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External
Since: Apr 05, 2006
Posts: 704
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(Msg. 76) Posted: Sat Oct 28, 2006 10:28 pm
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
Archived from groups: rec>photo>digital (more info?)
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Greg "_" wrote:
> In article <1162012380.161825.209820 DeleteThis @i3g2000cwc.googlegroups.com>,
> "Scott W" <biphoto DeleteThis @hotmail.com> wrote:
>
> > It depends on the lens, but if the lens is good then yes.
>
> What?
It takes a good lens to be diffraction limited.
>
> > If the lens
> > is wide angle then it gets much harder to be diffraction limited over
> > the whole field of view.
> >
> > Scott
>
> I think digital wide angle lenses are much more subject to diffraction
> limits than film cameras and the opposite is true of telephoto ones.
The same limits of spot size due to diffraction exist for telephoto
lenses as for wide-angle lenses. A wide-angle lens will more often
suffer from aberrations that might over shadow the effects of
diffraction but both long and short lenses will have the same limit at
the same f/number.
There is a hard limit to the DOF and total amount of resolved detail
that in imaging system can have, at least in one shot. And the DOF
drops fast as we push the detail up, and increase of 4 in total detail
captured requires a drop of the DOF by a factor of 4. As an example if
I have a image with 100 MP that is in focus from 20 ft to infinity then
if I increase the resolution to 400 MP the closest in focus point would
be 80 ft away. The field of view has a large impact on all of this but
you can only go so wide. When I am trying to get a photo will a lot of
pixels that are sharp I do two things, go wide angle and try to keep
anything in the foreground from being too close.
Roger Clark is pushing on this limit by taking a whole lot of photos
letting the camera focus for each one and stitching them, but this only
works for some scenes. A LF camera can tilt the film but this is also
very limited.
Scott |
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External
Since: May 22, 2006
Posts: 53
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(Msg. 77) Posted: Sun Oct 29, 2006 12:19 am
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
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In article <1162012380.161825.209820.TakeThisOut@i3g2000cwc.googlegroups.com>,
"Scott W" <biphoto.TakeThisOut@hotmail.com> wrote:
> It depends on the lens, but if the lens is good then yes.
What?
> If the lens
> is wide angle then it gets much harder to be diffraction limited over
> the whole field of view.
>
> Scott
I think digital wide angle lenses are much more subject to diffraction
limits than film cameras and the opposite is true of telephoto ones.
--
Reality-Is finding that perfect picture
and never looking back.
www.gregblankphoto.com |
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External
Since: Apr 05, 2006
Posts: 704
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(Msg. 78) Posted: Mon Oct 30, 2006 10:38 am
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
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acl wrote:
> Yes, but the angular resolution is determined by the diameter only
(it
> is proportional to 1/D, with D the diameter). So the radius of the min
> spot is f*this angle, with f the focal length; ie, proportional to
> f/D=aperture. This is what Paul Rubin was talking about.
It sounds to be that Paul believes that the diffracted spot size in the
image plane only depends on the aperture. He was saying after all that
the reason my f/32 image was soft because I was using a short FL, but
the softness will be the same regardless of the FL, if I am shooting at
f/32. To make this very simple, if you shoot at f/32 to higher with
digital camera that has around 6 micron pixels the image is going to be
soft. If you shoot with film at f/32 and scan at 4000 ppi the image is
going to be soft. If you should with film at f/64 and scan at 2000 ppi
the image is going to be soft.
Scott >> Stay informed about: The Megapixel Race |
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External
Since: Nov 23, 2005
Posts: 1029
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(Msg. 79) Posted: Mon Oct 30, 2006 10:58 am
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
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"Scott W" <biphoto DeleteThis @hotmail.com> writes:
> It sounds to be that Paul believes that the diffracted spot size in the
> image plane only depends on the aperture.
No I misunderstood what you were getting at. I meant on the final
projected image/print/whatever, whose magnification depends on the
original sensor size. >> Stay informed about: The Megapixel Race |
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External
Since: Apr 05, 2006
Posts: 704
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(Msg. 80) Posted: Mon Oct 30, 2006 3:31 pm
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
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Greg "_" wrote:
> In article <1162233505.699391.161600 RemoveThis @e3g2000cwe.googlegroups.com>,
> "Scott W" <biphoto RemoveThis @hotmail.com> wrote:
>
> > If you shoot with film at f/32 and scan at 4000 ppi the image is
> > going to be soft. If you should with film at f/64 and scan at 2000 ppi
> > the image is going to be soft.
