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That bokeh doesn't look like $1800 worth

 
 
Bruce
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      08-15-2011
Chris Malcolm <(E-Mail Removed)> wrote:
>Part of the problem is the effective aperture of the AF sensors. If,
>as is often the case, that's around f5.6, a properly calibrated AF
>system with no front or back focus will focus the lens perfectly at
>f5.6. Which isn't necessarily where sharpest f1.4 focus is. The
>problem with spherical aberration for example is that it most
>definitely is not.



While it is true that many lenses display focus shift, in other words
their plane of focus differs for differing apertures, I don't think it
is true that AF sensors are in any way optimised for f/5.6. I would
like to see a reference for that if you have one, because this is the
first time I have ever seen such a claim.

<snip>

>Plus with such extremely shallow DoF, if you're standing on your feet
>and hand holding the camera you might easily sway backwards or
>forwards a centimetre as you press the shutter. As might the person
>being photographed. In fact doing that slight sway deliberately is a
>way of coping with an AF system which has one centimetre of front or
>back focus with your portrait lens at f1.4.



My 'classic' portraits are all shot with the camera mounted on a
tripod. I always watch the sitter carefully to see if there is any
movement. If so, I refocus and shoot again. I use a remote release
and concentrate only on the sitter.


>I have the same annoying problem of retinal tearing and floaters in my
>aging eyes.



It's not pleasant. The cure, such as it is, is even more unpleasant.
I am not well disposed to having another session of uncomfortable and
decidedly painful laser treatment, so I have to live with it. It is
unfortunate that my non-dominant left eye is unaffected.


>These days I'd find focusing an old manual focus film SLR
>much harder, perhaps even impossible. But having an easily magnified
>and pannable live sensor view on the LCD makes accurate manual
>focusing easy enough for my old eyes it's not only quick but fun.



Which SLR is that?


>I suspect that many DSLRs which have had a heavy knock which luckily
>caused no damage in fact had their AF knocked slightly off. But most
>habitual AF users never notice.



The vast majority of DSLR users never notice anything.

 
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Chris Malcolm
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      08-17-2011
In rec.photo.digital Bruce <(E-Mail Removed)> wrote:
> Chris Malcolm <(E-Mail Removed)> wrote:
>>In rec.photo.digital Bruce <(E-Mail Removed)> wrote:


>>> The fact
>>> is, we are discussing the performance of an expensive specialist
>>> portrait lens. It is a lens that should reasonably be expected to
>>> offer reasonably smooth bokeh, but doesn't.

>>
>>> Whether the lens costs $1100 or $1800 is almost moot. Compared to the
>>> excellent Samyang/Rokinon product, they are both very expensive.

>>
>>Is not the good bokeh problem due to the awkward fact that a perfect
>>lens wih perfect wide open sharp focus would have poor bokeh? Because
>>out of focus highlights for example would turn into sharp edged
>>uniform discs, the "shower of coins"?
>>
>>So you can't have good smooth bokeh without compromising the wide open
>>sharpness of the lens.
>>
>>Which back in the old days of spherical lenses with spherical
>>aberration was a natural consequence of the differential focus of
>>spherical aberration.


> With respect, that's complete nonsense. A "perfect" lens for shooting
> people would not have harsh bokeh.


I agree. I was pointing out the incompatibility of achieving the best
possible portraiture bokeh and the best possible sharpness. Perfection
in one can only be achieved at the cost of imperfection in the
other. So the best portrait lens has to be a compromise.

> Some people, mainly those who approach photography from a purely
> theoretical point of view, worship MTF, believing that the higher the
> MTF, the closer that lens is to "perfection". Of course lenses with
> higher MTF figures tend to produce images that are apparently sharper,
> and more sharpness is always better, isn't it? Well, isn't it?


In terms of sharpness, yes. In terms of bokeh, since that has thereby
worsened, no.

