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In article <>, Neil
Harrington <> wrote:

> > it's really quite simple.
>
> It is indeed, and there's no need for you to try to complicate it.

i'm not complicating it at all. for something to be equivalent, it must
be equivalent in all aspects, not only the ones you feel like
comparing.

> The properly exposed photo may have more or less noise, depending on things
> such as sensor size, which does not change the ISO. There is no "normalize
> it for equivalency," whatever that is supposed to mean.

if a photo from one camera has more or less noise than a photo from a
different camera, then the two cameras didn't produce equivalent
images, did they?

In article <>, Neil
Harrington <> wrote:

> >>> it's really quite simple.
> >>
> >> It is indeed, and there's no need for you to try to complicate it.
> >
> > i'm not complicating it at all. for something to be equivalent, it
> > must be equivalent in all aspects, not only the ones you feel like
> > comparing.
>
> I take your point, but in trying to make something "equivalent in all
> aspects" here, you are attempting the impossible.

it's not impossible at all.

> ISO is ISO. It has to do with exposure, that's all. Small sensors will have
> more noise than large sensors at the same ISO. There is no way you can make
> them "equivalent in all aspects."

yes you can, simply by raising the iso of the larger sensor which
increases its noise to match that of the smaller and noisier sensor.

> >> The properly exposed photo may have more or less noise, depending on
> >> things such as sensor size, which does not change the ISO. There is
> >> no "normalize it for equivalency," whatever that is supposed to mean.
> >
> > if a photo from one camera has more or less noise than a photo from a
> > different camera, then the two cameras didn't produce equivalent
> > images, did they?
>
> Obviously not, and the difference obviously has nothing to do with ISO.
>
> What you're trying to do is something like putting the same 300-hp engine in
> a small sports car and a big truck, and then saying the horsepower must be
> "normalized" (as you call it) because the two don't accelerate the same. The
> difference in performance has nothing to do with, and does not change, the
> fact that the engine is still the same 300 hp regardless of what vehicle
> it's in.

nope. if you want to use a car analogy, put a 150hp motor in the
smaller and lighter car and a 300hp motor in the larger and heavier
car, and they both have the same 0-60 times.

an engine without a car isn't particularly useful, just as a lens
without a camera.

> It's the same with ISO. The fact that two different cameras produce
> different amounts of noise at the same ISO does not mean the ISO has to be
> "normalized" or otherwise tinkered with in either case.

it does if you want to call something equivalent.

In article <u8ednX->, Neil
Harrington <> wrote:

> >>> once you put
> >>> it on a camera, you *must* take into account the size of the sensor.
> >>>
> >>> you're also ignoring other characteristics of the image.
> >>>
> >>> if the noise and depth of field are different, the image is *not*
> >>> equivalent. you do not get to pick only one thing.
> >>
> >> You didn't stop where you should have stopped.
> >
> > or more accurately, you're stopping prematurely, ignoring things that
> > matter. why is that?
>
> Because they don't in fact matter in this connection.
>
> The f-number is the f-number. Period.

only without a camera or photo.

Neil Harrington <> wrote:
> Wolfgang Weisselberg wrote:

>> Of course. The tele converter spreads the image onto a larger
>> area (thus less light reaches the sensor (and the f/number rises
>> accordingly), but you could use a larger sensor --- theoretically
>> at least).

> That wouldn't change the f-number.

Of course it does.

Try this:
To spread the light from a 1x1 area onto a 2x2 area quadruples
the area lighted, quarters the light per area. Since the lens
is unchanged (and since the transmission didn't change (much)),
the f-stop must have doubled.

Or, try this:
To have the same angle of view (which you keep, after all) with a
sensor of 2 times the linear dimension, (which the 2x teleconverter
does) you need a lens twice the focal length. The teleconverter
does that without changing the lens, so the aperture stays the
same, but the effective focal length must have doubled. Since the
f/stop is effective focal length/effective aperture diameter,
the new f/stop value is doubled (as the focal length doubles).

> A different and I think more direct way
> of saying what you're saying is simply that (for example) a 2x tele
> converter doubles the focal length, thus doubling the f-number as well since
> the maximum aperture remains the same. All f/2.8 (for example) means is that
> the aperture size is the focal length divided by 2.8 -- which is why it's
> written just that way.

Same thing, different words. But I like the spreading and less
light per area better.

>> The famous 50mm f/0.7 was a reduced 80mm f/1.0. IIRC there were
>> just 4 mm between lens and film.

I must correct myself: s/80mm/70mm/

> Interesting. I had never heard of that one.

The NASA had some built to photograph the dark side of the moon.
Later, Kubrick used a lens for Barry Lyndon (where some scenes
were lit only by candles).

The 70mm was a German wartime night lens, btw., though the design
is prewar.

-Wolfgang

David Dyer-Bennet <> wrote:
> On Jun 16, 1:52Â*pm, Wolfgang Weisselberg <ozcvgt...@sneakemail.com>
>> David Dyer-Bennet <illegaln...@gmail.com> wrote:

>> > A 6MP E-PL2 would be a lot more valuable to me than the
>> > 12MP one they actually make! Â*But apparently I'm not normal
>> > (I've kind of gotten used to that over the years).

>> Is there *so* much difference between a 6MP camera and a 12MP
>> camera downsampled to 4.3MP, and then optionally upsampled back
>> to 6MP?

> Yeah, not really so bad. I have a personal problem with
> a workflow that involves deliberately throwing away information,
> though, which ends up meaning I see the junk when I'm
> working on the photo.

OK, then noone can help you

>> 100% crops aren't good to compare anything but per-pixel noise ---
>> which is only valuable on identical pixel counts. Â*(Noone looks
>> at *photos* at 100%, because they cannot see the image then.)

