Optimum Aperture for 150mm G-Claron?????

[Dr. Slick]

What would be the optimally sharp aperture for a 150mm
G-Claron? Shooting 30" paintings?


S.

[George Stewart]

I own this lens, and would recommend shooting it at f/22. I have no
scienfitic data to support this recommendation.

George

[f/256]

"George Stewart" > wrote in message
om...
> I own this lens, and would recommend shooting it at f/22. I have no
> scienfitic data to support this recommendation.

This may support you:
http://www.schneideroptics.com/photography/large_format_lenses/g-claron/pdf/g-claron_90_150.pdf

Guillermo

[Dr. Slick]

"f/256" > wrote in message . rogers.com>...
> "George Stewart" > wrote in message
> om...
> > I own this lens, and would recommend shooting it at f/22. I have no
> > scienfitic data to support this recommendation.
>
> This may support you:
> http://www.schneideroptics.com/photography/large_format_lenses/g-claron/pdf/g-claron_90_150.pdf
>
> Guillermo


How does this file say that the sharpest aperture is f22?

I rented this lens and shutter, and took pics at f16, they turned
out terribly fuzzy. So if f22 is the optimum, i find it hard to
believe that one f-stop away could look so bad. Someone at K and S
said that you have to stop way down to f45 with this lens. Maybe so?


Slick

[Kirk Fry]

(Dr. Slick) wrote in message >...
> What would be the optimally sharp aperture for a 150mm
> G-Claron? Shooting 30" paintings?
>
>
> S.

Depends on the magnification. At 1:1 probably f11, at infinity focus
it really does not get sharp until f22 and f32, by f64 it gets fuzzy
again due to diffusion of the small f stop (takes a microscope to see
it). The thing is designed as a close up lens between 4:1 and 1:4
magnification ratios. Large (30 inch) paintings will fall outside
that range on 4X5 film. You could of course use it on a 8 X 10 and
get into the range for pictures up close. Don't forget the bellows
factor in determining the exposure. Your other problem will be to get
the film plane parallel with the painting (not a trivial problem).

Good luck. Kirk

[BCampbell]

There must have been a defect in your rental lens. Mine is tack sharp at all
apertures I've ever used it at, probably F16 and smaller. I doubt that I've
ever used it wide open and maybe haven't used it at F11. I use it as a
general purpose lens, I seldom do real close-ups. I thought about getting
rid of it when I acquired a 135mm lens but the G Claron is so tiny and light
that carrying it around is no problem and I still find a use for it every
now and then.

The design of G Clarons is such that coverage continues to increase as it's
stopped down and with some focal lengths on some formats (e.g. the 210 on
8x10) it's necessary to stop down a couple stops to cover the format. I
don't think that's true of the 150 on 4x5 but I don't offhand remember the
coverage specs. I also don't see anything in the link here that says it's at
its best at F22 but maybe I missed something.

"Dr. Slick" > wrote in message
om...
> "f/256" > wrote in message
. rogers.com>...
> > "George Stewart" > wrote in message
> > om...
> > > I own this lens, and would recommend shooting it at f/22. I have no
> > > scienfitic data to support this recommendation.
> >
> > This may support you:
> >
http://www.schneideroptics.com/photography/large_format_lenses/g-claron/pdf/g-claron_90_150.pdf
> >
> > Guillermo
>
>
> How does this file say that the sharpest aperture is f22?
>
> I rented this lens and shutter, and took pics at f16, they turned
> out terribly fuzzy. So if f22 is the optimum, i find it hard to
> believe that one f-stop away could look so bad. Someone at K and S
> said that you have to stop way down to f45 with this lens. Maybe so?
>
>
> Slick

[Dr. Slick]

(Kirk Fry) wrote in message >...
> (Dr. Slick) wrote in message >...
> > What would be the optimally sharp aperture for a 150mm
> > G-Claron? Shooting 30" paintings?
> >
> >
> > S.
>
> Depends on the magnification. At 1:1 probably f11, at infinity focus
> it really does not get sharp until f22 and f32, by f64 it gets fuzzy
> again due to diffusion of the small f stop (takes a microscope to see
> it). The thing is designed as a close up lens between 4:1 and 1:4
> magnification ratios. Large (30 inch) paintings will fall outside
> that range on 4X5 film.