> >
> > Scott
>
> I don't agree with this statement as a matter of law,..just too many
> variables-by experience.
But all those other variables can only make things worse, not better.
Just to be clear on what I am calling soft, the bottom image to me is
soft, the one taken at f/32.
http://www.pbase.com/konascott/image/69244820
The one at f/8 I would not call soft.
Whatever lens you use at f/32 it is not going to be sharper then what I
got a f/32. And since my camera is sampling at close to 4000 ppi a
film scan at 4000 ppi of a shot at f/32 will not be any sharper then my
image at f/32, but it can be much softer.
And at f/64 will double the blurring and now a 2000 ppi scan can not
look any sharper then my image shot at f/32.
Scott >> Stay informed about: The Megapixel Race |
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External
Since: Nov 01, 2005
Posts: 329
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(Msg. 81) Posted: Mon Oct 30, 2006 5:22 pm
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
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"Scott W" <biphoto DeleteThis @hotmail.com> wrote in message
news:1161991822.719806.122760@k70g2000cwa.googlegroups.com...
> Greg "_" wrote:
> >
>> Sounds very hokey.
>
> It may sound hokey to you but none the less it is true. If you
> really
> care to learn there is plenty of literature that covers this area.
> A
> really good reference on optics and lens design is "Modern Optical
> Engineering" by Warren J. Smith.
Or read the explanations at:
<http://www.bobatkins.com/photography/technical/diffraction.html>
What several people apparently don't realize is that the f/number is
already a ratio between focal length and absolute aperture diameter.
Therefore the f/number by itself determines the diffraction spot
diameter.
--
Bart >> Stay informed about: The Megapixel Race |
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External
Since: Mar 23, 2006
Posts: 300
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(Msg. 82) Posted: Mon Oct 30, 2006 5:48 pm
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
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Bart van der Wolf wrote:
> "acl" <achilleaslazarides.RemoveThis@yahoo.co.uk> wrote in message
> news:1162227053.157509@seven.kulnet.kuleuven.ac.be...
> > Bart van der Wolf wrote:
> SNIP
> >> What several people apparently don't realize is that the f/number
> >> is already a ratio between focal length and absolute aperture
> >> diameter. Therefore the f/number by itself determines the
> >> diffraction spot diameter.
> >>
> >
> > Yes, but the angular resolution is determined by the diameter only
> > (it is proportional to 1/D, with D the diameter).
>
> Angular resolution yes, but the projection distance, and thus
> projected diameter, is also incorporated in the f/number. It is a
> constant regardless of focal length.
I know. That is what I said in the rest of my post. This part:
> > So the radius of the min spot is f*this angle, with f the focal
> > length; ie, proportional to f/D=aperture. This is what Paul Rubin
> > was talking about.
>
> > Take a look at equations 17 and 18 in
> > http://www.pha.jhu.edu/~jlotz/aoptics/node2.html >> Stay informed about: The Megapixel Race |
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External
Since: Jun 09, 2006
Posts: 270
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(Msg. 83) Posted: Mon Oct 30, 2006 5:56 pm
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
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Bart van der Wolf wrote:
>
> "Scott W" <biphoto.TakeThisOut@hotmail.com> wrote in message
> news:1161991822.719806.122760@k70g2000cwa.googlegroups.com...
>> Greg "_" wrote:
>> >
>>> Sounds very hokey.
>>
>> It may sound hokey to you but none the less it is true. If you really
>> care to learn there is plenty of literature that covers this area. A
>> really good reference on optics and lens design is "Modern Optical
>> Engineering" by Warren J. Smith.
>
> Or read the explanations at:
> <http://www.bobatkins.com/photography/technical/diffraction.html>
>
> What several people apparently don't realize is that the f/number is
> already a ratio between focal length and absolute aperture diameter.
> Therefore the f/number by itself determines the diffraction spot diameter.
>
Yes, but the angular resolution is determined by the diameter only (it
is proportional to 1/D, with D the diameter). So the radius of the min
spot is f*this angle, with f the focal length; ie, proportional to
f/D=aperture. This is what Paul Rubin was talking about.
Take a look at equations 17 and 18 in
http://www.pha.jhu.edu/~jlotz/aoptics/node2.html >> Stay informed about: The Megapixel Race |
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External
Since: May 22, 2006
Posts: 53
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(Msg. 84) Posted: Mon Oct 30, 2006 6:18 pm
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
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In article <1162233505.699391.161600.DeleteThis@e3g2000cwe.googlegroups.com>,
"Scott W" <biphoto.DeleteThis@hotmail.com> wrote:
> If you shoot with film at f/32 and scan at 4000 ppi the image is
> going to be soft. If you should with film at f/64 and scan at 2000 ppi
> the image is going to be soft.
