Digital BW, The Print

on 9/7/2002 1:33 AM, DigitalBlackandWhiteThePrint@yahoogroups.com at
DigitalBlackandWhiteThePrint@yahoogroups.com wrote:

> Message: 13
> Date: Fri, 06 Sep 2002 23:13:21 -0700
> From: Robert Morrison <rmorrison@...>
> Subject: Re: Shooting digital vs. film
> 
> On 9/6/02 8:06 PM, "Austin Franklin" <darkroom@...> wrote:
> 
>> Jerry,
>> 
>>> Good God Austin, who cares what an out of focus area looks like?
> 
> Oh my God, Jerry, you have committed the unthinkable utterance...bokeh
> rules!  If you still have any leica or contax lenses you should give them to
> charity (me) to do penitence!
> 
> :-)
> 
> Robert


Pure speculation here:  I think that the bokeh is not a property "designed"
into these lenses, but rather a function of the distance of the lens
position to the film plane.  When a lens is mounted at it's optimal distance
(the focal length is it not?), the lens can be made with the minimal amount
of glass.  An SLR throws a mirror in the way of the lens mounting position.
The lenses have to be designed to project the image to the film as if the
lens were mounted closer than it actually is.  This makes the lenses larger,
more complex, more expensive, and poor bokeh.

So Leitz lenses made for the leica SLR will not have the same performance as
the same focal lengths made for the rangefinder bodies. Once the focal
length discussed is longer than the distance from the film to the front of
the mirror, the design for all camera types can be the same for that lens.
 
-Bruce

Visit my website at:
http://home.earthlink.net/~smthopr

Hi Bruce,

> Pure speculation here:  I think that the bokeh is not a property
> "designed"
> into these lenses, but rather a function of the distance of the lens
> position to the film plane.

Nope.  It's intentional in the cases of Leica and Zeiss.  This paper will
show you what the key elements of the property are, and how they are
derived:

http://www.darkroom.com/MiscDocs/bokeh.pdf

Austin

on 9/7/2002 11:20 AM, DigitalBlackandWhiteThePrint@yahoogroups.com at
DigitalBlackandWhiteThePrint@yahoogroups.com wrote:

> Message: 10
> Date: Sat, 7 Sep 2002 13:17:10 -0400
> From: "Austin Franklin" <darkroom@...>
> Subject: RE: Re: bokeh :was Shooting digital vs. film
> 
> Hi Bruce,
> 
>> Pure speculation here:  I think that the bokeh is not a property
>> "designed"
>> into these lenses, but rather a function of the distance of the lens
>> position to the film plane.
> 
> Nope.  It's intentional in the cases of Leica and Zeiss.  This paper will
> show you what the key elements of the property are, and how they are
> derived:
> 
> http://www.darkroom.com/MiscDocs/bokeh.pdf
> 
> Austin

Thanks for the link. An interesting article.  I might still suggest that is
is possible that it is still easier to design or obtain "good" bokeh in a
lens that does not have to project back from in front of a viewfinder
mirror.  I base this thesis from motion picture lenses I've owned (all
ziess) that performed quite differently from each other.  The f-2.0 lenses
were small and could mount close to the film, the f-1.4 lenses could not be
placed so far back or they would hit the mirror.  The f1.4 lenses were much
more modern in design, yet had inferior bokeh, and general performance. This
may also have been due to the wide maximum aperture and the triangle shaped
iris (I learned this from the article!).

Many Cinematographers used to love a set of Cooke lenses, and said they had
a much better look than the ziess lenses.  They may have had great bokeh,
but they weren't sharp on the object that was supposed to be in focus!  And
lens flare was awful.  The new Cookes now have performance much more in line
with the new ziess lenses.

After watching many lens tests I will say that most Cinematographers pick
the lenses that look the sharpest where they are focused and ignore the
bokeh or out of focus areas.

The exception to this is anamorphic lenses used for wide screen movies.
They have ovals of confusion in the out of focus areas which can look ugly
on movie stars faces in close-ups.  Panavision used to build a "bokeh
correction element" into these anamorphic lenses, but they reduced the
overall sharpness of the lens.  To my knowledge, the newest anamorphic
lenses do not use these correction elements. So now you will never watch a
movie the same way again, you'll be looking for the bokeh, as some still
prefer the old lenses.

An interesting, yet a little off topic discussion. Thanks Austin
 
-Bruce

Visit my website at:
http://home.earthlink.net/~smthopr

Hi Bruce,

> Thanks for the link. An interesting article.

My pleasure.

> I might still
> suggest that is
> is possible that it is still easier to design or obtain "good" bokeh in a
> lens that does not have to project back from in front of a viewfinder
> mirror.

You might very well be right, I have no idea...  I've designed very little
optical stuff.  I'll pose that to Harold (the author of the article), as he
and I have discussed this issue at great lengths.

Regards,

Austin

Bruce writes:

> The exception to this is anamorphic lenses used
> for wide screen movies.  They have ovals of confusion
> in the out of focus areas which can look ugly
> on movie stars faces in close-ups.

Would an oval aperture (oriented 90 degrees to the oval of confusion)
correct this?

> So now you will never watch a movie the same way
> again, you'll be looking for the bokeh, as some still
> prefer the old lenses.

I want to know why the entire frame changes shape when focus is pulled from
a distant background to a near foreground.  You can see the whole image
bounce, if you look for it (once you notice it, it's hard to ignore).