> Unfortunately, more sharpness tend produces more undesirable
> artefacts. Perhaps they are acceptable or even not noticeable if you
> are shooting objects, but they are certainly not acceptable when you
> are shooting people. Harsh bokeh is a prime example. A lens that
> reproduces objects and documents in near-perfect detail often makes
> for a very unpleasant rendering of detail in a portrait.


> However, it *is* possible to have your cake and eat it. You can buy a
> portrait lens that is extremely sharp but still produces smooth bokeh
> - most professional portrait shooters will know of at least one. I
> can think of at least half a dozen.


> So please keep your "perfect" lenses for shooting things, rather than
> people. And please realise that aiming for highest MTF is not the
> route to perfection, unless you are a photographic sociopath who only
> shoots objects.


You are making the same point as I was, except that I see nothing
necessarily wrong with the character of photographers who might prefer
different trade offs in their lens designs, perhaps because they have
different preferences of subjects and styles. Multi-factorial
perfection will always be to some extent a question of taste and
purposes.

--
Chris Malcolm

 
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John Turco
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      08-18-2011
tony cooper wrote:
>
> > On Thu, 11 Aug 2011 05:46:21 -0700 (PDT), RichA <(E-Mail Removed)>
> > wrote:
> >
> >> On Aug 11, 7:58 am, PeterN <(E-Mail Removed)> wrote:
> >>
> >> > RichA wrote:
> >> >
> >> > Scoundrel.
> >>
> >> Your lack of a proper response is telling us that you have no reply.

>
>
> > The response fits your actions to a TEE.

>
> I would write "to a t", but the "tee" version is common. Like most
> phrases, the origin is not really known but it is probably a reference
> based on "to a tittle".
>
> A "tittle" is a tiny amount best known in the Biblical phrase "jot or
> tittle". (Matthew 5:1 "For verily I say unto you, Till heaven and
> earth pass, one jot or one tittle shall in no wise pass from the law,
> till all be fulfilled."
>
> The "tee" version could not be a reference to a golf tee because the
> phrase is recorded as first appearing in 1693.



Y.A. Tittle was a notable New York Giants quarterback of the early
1960's. The Chicago Bears really "teed" off on him and intercepted
five of his passes, during the 1963 NFL championship game (Chi. 14,
NY 10).

Then, again, the Bears were formerly famous for introducing the "T"
offensive formation. It helped them demolish the Washington Redskins
(73-0), in winning the 1940 NFL tittle (oops...I'd meant "title").

--
Cordially,
John Turco <(E-Mail Removed)>

Marie's Musings <http://fairiesandtails.blogspot.com>
 
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John Turco
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      08-18-2011
tony cooper wrote:
>
> > On Fri, 12 Aug 2011 21:27:11 -0400, PeterN
> > <(E-Mail Removed)> wrote:
> >
> >> On 8/12/2011 9:00 PM, Savageduck wrote:

> >
> > <sniP>
> >
> >
> >> I suspect we were all taken in by Rich's initial implication of the
> >> newer and more costly "G" lens.
> >> I believe that Rich draws hasty, and often erroneous conclusions by
> >> misreading, or only seeing what he wants to see. In this case Rich was
> >> hoisted by his own petard, and here I am going to give him the benefit
> >> of doubt, by not reading the dpreview forum subject line correctly. Then
> >> taking the leap to assume that the shots were made with the new lens,
> >> giving him another gripe target.
> >>
> >> However there is still the smell of a deliberate manipulation by Rich,
> >> as he only implied that the $1800 "G" lens was under discussion by the
> >> remark in his OP subject line;

> >
> > Was your second paragraph a deliberate pun?
> > IIRC the expression :hoisted on his own petard" is a derivation of the
> > French expression that translates: "smell his own farts."

