Why SLRs have shallower DOF than point-and-shoot cameras

Started Jul 25, 2012 | Discussions thread
PepsiCan
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Re: You're both wrong
In reply to carlvalle com, 10 months ago

carlvalle com wrote:

its not focal length - its only fstop and image magnification - short and long lenses have exactly the same dof (coc) at the same fstop. the reason p&s cameras appear to have greater dof is that they re already at diffraction limited fstops due to the required small coc - that is why a 12mpix p&s doesn't have the IQ of a 12mpix half frame dslr, much less a full frame. It is also why a medium format camera appears to have so much more dof, you don't have to magnify the sensor image as much so bigger coc's can be used. This is also why medium format lenses do not need to be as sharp as 35mm lenses do. dof is not defined at the sensor it is the final print / image where the effective dof is determined.

DOF is determined by:

- Focal length: the wider the deeper the DOF all else equal (note: when comparing focal lengths you need to standardise to the same format. A 6mm lens on a P&S compared to 6mm on an FX camera needs to be converted to the FX equivalent focal length to be compared.)

- Aperture: the larger the aperture, the narrower the DOF, all else equal

- Sensor size: the larger the sensor (irrespective the pixel size), the narrower the DOF, all else equal

- Distance to the subject: the closer the subject, the narrower the DOF, all else equal

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