I told the people at KS that my art was from 8.5"x11" up to
3'x4'.

They and many here have recommended a G-Claron 150mm for this
size work, so i don't think this was it.

I might rent it out again, and do a more thorough analysis.

S.

[Kirk Fry]

(Dr. Slick) wrote in message >...
> (Kirk Fry) wrote in message >...
> > (Dr. Slick) wrote in message >...
> > > What would be the optimally sharp aperture for a 150mm
> > > G-Claron? Shooting 30" paintings?
> > >
> > >
> > > S.
> >
> > Depends on the magnification. At 1:1 probably f11, at infinity focus
> > it really does not get sharp until f22 and f32, by f64 it gets fuzzy
> > again due to diffusion of the small f stop (takes a microscope to see
> > it). The thing is designed as a close up lens between 4:1 and 1:4
> > magnification ratios. Large (30 inch) paintings will fall outside
> > that range on 4X5 film.
>
>
> I told the people at KS that my art was from 8.5"x11" up to
> 3'x4'.
>
> They and many here have recommended a G-Claron 150mm for this
> size work, so i don't think this was it.
>
> I might rent it out again, and do a more thorough analysis.
>
> S.

Dr. S,

My answer may have sounded too negative. If I were doing the job for
the paintings that is the lens I would choose (unless you have
infinite $ and can afford a large format macro-copy lens.) This lens
design is pretty forgiving of being slightly outside the design range.
I have several G-clarons and they are superb lenses. You just have
to stop them down to f22 at infinity focus (landscapes outside), you
will not be at infinity for the paintings. Go ahead and try one.
There are lots of process lenses out there too that would work but
they don't have shutters.

Kirk

[Mike]

I use my 150G on both 4x5 and 5x7. Great lens, lightweight with a
goodly amount of coverage. I generally use this lens at f22 and more
than pleased with the results.

- Mike


On Thu, 12 Feb 2004 13:00:23 GMT, "BCampbell"
> wrote:

>There must have been a defect in your rental lens. Mine is tack sharp at all
>apertures I've ever used it at, probably F16 and smaller. I doubt that I've
>ever used it wide open and maybe haven't used it at F11. I use it as a
>general purpose lens, I seldom do real close-ups. I thought about getting
>rid of it when I acquired a 135mm lens but the G Claron is so tiny and light
>that carrying it around is no problem and I still find a use for it every
>now and then.
>
>The design of G Clarons is such that coverage continues to increase as it's
>stopped down and with some focal lengths on some formats (e.g. the 210 on
>8x10) it's necessary to stop down a couple stops to cover the format. I
>don't think that's true of the 150 on 4x5 but I don't offhand remember the
>coverage specs. I also don't see anything in the link here that says it's at
>its best at F22 but maybe I missed something.
>
>"Dr. Slick" > wrote in message
om...
>> "f/256" > wrote in message
. rogers.com>...
>> > "George Stewart" > wrote in message
>> > om...
>> > > I own this lens, and would recommend shooting it at f/22. I have no
>> > > scienfitic data to support this recommendation.
>> >
>> > This may support you:
>> >
>http://www.schneideroptics.com/photography/large_format_lenses/g-claron/pdf/g-claron_90_150.pdf
>> >
>> > Guillermo
>>
>>
>> How does this file say that the sharpest aperture is f22?
>>
>> I rented this lens and shutter, and took pics at f16, they turned
>> out terribly fuzzy. So if f22 is the optimum, i find it hard to
>> believe that one f-stop away could look so bad. Someone at K and S
>> said that you have to stop way down to f45 with this lens. Maybe so?
>>
>>
>> Slick
>
>

[Dr. Slick]

(Kirk Fry) wrote in message >...
>
> Dr. S,
>
> My answer may have sounded too negative. If I were doing the job for
> the paintings that is the lens I would choose (unless you have
> infinite $ and can afford a large format macro-copy lens.)


Just out of curiousity, what sort of large format macro-copy
lenses could you or anyone else recommend?



This lens
> design is pretty forgiving of being slightly outside the design range.
> I have several G-clarons and they are superb lenses. You just have
> to stop them down to f22 at infinity focus (landscapes outside), you
> will not be at infinity for the paintings. Go ahead and try one.
> There are lots of process lenses out there too that would work but
> they don't have shutters.
>
> Kirk

Like i said, if f22 is the sweet spot up close, i find it hard
to believe that my f16 pics turned out so blurry.