>
> That's funny.
>
> Actually, it's not "on", either. It's "by" or "with". And, it's
> "hoist". A petard is a small bomb. If you are holding the bomb when
> it blows up, you are hoist by your own petard...blown into the air.
>
> For some reason, many people think a petard is a spear or something
> like that. 'Tis not.
>
> In Hamlet, though, Willy S. wrote: "For tis the sport to have the
> enginer Hoist with his owne petar".
>
> Willy didn't have spell-check.



In recent years, here on <news:rec.photo.digital>, I distinctly recall
this same, ridiculous "petard" confubulation, manifesting itself. If
I'm not mistaken, the culprits (e.g., Tony Cooper) were identical,
then as now.

I'd wrongly assumed that you "gentlemen" had outgrown such sophomoric
behavior, long ago; what have >you< to say for yourself, Antoine?

--
Cordially,
John Turco <(E-Mail Removed)>

Marie's Musings <http://fairiesandtails.blogspot.com>
 
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Chris Malcolm
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      08-19-2011
In rec.photo.digital Bruce <(E-Mail Removed)> wrote:
> Chris Malcolm <(E-Mail Removed)> wrote:


>>Part of the problem is the effective aperture of the AF sensors. If,
>>as is often the case, that's around f5.6, a properly calibrated AF
>>system with no front or back focus will focus the lens perfectly at
>>f5.6. Which isn't necessarily where sharpest f1.4 focus is. The
>>problem with spherical aberration for example is that it most
>>definitely is not.


> While it is true that many lenses display focus shift, in other words
> their plane of focus differs for differing apertures, I don't think it
> is true that AF sensors are in any way optimised for f/5.6.


They're not. But they are sort of by accident. The way DSLR autofocus
sensors work is to have two sensors spaced equally on each side of the
lens centre. The wider apart the better for accurate focus. But they
shouldn't be so far apart that a small aperture lens doesn't reach
that wide apart. Because if so autofocus won't work on that lens. So
because many zooms stop down to max apertures of f5.6 or even f6.3 at
the long end the AF sensors often sit at around an effective aperture
of f6ish.

That's why AF struggles with zooms which stop down to f6.3 max at the
long end, and why AF won't work with lenses of max (or fixed) aperture
of f8, such as catadioptric 500mm and longer lenses. (With the
exception of the rather clever Minolta/Sony 500mm cat and AF design)

An effectively f6ish AF sensor set will cause focus errors with
spherical lens designs such as the very common old fashioned design
but rather good "nifty fifty" 50mm f1.4 lenses, because spherical
aberration means that there is aperture related focus drift.

So the more expensive DSLRS will often have extra AF sensors spaced
apart at around an effective aperture of f2ish which are only used
when lenses of wider aperture are being used at wider apertures.

<snip>

>>These days I'd find focusing an old manual focus film SLR
>>much harder, perhaps even impossible. But having an easily magnified
>>and pannable live sensor view on the LCD makes accurate manual
>>focusing easy enough for my old eyes it's not only quick but fun.


> Which SLR is that?


Sony Alpha 550. I think most recent Sony Alphas have that feature. I
have found it so surprisingly useful that I've added it to my list of
essential features in my next camera.

--
Chris Malcolm
 
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Chris Malcolm
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      08-20-2011
In rec.photo.digital Paul Furman <(E-Mail Removed)> wrote:
> Chris Malcolm wrote:
>> In rec.photo.digital Paul Furman<(E-Mail Removed)> wrote:
>>> PeterN wrote:
>>>> On 8/10/2011 6:46 AM, Bruce wrote:
>>>>>
>>>>> http://www.flickr.com/groups/afs85mmf14g/
>>>>> http://www.flickr.com/groups/1437990@N23/
>>>>>
>>>>
>>>> And what was the f stop for those images.

>>
>>> You can generally get exif for each from the [Actions v] menu, next to
>>> [favorite] above left of the image. Inconvenient to check a bunch though.

>>
>> And not much point anyway when the lens in question is a fully manual
>> lens with no electronics which can't tell the camera its aperture.


