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Old Feb 16, 2008, 11:28 AM   #1
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Found this while I was out cutting the roses down to the ground. Used a car window shade, black side for the background and silver side for (not in picture) a little added light. Focus is not as sharp as I think it should be, not sure if the subject or I moved after locking the focus in place. Shot with a 40D, 17-85 EF-S with a UV filter and lens hood using single point focus (one little red square) in Tv mode in RAW. Any ideas or suggestions would be helpful. Metering was set to Partial Metering but that shouldn't effect focusright.


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Old Feb 17, 2008, 5:27 PM   #2
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We've all been there thinking that there is a focus problem, and sometimes there is and sometimes it is technique...... I've had both.

I would do some tests on a tripod to see what you actually have before panicking. There are numerous ways to do this, one I've used it shooting books/DVD's at slightly different distances from the camera (you can do them touching in most cases or about 1cm apart) so you have something like this. I've done this asa top view of the DVD's books and you focus on the front of the middle one and see which is sharpest. Make sure that you use only centre point, and have something with good contrast and not a lot of reflection to aim at..

_________

_________

_________ Focus on this one

_________

_________





:|Position camera on tripodhere with the lens as max zoom and widest aperture. Also be sure to have good light on the subject so that the camera is not struggling to get AF lock. Also don't have the camera too close to the target as when getting near to minimum focus distance things can change a little.

Now shoot some off and see what is going on when reviewing the images. Are you getting sharp results on the target DVD or is it one of those in front or behind?

Let us know how you get on.


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Old Feb 18, 2008, 11:58 AM   #3
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Wasn't really panicking too much as I was pretty sure the problem was operator error and not camera error. Do like your idea for the DOF tests, should give me a good feel for what the camera will do and how I should adjust what I need to do in order to get the shot each time.

Thanks,

Craig

P.S.

I know I posted this reply last night but not sure where it ended up. So if it shows up in the wrong thread sorry.:?
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Old Feb 19, 2008, 8:23 AM   #4
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The test Mark was referring to is designed to show you if your Autofocus is working properly (your focus point is sharper, versus the camera focusing behind or in front of your focus point).

I'd check it just to make sure you don't have a camera or lens problem impacting AF accuracy. But, I doubt that's the issue with that photo. You've got a *very* shallow Depth of Field shooting at closer ranges and wider apertures (smaller f/stop numbers). So, focus point is critical, and using a tripod is a very good idea. If you lean even a tiny bit after locking focus, it's going to throw it off. Some users prefer manual focus for Macros, too.

Also, most lenses are softer at their widest aperture settings (and you were shooting with the aperture wide open, using f/5.6 at the long end of your zoom range).

If you want more depth of field (more of the image in focus as you get further away from your focus point), use a smaller aperture (higher f/stop number). Also, most lenses are sharper a couple of stops down from wide open. IOW, depth of field considerations aside, you'll probably get sharper photos using f/11 versus f/5.6. For macros, you may want to use an even smaller aperture, depending on how much of the image you want to be in focus.

But, using a smaller aperture (higher f/stop number) will also impact shutter speed. You'll get slower shutter speeds for any given lighting and ISO speed as you use smaller aperture settings for more depth of field). That's another reason a tripod is a good idea for macros.

To get a better understanding of Depth of Field, see this online calculator. Simply select your camera model, the focal length you want to shoot at (for example, 85mm), your focus distance and aperture and it will show you depth of field.

http://www.dofmaster.com/dofjs.html

To get a better understanding of how aperture, ISO speed (shown as film speed in this calculator), and lighting impact the shutter speed a camera will need for proper exposure, see this online exposure calculator:

http://www.robert-barrett.com/photo/...alculator.html

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Old Feb 19, 2008, 3:22 PM   #5
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Well guys, I will try all suggestions given here and post the results back in this thread. Itwon't be the same flower shot as my wife tried helping me in the garden and cut that flower downbut I'm sure I'll find something to shot (not the wife) around the house.:G

Thanks,

Craig
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Old Feb 21, 2008, 2:58 PM   #6
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Hey maybe I'm getting the hang of the focusing thing after all, this new attempt looks pretty good, I think.


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Old Feb 22, 2008, 3:42 PM   #7
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Hi Calicajun,

Wow, I agree this second photo looks much superior to the first one! Not just in focus, but lighting, colour and background too.

Very nicely done!

Glad you didn't have any problems with your wife allowing you in getting a flower shot! :-)

Regards,

Paul



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Old Feb 22, 2008, 5:23 PM   #8
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Thanks, now all I have to learn is how to do that every time I shoot. BTW, thanks for reminding me about the background, better give my daughter back her bed sheet.

Thanks again,

Craig
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Old Feb 24, 2008, 7:34 AM   #9
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Calicajun wrote:
Quote:
Thanks, now all I have to learn is how to do that every time I shoot...
-> You don't haveto...
IMO you got it and you can do it everytime!

The difference is in the use of flash in your 2nd shot and not a camera focusing issue:
1. Like JimC has already alluded to - for Macro shot you need to increase the DOF (which you did from f/5.6 to f/11) which makes entire flower come into focus at close distance, but also helps the additional lighting in #2
2. The flash not only increase the saturation and contrast, but also with its characteristic light fall-off with distance darken the background (and f/11 makes it more so)

You might want to lower the flash a little or get it off the camera all together as you can solve the slight shadow underneath the bulb and on the stem of the 2nd tulip
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