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Nikon D70: Dark Circular Marks in Sky



 
 
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  #1  
Old December 14th 06, 10:36 PM posted to rec.photo.digital
Tim
external usenet poster
 
Posts: 74
Default Nikon D70: Dark Circular Marks in Sky

Alfred Molon wrote:
In article 1122588119.285579@ftpsrv1, frederick says...


The fact that the dust is visible, and that the image is not very
sharp indicates to me that a very small aperture was used - as does
the motion blur which tells me that a fast shutter speed was not
used. Above about f11, sharpness will be lost on a dslr like the D70



At what aperture is the diffraction limit for a camera like the D70 ?



Take a look.
http://www.geocities.com/angels2000photos/diffract.jpg
I think that you can see slight loss of acutance even at f11 - but not
enough that you would even notice on a print - even a large one. By
f16 it's pretty visible, by f22 it's very significant. Those are 1:1
crops, but I think loss of sharpness is going to be noticeable on
anything but a very small print by the time you get to f16 of greater.
http://www.geocities.com/angels2000photos/diffract.jpg


Frederick
Thanks for that info - I'm a pretty much a noob at this lark
Do you have any links for further reading easily to hand

TIA
Tim

http://www.timdenning.myby.co.uk/


  #2  
Old December 15th 06, 01:21 AM posted to rec.photo.digital
frederick
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Posts: 1,525
Default Nikon D70: Dark Circular Marks in Sky

Tim wrote:
Alfred Molon wrote:
In article 1122588119.285579@ftpsrv1, frederick says...


The fact that the dust is visible, and that the image is not very
sharp indicates to me that a very small aperture was used - as does
the motion blur which tells me that a fast shutter speed was not
used. Above about f11, sharpness will be lost on a dslr like the D70

At what aperture is the diffraction limit for a camera like the D70 ?


Take a look.
http://www.geocities.com/angels2000photos/diffract.jpg
I think that you can see slight loss of acutance even at f11 - but not
enough that you would even notice on a print - even a large one. By
f16 it's pretty visible, by f22 it's very significant. Those are 1:1
crops, but I think loss of sharpness is going to be noticeable on
anything but a very small print by the time you get to f16 of greater.
http://www.geocities.com/angels2000photos/diffract.jpg


Frederick
Thanks for that info - I'm a pretty much a noob at this lark
Do you have any links for further reading easily to hand


http://www.cambridgeincolour.com/tutorials.htm
http://www.cambridgeincolour.com/tut...otography.htm#

I think that is a good source of information - and particularly in
explaining the effects of sensor format, aperture, focal length on DOF,
taking into account diffraction, and most importantly the different
parameters that apply for assessing sharpness on final prints - such as
size of print and viewing distance. It also explains why trade-off
between loss of acutance or resolution from diffraction may be
acceptable when extra depth of field is desired.
  #3  
Old December 16th 06, 11:22 AM posted to rec.photo.digital
Tim
external usenet poster
 
Posts: 74
Default Nikon D70: Dark Circular Marks in Sky

Tim wrote:
Alfred Molon wrote:
In article 1122588119.285579@ftpsrv1, frederick says...


The fact that the dust is visible, and that the image is not very
sharp indicates to me that a very small aperture was used - as
does the motion blur which tells me that a fast shutter speed was
not used. Above about f11, sharpness will be lost on a dslr like
the D70

At what aperture is the diffraction limit for a camera like the
D70 ?

Take a look.
http://www.geocities.com/angels2000photos/diffract.jpg
I think that you can see slight loss of acutance even at f11 - but
not enough that you would even notice on a print - even a large
one. By f16 it's pretty visible, by f22 it's very significant. Those
are 1:1 crops, but I think loss of sharpness is going to be
noticeable on anything but a very small print by the time you get
to f16 of greater.
http://www.geocities.com/angels2000photos/diffract.jpg


Frederick
Thanks for that info - I'm a pretty much a noob at this lark
Do you have any links for further reading easily to hand


http://www.cambridgeincolour.com/tutorials.htm
http://www.cambridgeincolour.com/tut...otography.htm#

I think that is a good source of information - and particularly in
explaining the effects of sensor format, aperture, focal length on
DOF, taking into account diffraction, and most importantly the
different parameters that apply for assessing sharpness on final
prints - such as size of print and viewing distance. It also
explains why trade-off between loss of acutance or resolution from
diffraction may be acceptable when extra depth of field is desired.


Thanks for the reply Frederick I'll have a read later
Best regards

Tim

--
http://www.timdenning.myby.co.uk/


 




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