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Old Oct 8, 2008, 3:55 AM   #11
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OK, the basics of DOF.

DOF is a function of the aperture, the focal length (the actual focal length not the 35mm equivalent), the distance from the camera that you are focused at.

So to make the DOF wider you can change any of the 3 parameters. A narrower aperture (higher f number), focus further from the camera or use a wider angle.

So this last point is where you are getting a difference with the two cameras. From the exif you are using 37mm on the XSi this will give the same field of view as 9.8mm on the A560 so that is a huge difference.

Now if you are focused a long way away, all that will be affected is how close to the camera is in focus as it should be at infinity, however if your focus point is close to the camera then you will have an area out of focus both near and far.

I would get out and ensure that you have focused on the tree line and if you are getting this sort of photo again I would say that there is something more that needs investigating. Are other photos looking OK? Are you set on high quality/resolution?
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Old Oct 8, 2008, 7:51 AM   #12
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I think I understand the basics of apature and DOF. And I suppose that I didn't post my best example photo, because I took others with the lens set to 18mm with a very similar, blurry result. But I had no idea that mm settings would be completely different from one camera to another.

"From the exif you are using 37mm on the XSi this will give the same field of view as 9.8mm on the A560 so that is a huge difference."

I'll have to admit, I don't understand what you mean. Same "field of view?" Forgive my newbie questions.

Regarding focus, I tried a variety of approaches. The XSi has a 9-point AF, and each time I took a picture, a number of the points would light up as being in focus, some near and some far away. So I assumed it was working. I believe I also tried a single point focus at the treeline, but I can recall for sure.

Yes, my camera is set to the highest quality and resolution. I guess I'll have to get back out there and keep trying.
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Old Oct 8, 2008, 7:56 AM   #13
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Boldstar wrote:
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"From the exif you are using 37mm on the XSi this will give the same field of view as 9.8mm on the A560 so that is a huge difference."

I'll have to admit, I don't understand what you mean. Same "field of view?" Forgive my newbie questions.

To have the same field of view basically means for things to look the same. The same length lens on 2 different cameras will give differing results as the sensor sizes are different. The bigger the sensor (say the XSi) the longer the lens needs to be for things to look the same and conversely the smaller the sensor (say the A560) the wider the lens has to be. If you had a 37mm lens on the A560 it would be a pretty long telephoto one about twice as much zoom as you have as a maximum now on it.



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Old Oct 8, 2008, 11:03 AM   #14
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I think I found the answer! Auto-focus.

I was under the impression that when using the 9-point AF, that whatever points lit up red would be in-focus. Apparently I was wrong. I just read in the manual that "the AF point covering the closest subject will be selected to focus."

Duh. I wonder if I should have already known that. Either way, I assume the answer would be to set only the center-point as focus and turn off the other 8 points. I already know how to do that and I prefer to shoot that way... so I'll have to wait for another non-overcast day to try again.

Thanks to everyone for their input.
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Old Oct 10, 2008, 5:49 AM   #15
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I couldn't help but notice that those shots were taken at different times of day, as you can tell by the shadows.

Lighting can have a huge impact on images. So, when comparing cameras, make sure that you're taking them in the same conditions (same subject, same lighting).

Also, make sure you frame the images the same way (subjects occupying the same percentage of the frame). If you were zoomed in more with the A560, then you'll have more pixels representing your subjects (i.e., the trees in the crops you posted). You didn't post a downsized A560 image we could see for comparison (you only posted a crop from that one). I suspect that you may have been zoomed in more using the other camera (and the lighting was very different, too).

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Old Oct 10, 2008, 6:32 AM   #16
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Those are excellent observations JimC.

Yes, the photos were taken a few hours apart. The A560 shot was taken a few hours before the XSi version. I wondered if that might have something to do with the difference, but I still found it hard to believe that my thousand-dollar DSLR couldn't match the focus or clarity of a $100-dollar point-and-shoot.

As far framing and zoom goes, I picked very similar versions of the photo for each camera. The cropped images look slightly different because the over all pixel size of each photo was different (the XSi shot being much larger to begin with). I hope that makes sense. Meaning, looking at the non-cropped, non-zoom version of each shot, they look nearly identical except for the more vibrant colors of the A560 image.

Thank you for your input. I'm still waiting on suitable conditions to try the photo again.
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