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Old Mar 3, 2012, 10:36 AM   #1
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Default Need macro DOF advice

I've been playing around with macro shots in my yard lately and no matter what I do it always seems like my depth of field is so shallow that I can't get the entire subject in focus. I'm using the Macro mode on my T3i for these pictures and it won't allow any changes to the f-stop in that mode. Should I be disregarding that mode entirely and stick with Manual mode? I'm using an EF-S 17-55 f/2.8 and it has a minimum focusing distance of 1.15 feet so maybe I'm just using the wrong lens.

Here's an example of what I mean. The back of the daffodil is in focus pretty well but it leaves the nose blurred. If I adjust to bring the nose into focus then the back is blurred. Thanks for any comments and advice.


Almost by Quadna71, on Flickr
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Old Mar 3, 2012, 11:25 AM   #2
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The Exif info for the shot isn't intact, so I can't tell what settings were used, which makes specific advice difficult. In general, I would say to use Aperture priority mode, with a setting of f/8 to begin with. Manually focus the lens to its closest setting and move in on the subject until its in focus. Depending on the light, you may need flash or a tripod.

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Old Mar 3, 2012, 12:43 PM   #3
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The closer the focus distance, the more shallow the Depth of Field. That's not going to change.

The larger the aperture, the more shallow the DoF. That's not going to change.

If you want to focus close, yet get a deeper DoF, you need to use a smaller aperture (numerically larger f-number.)

If the Macro mode won't let you select a smaller aperture, stop using the Macro mode.

Note, however, that using a smaller aperture means less light gets through the lens during the exposure, so you'll need to use either a longer shutter speed (risking motion blur due to camera shake), a higher ISO setting (risking image noise), or supplimental light.
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Old Mar 3, 2012, 5:24 PM   #4
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The EXIF is there if you view the photo on Flickr:

Exposure 0.004 sec (1/250)
Aperture f/4.0
Focal Length 51 mm
ISO Speed 100

I understand how aperture works, but was just wondering if someone knew how to vary the f number while in Macro mode. It doesn't seem to allow me to adjust much in the way of settings and the book that came with the camera doesn't really elaborate much on Macro mode other than to define what Macro is. It seems to want to set the f number all automatically which sort of limits you. I realize that if I would've bumped to a smaller aperture of say f/8 instead of f/4 then I'd have had all the depth I need; I guess if I can't make the adjustments in Macro I'll just stick to Aperture Priority or Manual. Thanks guys.
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Old Mar 3, 2012, 5:58 PM   #5
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I would really stop down allot more to F16. With a true macro lens, I routinely shoot at f16 to F20 when I am shooting upclose.
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Old Mar 3, 2012, 9:09 PM   #6
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In true macro (life-size and bigger) even at f/16 or more your dof can be measured in millimeters.
Hence all the neat new focus stacking programs and tools
like Helicon Focus and computer controlled stepping macro rails like the stack shot
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Old Mar 3, 2012, 9:26 PM   #7
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I seen them, but I am pp lazy. I have if I want less dof, I shot at f32

This shows how thin dof can be when shooting macro.
http://forums.steves-digicams.com/cl...e-up-lens.html
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Old Mar 4, 2012, 6:14 AM   #8
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With Quadna71's kit, at the minimum focus distance of 35cm, the longest focal length, and an aperture of f/2.8, the total DoF is less than 4mm. At f/16, it's more than 20mm, but that's still less than an inch.

f/16 is smaller than the diffraction limit of the T3i, so smaller apertures will reduce image quality.

What Quadna71 really needs is a longer lens. The Canon 17-55/2.8 is excellent, but not for this.
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Old Mar 4, 2012, 2:00 PM   #9
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A longer Macro lens can help, but they can be expensive.

A tripod and ring flash will allow you to shoot at small apertures, but diffraction can become an issue.

Your only alternative is focus stacking.
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Old Mar 4, 2012, 2:33 PM   #10
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The photo above would be more likely classified a close-up, rather than a macro, so macro mode is probably not appropriate. Just using a smaller aperture should give good results.

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