive. The painter adds paint to the canvas. Photography is subtractive. The photographer removes (or at least reduces prominence of) undesirable, unnecesary and unwanted elements from a scene using compositional techniques. One of them is "DOF control" which is used to place some elements in focus and others out of focus, at least reducing their prominence and sometimes eliminating them entirely if extremely out of focus. 3. With most lens formulations, apertures tighter than f/16 suffer from "diffraction limiting." Diffraction is the spreading of light as it passes by an edge (in this case the aperture diaphragm). If the edge is part of a hole or slit and it's narrow enough, you get interference patterns from the spreading of the light waves. In a camera lens this causes degradation of image sharpness. f/16 is typically on the boundary of diffraction limiting. This is why many lenses do not stop down farther to f/22 and beyond, particularly wide angle lenses in which diffraction limiting can be prominent. I try to keep to nothing tighter than f/11 unless absolutely necessary. 4. I don't always place critical focus on the subject. Instead I ask myself: About Jiyang's remarks: -- John
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Constance Reid |
Jeff - I am interested in learning more about the "critical focus spot is the sharpest point of focus" - is there a reference to which you can direct me? Thank you.
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John A. Lind |
Contstance, The "critical focus" spot is the distance at which the lens is focused. There will be a range of distances in front and behind this exact distance that "appears" to be in focus. This is called the depth of field. How far in front and behind the critical focus distance the depth of field extends depends (primarily) on four factors: Further details get into the complexities of optics, and how humans perceive what is and is not in focus in a print at a standard viewing distance (for that print size) with an average unaided eye. See the following tutorials about lens optics, depth of field, circle of confusion, and hyperfocal focusing: Notes: -- John
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Jeff S. Kennedy |
One minor point John, and correct me if I'm wrong or have forgotten something, but DOF has less to do with format and more to do with focal length. For example a 50mm lens has the same DOF characteristics regardless of format. It's angle of view changes. In 35mm it is a normal lens, in MF it is a wide angle, and in LF it is a fisheye but the DOF characteristics are the same.
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John A. Lind |
Jeff, Ack! I gotta go back to my spreadsheets with all the formulae in them and see. The film format determines the maximum acceptable diameter for a circle of confusion on the film. As the film size increases, so does this value, which is admittedly subjective because it's based on human perception. For 35mm small format I use a very conservative 0.025mm and Kodak uses the equivalent of 0.033mm when touting digital printing capabilities, which is a "stretch." For 645 medium format, I use 0.050mm whereas 0.060mm is commonly used for 6x6 and 0.065 for 6x7. Never plugged in values for the same focal length for different film formats. I'm banging this in on the keyboard during lunch; I'll post another reply after getting a chance to play with my spreadsheet after work. -- John
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John A. Lind |
Jeff, My "gut" tells me if: Example: Gotta check this out later to see if it works out in all the numbers and if I can follow it through all the equations. -- John
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Jeff S. Kennedy |
No, I think you've got it mixed up. A 50mm (or any focal length for that matter) has the same DOF characteristics regardless of the format. 50mm is 50mm. That's why formats larger than 35mm are said to have more limited DOF. For example, in 35mm if you want to shoot with a wide angle you would use a 28mm which has a large DOF. To get the same effect in MF you would use a 50mm which has the same DOF as any 50mm. In LF you would need a lens something along the lines of 125mm (just a quick guess) which would give you the DOF of any other 125mm lens. DOF is a function of focal length and aperture period. 50mm is 50mm. 90mm is 90mm. Etc.
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John A. Lind |
Jeff, This thread has drifted a little, and we may have lost Constance in the techno-babble already posted, but I'll put in a reply with all the techno-babble behind it anyway. Took me a while to sort it all out. My "gut" feeling was only half right, and you're correct that a larger film format does reduce the DOF for same distance, aperture and AOV (equivalent focal lengths). The allowable increase in the maximum diameter circle of confusion for a larger film format (which defines near and far DOF limits) compensates some, but not enough. More about this in the following points: 1. The circle of confusion size on film remains the same for a focal length, focus distance, and aperture regardless of film format when considering an alternate object at a distance other than the focus distance. It's purely similar triangles with the image cones and where they intersect with the film plane. 2. When composing the same photograph using two film formats, same focus distance, and equivalent focal lengths for the same AOV, the maximum circle of confusion diameter is allowed to be bigger with the larger film format for the same level of sharpness in a print. The larger piece of film will be magnified less to make the same size print (e.g. 35mm format to 11x14 versus 6x9 to 11x14). This compensates some compared to zero change in circle of confusion size on film, but not enough. 3. Why? 4. What's all this mean? It's an approximation, but my guess is the 6x7 format you use would have to be stopped down by about 2 f-stops to get the same DOF at the same distance using an equivalent lens (same AOV) compared to 35mm format. -- John
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BetterPhotoJim.com - Jim Miotke  Contact Jim Miotke Jim Miotke's Gallery |
My head is spinning in circles of confusion :)
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Jeff S. Kennedy |
I'm sorry. I wasn't paying attention. Could you repeat that?
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Carl |
Clear as mud - make sure to drink lotsa coffee before reading! LOL
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Patrick J. Whalen |
I might as well add my 2 cents worth. As far as sunsets being boring or cliche, I disagree, they are all beautiful and all are different, granted,sometimes something in the forground adds interest but I feel it should be a challenge to properly capture the rainbow of colors that are often present at sunrise or sunset. With that said, the question about depth of field, one of the greatest landscape and scenery photographers, Ansel Adams,achieved many of his astonishing photographs by using F64 for maximum depth of field.
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Jeff S. Kennedy |
Patrick I find sunsets to be boring because everyone takes them. My dad was a sunset-aholic. I've seen so many that I'd much rather experience one firsthand than to see another picture of one. As for AA shooting at F64, he used large format cameras. It was necessary to shoot at such a small aperture to attain enough DOF for what he was doing. On a LF lens f64 is not even necessarily the smallest aperture.
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