On 5 Nov 2009 02:02:28 GMT, Chris Malcolm <cam@holyrood.ed.ac.uk> wrote:
>
>You've got it back to front. Since diffraction increases as the lens
>is stopped because because of the change of proportion of lens area to
>lens circumference, the test works for all cases EXCEPT when the
>widest aperture is sharpest.
Go educate your useless **** of an ignorant moron troll self. Resolution
increases with objective optics diameter. IF those optics are of
diffraction limited quality.
Dudley Hanks wrote:
> I've heard a lot about how the cropped sensor cameras are defraction limited
> to around f/8 - f/11, so I thought I'd see what kind of an image my XSi puts
> out at a small aperture.
>
> I snapped on my 50mm f/1.8 lens and set it up to take a picture at f/22,
> with a shutter speed of 1 sec.
>
> How did it turn out?
The only way to know is to do a test in series. It looks soft to me.
Sometimes that's OK though, sometimes DOF is more important. This photo: http://www.flickr.com/photos/edgehill/4075980407
had DOF as a priority though I didn't exceed the diffraction limits and
the lens is near optimum wide open. The power lines in the upper left
are soft due to tilting the focus plane.
Dudley Hanks wrote:
> "Chris Malcolm" <cam@holyrood.ed.ac.uk> wrote in message
> news:7ldt5gF3cimtaU1@mid.individual.net...
>> Dudley Hanks <dhanks@blind-apertures.ca> wrote:
>>
>>> "David J Taylor"
>>> <david-taylor@blueyonder.not-this-bit.nor-this.co.uk.invalid> wrote in
>>> message news:t6aIm.1501$Ym4.551@text.news.virginmedia.com. ..
>>>> "Dudley Hanks" <> wrote in message
>>>> news:4U9Im.50459$Db2.29545@edtnps83...
>>>>> I've heard a lot about how the cropped sensor cameras are defraction
>>>>> limited to around f/8 - f/11, so I thought I'd see what kind of an
>>>>> image
>>>>> my XSi puts out at a small aperture.
>>>>>
>>>>> I snapped on my 50mm f/1.8 lens and set it up to take a picture at
>>>>> f/22,
>>>>> with a shutter speed of 1 sec.
>>>>>
>>>>> How did it turn out?
>>>>>
>>>>> http://www.snaps.blind-apertures.ca/...erPortrait.jpg
>>>>> (quick
>>>>> download)
>>>>>
>>>>> http://www.snaps.blind-apertures.ca/...raitWinter.jpg
>>>>> (full
>>>>> size)
>>>>>
>>>>> Take Care,
>>>>> Dudley
>>>> Difficult to say, Dudley. Yes, the image isn't "tack sharp" (a term I
>>>> loathe), so there could be some diffraction visible, but I'm also not
>>>> convinced that the subject didn't move within the 1 second exposure!
>>>>
>>>> Cheers,
>>>> David
>>> Thanks, David, I'll try it again with an inanimate object, or a faster
>>> shutter speed.
>>> I suppose, if the test is to be useful, I should also take an equivalent
>>> pic
>>> of the subject using a wider aperture so the two images can be compared.
>> The diffraction limit of aperture is usually taken to be the last
>> aperture in a decreasing series of sharper apertures, i.e., stopping
>> down further makes the image softer because of diffraction. But that's
>> not a fixed aperture, it depends on such things as the exact sensor
>> pixel size (or crop factor) not just the nominal "1.5", on the
>> resolution of the lens, and whether you're looking at the centre of
>> the image or the edges or some compromise between the two. Why
>> should it depend on those? Because the point at which an extra stop's
>> worth of diffraction softening becomes larger than how much other
>> kinds of lens aberration are being improved by stopping down obviously
>> will depend on the size of those other errors. In other words better
>> lenses will have larger sharpest apertures.
>>
>> I find for example on my Sony A350 that my general purpose zoom is
>> usually sharpest at f8, but at its soft extremes that becomes f11, and
>> my 50mm prime is sharpest at f5.6.
>>
>> This can only be established for your camera and each of your lenses
>> by taking a comparative series of shots while varying the aperture. On
>> zooms it may change with focal length.
>>
>> --
>> Chris Malcolm
>
> Thanks, Chris, that's good info to have.
>
> This is a pretty cheap lens, and I think its a bit soft to begin with.
The 50mm/F1.8II is a surprisingly good lens for the money. I've taken a
lot of excellent shots with mine, so please don't sell it short!
I've since 'upgraded' to a 50mm/F1.4, but it's not as much of an
improvement as you might expect from the price difference.
--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------
Better Info wrote:
> On 4 Nov 2009 17:49:36 GMT, Chris Malcolm <cam@holyrood.ed.ac.uk> wrote:
>
>> Dudley Hanks <dhanks@blind-apertures.ca> wrote:
>>
>>> "David J Taylor"
>>> <david-taylor@blueyonder.not-this-bit.nor-this.co.uk.invalid> wrote in
>>> message news:t6aIm.1501$Ym4.551@text.news.virginmedia.com. ..