S.

[Dr. Slick]

(Mike) wrote in message >...
> I use my 150G on both 4x5 and 5x7. Great lens, lightweight with a
> goodly amount of coverage. I generally use this lens at f22 and more
> than pleased with the results.
>
> - Mike


And this is using the lens up close?

I wonder why my f16 pics turned out so fuzzy...the lens looked
perfectly good. I think i might rent it again and look a bit closer.


S.

[Mike]

Both close for still life and at infinity for landscapes. For outdoor
work I found a lens shade to be beneficial. I found a 35.5 to 49mm
step up ring and used a rubber lenshood for a 50mm lens.

By the way, the step up ring is a good investment for this lens so you
can mount filters, lens cap etc


- Mike


On 13 Feb 2004 13:23:07 -0800, (Dr. Slick) wrote:

(Mike) wrote in message >...
>> I use my 150G on both 4x5 and 5x7. Great lens, lightweight with a
>> goodly amount of coverage. I generally use this lens at f22 and more
>> than pleased with the results.
>>
>> - Mike
>
>
> And this is using the lens up close?
>
> I wonder why my f16 pics turned out so fuzzy...the lens looked
>perfectly good. I think i might rent it again and look a bit closer.
>
>
>S.

[sympatico.ca]

> How does this file say that the sharpest aperture is f22?
>
> I rented this lens and shutter, and took pics at f16, they turned
> out terribly fuzzy. So if f22 is the optimum, i find it hard to
> believe that one f-stop away could look so bad. Someone at K and S
> said that you have to stop way down to f45 with this lens. Maybe so?

It's not the lens (presuming it's working correctly) - you should not be
getting "terribly fuzzy" pix using it at f16 - it will work just fine at f16
at 1:1 or infinity. It's either the setup, focus, vibration, mismounting of
the lens or a lens malfunction. I've used this and other G-Claron lenses for
museum/artwork copy work with no problem. Sometimes (due to certain
expediencies) at f11, though usually at f22/32. Using it at f16 wasn't what
caused your problem. (I've also used them for plenty of landscape/urban
landscape work on 4x5 and 8x10, at all sorts of apertures)

also:

> Depends on the magnification. At 1:1 probably f11, at infinity focus
> it really does not get sharp until f22 and f32

is pretty much bunkum - as is the whole "flat field" lens mythology. Best
debunking of all that is a paper on Wisners site

[Reciprocity Failure]

I agree, I think there's much too much emphasis here on the optimum range
and aperture of the lens. All lenses are optimized for some magnification or
magnification range. My APO Symmar 210mm lens is optimized ror 1:10 to
infinity I believe but I use it all the time at closer ranges without giving
it a thought. I also have used my two G Claron lenses at all sorts of
different magnificiation ratios and they seem to produce excellent results
at all ranges.

With all lenses I select the aperture on the basis of what is needed to
obtain the desired depth of field and no more, not on the basis of what the
lens designer says is the "optimum" aperture. I think that insufficient
depth of field from too wide an aperture, or probably even the effects of
diffraction from too small an aperture, will be more apparent in a print
than will failure to use the theorietical "optimum" aperture.

> wrote in message
.. .
>
> > How does this file say that the sharpest aperture is f22?
> >
> > I rented this lens and shutter, and took pics at f16, they turned
> > out terribly fuzzy. So if f22 is the optimum, i find it hard to
> > believe that one f-stop away could look so bad. Someone at K and S
> > said that you have to stop way down to f45 with this lens. Maybe so?
>
> It's not the lens (presuming it's working correctly) - you should not be
> getting "terribly fuzzy" pix using it at f16 - it will work just fine at
f16
> at 1:1 or infinity. It's either the setup, focus, vibration, mismounting
of
> the lens or a lens malfunction. I've used this and other G-Claron lenses
for
> museum/artwork copy work with no problem. Sometimes (due to certain
> expediencies) at f11, though usually at f22/32. Using it at f16 wasn't
what
> caused your problem. (I've also used them for plenty of landscape/urban
> landscape work on 4x5 and 8x10, at all sorts of apertures)
>
> also:
>
> > Depends on the magnification. At 1:1 probably f11, at infinity focus
> > it really does not get sharp until f22 and f32
>
> is pretty much bunkum - as is the whole "flat field" lens mythology. Best
> debunking of all that is a paper on Wisners site
>
>

