On 8/10/2015 8:19 AM, Sawyer, Edward wrote:
Let me be more specific. The subject intentionally refers to two qualities. They tend to be found in the same lenses,
may be the result of the same optical qualities, but are distinct to describe:
1. To me, great bokeh is most easily demonstrated by OoF small, bright objects. They are proper Airy disks, bright in
the center, declining fairly rapidly into nothing, with no discernible edge. This appearance affects the quality of the
whole image is a way that I find hard to describe.
It is possible to at least partially correct bright edged bokeh in post and this may help show what I'm describing.
<http://www.moosemystic.net/Gallery/tech/Bokeh/_MG_6431.htm> But it's not as good as a lens that gets it right to begin
with.
2. The focal quality I would like to have available to me in small format, but only see in LF images, is one in which
small details are clearly defined, but without hard edges. Sort of the reverse of the effect of USM. :-)
More than that. Medium and especially large format often use simpler
lenses that still have great bokeh are another reason (tessars come to
mind).
But that's not "it". I have a '50s Zeiss Jena 50/2.8 Tessar T in M42 mount and
a Rollei 35 with 40/3.5 Tessar.
1. Neither has the focal qualities I'm looking for.
2. Both produce relatively large, evenly bright highlight disks with distinct edges. The Zeiss is a preset, so it has
multiple aperture blades (14?) and its disks are round, while the Rollei has six, so its disks are hexagonal. In this
respect, they are much like the samples I posted. Some contemporary lenses, particularly zooms, go even further,
producing disks with dark centers and hard, bright edges. I have shots with an OM 50/1.8 where the highlights are
actually donuts.
<http://www.moosemystic.net/Gallery/tech/Lenses/Misc/5018bokeh.htm>
If you look at the top left of this comparison, you'll see how similar the Tessar bokeh is to an OM 50/1.4.
<http://www.moosemystic.net/Gallery/tech/Lenses/50mm_lenses/50mmcomp.htm>
The LBSF is a very simple design, a cemented doublet. Yet it does not improve
much on the bokeh of the Tessar.
[To be fair, I'm only focusing on one aspect of this interesting lens. It uses (as do all their later/current optics but
the new Velvet.) an interesting waterhouse stop system where the metal disks are suspended between three little magnets.
Less convenient than a conventional diaphragm, it allows multi opening aperture plates, like those in some specialized
soft focus lenses of film days. You can see them on the bottom right of this page.
<http://store.lensbaby.com/products/Soft-Focus-Optic.html> They do very different things to image qualities. Changing
apertures is remarkably easier than on other lenses with interchangeable waterhouse stops I've used. I can even do it
easily from behind the camera.]
Also the larger film format gives better tonalities than smaller analog or
anything digital.
First, that's not part of what I'm concerned with. Also, I am not entirely convinced of this. Really smooth tonal
graduations/qualities are far less common with small format, but I have seen some that are beautiful. Tina has posted
some M Monochrome images with exquisite tonality.
Effective apertures are of course more in favor of large format as well. A
f/5.6 lens on 4x5 is approx. equal to a f/1.4 lens on 35mm in terms of
bokeh, etc.
You are mixing things up again. What you say is true of DoF, but that doesn't necessarily apply to the quality of bokeh
I describe above. Nor to the focal quality of fine detail.
Definitional Moose
--
What if the Hokey Pokey *IS* what it's all about?
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