>>>> "Dudley Hanks" <> wrote in message news:4U9Im.50459$Db2.29545@edtnps83...
>>>>> I've heard a lot about how the cropped sensor cameras are defraction
>>>>> limited to around f/8 - f/11, so I thought I'd see what kind of an image
>>>>> my XSi puts out at a small aperture.
>>>>>
>>>>> I snapped on my 50mm f/1.8 lens and set it up to take a picture at f/22,
>>>>> with a shutter speed of 1 sec.
>>>>>
>>>>> How did it turn out?
>>>>>
>>>>> http://www.snaps.blind-apertures.ca/...erPortrait.jpg (quick
>>>>> download)
>>>>>
>>>>> http://www.snaps.blind-apertures.ca/...raitWinter.jpg (full
>>>>> size)
>>>>>
>>>>> Take Care,
>>>>> Dudley
>>>> Difficult to say, Dudley. Yes, the image isn't "tack sharp" (a term I
>>>> loathe), so there could be some diffraction visible, but I'm also not
>>>> convinced that the subject didn't move within the 1 second exposure!
>>>>
>>>> Cheers,
>>>> David
>>> Thanks, David, I'll try it again with an inanimate object, or a faster
>>> shutter speed.
>>> I suppose, if the test is to be useful, I should also take an equivalent pic
>>> of the subject using a wider aperture so the two images can be compared.
>> The diffraction limit of aperture is usually taken to be the last
>> aperture in a decreasing series of sharper apertures, i.e., stopping
>> down further makes the image softer because of diffraction. But that's
>> not a fixed aperture, it depends on such things as the exact sensor
>> pixel size (or crop factor) not just the nominal "1.5", on the
>> resolution of the lens, and whether you're looking at the centre of
>> the image or the edges or some compromise between the two. Why
>> should it depend on those? Because the point at which an extra stop's
>> worth of diffraction softening becomes larger than how much other
>> kinds of lens aberration are being improved by stopping down obviously
>> will depend on the size of those other errors. In other words better
>> lenses will have larger sharpest apertures.
>>
>> I find for example on my Sony A350 that my general purpose zoom is
>> usually sharpest at f8, but at its soft extremes that becomes f11, and
>> my 50mm prime is sharpest at f5.6.
>>
>> This can only be established for your camera and each of your lenses
>> by taking a comparative series of shots while varying the aperture. On
>> zooms it may change with focal length.
>
> Your test won't work.
Please, get back to us when you grow a clue. Bye!
--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------
Dudley Hanks wrote:
> I've heard a lot about how the cropped sensor cameras are defraction limited
> to around f/8 - f/11, so I thought I'd see what kind of an image my XSi puts
> out at a small aperture.
>
> I snapped on my 50mm f/1.8 lens and set it up to take a picture at f/22,
> with a shutter speed of 1 sec.
>
> How did it turn out?
[...]
> http://www.snaps.blind-apertures.ca/...nter.jpg*(full
> size)
I'll go ****her than previous respondents: That photo, from a Canon
XSi at f/22, is obviously not diffraction limited.
The statements you'll hear of the diffraction limit assume everything
else it practically optimal: rock-steady subject, tripod mount,
perfect focus, and unless the claim is about a particular lens, they
mean a laudably sharp one.
Dudley Hanks wrote:
> "David J Taylor"
> <david-taylor@blueyonder.not-this-bit.nor-this.co.uk.invalid> wrote in
> message news:t6aIm.1501$Ym4.551@text.news.virginmedia.com. ..
>> "Dudley Hanks" <> wrote in message news:4U9Im.50459$Db2.29545@edtnps83...
>>> I've heard a lot about how the cropped sensor cameras are defraction
>>> limited to around f/8 - f/11, so I thought I'd see what kind of an image
>>> my XSi puts out at a small aperture.
>>>
>>> I snapped on my 50mm f/1.8 lens and set it up to take a picture at f/22,
>>> with a shutter speed of 1 sec.
>>>
>>> How did it turn out?
>>>
>>> http://www.snaps.blind-apertures.ca/...erPortrait.jpg (quick
>>> download)
>>>
>>> http://www.snaps.blind-apertures.ca/...raitWinter.jpg (full
>>> size)
>>>
>>> Take Care,
>>> Dudley
>> Difficult to say, Dudley. Yes, the image isn't "tack sharp" (a term I
>> loathe), so there could be some diffraction visible, but I'm also not
>> convinced that the subject didn't move within the 1 second exposure!
>>
> Thanks, David, I'll try it again with an inanimate object, or a faster
> shutter speed.