>
> Scott
I don't agree with this statement as a matter of law,..just too many
variables-by experience.
--
Reality-Is finding that perfect picture
and never looking back.
www.gregblankphoto.com >> Stay informed about: The Megapixel Race |
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External
Since: May 22, 2006
Posts: 53
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(Msg. 85) Posted: Mon Oct 30, 2006 9:15 pm
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
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In article <1162251105.540338.107670.TakeThisOut@k70g2000cwa.googlegroups.com>,
"Scott W" <biphoto.TakeThisOut@hotmail.com> wrote:
> Greg "_" wrote:
> > In article <1162233505.699391.161600.TakeThisOut@e3g2000cwe.googlegroups.com>,
> > "Scott W" <biphoto.TakeThisOut@hotmail.com> wrote:
> >
> > > If you shoot with film at f/32 and scan at 4000 ppi the image is
> > > going to be soft. If you should with film at f/64 and scan at 2000 ppi
> > > the image is going to be soft.
> > >
> > > Scott
> >
> > I don't agree with this statement as a matter of law,..just too many
> > variables-by experience.
>
> But all those other variables can only make things worse, not better.
> Just to be clear on what I am calling soft, the bottom image to me is
> soft, the one taken at f/32.
> http://www.pbase.com/konascott/image/69244820
> The one at f/8 I would not call soft.
> Whatever lens you use at f/32 it is not going to be sharper then what I
> got a f/32. And since my camera is sampling at close to 4000 ppi a
> film scan at 4000 ppi of a shot at f/32 will not be any sharper then my
> image at f/32, but it can be much softer.
>
> And at f/64 will double the blurring and now a 2000 ppi scan can not
> look any sharper then my image shot at f/32.
>
> Scott
I have a problem with the test, the "densities" differ.
--
"As democracy is perfected, the office represents, more and more closely,
the inner soul of the people. We move toward a lofty ideal. On some great
and glorious day the plain folks of the land will reach their heart's desire
at last, and the White House will be adorned by a downright moron."
- H. L. Mencken, in the Baltimore Sun, July 26, 1920.
Reality-Is finding that perfect picture
and never looking back.
www.gregblankphoto.com >> Stay informed about: The Megapixel Race |
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External
Since: Nov 01, 2005
Posts: 329
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(Msg. 86) Posted: Tue Oct 31, 2006 2:13 am
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
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"acl" <achilleaslazarides RemoveThis @yahoo.co.uk> wrote in message
news:1162227053.157509@seven.kulnet.kuleuven.ac.be...
> Bart van der Wolf wrote:
SNIP
>> What several people apparently don't realize is that the f/number
>> is already a ratio between focal length and absolute aperture
>> diameter. Therefore the f/number by itself determines the
>> diffraction spot diameter.
>>
>
> Yes, but the angular resolution is determined by the diameter only
> (it is proportional to 1/D, with D the diameter).
Angular resolution yes, but the projection distance, and thus
projected diameter, is also incorporated in the f/number. It is a
constant regardless of focal length.
<http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm#>
gives another, slightly more in-depth (because they add the sensel
size), view on the interactions.
The *angular* resolution (important in Astronomy and Microscopy) view
on diffraction is explained in more detail here:
<http://micro.magnet.fsu.edu/primer/lightandcolor/diffractionhome.html>
The diffraction spot *diameter* size in photography, for 555nm (green
light),
is equal to 1.22 x 0.555 x 2 x 'f/number' = 1.3542 x 'f/number' (in
microns).
--
Bart
> So the radius of the min spot is f*this angle, with f the focal
> length; ie, proportional to f/D=aperture. This is what Paul Rubin
> was talking about.
> Take a look at equations 17 and 18 in
> http://www.pha.jhu.edu/~jlotz/aoptics/node2.html >> Stay informed about: The Megapixel Race |
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External
Since: Apr 05, 2006
Posts: 704
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(Msg. 87) Posted: Tue Oct 31, 2006 7:33 am
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
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David J. Littleboy wrote:
> "ASAAR" <caught DeleteThis @22.com> wrote:
> >
> > So the diffraction spot won't be smaller than the sensels used by
> > my P&S for any of its apertures, since its maximum aperture is only
> > slightly greater than f/4. But the diffraction limited spot size
> > can easily be smaller than the sensel size for APS-C and FF cameras
> > given a large enough lens aperture. But if my estimates for sensel
> > sizes is approximately correct, the limiting aperture for 8mp APS-C
> > cameras falls between f/4 and f/5.6, and the limiting aperture for
> > 12mp FF cameras falls between f/5.6 and f/8. Does this sound right?