[Tom Monego]

>> Dr. S,
>>
>> My answer may have sounded too negative. If I were doing the job for
>> the paintings that is the lens I would choose (unless you have
>> infinite $ and can afford a large format macro-copy lens.)
>
>
> Just out of curiousity, what sort of large format macro-copy
>lenses could you or anyone else recommend?
The 4 element Apos G-Claron, Apo Ronar, Apo Artar all need a focal length of
210mm (as do Micro Nikors they are 6 not 4 element) to cover 4x5 without fall
off (180 may do but 210 is a much more common focal length. The newer Apo
lenses The Apo Symmar or Apo Sironar will cover 4x5 at infinity, but I don't
know if these are flat field. But then again any tessar formula lens of 180mm
or above should give you the pics you need.
>
>
>
>This lens
>> design is pretty forgiving of being slightly outside the design range.
>> I have several G-clarons and they are superb lenses. You just have
>> to stop them down to f22 at infinity focus (landscapes outside), you
>> will not be at infinity for the paintings. Go ahead and try one.
>> There are lots of process lenses out there too that would work but
>> they don't have shutters.
>>
>> Kirk
>
> Like i said, if f22 is the sweet spot up close, i find it hard
>to believe that my f16 pics turned out so blurry.

I'm using a 210mm G_Claron that I got off a graphics camera, mounted it on a
Ysarex shutter from a Polaroid MP-3, and the sharpness at f11-32 is fine
copying art work. How are you focusing? I have to admit I never try to focus
stoped down. When I had an 8x10 I screwed up a lot of film trying to get a
good focus stopped down, too much depth of field, so I focus wide open, stop
down check alignment. I understand that many older lenses had substatial focus
shift when stopping down, just have avoided those lenses. Just wondering if
you are trying too hard.

Tom

[Dr. Slick]

(Tom Monego) wrote in message news:<1uNYb.9293$Dc2.3094@lakeread01>...


> >
> > Like i said, if f22 is the sweet spot up close, i find it hard
> >to believe that my f16 pics turned out so blurry.
>
> I'm using a 210mm G_Claron that I got off a graphics camera, mounted it on a
> Ysarex shutter from a Polaroid MP-3, and the sharpness at f11-32 is fine
> copying art work. How are you focusing? I have to admit I never try to focus
> stoped down. When I had an 8x10 I screwed up a lot of film trying to get a
> good focus stopped down, too much depth of field, so I focus wide open, stop
> down check alignment. I understand that many older lenses had substatial focus
> shift when stopping down, just have avoided those lenses. Just wondering if
> you are trying too hard.
>

That was the first piece of advice i got from the seller, always
focus at the widest aperture, then stop down. I don't think the
G-Claron had a focus shift, and at any rate, the isn't really enough
light to do this at f16, at least not with my lighting.


S.

[JCPERE]

>: (Tom Monego)

>The 4 element Apos G-Claron, Apo Ronar, Apo Artar

The G-Claron is a 6 element lens. Stopped down to f45 a 150 will cover 5x7 at
infinity and beyond.
Chuck

[Tom Monego]

In article >,
says...
>
>>: (Tom Monego)
>
>>The 4 element Apos G-Claron, Apo Ronar, Apo Artar
>
>The G-Claron is a 6 element lens. Stopped down to f45 a 150 will cover 5x7 at
>infinity and beyond.
>Chuck


Always thought the G-Claron was an Artar formula, one of the more elegant
designs for older lenses. 5x7 at f45 at 1:1 possible not infinity though, my
210 G-Claron gives me some movements but has a definite limit on 4x5. This is a
repro camera lens, thew one I have is off an old stat camera never used for
anything but kodaliths, a very nice lens. I'll check the Schneider web site
though I could be wrong about the formula.

Tom

[sympatico.ca]

> Always thought the G-Claron was an Artar formula, one of the more elegant
> designs for older lenses. 5x7 at f45 at 1:1 possible not infinity though,
my
> 210 G-Claron gives me some movements but has a definite limit on 4x5. This
is a
> repro camera lens, thew one I have is off an old stat camera never used
for
> anything but kodaliths, a very nice lens. I'll check the Schneider web
site
> though I could be wrong about the formula.

my 210 G-Claron covered 8x10 with about 1" of rise/fall @f 22 and aboutr 1
3/4" @ f32 1/2

exactly how much movment are you lookignfor on your 4x5... and is it a
G-Claron or a Repro Claron?

