Extension tubes

A forum to ask questions, post setups, and generally discuss anything having to do with photomacrography and photomicroscopy.

Moderators: MacroMike, nzmacro, Ken Ramos, twebster, S. Alden

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Kenv
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Joined: Mon May 24, 2004 6:51 pm
Location: New Zealand

Extension tubes

Post by Kenv »

If I use an extension tube to get closer to the subject does this shrink the DOF in the same way as getting physically closer with the lens?
Ken
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Charles Krebs
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Location: Issaquah, WA USA

Post by Charles Krebs »

No matter how you arrive at a given magnification on a given camera format, the depth of field will be the same at the same effective aperture.

So... if you use a 55mm lens with extension tubes to get 2X (2:1) magnification, and then you use a 105mm lens with extension to also get 2X (2:1), the depth of field will be the same for the same aperture.

The reason it seems you can get so much more depth of field with a point-and-shoot digital camera compared to say, a 35mm camera, is that the sensor (format size) is much smaller (for example 7.2 x 5.3 mm is common) while the 35mm frame is 36x24mm. The small sensor requires a much lower magnification to "fill the frame" with your subject than the 35mm camera. Lower magnification=greater depth-of-field.

There really is no one "magic" method or equipment combo that will provide any more DOF than any other method used to get the same magnification (on a given format!)

If you go to a smaller format you will get more DOF when "filling the frame" with the same subject. And as long as there is adequate resolution (as there certainly is with the smaller digital sensors... all you need to do is look at the fantastic macro images on this site that were made using digital point-and-shoot cameras) you can get great results.

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Kenv
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Joined: Mon May 24, 2004 6:51 pm
Location: New Zealand

Post by Kenv »

Thanks for that info Charles.
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