>
> I suppose, if the test is to be useful, I should also take an equivalent pic
> of the subject using a wider aperture so the two images can be compared.
If you are serious about being able to tell include a few ball bearings
on black velvet in the picture composition. Specular highlights are
about the easiest thing to see if an image is diffraction limited.
Or you could just use a pinhole over the lens and a verry long exposure.
"Bob Larter" <bobbylarter@gmail.com> wrote in message
news:4af2c78c$1@dnews.tpgi.com.au...
> Dudley Hanks wrote:
>> "Chris Malcolm" <cam@holyrood.ed.ac.uk> wrote in message
>> news:7ldt5gF3cimtaU1@mid.individual.net...
>>> Dudley Hanks <dhanks@blind-apertures.ca> wrote:
>>>
>>>> "David J Taylor"
>>>> <david-taylor@blueyonder.not-this-bit.nor-this.co.uk.invalid> wrote in
>>>> message news:t6aIm.1501$Ym4.551@text.news.virginmedia.com. ..
>>>>> "Dudley Hanks" <> wrote in message
>>>>> news:4U9Im.50459$Db2.29545@edtnps83...
>>>>>> I've heard a lot about how the cropped sensor cameras are defraction
>>>>>> limited to around f/8 - f/11, so I thought I'd see what kind of an
>>>>>> image
>>>>>> my XSi puts out at a small aperture.
>>>>>>
>>>>>> I snapped on my 50mm f/1.8 lens and set it up to take a picture at
>>>>>> f/22,
>>>>>> with a shutter speed of 1 sec.
>>>>>>
>>>>>> How did it turn out?
>>>>>>
>>>>>> http://www.snaps.blind-apertures.ca/...erPortrait.jpg
>>>>>> (quick
>>>>>> download)
>>>>>>
>>>>>> http://www.snaps.blind-apertures.ca/...raitWinter.jpg
>>>>>> (full
>>>>>> size)
>>>>>>
>>>>>> Take Care,
>>>>>> Dudley
>>>>> Difficult to say, Dudley. Yes, the image isn't "tack sharp" (a term I
>>>>> loathe), so there could be some diffraction visible, but I'm also not
>>>>> convinced that the subject didn't move within the 1 second exposure!
>>>>>
>>>>> Cheers,
>>>>> David
>>>> Thanks, David, I'll try it again with an inanimate object, or a faster
>>>> shutter speed.
>>>> I suppose, if the test is to be useful, I should also take an
>>>> equivalent pic
>>>> of the subject using a wider aperture so the two images can be
>>>> compared.
>>> The diffraction limit of aperture is usually taken to be the last
>>> aperture in a decreasing series of sharper apertures, i.e., stopping
>>> down further makes the image softer because of diffraction. But that's
>>> not a fixed aperture, it depends on such things as the exact sensor
>>> pixel size (or crop factor) not just the nominal "1.5", on the
>>> resolution of the lens, and whether you're looking at the centre of
>>> the image or the edges or some compromise between the two. Why
>>> should it depend on those? Because the point at which an extra stop's
>>> worth of diffraction softening becomes larger than how much other
>>> kinds of lens aberration are being improved by stopping down obviously
>>> will depend on the size of those other errors. In other words better
>>> lenses will have larger sharpest apertures.
>>>
>>> I find for example on my Sony A350 that my general purpose zoom is
>>> usually sharpest at f8, but at its soft extremes that becomes f11, and
>>> my 50mm prime is sharpest at f5.6.
>>>
>>> This can only be established for your camera and each of your lenses
>>> by taking a comparative series of shots while varying the aperture. On
>>> zooms it may change with focal length.
>>>
>>> --
>>> Chris Malcolm
>>
>> Thanks, Chris, that's good info to have.
>>
>> This is a pretty cheap lens, and I think its a bit soft to begin with.
>
> The 50mm/F1.8II is a surprisingly good lens for the money. I've taken a
> lot of excellent shots with mine, so please don't sell it short!
> I've since 'upgraded' to a 50mm/F1.4, but it's not as much of an
> improvement as you might expect from the price difference.
Originally, I bought it for my Canon A2, but didn't use it a lot. I used it
a bit for blurred background shots of the kids, flowers, etc.
However, with the crop factor of the XSi, it's now a great portrait lens,
and it still has a fairly respectable aperture when I add in my 2x
converter, giving me a (35mm equiv) f/3.5 160mm lens.
I'm finding myself falling back on it a lot these days.
On Thu, 05 Nov 2009 23:39:40 +1000, Bob Larter <bobbylarter@gmail.com>
wrote in <4af2c78c$1@dnews.tpgi.com.au>:
>The 50mm/F1.8II is a surprisingly good lens for the money. I've taken a
>lot of excellent shots with mine, so please don't sell it short!
>I've since 'upgraded' to a 50mm/F1.4, but it's not as much of an
>improvement as you might expect from the price difference.
