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FF sensors: is 80MP needed?

 
 
Roger N. Clark (change username to rnclark)
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      10-16-2006
frederick wrote:

> Roger N. Clark (change username to rnclark) wrote:
>
>> Digital
>> also has much greater dynamic range.

>
>
> How dare you keep saying that - when believing the reverse is the raison
> d'Ítre for the quaint obsession some have for 35mm.




 
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Ilya Zakharevich
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      10-16-2006
[A complimentary Cc of this posting was sent to
Roger N. Clark (change username to rnclark)
<(E-Mail Removed)>], who wrote in article <(E-Mail Removed)>:
> > Irrelevant. You are discussing lens+sensor vs lens+film. I'm
> > discussing lens+sensor vs lens+ideal_sensor.


> Theory is fine, but you must consider all factors.


One can never consider all factors. It is important to consider *key*
factors - of course.

> One factor you have not considered, [...] is not just resolution,
> but [...]


Since all I was considering was resolution, it is not surprising I did
not consider other factors. (Especially since I already addressed
"other factors" in my other posts; here I concentrated on some "new"
experiments.)

> Digital has a much higher signal-to-noise ratio


Such a blank statement is definitely wrong; you mean the same
exposition, and it is not applicable to my comparison. E.g, with the
current technology digital will give much worse noise than film if the
exposition of digital is 20x smaller than of film . And note that
this is quite probably holds when you compare LF film to FF digital
(but I do not remember the details of the exposition you used...) -
count number of photons per "pixel" (I mean square with size
determined by the MTF curve).

> ... that greatly influences perceived image detail.


Film has practically no noise when correctly exposed with aperture
f/32 - or much smaller f-number.

> Digital also has much greater dynamic range.


IMO, this remains to be proven yet (though I suspect that the proof
*will* support your claim - I just *have not seen* it).

Your investigation is very interesting, but, IMO, it completely missed
the point. Essentially, you measured the noise of 6um square of film
vs 8um square of semiconductor. So, film's noise *at these extremely
high spacial frequencies* turns out to be much more than digital
sensors'; fine. But, as you probably saw it in many posts about your
experiments, it is the noise at much lower spacial frequencies what
many people consider the measure of dynamic range.

So how one could measure "true dynamic range"? Essentially, one
cannot separate dynamic range from resolution; e.g., in each
exposition zone, one could measure the S/N ratio at different spacial
frequencies, and find at which frequency S/N ratio goes above 3 (or
some other reasonable number).

One gets a curve of (thus defined) spacial resolution per degree of
underexposition; *this curve*, IMO, is the measure of dynamic range.

Again: I agree with you that such an investigation will *most
probably* give film much lower mark than digital sensor - but 10x20in
film is practical, and digital is not. BTW, the question I addressed
in my initial posting is also related to this: for which f-numbers
this advantage of film will disappear, since FF digital sensor may
behave as well as HUGE area of film.

Thanks,
Ilya
 
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Ilya Zakharevich
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      10-16-2006
[A complimentary Cc of this posting was sent to
frederick
<(E-Mail Removed)>], who wrote in article <1160974662.417746@ftpsrv1>:
> Would you like to qualify your "lack of being impressed" by some
> objective measure of your own


Already the second paragraph contains complete BS:

And with that smaller focal length is around a 2.5 times increase
in available depth of field.

Anyone knows that switching formats does not bring any change in DoF -
if one WANTS to produce identical images, one can.

Different formats produce non-identical results only because of
different "effective MP count", and lens quality at the used f-stop
(well, QE may also enter the picture, e.g., when you compare film to
digital). You just use f-stop "proportional" to the formfactor, and
everything else comes out to be identical.

Let me repeat:

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)

Hope this helps,
Ilya
 
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Matt Clara
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      10-16-2006
"Scott W" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com...
> Matt Clara wrote:
> > I haven't used 10 mp, so I don't know, but I suspect it would lack

> in one
>> way, and that's the same way the 6-8 mp cameras do: upon enlargement they
>> begin to break down rather quickly. To me this speaks to overall levels
>> of
>> infomation present in the two mediums, but it could be any number of
>> reasons. Enlargement, of course, isn't the reason digital is eclipsing
>> 35mm, and even there it's good enough for some purposes. I still shoot
>> my
>> formals as well as some select other shots with medium-format film
>> precisely
>> because it can be blown up poster-size with little detraction to the
>> image,
>> provided it's a sharp, well exposed negative, of course.