> I work at 100% a lot while retouching. Or 200%.

OK, but then you are not looking at the photos, but at tiny details
you need larger to properly edit them. And if it wasn't for the
12 MPix, you'd need 141% and 283%.

-Wolfgang

On Jun 17, 4:50*pm, Wolfgang Weisselberg <ozcvgt...@sneakemail.com>
wrote:
> David Dyer-Bennet <illegaln...@gmail.com> wrote:
> > On Jun 16, 1:52*pm, Wolfgang Weisselberg <ozcvgt...@sneakemail.com>
> >> David Dyer-Bennet <illegaln...@gmail.com> wrote:
> >> > A 6MP E-PL2 would be a lot more valuable to me than the
> >> > 12MP one they actually make! *But apparently I'm not normal
> >> > (I've kind of gotten used to that over the years).
> >> Is there *so* much difference between a 6MP camera and a 12MP
> >> camera downsampled to 4.3MP, and then optionally upsampled back
> >> to 6MP?
> > Yeah, not really so bad. *I have a personal problem with
> > a workflow that involves deliberately throwing away information,
> > though, which ends up meaning I see the junk when I'm
> > working on the photo.
>
> OK, then noone can help you

Fair enough. It's not, basically, a photographic problem,
and hence outside the remit of this newsgroup.

> >> 100% crops aren't good to compare anything but per-pixel noise ---
> >> which is only valuable on identical pixel counts. *(Noone looks
> >> at *photos* at 100%, because they cannot see the image then.)
> > I work at 100% a lot while retouching. *Or 200%.
>
> OK, but then you are not looking at the photos, but at tiny details
> you need larger to properly edit them. *And if it wasn't for the
> 12 MPix, you'd need 141% and 283%.

For both dust on the sensor, and actual image details,
they'll be twice as big (in pixels; same size in physical
on-sensor image dimensions) on the 6MP sensor, so I won't
need to enlarge more to get my usual on-screen working
size.

David Dyer-Bennet <> wrote:

>> > I work at 100% a lot while retouching. Â*Or 200%.

>> OK, but then you are not looking at the photos, but at tiny details
>> you need larger to properly edit them. Â*And if it wasn't for the
>> 12 MPix, you'd need 141% and 283%.

> For both dust on the sensor, and actual image details,
> they'll be twice as big (in pixels; same size in physical
> on-sensor image dimensions) on the 6MP sensor,

Huh?
- A dust speck of the same size will cover 2x more pixels on the 12 MPix
sensor.
- Choosing the same framing, image details will cover 2x more pixels per
same-sized detail on the 12 MPix sensor.

Thus at 100% pixel view, details and dust on the 6 MPix sensor
will be smaller.
At least to my understanding.

Maybe I'm just misreading you ...

> so I won't need to enlarge more to get my usual on-screen working
> size.

Sorry, I don't get it.

-Wolfgang

nospam <> wrote:

> i'm not complicating it at all. for something to be equivalent, it must
> be equivalent in all aspects, not only the ones you feel like
> comparing.

I disagree. If one is evaluating several options by some
measurements/standards/weighting, then two options are equivalent when
the measurements/standards/weighting returns the same result.

This does not imply they are identical, because if they were
identical, they would be more than just equivalent --- and wouldn't
be two separate options.

Example: Time needed to get to work.
If using public transport and using the car (including searching
for parking space and walking from there to work) take the same
time, they are equivalent in their time need. That doesn't imply
they are identical, cost the same, have the same ecological
footprint, are like in their susceptibility to strikes and/or
traffic jams and/or bad weather, etc.

> if a photo from one camera has more or less noise than a photo from a
> different camera, then the two cameras didn't produce equivalent
> images, did they?

They don't produce *identical* images, but unless the noise *does*
have a *relevant* (as in visible and noticeable) impact on the
final product, they are very much equivalent.



See also Merriam-Webster's reliable book:

Definition of EQUIVALENT
1 : equal in force, amount, or value; also : equal in area or
volume but not superposable <a square equivalent to a triangle>
2 a : like in signification or import
b : having logical equivalence <equivalent statements>
3 : corresponding or virtually identical especially in effect
or function
4 : obsolete : equal in might or authority
5 : having the same chemical combining capacity <equivalent
quantities of two elements>
6 a : having the same solution set <equivalent equations>
b : capable of being placed in one-to-one correspondence
<equivalent sets>
c : related by an equivalence relation

Note 1 --- NOT SUPERPOSABLE --- not identical.
Note 5 --- different elements --- not identical.
Note 6a --- same solution set --- doesn't mean identical equations,
for example.


Definition of IDENTICAL
1 : being the same : selfsame <the identical place we stopped before>
2 : having such close resemblance as to be essentially the same <identical
hats> —often used with to or with
3 a : having the same cause or origin <identical infections>
b : monozygotic


-Wolfgang

nospam <> wrote:

> an f/number by itself is independent of any sensor size. once you put
> it on a camera, you *must* take into account the size of the sensor.

Nope.

Take an 8 MPix 1.6x crop sensor and a 21 MPix 35mm sensor ---
and crop the 21 MPix sensor to 1.6x somewhere between sensor
exposure and final output.

They're not only equivalent, they're *identical*.

> if the noise and depth of field are different, the image is *not*
> equivalent. you do not get to pick only one thing.

And a triangle can be equivalent in size to a square. Too.

-Wolfgang

tony cooper <> wrote:

> Only if the pint glass has perpendicular sides, and I've never seen
> one like that.

You haven't been to Cologne, then.

http://www.naturarena.de/img/Bilder/..._neu_kopie.jpg
http://www.yopi.de/image/prod_pics/5237/e/5237527.jpg
http://bilder.afterbuy.de/images/749..._Stange_03.jpg

-Wolfgang