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Re: [OM] Bokeh, shmokeh [was Heliar (Was: 50mm 1.8 (Re: Hoarding & Varim

Subject: Re: [OM] Bokeh, shmokeh [was Heliar (Was: 50mm 1.8 (Re: Hoarding & Varimagni))]
From: "Carlos J. Santisteban" <zuiko21@xxxxxxxxx>
Date: Mon, 31 Jan 2011 09:51:49 +0100
Hi Moose, Mike and all,

From: Moose <olymoose@xxxxxxxxx>
>To illustrate, here are simulated samples of the far ends small source
highlight bokeh.
><http://www.moosemystic.net/Gallery/tech/Lenses/Misc/Bokeh_Simulation.htm>
>
>ULeft = really bad. If you don't think this is realistic, look at the top
image here.
<http://www.moosemystic.net/Gallery/tech/Lenses/Misc/5018bokeh.htm>

There are worse examples out there... Nikkor 50/1.8, for instance.

>LLeft = not so bad, but still annoys me. If you look at the overhead lights
on the left of "Cowboy Passenger", a couple
>brightish and one below them quite dim, you will see the same sort of
slightly darker center, surrounded by a bright
>halo.

But as mentioined in an earlier post, it could be the sharpening for web
presentation.

>URight = Pretty perfect, a nice airy disk, bright in the middle and gently
feathering off into invisibility. This is a
>good example, but comes at the price of softness in the focal plane.

Not necessarily. AFAIK, the Airy disk is the actual rendering of a point
lightsource by a "perfect" optical system. But I agree that sometimes a
sharp focal plane is achieved via overcorrecting the spherical aberration,
leading to the edgy bokeh of the ULeft sample.

>This is pretty darn good bokeh for a highly
>corrected lens that's very sharp in the focal plane.
><http://www.moosemystic.net/Gallery/tech/Lenses/SIMA/pages/27__0116.htm>

Well, a 105mm at such close distance, even at f/4 blurs the background a
lot, which may hide some edginess...

>Nope, I don't know of a 50 mm with great bokeh.

Not every 50mm is a double-Gauss formula ;-) Did you see any samples with
the CV Skopar 50/2.5?

<http://www.flickr.com/photos/zuiko21/4874932557/sizes/l/>
<http://www.flickr.com/photos/zuiko21/4874935297/sizes/l/>
<http://www.flickr.com/photos/zuiko21/4874876963/sizes/l/>
<http://www.flickr.com/photos/zuiko21/4874889045/sizes/l/>
<http://www.flickr.com/photos/zuiko21/4875543028/sizes/l/>
<http://www.flickr.com/photos/zuiko21/4875498024/sizes/l/>
<http://www.flickr.com/photos/zuiko21/4875503124/sizes/l/>
<http://www.flickr.com/photos/zuiko21/4875499648/sizes/l/>
<http://www.flickr.com/photos/zuiko21/4874915003/sizes/l/>

And about foreground bokeh:

<http://www.flickr.com/photos/zuiko21/4874921027/sizes/l/>

>Guess I need to start a roll of film,

Yes, you should :-)

>file off the back of the CZJ

I've got no 5D, but the Contax RTS, with its large mirror (it has a gorgeous
vierfinder)
>Tessar or just use its center on the 300D as a start.

Tessars show lower performance than most double-Gauss but have a very nice
rendering. I did a photoshoot with a (modern) Zeiss 45/2.8 pancake on my old
300D, and it came out fine -- despite some focusing problems. But that pics
are buried into one of the harddisks "floating" at home...

From: usher99@xxxxxxx
>I think it is probably
>correct that it is easier to design lenses with smoother bokeh in
>larger formats.

Well, you're right in that LF has less DOF than smaller formats, thus making
easier to blur *more*, but not necessarily *better*^.

>Bokeh in some respects can be a zero sum game as if the
>foreground is improved the background may suffer

Yes, I'm afraid it's a typical design consecuence... anyway, I usually
dislike blurred foregrounds, so not an issua to me -- provided the
"background bokeh" is nice. Thanks for the link!

>As Nasse and Moose both state the nature of the bokeh is complicated in
>any given lens and can depend not only on the relative
>foreground/subject/ background distances but focusing distance as well
>as aperture of course.

And aberration correction...

Cheers,
-- 
Carlos J. Santisteban Salinas
IES Turaniana (Roquetas de Mar, Almeria)
<http://cjss.sytes.net/>
-- 
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