Interesting Panasonic TZ1 feature

On Jun 29, 3:58 pm, "David J Taylor" <david-tay....TakeThisOut@blueyonder.not-this-
part.nor-this-bit.co.uk> wrote:
> ~~NoMad~~ wrote:
> > After owning a TZ1 for over a year now, I just noticed an interesting
> > feature.
>
> > The TZ1 has only two aperture settings F2.8 and F5 at wide angle.
> > Zoom it out 10x and the two settings become F4.2 and F7.1. No wonder
> > they don't have a manual mode in this camera with only two aperture
> > settings. I haven't noticed any abnormal loss in Depth of Field with
> > this camera and I consider the pictures it produces excellent.
>
> > I wonder if other P&S cameras have the same limited aperture settings?
>
> > NM
>
> All small-sensor cameras are limited in the smaller physical apertures
> (higher f/numbers) because of the onset of diffraction effects at the
> smaller apertures restricting image sharpness. At f/16, the pictures
> would be noticeably worse. If they don't have a big maximum aperture,
> then the f/number range may indeed by quite restricted.
>
> David

That raises an interesting question: Have any *empirical* studies
been done regarding small-sensor cameras (or, rather, very short focal-
length lenses), WRT at what point the lenses become diffraction-
limited? I am relatively new to digital photography, and initially
found it difficult to remember that you just plain cannot stop a lens
down on a digital camera as much as you might unthinkingly do with a
larger format camera.

--
YOP...
 >> Stay informed about: Interesting Panasonic TZ1 feature 

[A complimentary Cc of this posting was sent to
~~NoMad~~
<understanding.engine.DeleteThis@gmail.com>], who wrote in article <f63qqd$6ti$1@registered.motzarella.org>:
> After owning a TZ1 for over a year now, I just noticed an interesting
> feature.
>
> The TZ1 has only two aperture settings F2.8 and F5 at wide angle. Zoom it
> out 10x and the two settings become F4.2 and F7.1.

Remember the scaling law w.r.t. the sensor size. One can get
identical pictures from sensors of different sizes, PROVIDED (quote
from my older post):

The physical laws of scaling are the following: to produce the same
image from N times smaller sensor (linearly) one needs to:

a) have the same count of pixels;

b) have the same QE;

c) have the same readout noise;

d) have the same full well;

e) have the same exposure time;

f) use N times higher aperture (measured as an F-number, e.g., 1/45);

g) have the same "quality" of the lens (e.g, measured as quotient
of actual MTF of the lens to MTF of diffraction-limited lens)

So, e.g., comparing 1/2.5"-sensor with full-frame (which is 8/3"), the
aperture is translated to 2.8*N, 5*N, 4.2*N, and 7.1*N, with N being
8/3/(1/2.5)=6.6. This makes your apertures equivalent to f/19, f/33,
f/28 and f/47 (when comparing to full-frame).

I do not know the sensor size of TZ1, so you may need to recalculate.
Anyway, did you ever used apertures much smaller than f/47 with
full-frame? 1/4

Hope this helps,
Ilya
 >> Stay informed about: Interesting Panasonic TZ1 feature 

Nervous Nick wrote:
[]
> That raises an interesting question: Have any *empirical* studies
> been done regarding small-sensor cameras (or, rather, very short
> focal- length lenses), WRT at what point the lenses become
> diffraction- limited? I am relatively new to digital photography,
> and initially found it difficult to remember that you just plain
> cannot stop a lens down on a digital camera as much as you might
> unthinkingly do with a larger format camera.

I do hope someone can answer your question, but knowing the way in which
marketing /can/ drive engineering, I suspect that cameras are already at
or beyond that limit! However, as people's expectations may be less with
small-sensor cameras, perhaps it doesn't matter as much if some
diffraction shows. I think it would just be a lack of sharpness rather
than anything unpleasant. To keep noise down, you may stick with ISO 100,
so not having a smaller aperture may not matter as much. In any case, you
already have greater depth-of-field.

Cheers,
David
 >> Stay informed about: Interesting Panasonic TZ1 feature 

On Jun 29, 10:56 pm, "David J Taylor" <david-tay....TakeThisOut@blueyonder.not-
this-part.nor-this-bit.co.uk> wrote:
> Nervous Nickwrote:
>
> []
>
> > That raises an interesting question: Have any *empirical* studies
> > been done regarding small-sensor cameras (or, rather, very short
> > focal- length lenses), WRT at what point the lenses become
> > diffraction- limited? I am relatively new to digital photography,
> > and initially found it difficult to remember that you just plain
> > cannot stop a lens down on a digital camera as much as you might
> > unthinkingly do with a larger format camera.
>
> I do hope someone can answer your question, but knowing the way in which
> marketing /can/ drive engineering, I suspect that cameras are already at
> or beyond that limit!

