Diffraction is a physical characteristic of the focal ratio and has
nothing to do with the lens itself. At any given focal ratio the
minimum size that can be imaged of a point source of light is referred
to as the "airy disc" and it is determined by the focal ratio. Poor
optics may make the minimum size larger but never smaller. Therefore
the maximum theoretical resolution obtainable is determined by the
aperture. When the minimum size of the airy disc exceeds the size of an
individual pixel it means the the maximum resolution obtainable at that
aperture is less then the pixel count on the sensor.
For a 4/3 size sensor of 5MP (E-1) the size of the Airy disc equals the
pixel size at about f/8 or f/9... and that assumes perfect optics. But
it's sort of a squishy number since the size of the Airy disc also
varies with wavelength of light. At f/8 you might be resolving all the
green and blue pixels but not all the red ones (longer wavelength)
But things that are out of focus are not resolved either. Smaller
apertures lead to greater depth of field while at the same time reducing
ultimate resolution. Somewhere there's a happy median.
Chuck Norcutt
On 6/23/2012 5:49 PM, Jim Nichols wrote:
> Thanks, Chuck. I'm not sure about the theoretical point where diffraction
> becomes noticeable with this lens. I have found that, in the past, f/13
> results in good images, while f/18 is not as sharp. That is one technical
> area that I don't care to visit.
>
> Jim Nichols
> Tullahoma, TN USA
> ----- Original Message -----
> From: "Chuck Norcutt" <chucknorcutt@xxxxxxxxxxxxxxxx>
> To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
> Sent: Saturday, June 23, 2012 4:37 PM
> Subject: Re: [OM] IMG: More Skippers
>
>
>> I prefer the f/13 shot and would blur the background if needed. f/13 is
>> a bit into diffraction territory for an E-1. You might get marginally
>> sharper results by sticking to f/9 or f/8.
>>
>> Chuck Norcutt
>>
>>
>> On 6/23/2012 2:49 PM, Jim Nichols wrote:
>>> I received some valuable tips yesterday from Dean Hansen, on using
>>> lighting angles to bring out the texture and details of butterfly
>>> wings. I tried to round up some subjects today to put them into
>>> practice.
>>>
>>> Since the sun provides the only light source for my work, it comes
>>> down to insect angles and camera position. The first was done with
>>> the lens at f/13 for details. The light brought out the texture of
>>> the wings, but the background was not as far OOF as I would have
>>> liked.
>>>
>>> http://gallery.leica-users.org/v/OldNick/Skipper+14.jpg.html
>>>
>>> I opened up to f/5.6 for the second shot, and, although the light
>>> angle did not pick up the texture as well, the bokeh is better.
>>>
>>> http://gallery.leica-users.org/v/OldNick/Skipper+26.jpg.html
>>>
>>> E-1 and Zuiko Digital 35 Macro
>>>
>>> Comments and critiques welcomed.
>>>
>>> Jim Nichols Tullahoma, TN USA
>>>
>>
>> --
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>>
>
>
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