[Reciprocity Failure]

Tom said:

> my 210 G-Claron gives me some movements but has a definite limit on 4x5.

That's very strange. I used a 210 G Claron on 8x10 and had ample room for
movements (ample by my standards at least, possibly limited by others' but
definitely room for some movements) when stopped down to about f22 or
smaller. I used it with 8x10 mostly for exterior architecture and don't
recall having any problem with any movement limits.

"Tom Monego" > wrote in message
...
> In article >,
> says...
> >
> >>: (Tom Monego)
> >
> >>The 4 element Apos G-Claron, Apo Ronar, Apo Artar
> >
> >The G-Claron is a 6 element lens. Stopped down to f45 a 150 will cover
5x7 at
> >infinity and beyond.
> >Chuck
>
>
> Always thought the G-Claron was an Artar formula, one of the more elegant
> designs for older lenses. 5x7 at f45 at 1:1 possible not infinity though,
my
> 210 G-Claron gives me some movements but has a definite limit on 4x5. This
is a
> repro camera lens, thew one I have is off an old stat camera never used
for
> anything but kodaliths, a very nice lens. I'll check the Schneider web
site
> though I could be wrong about the formula.
>
> Tom
>

[Dan Fromm]

"Reciprocity Failure" > wrote in message >...
> Tom said:
>
> > my 210 G-Claron gives me some movements but has a definite limit on 4x5.
>
> That's very strange. I used a 210 G Claron on 8x10 and had ample room for
> movements (ample by my standards at least, possibly limited by others' but
> definitely room for some movements) when stopped down to about f22 or
> smaller. I used it with 8x10 mostly for exterior architecture and don't
> recall having any problem with any movement limits.
>
> "Tom Monego" > wrote in message
> ...
> > In article >,
> > says...
> > >
> > >>: (Tom Monego)
>
> > >>The 4 element Apos G-Claron, Apo Ronar, Apo Artar
> > >
> > >The G-Claron is a 6 element lens. Stopped down to f45 a 150 will cover
> 5x7 at
> > >infinity and beyond.
> > >Chuck
> >
> >
> > Always thought the G-Claron was an Artar formula, one of the more elegant
> > designs for older lenses. 5x7 at f45 at 1:1 possible not infinity though,
> my
> > 210 G-Claron gives me some movements but has a definite limit on 4x5. This
> is a
> > repro camera lens, thew one I have is off an old stat camera never used
> for
> > anything but kodaliths, a very nice lens. I'll check the Schneider web
> site
> > though I could be wrong about the formula.
> >
> > Tom
> >

Per Schneider's literature, with which my 55/8 agrees, the
Repro-Claron is a 4 elements in 4 groups dialyte similar to the Artar.
It covers a fairly narrow angle at infinity. Perhaps Tom was
thinking of a Repro-Claron.

The G-Claron is a 6/4 plasmat type with much wider coverage.

Cheers,

Dan

[John]

On 19 Feb 2004 11:47:37 GMT, (JCPERE) wrote:

>>: (Tom Monego)
>
>>The 4 element Apos G-Claron, Apo Ronar, Apo Artar
>
>The G-Claron is a 6 element lens. Stopped down to f45 a 150 will cover 5x7 at
>infinity and beyond.
>Chuck

I'm surprised since it is reported to have only 192mm @ f22.


Regards,

John S. Douglas, Photographer - http://www.darkroompro.com
Please remove the "_" when replying via email

[Reciprocity Failure]

The specs of the G Claron lenses don't reflect their covereage because the
design of the lens is such that the coverage continues to increase as the
aperture is stopped down. There's a more detailed and technical discussion
of this aspect of the G Claron design on the Wisner web site in the Q and A
part. But the end result is that the G Clarons have much greater coverage
than their published specs indicate, not because Schneider is conservative
with its coverage numbers (though it might be, I don't know) but because of
the design of the lens. The 210 G Claron, the specs of which would indicate
that it can't be used at all on 8x10, actually can not only be used but used
with a good bit of room for movements when stopped down.