So you seem to be saying that most of these lenses would be
diffraction limited when *wide open.* Which makes sense considering
the much smaller scale we are talking about.*

However, as people's expectations may be less with
> small-sensor cameras, perhaps it doesn't matter as much if some
> diffraction shows. I think it would just be a lack of sharpness rather
> than anything unpleasant. To keep noise down, you may stick with ISO 100,
> so not having a smaller aperture may not matter as much. In any case, you
> already have greater depth-of-field.

See, there is where I got messed up initially; in thinking that you
would get greater depth of field by stopping down, when you already
*have* that greater depth of field inherent to the smaller scales.

Cheers!

--
YOP...

*By "a point where a lens becomes diffraction limited* I mean, the f-
stop past, where if you stop down any further, you get no net gain in
sharpness, and indeed begin to experience loss in sharpness. You can
actually view this phenomenon under an enlarger, for example, if you
carefully look at film grain through your enlarging magnifier while
stopping down the lens. As you stop down, the grain will appear to
become sharper, up to a certain f-stop, past which the sharpness
degenerates. It is at that crucial f-stop that the lens is said to be
"diffraction-limited," as in, for example, "diffraction-limited at f/
11".
 >> Stay informed about: Interesting Panasonic TZ1 feature 

~~NoMad~~ presented the following explanation :
> After owning a TZ1 for over a year now, I just noticed an interesting
> feature.
>
> The TZ1 has only two aperture settings F2.8 and F5 at wide angle. Zoom it out
> 10x and the two settings become F4.2 and F7.1. No wonder they don't have a
> manual mode in this camera with only two aperture settings. I haven't noticed
> any abnormal loss in Depth of Field with this camera and I consider the
> pictures it produces excellent.
>
> I wonder if other P&S cameras have the same limited aperture settings?
>
> NM

Yes, my Casio EX-Z850 has the same feature. 2 f-stop settings per
zoom.
 >> Stay informed about: Interesting Panasonic TZ1 feature 

Nervous Nick wrote:
[]
> So you seem to be saying that most of these lenses would be
> diffraction limited when *wide open.* Which makes sense considering
> the much smaller scale we are talking about.*

I haven't done the sums, but, yes, that is possible.

>> However, as people's expectations may be less with
>> small-sensor cameras, perhaps it doesn't matter as much if some
>> diffraction shows. I think it would just be a lack of sharpness
>> rather than anything unpleasant. To keep noise down, you may stick
>> with ISO 100, so not having a smaller aperture may not matter as
>> much. In any case, you already have greater depth-of-field.
>
> See, there is where I got messed up initially; in thinking that you
> would get greater depth of field by stopping down, when you already
> *have* that greater depth of field inherent to the smaller scales.
>
> Cheers!

Yes, it's one of the prime differences between small-sensor cameras and
DSLRs. On the small sensor camera there is less need to stop down to
increase DoF. Of course, sometimes you want a large DoF to have
everything sharp, and sometimes a small DoF to isolate the main subject.
In practice, I find that with the longer end of the zoom (say 200mm+) on a
Panasonic FZ5, you can isolate the subject quite well, but you could do so
at a shorter focal length (say 50mm) on a DSLR with an f/1.8 lens.

Cheers,
David
 >> Stay informed about: Interesting Panasonic TZ1 feature 

Nervous Nick wrote:

>
> That raises an interesting question: Have any *empirical* studies
> been done regarding small-sensor cameras (or, rather, very short
> focal- length lenses), WRT at what point the lenses become
> diffraction-
> limited? I am relatively new to digital photography, and initially
> found it difficult to remember that you just plain cannot stop a lens
> down on a digital camera as much as you might unthinkingly do with a
> larger format camera.
>
You might find this web page of interest:

http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm
 >> Stay informed about: Interesting Panasonic TZ1 feature 

[A complimentary Cc of this posting was sent to
Nervous Nick
<nervous.nick RemoveThis @gmail.com>], who wrote in article <1183206400.777486.80230 RemoveThis @g4g2000hsf.googlegroups.com>:
> So you seem to be saying that most of these lenses would be
> diffraction limited when *wide open.*

This would not make any sense. The lenses are so tiny, that making
them 1.5 as large would not add more than a few cents to the cost.

If they were diffraction-limited at f/1.5N, they would be of quite good
quality at f/N. You gain a full f-stop with very minor change in price.

But what I *have* seen is that some of the best P&S cameras give the
*best resolution* when wide open. This means that they are not
diffraction-limited when wide open, but not-very-far-away-from
diffraction-limited when wide open.

(E.g., IIRC, G5 has its best resolution at f/2.8.)

Hope this helps,
Ilya
 >> Stay informed about: Interesting Panasonic TZ1 feature