> You can with a Nikon D200, D300, D700, etc. For example:
> http://www.flickr.com/photos/janeyka...36030540/meta/
> http://www.flickr.com/photos/fab64/6036929578/meta/


> Exif is above the photo, in the [Actions] menu... but it's inconvenient...


The fully manual Samyang can't tell the camera what its aperture has
been set to, so the camera will report nonsense, e.g. an aperture of
f1 or f0. That can mess up the camera's autoexposure, in some cameras
more than others, depending on how co-operative they are with alien
manual lenses.

Some folk who bought the fully manual Samyang had it modded with the
addition of a chip so the lens *type* can be reported to the
camera. And Samyang have produced a later version of the lens which
does simply report a lens type, because with some cameras that allows
you to get a form of semi-autoexposure from an otherwise
unco-operative camera. And of course some people do edit the EXIF data
to put in the aperture. If they can remember it properly and don't
make a typo.

A few of my own photographs with it report the lens and aperture
properly in the EXIF data because I edited it to do that. But the
method was inconvenient and clunky and I soon gave up doing it. I also
sometimes forget to note the apertures, especially when working at
speed such as photographing animals. So sometimes I guess -- and
possibly guess wrong. And often simply don't report the aperture in
any way.

An editing typo seems to have happened in the first case you report
above, since the EXIF data reports f2.5, an intermediate aperture
which the lens doesn't do.

So you do have to regard the EXIF data of the Samyang -- if any is
supplied -- with a little suspicion.

--
Chris Malcolm
 
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PeterN
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      08-20-2011
On 8/20/2011 4:42 AM, Chris Malcolm wrote:
> In rec.photo.digital Paul Furman<(E-Mail Removed)> wrote:
>> Chris Malcolm wrote:
>>> In rec.photo.digital Paul Furman<(E-Mail Removed)> wrote:
>>>> PeterN wrote:
>>>>> On 8/10/2011 6:46 AM, Bruce wrote:
>>>>>>
>>>>>> http://www.flickr.com/groups/afs85mmf14g/
>>>>>> http://www.flickr.com/groups/1437990@N23/
>>>>>>
>>>>>
>>>>> And what was the f stop for those images.
>>>
>>>> You can generally get exif for each from the [Actions v] menu, next to
>>>> [favorite] above left of the image. Inconvenient to check a bunch though.
>>>
>>> And not much point anyway when the lens in question is a fully manual
>>> lens with no electronics which can't tell the camera its aperture.

>
>> You can with a Nikon D200, D300, D700, etc. For example:
>> http://www.flickr.com/photos/janeyka...36030540/meta/
>> http://www.flickr.com/photos/fab64/6036929578/meta/

>
>> Exif is above the photo, in the [Actions] menu... but it's inconvenient...

>
> The fully manual Samyang can't tell the camera what its aperture has
> been set to, so the camera will report nonsense, e.g. an aperture of
> f1 or f0. That can mess up the camera's autoexposure, in some cameras
> more than others, depending on how co-operative they are with alien
> manual lenses.
>
> Some folk who bought the fully manual Samyang had it modded with the
> addition of a chip so the lens *type* can be reported to the
> camera. And Samyang have produced a later version of the lens which
> does simply report a lens type, because with some cameras that allows
> you to get a form of semi-autoexposure from an otherwise
> unco-operative camera. And of course some people do edit the EXIF data
> to put in the aperture. If they can remember it properly and don't
> make a typo.
>
> A few of my own photographs with it report the lens and aperture
> properly in the EXIF data because I edited it to do that. But the
> method was inconvenient and clunky and I soon gave up doing it. I also
> sometimes forget to note the apertures, especially when working at
> speed such as photographing animals. So sometimes I guess -- and
> possibly guess wrong. And often simply don't report the aperture in
> any way.
>
> An editing typo seems to have happened in the first case you report
> above, since the EXIF data reports f2.5, an intermediate aperture
> which the lens doesn't do.
>
> So you do have to regard the EXIF data of the Samyang -- if any is
> supplied -- with a little suspicion.
>


My D300 allows me to st the information in camera.

