TG-2 sample shot at ISO 100 and my initial impression

Started Mar 28, 2013 | Discussions thread
BorisK1
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Re: TG-2 sample shot at ISO 100 and my initial impression
In reply to Jefftan, Mar 29, 2013

Jefftan wrote:

BorisK1 wrote:

Jefftan wrote:

BorisK1 wrote:

Jefftan wrote:

What I found is for wide position F2.8 is sharper than F2

That actually makes sense.  I ran the numbers in an online calculator:

http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

and it says that a camera with a 1/2.3" sensor will only hit diffraction limit at f:4.

Hi Borisk1

I have another diffraction calculator from the same site which show

http://www.cambridgeincolour.com/tutorials/diffraction-photography-2.htm

Sorry, I wasn't clear.  The calculator I used, showed that at F:4, the shot becomes "diffraction limited", but at F:2.8, it is not.  There wasn't a selection of F:3, so I didn't try it.

Here's my (very limited) understanding of the concepts involved.

The "Airy disk":  When you take a picture of a single dot, the lens (because of diffraction) projects it on the sensor as a circle. (We're talking of an "ideal" lens here.  Real lenses introduce optical imperfections that will make the shape not-quite-circular, and possibly colored).

The resolution becomes "diffraction limited" when the diameter of the airy disk is larger than the pixel pitch.  The diameter of the airy disk increases as you close down the aperture.

Closing the aperture down past the diffraction limit reduces resolution.

Boris

So why are there 2 calculators on the same site? Are they the same?

They use the same math, but answer different questions.  The one I used (Advanced Diffraction Calculator) takes values for the aperture, sensor size, and resolution, and calculates the corresponding size of the airy disk.  The one that you used (Diffraction Limit Calculator), takes sensor size and resolution, and calculates the aperture at which the airy disk size becomes equal to the pixel size.

I merely wanted to see if f:2.8 on TG-2 is diffraction limited.  Both calculators say "no".

Note that TG-1/2 aperture is a combination of an iris and an ND filter.  Closing down past f:2.8 is done by enabling the ND filter, and does not affect the size of the airy disk.

Boris

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