>
> I think you need to redo your calculations. In real life, 5D images look
> _great_ at f/16, still pretty good at f/22, but noticeably soft at f/32.
>
> David J. Littleboy
> Tokyo, Japan
That sounds about right, on the 20D f/16 is still looking good but just
a bit softer then f/8. With the larger pixels on the 5D my f/16 would
be about the same as your f/22. At f/32 the 20D is getting very soft.
The diffraction spot has to be a fair bit larger then a pixel to have
much effect. When people give the diameter of the diffraction spot it
is all the way to the first zero, most of the energy is in a smaller
circle.
Scott >> Stay informed about: The Megapixel Race |
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External
Since: Aug 15, 2006
Posts: 48
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(Msg. 88) Posted: Tue Oct 31, 2006 8:11 am
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
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In article <4546a34c$0$324$e4fe514c@news.xs4all.nl>, Bart van der Wolf
says...
> The diffraction spot *diameter* size in photography, for 555nm (green
> light),
> is equal to 1.22 x 0.555 x 2 x 'f/number' = 1.3542 x 'f/number' (in
> microns).
Does this mean that a camera with 6 micrometer pixels (as most APS-C
DSLRs) is diffraction limited at something like F4.5 (6/1.35) ?
--
Alfred Molon
------------------------------
Olympus 50X0, 7070, 8080, E300, E330, E400 and E500 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
Olympus E330 resource - http://myolympus.org/E330/ >> Stay informed about: The Megapixel Race |
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External
Since: Aug 02, 2005
Posts: 3972
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(Msg. 89) Posted: Tue Oct 31, 2006 8:11 am
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
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On Tue, 31 Oct 2006 08:11:16 +0100, Alfred Molon wrote:
>> The diffraction spot *diameter* size in photography, for 555nm (green
>> light),
>> is equal to 1.22 x 0.555 x 2 x 'f/number' = 1.3542 x 'f/number' (in
>> microns).
>
> Does this mean that a camera with 6 micrometer pixels (as most APS-C
> DSLRs) is diffraction limited at something like F4.5 (6/1.35) ?
Someone recently posted a link (possibly in this thread) to a page
titled "Optimum Aperture - Format size and diffraction". It has one
table linking "Lens Aperture" to the "Diffraction Limited Spot Size
(microns)" and another table having three columns, "Format Size"
(film or sensor size), "Typical COF value (microns)" and "Limiting
Aperture for a sharp 8 x 10 print". According to this table, full
frame 35mm (36mm x 24mm) has a limiting aperture of f/22, APS-C
(22.5mm x 15mm) has a limiting aperture of f/16, and 1/1.8" (7.1mm x
5.3mm) and 1/2.5" (5.7mm x 4.3mm) reach their limits at f/5 and f/4,
respectively. Notice that these values relate the Circle of
Confusion needed for sharp 8" x 10" prints to the film or sensor
size, and isn't relating anything to film grain size or sensor pixel
size.
http://www.bobatkins.com/photography/technical/diffraction.html >> Stay informed about: The Megapixel Race |
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External
Since: Aug 26, 2005
Posts: 1150
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(Msg. 90) Posted: Tue Oct 31, 2006 11:56 am
Post subject: Re: The Megapixel Race [Login to view extended thread Info.]
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"ASAAR" <caught DeleteThis @22.com> wrote:
>
> So the diffraction spot won't be smaller than the sensels used by
> my P&S for any of its apertures, since its maximum aperture is only
> slightly greater than f/4. But the diffraction limited spot size
> can easily be smaller than the sensel size for APS-C and FF cameras
> given a large enough lens aperture. But if my estimates for sensel
> sizes is approximately correct, the limiting aperture for 8mp APS-C
> cameras falls between f/4 and f/5.6, and the limiting aperture for
> 12mp FF cameras falls between f/5.6 and f/8. Does this sound right?
I think you need to redo your calculations. In real life, 5D images look
_great_ at f/16, still pretty good at f/22, but noticeably soft at f/32.
David J. Littleboy
Tokyo, Japan >> Stay informed about: The Megapixel Race |
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