Makes a sharp f/90

Every time I see a 16.5" or 19" APO-Artar up for sale, (and I haven't
been able to snag one yet) the seller always likes to say, "Makes a
sharp f/90" Is that possible with these or other process lenses? I
don't dare go past f/45 with my sharpest lens, a 240 Apochromatic
Fuji, which goes to f/90.

I made a question a few years ago, (which was misconstrued) about
whether older lenses used by the infamous f/64 folks were somehow more
capable of sharp images at smaller stops. The question does not
concern the aesthetic choice of the f/64 group for all over sharpness
to counter the soft psuedo art trend that continued to linger.

"Ken Smith" wrote in message
om...
Every time I see a 16.5" or 19" APO-Artar up for sale, (and I haven't
been able to snag one yet) the seller always likes to say, "Makes a
sharp f/90" Is that possible with these or other process lenses? I
don't dare go past f/45 with my sharpest lens, a 240 Apochromatic
Fuji, which goes to f/90.

I made a question a few years ago, (which was misconstrued) about
whether older lenses used by the infamous f/64 folks were somehow more
capable of sharp images at smaller stops. The question does not
concern the aesthetic choice of the f/64 group for all over sharpness
to counter the soft psuedo art trend that continued to linger.

The depth of field is greater at f/90, but diffraction limitation will
reduce the maximum theoretical resolution possible with the lens (which is
probably not a big issue for 8x10 negatives).

Ken Smith wrote:
Every time I see a 16.5" or 19" APO-Artar up for sale, (and I haven't
been able to snag one yet) the seller always likes to say, "Makes a
sharp f/90" Is that possible with these or other process lenses? I
don't dare go past f/45 with my sharpest lens, a 240 Apochromatic
Fuji, which goes to f/90.

It depends on the degree of enlargement of the image. The Aery disc at
f/90 has diameter about 0.06 mm. That would allow about 2 X enlargement.


I made a question a few years ago, (which was misconstrued) about
whether older lenses used by the infamous f/64 folks were somehow more
capable of sharp images at smaller stops. The question does not
concern the aesthetic choice of the f/64 group for all over sharpness
to counter the soft psuedo art trend that continued to linger.

"Mark A" wrote in message
...

The depth of field is greater at f/90, but diffraction limitation will
reduce the maximum theoretical resolution possible with the lens (which is
probably not a big issue for 8x10 negatives).

With respect, you are getting a bit carried away with the impressionistic
desktop metrics. Do a picture. Unless the lens is abysmal to begin with,
diffraction at F90 don't mean squat on a properly focused and exposed 8x10"
negative. It's about degree of enlargement, acceptable COC. Shoot F90 (with
a proper lens) and be happy.

One thing I've found that is important (to me) is the shape of the diaphram.
If you go cheap and use a diaphram (aperture) with just a few leaves and
therefore have a rough octagon, the bokeh (if there is any in the
composition) is just ugly. YMMV.

The depth of field is greater at f/90, but diffraction limitation will
reduce the maximum theoretical resolution possible with the lens (which
is
probably not a big issue for 8x10 negatives).

With respect, you are getting a bit carried away with the impressionistic
desktop metrics. Do a picture. Unless the lens is abysmal to begin with,
diffraction at F90 don't mean squat on a properly focused and exposed
8x10"
negative. It's about degree of enlargement, acceptable COC. Shoot F90
(with
a proper lens) and be happy.

One thing I've found that is important (to me) is the shape of the
diaphram.
If you go cheap and use a diaphram (aperture) with just a few leaves and
therefore have a rough octagon, the bokeh (if there is any in the
composition) is just ugly. YMMV.

That's what I said. It's not an issue with a 8x10 negative. Are you blind?

"Mark A" wrote in message
...

That's what I said. It's not an issue with a 8x10 negative. Are you blind?

Ma faute. To Mark A. and readers: my apology.

--
jjs - 'blind before coffee'

(Ken Smith) wrote in message . com...
Every time I see a 16.5" or 19" APO-Artar up for sale, (and I haven't
been able to snag one yet) the seller always likes to say, "Makes a
sharp f/90" Is that possible with these or other process lenses? I
don't dare go past f/45 with my sharpest lens, a 240 Apochromatic
Fuji, which goes to f/90.

I made a question a few years ago, (which was misconstrued) about
whether older lenses used by the infamous f/64 folks were somehow more
capable of sharp images at smaller stops. The question does not
concern the aesthetic choice of the f/64 group for all over sharpness
to counter the soft psuedo art trend that continued to linger.

Don't forget that f90 on 19" is a LARGER diameter tahn f45 on 240mm.

f-stop
focal length 90 64 45
Inches mm aperture d(mm)
240 2.67 3.75 5.33
16.50 419.10 4.66 6.55 9.31
19.00 482.60 5.36 7.54 10.72

Is this not correct?

Collin

"Collin Brendemuehl" wrote in message
om...
(Ken Smith) wrote in message
. com...

Don't forget that f90 on 19" is a LARGER diameter tahn f45 on 240mm.

f-stop
focal length 90 64 45
Inches mm aperture d(mm)
240 2.67 3.75 5.33
16.50 419.10 4.66 6.55 9.31
19.00 482.60 5.36 7.54 10.72

Is this not correct?

Unfortunately diffraction is directly proportional to the f-stop and not
just inversely proportional to the aperture diameter, in other words, like
doesn't really care if the hole is big or small, it cares about the ratio
focal_length / aperture_diameter. All lenses at f/90 would have similar
diffraction, but as it has been already mentioned in this thread, for equal
size prints, shooting big formats has the advantage of requiring less
enlargement which in turn lessen the impact of diffraction, compared to
smaller formats.

Guillermo

Leonard Evens wrote in message ...
Ken Smith wrote:
Every time I see a 16.5" or 19" APO-Artar up for sale, (and I haven't
been able to snag one yet) the seller always likes to say, "Makes a
sharp f/90" Is that possible with these or other process lenses? I
don't dare go past f/45 with my sharpest lens, a 240 Apochromatic
Fuji, which goes to f/90.

It depends on the degree of enlargement of the image. The Aery disc at
f/90 has diameter about 0.06 mm. That would allow about 2 X enlargement.


I made a question a few years ago, (which was misconstrued) about
whether older lenses used by the infamous f/64 folks were somehow more
capable of sharp images at smaller stops. The question does not
concern the aesthetic choice of the f/64 group for all over sharpness
to counter the soft psuedo art trend that continued to linger.


So sure, an 8x10 contact is going to look alright. But we who
are somewhat fanatic about glassy clarity are not carrying 8x10's
around for the exercise. If any lens that promises a sharp f/90, or
f/64 are not any better than my Fuji at f/90, or f/64 I would never
use them at that aperature.
aren't making pictures that look O.K.

Ken Smith wrote:


I made a question a few years ago, (which was misconstrued) about
whether older lenses used by the infamous f/64 folks were somehow more
capable of sharp images at smaller stops.

The physics of the diffraction of light were the same in 1932 as they are today.

A very minor effect is that the films of 1932 probably had more blue sensitivity
relative to their red sensitivity than current films. Since blue light has a
smaller wavelength than red light, diffraction blurring will be less.

The reason that people perceive Group f/64 versus sharpness as a paradox is that
the paradox perceivers are thinking of small formats such as 35 mm. The members
of Group f/64 were using large formats such as 8x10. A contact print made from
8x10 neg taken at f64 will have much less diffraction blurring than a 8x10 print
made by enlarging a 35 mm neg taken at f64.

--Michael