"John" > wrote in message
...
> On 19 Feb 2004 11:47:37 GMT, (JCPERE) wrote:
>
> >>: (Tom Monego)
> >
> >>The 4 element Apos G-Claron, Apo Ronar, Apo Artar
> >
> >The G-Claron is a 6 element lens. Stopped down to f45 a 150 will cover
5x7 at
> >infinity and beyond.
> >Chuck
>
> I'm surprised since it is reported to have only 192mm @ f22.
>
>
> Regards,
>
> John S. Douglas, Photographer - http://www.darkroompro.com
> Please remove the "_" when replying via email

[Tom Monego]

>
>Per Schneider's literature, with which my 55/8 agrees, the
>Repro-Claron is a 4 elements in 4 groups dialyte similar to the Artar.
> It covers a fairly narrow angle at infinity. Perhaps Tom was
>thinking of a Repro-Claron.
>
>The G-Claron is a 6/4 plasmat type with much wider coverage.
>
>Cheers,
>
>Dan


Read the same thing, I was confusing a Repro Claron with G-Claron, but
Schneider is saying the 210 G-Claron has a 260mm coverage at f22 hardly 8x10
material, does the circle of coverage extend that much at smaller apertures?

Tom

[Stacey]

Tom Monego wrote:

>
>>
>>Per Schneider's literature, with which my 55/8 agrees, the
>>Repro-Claron is a 4 elements in 4 groups dialyte similar to the Artar.
>> It covers a fairly narrow angle at infinity. Perhaps Tom was
>>thinking of a Repro-Claron.
>>
>>The G-Claron is a 6/4 plasmat type with much wider coverage.
>>
>>Cheers,
>>
>>Dan
>
>
> Read the same thing, I was confusing a Repro Claron with G-Claron, but
> Schneider is saying the 210 G-Claron has a 260mm coverage at f22 hardly
> 8x10 material, does the circle of coverage extend that much at smaller
> apertures?
>
>

Yes
--

Stacey

I own the 210 mm G-Claron and use it on an 8x10 with some movements. It is
a plasmat lens not an artar style. I don't know about the 150mm but I am
sure Chuck knows what he is talking about as I have seen a lot of his images
and they are excellent.

lee\c
"Reciprocity Failure" > wrote in message
.com...
> The specs of the G Claron lenses don't reflect their covereage because the
> design of the lens is such that the coverage continues to increase as the
> aperture is stopped down. There's a more detailed and technical discussion
> of this aspect of the G Claron design on the Wisner web site in the Q and
A
> part. But the end result is that the G Clarons have much greater coverage
> than their published specs indicate, not because Schneider is conservative
> with its coverage numbers (though it might be, I don't know) but because
of
> the design of the lens. The 210 G Claron, the specs of which would
indicate
> that it can't be used at all on 8x10, actually can not only be used but
used
> with a good bit of room for movements when stopped down.
>
> "John" > wrote in message
> ...
> > On 19 Feb 2004 11:47:37 GMT, (JCPERE) wrote:
> >
> > >>: (Tom Monego)
> > >
> > >>The 4 element Apos G-Claron, Apo Ronar, Apo Artar
> > >
> > >The G-Claron is a 6 element lens. Stopped down to f45 a 150 will cover
> 5x7 at
> > >infinity and beyond.
> > >Chuck
> >
> > I'm surprised since it is reported to have only 192mm @ f22.
> >
> >
> > Regards,
> >
> > John S. Douglas, Photographer - http://www.darkroompro.com
> > Please remove the "_" when replying via email
>
>

[Reciprocity Failure]

Yes. The 210 covers 8x10 at F22, possibly F16.

"Tom Monego" > wrote in message
...
>
> >
> >Per Schneider's literature, with which my 55/8 agrees, the
> >Repro-Claron is a 4 elements in 4 groups dialyte similar to the Artar.
> > It covers a fairly narrow angle at infinity. Perhaps Tom was
> >thinking of a Repro-Claron.
> >
> >The G-Claron is a 6/4 plasmat type with much wider coverage.
> >
> >Cheers,
> >
> >Dan
>
>
> Read the same thing, I was confusing a Repro Claron with G-Claron, but
> Schneider is saying the 210 G-Claron has a 260mm coverage at f22 hardly
8x10
> material, does the circle of coverage extend that much at smaller
apertures?
>
> Tom
>