>
> This seems like a bit of bait and switch to me, you seem to claim that
> 35mm film is better then an 8 MP DSLR but then you say you are using MF
> film. Clearly MF will easily beat an 8 MP DLSR but I have yet to see a
> color image from 35mm film that beats a 8 MP DSLR and the vast majority
> of 35mm film scans fall far short of a 8 MP DSLR.
>
>


You're right Scott, I should have mentioned that I have shot 35mm right
along side digital, plus I used to shoot nothing but 35mm, and 35mm blows up
better. I also think I get more keepers with 35mm, and fewer exposure
problems, but the ability to see those problems with the digital is
priceless and the fact that I don't have to pay for 15 rolls of development
and prints isn't priceless, I can see a very real savings there, though it's
traded for lots of time in front of a computer. As for your inability to
see that 35mm beats digital in most forms today, I suggest you simply don't
have the experience there, or you would. And I'm not talking about scans of
35mm--you don't have to scan it to get the job done, see.

--
Regards,
Matt Clara
www.mattclara.com


 
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Scott W
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      10-16-2006
Matt Clara wrote:
>And I'm not talking about scans of
> 35mm--you don't have to scan it to get the job done, see.


But scanning is about the only way we have to compare, unless you want
to come to Hawaii with your prints. If you are trying to say that
optical prints show more detail then it should be easy to scan the
optical print.

The best that I have seen by far is a scan Max Perl did and whereas the
35mm shot showed more detail then an 8 MP camera when printed out they
were about the same quality due to the grain in the film scan.

Since I would not do a workflow that does not have the image in a
digital form at some point if it can't be scanned it is not of much
value to me. And since I have yet to see anyone demonstrate that a
workflow that does not scan the film can produce a better image when
when you scan film I am not going to take that on faith.

Scott

 
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Neil Ellwood
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      10-16-2006
David J. Littleboy wrote:

>
> "Greg "_"" <grey_egg@greg_photo.com> wrote:
>>> >> If you want to use monochrome film - a material that has
>>> >> incomparably inconvenient performance compared with even the
>>> >> cheap digital cameras that they now sell at the supermarket
>>> >
>>> > Right <smirk :^>
>>> yawn.
>>> 25 iso monochrome....
>>> zzzzzz

>>
>> Reasonably few B&W shooting photographers shoot 25 asa BW film on a
>> consistent, none I know personally.

>
> That's because most of them have been discontinued. Panatomic X and
> Tech Pan are history. (I think there's still an Agfa film in
> production, though.)
>
> Panatomic-X is the reason I hate 35mm. At 11x14, Plus-X in 645 looks
> way better than Panatomic X in 35mm, and is two stops faster. ISO 25
> gets real painful when you want to use either a red filter or a
> polarizer.
>
> Nowadays, TMX 100 is close to what the ISO 25 films used to be in
> terms of grain and resolution, although some people complain they
> don't like its tonal rendition. TMX 100 in 6x7 will edge out the 5D,
> though.

About 40 or so years ago over a period of a couple of years I used
micro-neg pan developed in Dilute FX1a developer (designed by Geoffrey
W. Crawley and published in BJP) rated at 8asa and although it was slow
the results were pleasing but not for action. The grain could hardly be
seen.

--
Delete l to reply.
 
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frederick
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      10-16-2006
Scott W wrote:
> Matt Clara wrote:
>> And I'm not talking about scans of
>> 35mm--you don't have to scan it to get the job done, see.

>
> But scanning is about the only way we have to compare, unless you want
> to come to Hawaii with your prints. If you are trying to say that
> optical prints show more detail then it should be easy to scan the
> optical print.
>
> The best that I have seen by far is a scan Max Perl did and whereas the
> 35mm shot showed more detail then an 8 MP camera when printed out they
> were about the same quality due to the grain in the film scan.
>
> Since I would not do a workflow that does not have the image in a
> digital form at some point if it can't be scanned it is not of much
> value to me. And since I have yet to see anyone demonstrate that a
> workflow that does not scan the film can produce a better image when
> when you scan film I am not going to take that on faith.
>
> Scott
>

I have had plenty of experience with 35mm optical process prints from
negative and transparency - and have a big portfolio of larger
(>10xprints that I can easily compare. Most of the larger prints I
made from 35mm used Fuji iso 50 and Cibachrome. I always carried two
slr bodies, one loaded with iso50 transparency for enlargements, the
other loaded with iso 200 negative film because iso 50 is practically
useless for handheld shooting in less than ideal light, yet ideal light
is seldom what you want for taking interesting pictures.
Scanned 35mm negative film printed with light-jet leaves the optical
process cibachrome prints in the dust for reproducing detail. Inkjet
prints direct from digital look better again, and are almost infinitely
more convenient.
I really couldn't care less about technical arguments - how the picture
looks is the most important factor. A few years ago, I realised that
snapshots taken from an inexpensive pocket sized 4mp P&S digital were
practically as good as what I could get with iso200 35mm. 35mm film is
dead - there is no point at all now that dslr cameras are affordable.
 