--
Peter
 
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PeterN
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      08-26-2011
On 8/26/2011 2:07 AM, Paul Furman wrote:
> PeterN wrote:
>> On 8/20/2011 4:42 AM, Chris Malcolm wrote:
>>> In rec.photo.digital Paul Furman<(E-Mail Removed)> wrote:
>>>> Chris Malcolm wrote:
>>>>> In rec.photo.digital Paul Furman<(E-Mail Removed)> wrote:
>>>>>> PeterN wrote:
>>>>>>> On 8/10/2011 6:46 AM, Bruce wrote:
>>>>>>>>
>>>>>>>> http://www.flickr.com/groups/afs85mmf14g/
>>>>>>>> http://www.flickr.com/groups/1437990@N23/
>>>>>>>>
>>>>>>>
>>>>>>> And what was the f stop for those images.
>>>>>
>>>>>> You can generally get exif for each from the [Actions v] menu,
>>>>>> next to
>>>>>> [favorite] above left of the image. Inconvenient to check a bunch
>>>>>> though.
>>>>>
>>>>> And not much point anyway when the lens in question is a fully manual
>>>>> lens with no electronics which can't tell the camera its aperture.
>>>
>>>> You can with a Nikon D200, D300, D700, etc. For example:
>>>> http://www.flickr.com/photos/janeyka...36030540/meta/
>>>> http://www.flickr.com/photos/fab64/6036929578/meta/
>>>
>>>> Exif is above the photo, in the [Actions] menu... but it's
>>>> inconvenient...
>>>
>>> The fully manual Samyang can't tell the camera what its aperture has
>>> been set to, so the camera will report nonsense, e.g. an aperture of
>>> f1 or f0. That can mess up the camera's autoexposure, in some cameras
>>> more than others, depending on how co-operative they are with alien
>>> manual lenses.
>>>
>>> Some folk who bought the fully manual Samyang had it modded with the
>>> addition of a chip so the lens *type* can be reported to the
>>> camera. And Samyang have produced a later version of the lens which
>>> does simply report a lens type, because with some cameras that allows
>>> you to get a form of semi-autoexposure from an otherwise
>>> unco-operative camera. And of course some people do edit the EXIF data
>>> to put in the aperture. If they can remember it properly and don't
>>> make a typo.
>>>
>>> A few of my own photographs with it report the lens and aperture
>>> properly in the EXIF data because I edited it to do that. But the
>>> method was inconvenient and clunky and I soon gave up doing it. I also
>>> sometimes forget to note the apertures, especially when working at
>>> speed such as photographing animals. So sometimes I guess -- and
>>> possibly guess wrong. And often simply don't report the aperture in
>>> any way.
>>>
>>> An editing typo seems to have happened in the first case you report
>>> above, since the EXIF data reports f2.5, an intermediate aperture
>>> which the lens doesn't do.
>>>
>>> So you do have to regard the EXIF data of the Samyang -- if any is
>>> supplied -- with a little suspicion.
>>>

>>
>> My D300 allows me to st the information in camera.

>
> The Nikon mount on more advanced models uses a mechanical tab to relay
> where the aperture ring is turned to, for compatibility with old lenses
> that lack electric contacts. You have to enter the max aperture so it
> knows where it's starting. The f/2.5 reading is suspicious. That might
> mean they had it set up for another lens or it was set to an
> intermediate aperture... I'm not sure.
>


It might have been set wrong. I simply find that feature convenient. My
EXIF date gets interesting when I use a teleconverter and/or extension
tubes on my old 200mm micro. While the EXIF data will be off, there is
little effect on actual exposure.

--
Peter
 
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