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Old Apr 30, 2009, 5:02 PM   #1
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I am really trying to understand my camera. Being new to DSLR and a senior I find it difficult to remember things!! I was trying depth of field. I do have a book but I still get confused. I want my images to be the flower in the foreground clear and the background blurred.If I have the camera at f 5.6 why sometimes when I am taking flowers is the depth of field completely blurred (the way I want it) and why is it sometimes not blurred.

The setting for the one I really liked was ISO400 200 mm f5.6 1/2500 - then another image at the same settings will be completely different. Am I making any sense and is this where I ask - or could anyone recommend a site that would explain how DOF works.

At the moment I am only using this lense. We are going to Europe in June and I am hoping to know how to take some relatively good shots. Thank you.
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Old Apr 30, 2009, 5:28 PM   #2
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Don't worry you are not the first and won't be the last to ask this question.

There are are two other aspects to dof in your situation apart from aperture that you are not looking at. These are focal length and distance to subject.

To get a shallow dof you can do this by making the aperture as wide as possible (smaller f number), us a longer focal length (so nearer the 200mm end) and get closer to the subject. Doing these things will give what you want. If you are nearer the 18mm end it will be pretty hard with any aperture to get the shallow dof etc.

Hope that helps.
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Old Apr 30, 2009, 5:30 PM   #3
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OK, you have 2 shots. In both shots you're saying you had the lens at 200mm and 5.6 right?

If that's true, there are 2 other factors which contribute to how blurred the background is:

1. How far away you are from the flower you are focusing on. If you take one photo from 5 feet away and the other from 10 feet away the photo from 5 feet away will have a more blurred background.

2. How far the background is from the flower you are photographing. Let's say the DOF for a given shot is 3 feet. If objects in the background are only 4 feet behind your subject they'll still be in reasonably good focus but if they're 20 feet behind then they will be very blurred.

The above two points ASSUME you used the same aperture (5.6) and same focal length (200mm) for both shots.
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Old Apr 30, 2009, 5:34 PM   #4
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Yay John, I beat you for once LOL
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Old Apr 30, 2009, 5:35 PM   #5
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Mark1616 wrote:
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Yay John, I beat you for once LOL
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Old Apr 30, 2009, 5:53 PM   #6
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When words are just not enough LOL.
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Old Apr 30, 2009, 6:14 PM   #7
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Thank you Mark and John. I think I begin to understand. The image I really liked was of a branch I focused on with a lake in the background. So, if I wanted to highlight one tulip in a bed of flowers can you tell me the approximate settings? When I try to stop down (?) from 5.6 sometimes it will not let me do that.

My niece learned all this stuff in a high school course. We never were so lucky when I went to school!!!
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Old Apr 30, 2009, 6:18 PM   #8
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Shari wrote:
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When I try to stop down (?) from 5.6 sometimes it will not let me do that.
stopping down means going to a larger f-number. You mean "open up" to go to a lower f-number. It won't let you do it because the lens is not capable of a lower f-number.

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So, if I wanted to highlight one tulip in a bed of flowers can you tell me the approximate settings?
that will be very difficult to do with your current lens. That is why there are macro lenses - lenses that let you get closer to your subject and still focus and even allow f2.8. The wider aperture (f2.8 vs 5.6) and the fact the lens allows you to get closer results in shallower DOF.
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Old Apr 30, 2009, 7:32 PM   #9
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Thank you so much John. For now I will have to use Photoshop to blur that background. I just told my husband I will have to get another lense so I can take the springtime flowers - all he understands about all this is that it is expensive.
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Old Apr 30, 2009, 8:01 PM   #10
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John, my lense is 3.5 - 5.6. Would I be opening up to 3.5 when in A mode?

Thanks
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