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02/10/2008 12:40:02 PM · #1 |
I shot numerous puddles, ponds, etc. trying to get a shot for this challenge. My camera seemed to focus like I would have expected it to - apparently on the surface of the water. However, when I tried a few shots that had to be set up so to speak, I found that it appeared my camera was not focusing on the surface, but on the apparent distance to the object in the reflection. I tried many experiments to see if this was just my imagination, and it wasn't.
Can someone explain this phenomenon? Or am I on drugs I don't know about?
After the challenge I can give more details as to what I was experiencing and the conditions. But I am on the fence about a re-shoot and would like to try and understand this so perhaps I can get the results I desire. |
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02/10/2008 12:47:57 PM · #2 |
| What AF mode do you use? Your 20D has 7 (or 9) AF zones and if you're using a mode that allows the camera to select which one to use, it will select the area where it detects the best contrasting zones or edges. You can select which one of these zones the camera uses. I have mine set to the center point so I can compose my shot with my focus point in the center, half press for AF, then recompose and shoot. |
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02/10/2008 12:48:02 PM · #3 |
The focusing system is going to look for the highest contrast within the area it covers. If that happens to be the reflection and not the puddle itself, then it'll focus on the reflection. For a complicated setup like this, you may have to focus manually to ensure that what *you* want to be in focus is actually focused.
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02/10/2008 12:52:31 PM · #4 |
| Center focus point selected. Focus manually. It is the distance that has me confused. Focus seems to be to the actual distance to the object in the reflection as opposed to the distance between the camera and the reflective surface. |
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02/10/2008 01:38:04 PM · #5 |
You're not on drugs, that's just the way it is.
You're seeing an object as a reflection, but you're only seeing it because light reflects off it.
That light is travelling from the object via the reflection to your eye/lens.
Makes sense that you should have to focus on all of that distance, not just part of it.
Sorry about my VERY amateur explanation, I'm sure someone will come up with a much better one soon (if they haven't beaten me to it already while I am typing). |
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02/10/2008 02:13:02 PM · #6 |
| Try a different aperture, see what that does for the focus. |
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02/10/2008 03:13:25 PM · #7 |
If you stand in front of a mirror, 6 feet away, and focus on your reflection then check the distance you are focused on, you will find that the lens focused at 12 feet, not 6 feet; the reflection is 12 feet "away" from the camera, optically. If the mirror were set up outside and the reflection included yourself and mountains int he BG behind you, it's very possible that the figure in the reflection would be in focus (assuming that's what you focused on) and the mountains would be OOF if your aperture was not small enough to generate 12-feet-to-infinity DOF...
R. |
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