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Old Feb 18, 2004, 9:20 AM   #1
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Default Depth of field question

Greetings...I'm a digital camera newbie with 20+ years experience with a Pentax K1000 (manual controlled, film SLR). I read somewhere on the net that aperture setting has no affect on depth of field on a digicam, is this true? If so, anyone want to buy a Canon G5?

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Old Feb 18, 2004, 9:59 AM   #2
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You can read all sorts of things on the net, including incorrect things such as the one you mention. Keep your camera, aperture works the same way in digital as it did with your Pentax. Most of the things you learned with your Pentax carry directly over to the digital world.
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Old Feb 18, 2004, 10:15 AM   #3
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If your digital camera is not a DSLR it has a small sensor and the DOF is much larger than it would be on a comparable aperture setting and focal length on a 35mm camera. If you bought a DSLR the sensor is still smaller than the 35mm negative and you will get greater DOF, but you can still blur a background like you did with 35mm just not quite as successfully.

As ohenry says, the principle is still the same. The results are a lot different than you are accustomed to though.
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Old Feb 18, 2004, 1:55 PM   #4
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Most digicams state their focal length in terms of 35mm equiv. That works well for estimating the Field of View, but not for depth of field. The actual focal length is typically about a factor of five smaller than the 35mm equiv, i.e., 50mm equiv is something like 10mm actual focal length. Even with the needed smaller Circle of Confusion to account for a smaller sensor/"film", that means a much larger depth of field for the same field of view.

It is still far from infinite though.
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Old Feb 18, 2004, 4:32 PM   #5
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Default Re: Depth of field question

Quote:
Originally Posted by berniec
I read somewhere on the net that aperture setting has no affect on depth of field on a digicam, is this true?
While you can get wonderful and useful information on the Internet, you also risk getting many incorrect ones like the one you quoted. Depth of field (DOF) is a lens characterstic, and as long as you have a lens for recording images, the DOF will be there. However, since most digital cameras have smaller sensors and lenses must have shorter focal length to match the smaller sensors, DOF is larger than that of the 35mm cameras, which, in turn, have larger DOF than those of the 6x6 and 645 cameras. Take a look at the "Depth of Field" page of my Nikon Coolpix 4500 user guide for the details.

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http://www.cs.mtu.edu/~shene/DigiCam
Nikon Coolpix 950/990/995/2500/4500/5700 User Guide
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Old Feb 19, 2004, 12:15 AM   #6
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While it's blatantly incorrect to suggest aperture on digicams have no effect on its depth of field, it is true to some extent that it has less of an effect compared to full sized sensors on DSLR and traditional 35mm film - as has been mentioned in previous posts.

This is partly why you don't see digicams with apertures smaller than say F/8 or F/11 - because there is no practical benefit in smallers apertures with sensor sizes as they are.

eg. try getting decent bokeh at even F/2.8 on your G5.

Here's one of my favourite reads on this very subject of DOP in digicams. Scroll to the very bottom of the page:

http://www.dansdata.com/phototute.htm
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Old Feb 19, 2004, 8:19 AM   #7
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Quote:
Originally Posted by Onyx
... This is partly why you don't see digicams with apertures smaller than say F/8 or F/11 - because there is no practical benefit in smallers apertures with sensor sizes as they are. ...
There have been several times when I wished I could have had a greater depth of field. The reason digicams do not have a smaller aperature is diffraction. When the aperature becomes small, a "blurriness" will result - small in an absolute size measurement, not in terms of f/stops. The same reason a lens means that an 8x10" camera will often stop down to f/128 while 35mm lenses are typically limited to ~f/22.
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