What you get for the money with the f/1.4 over the f/1.8 is speed,
not IQ.
--
Best regards,
John
Buying a dSLR doesn't make you a photographer,
it makes you a dSLR owner.
"The single most important component of a camera
is the twelve inches behind it." -Ansel Adams
On Thu, 05 Nov 2009 23:40:44 +1000, Bob Larter <bobbylarter@gmail.com>
wrote:
>Better Info wrote:
>> On 4 Nov 2009 17:49:36 GMT, Chris Malcolm <cam@holyrood.ed.ac.uk> wrote:
>>
>>> Dudley Hanks <dhanks@blind-apertures.ca> wrote:
>>>
>>>> "David J Taylor"
>>>> <david-taylor@blueyonder.not-this-bit.nor-this.co.uk.invalid> wrote in
>>>> message news:t6aIm.1501$Ym4.551@text.news.virginmedia.com. ..
>>>>> "Dudley Hanks" <> wrote in message news:4U9Im.50459$Db2.29545@edtnps83...
>>>>>> I've heard a lot about how the cropped sensor cameras are defraction
>>>>>> limited to around f/8 - f/11, so I thought I'd see what kind of an image
>>>>>> my XSi puts out at a small aperture.
>>>>>>
>>>>>> I snapped on my 50mm f/1.8 lens and set it up to take a picture at f/22,
>>>>>> with a shutter speed of 1 sec.
>>>>>>
>>>>>> How did it turn out?
>>>>>>
>>>>>> http://www.snaps.blind-apertures.ca/...erPortrait.jpg (quick
>>>>>> download)
>>>>>>
>>>>>> http://www.snaps.blind-apertures.ca/...raitWinter.jpg (full
>>>>>> size)
>>>>>>
>>>>>> Take Care,
>>>>>> Dudley
>>>>> Difficult to say, Dudley. Yes, the image isn't "tack sharp" (a term I
>>>>> loathe), so there could be some diffraction visible, but I'm also not
>>>>> convinced that the subject didn't move within the 1 second exposure!
>>>>>
>>>>> Cheers,
>>>>> David
>>>> Thanks, David, I'll try it again with an inanimate object, or a faster
>>>> shutter speed.
>>>> I suppose, if the test is to be useful, I should also take an equivalent pic
>>>> of the subject using a wider aperture so the two images can be compared.
>>> The diffraction limit of aperture is usually taken to be the last
>>> aperture in a decreasing series of sharper apertures, i.e., stopping
>>> down further makes the image softer because of diffraction. But that's
>>> not a fixed aperture, it depends on such things as the exact sensor
>>> pixel size (or crop factor) not just the nominal "1.5", on the
>>> resolution of the lens, and whether you're looking at the centre of
>>> the image or the edges or some compromise between the two. Why
>>> should it depend on those? Because the point at which an extra stop's
>>> worth of diffraction softening becomes larger than how much other
>>> kinds of lens aberration are being improved by stopping down obviously
>>> will depend on the size of those other errors. In other words better
>>> lenses will have larger sharpest apertures.
>>>
>>> I find for example on my Sony A350 that my general purpose zoom is
>>> usually sharpest at f8, but at its soft extremes that becomes f11, and
>>> my 50mm prime is sharpest at f5.6.
>>>
>>> This can only be established for your camera and each of your lenses
>>> by taking a comparative series of shots while varying the aperture. On
>>> zooms it may change with focal length.
>>
>> Your test won't work.
>
>Please, get back to us when you grow a clue. Bye!
Bob Larter's legal name: Lionel Lauer
Home news-group, an actual group in the "troll-tracker" hierarchy:
alt.kook.lionel-lauer (established on, or before, 2004)
Registered Description: "the 'owner of several troll domains' needs a group where he'll stay on topic."
On Fri, 06 Nov 2009 11:56:53 +1000, Bob Larter <bobbylarter@gmail.com>
wrote:
>John Navas wrote:
>> On Thu, 05 Nov 2009 23:39:40 +1000, Bob Larter <bobbylarter@gmail.com>
>> wrote in <4af2c78c$1@dnews.tpgi.com.au>:
>>
>>> The 50mm/F1.8II is a surprisingly good lens for the money. I've taken a
>>> lot of excellent shots with mine, so please don't sell it short!
>>> I've since 'upgraded' to a 50mm/F1.4, but it's not as much of an
>>> improvement as you might expect from the price difference.
>>
>> What you get for the money with the f/1.4 over the f/1.8 is speed,
>> not IQ.
>
>The f1.4 also has more aperture blades, so the bokeh is a bit nicer as well.
Post-processing plugins with depth-map masks afford an infinite number of
aperture blades for bokeh, as well as even emulating catadioptric lens
systems no matter what camera took the image, and more.
Re: small aperture test 
Linear Mode
