On Tuesday, 6 October 2015 18:18:11 UTC+1, NY wrote:
"whisky-dave" wrote in message
...
On Tuesday, 6 October 2015 12:32:28 UTC+1, NY wrote:
"whisky-dave" wrote in message
...
so you don't need a mirror lens for bokeh, I knew this in the mid 70s
Bokeh isn't new.

I never suggested that you did. I simply said that the bokeh of a mirror
lens was characteristic - a doughnut shape on any bright highlight which
is
very out of focus, rather than a solid disc or solid polygon in the shape
of
the lens aperture that you'd get with a purely refractive lens.

If you knoew a little about photography you'd have know that bokeh isn't
new,
and over 100 years old an nothing to do with mirror lenes, other than that
mirror lenes made bokeh come back into the spotlight (sort of pun
intented).

Which is why if you want to teach photography you do NOT start with a
digital camera you can end with one of course.

I'm puzzled. I haven't said anywhere that bokeh is new or that you only get
it with mirror lenses or that you need a digital camera or a film camera to
see its effects. Since it is basic optics, I'd expect it to have been known
about since early photography if not before that going back to the days of
the camera obscura. And since early cameras used larger negatives and
therefore longer focal length lenses for the same field of view, it was
probably more apparent on older cameras since a 50 mm *equivalent* lens on a
large plate camera will have shallower depth of field than a 50 mm for a 35
mm camera at the same aperture. It is also possible that the shape of
highlights and therefore the nature of the bokeh will have changed over the
years as lens design has been refined.

Maybe is because you said
"Mirror lenses also have very characteristic bokeh. But I won't make
disparaging comments if people have to google to find out what bokeh is and
what is characteristic about that of a mirror lens! "

Only those that have never done photography wouldn't know the above.
Which is what makes photography differnt from deciding whether film or digital is best is irrelivant to photography that is the point.

It is a feature of all lenses that out of focus objects are rendered in a
way that is characteristic of that lens. I've seen reviews and specimen
photos of lenses for many years which show that some lenses give a "nicer"
bokeh and others give a more intrusive bokeh.

Irrespective of film or digital media, and mirror lenes.



It so happens that mirror
lenses give a very recognisable doughnut-shaped blur on highlights which (as
far as I am aware) is not apparent on conventional refractive lenses -
something that I referred to in passing a while ago in this thread.

Yes adn this was not considered to be a good thing unless you wanted bokeh.
I remmerb sports photographers not being 'keen' on it because iof it's distraction, it might have lokoed cool or arty but it was seen as a downside of a mirror lens rahter than an advantage.


To the best of my knowledge, a film camera and a digital camera with the
same lens, the same size sensor and using the same aperture will give the
same picture, in terms of depth of field and the amount and "look" of blur
(bokeh). I can't see why you would learn more about bokeh with a film camera
than a digital, but if you think differently, I'd be most interested to hear
your reasoning.

Because people knew about this some 100 years before the digital camera existed. People that knew about photography rather than comparing film to digital would know about this.


In fact you don't even need a film/sensor to see it - it's visible on the
ground glass focussing screen of an SLR (film/digital) even before you take
a picture, though the graininess of the screen may obscure some of the
detail which may only be visible in the finished slide/print/digital
picture.