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Old Dec 15, 2004, 5:53 PM   #1
RDV
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I have been doing some research on COF & DOF and trying to get a better understanding. These 2 shots were taken with the FZ20 with a canon 250D close up lens. I found this creature on my plant inside. The first has his legs closer to the lens in focus and the second has his body in focus. I took 40 shots and could onlyget parts ofit in focus.Does this indicate the DOF for this lens and zoom is about the width of his body? I've noticed some of the close ups on this forum have part of the image in focusand others have the entire bug in focus. I used manual mode F8. What lens would I need to get this close and have all in focus? I am new and hope you guys don't think I'm being lazy for asking these questions.
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Old Dec 15, 2004, 5:55 PM   #2
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Old Dec 15, 2004, 8:12 PM   #3
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No, a lot of this is up to you really. You see in the first shot how you have more of the plant in focus in the front of the subject. Now if you sacrifice that front focus and move mm forward, the main subject would now be in the DOF.

In the second shot the opposite is true. The focus on the plant in the background is sharper than in the first shot. that means you have covered the subject better. Easy huh.

If we take a fly for example side on, it will look obviously look that more is in focus. Head on and it loses DOF fast. Thats at higher ratios. AIM FOCUS AT THOSE EYES :-)

At higher ratiosone thing that becomes your best friend, is selective focus. Thats what you have missed in that top shot. With selective focus in macro, as long as the eye is sharp, most other things will be forgiven.

Next is magnification that the CCD causes. Lets take a fly from300 mm away for example. More DOF is covering that, correct. Now we crop that shot and it appears that more of the fly is in DOF range. Ok now a few around do this all the time. Easy to spot when you are used to it. Why ?? Because we know for a certain ratio size what should be in focus at F/8 and what shouldn't be. Most only fool themselves.

We see it mentioned often that our smaller cameras and CCD sizes have more DOF compared to film. Sort of correct and sort of wrong. We do because our smaller CCDs are virtually cropping the image to start with. So it comes down to only one thing, image magnification.

Phew, long one :-). The higher ratio you want, you will correspondingly lose more DOF. With the eye of a fly full frame, DOF is virtually non existent. If we pull back so just the fly is in the shot, the whole fly, DOF now measuresmillimeters. It also comes down to the optics you are using for ratio size. Even though everything is at F/8, it diminishes very quickly as we move in.

Sorry, I'm getting carried away again, LOL. Long one but no real easy answer. Your shots have an easy answer though, select that focus :-)

Danny.




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Old Dec 15, 2004, 10:41 PM   #4
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amen brother
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