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frederick
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      10-16-2006
Ilya Zakharevich wrote:
> [A complimentary Cc of this posting was sent to
> frederick
> <(E-Mail Removed)>], who wrote in article <1160974662.417746@ftpsrv1>:
>> Would you like to qualify your "lack of being impressed" by some
>> objective measure of your own

>
> Already the second paragraph contains complete BS:
>
> And with that smaller focal length is around a 2.5 times increase
> in available depth of field.
>
> Anyone knows that switching formats does not bring any change in DoF -
> if one WANTS to produce identical images, one can.
>

Only when maximum DOF is the objective. Not when shallow DOF is sought.
>
> Different formats produce non-identical results only because of
> different "effective MP count", and lens quality at the used f-stop
> (well, QE may also enter the picture, e.g., when you compare film to
> digital). You just use f-stop "proportional" to the formfactor, and
> everything else comes out to be identical.
>

You have quoted selectively:
"The only downside to my new system is working with depth of field. On
my 4x5 Linhof, I have a focusing gauge that allows me to quickly
determine the optimum f stop for each situation. With the Mamiya and the
zoom lenses, this is much harder to determine. On the plus side, a
composition that required a 200mm on the 4x5 needs only an 80mm for the
P45 sensor. And with that smaller focal length is around a 2.5 times
increase in available depth of field."

That comment "available depth of field" doesn't have to mean as you
assume it could.
 
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Ilya Zakharevich
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      10-16-2006
[A complimentary Cc of this posting was sent to
frederick
<(E-Mail Removed)>], who wrote in article <1161030861.1650@ftpsrv1>:
> > Anyone knows that switching formats does not bring any change in DoF -
> > if one WANTS to produce identical images, one can.


> Only when maximum DOF is the objective. Not when shallow DOF is sought.


When true, this is a part of what I said: one needs the same "lens
quality at the used f-stop". When/If you can open 35mm-formfactor
lens to the same entry pupil as the LF lens (with the same "optical
build quality"), they create identical images (only scaled
differently) - same diffraction, "same" abberations, same DoF. Of
course, this "If/when" is rarely possible...

> > Different formats produce non-identical results only because of
> > different "effective MP count", and lens quality at the used f-stop
> > (well, QE may also enter the picture, e.g., when you compare film to
> > digital). You just use f-stop "proportional" to the formfactor, and
> > everything else comes out to be identical.


> You have quoted selectively:
> "The only downside to my new system is working with depth of field. On
> my 4x5 Linhof, I have a focusing gauge that allows me to quickly
> determine the optimum f stop for each situation. With the Mamiya and the
> zoom lenses, this is much harder to determine. On the plus side, a
> composition that required a 200mm on the 4x5 needs only an 80mm for the
> P45 sensor. And with that smaller focal length is around a 2.5 times
> increase in available depth of field."
>
> That comment "available depth of field" doesn't have to mean as you
> assume it could.


I do not agree with you. Read: "on the plus side"; obviously, he
thinks that with smaller formfactor he will have larger depth of
field. (This is only true if he would use the same f-stop; but when
you convert to a more open f-stop needed to get the same diffraction
[measured in the subject space, i.e., in angular units], one gets
exactly the same DoF...)

Yours,
Ilya
 
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frederick
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      10-16-2006
Ilya Zakharevich wrote:
> [A complimentary Cc of this posting was sent to
> frederick
> <(E-Mail Removed)>], who wrote in article <1161030861.1650@ftpsrv1>:
>>> Anyone knows that switching formats does not bring any change in DoF -
>>> if one WANTS to produce identical images, one can.

>
>> Only when maximum DOF is the objective. Not when shallow DOF is sought.

>
> When true, this is a part of what I said: one needs the same "lens
> quality at the used f-stop". When/If you can open 35mm-formfactor
> lens to the same entry pupil as the LF lens (with the same "optical
> build quality"), they create identical images (only scaled
> differently) - same diffraction, "same" abberations, same DoF. Of
> course, this "If/when" is rarely possible...
>
>>> Different formats produce non-identical results only because of
>>> different "effective MP count", and lens quality at the used f-stop
>>> (well, QE may also enter the picture, e.g., when you compare film to
>>> digital). You just use f-stop "proportional" to the formfactor, and
>>> everything else comes out to be identical.

>
>> You have quoted selectively:
>> "The only downside to my new system is working with depth of field. On
>> my 4x5 Linhof, I have a focusing gauge that allows me to quickly
>> determine the optimum f stop for each situation. With the Mamiya and the
>> zoom lenses, this is much harder to determine. On the plus side, a
>> composition that required a 200mm on the 4x5 needs only an 80mm for the
>> P45 sensor. And with that smaller focal length is around a 2.5 times
>> increase in available depth of field."
>>
>> That comment "available depth of field" doesn't have to mean as you
>> assume it could.

>
> I do not agree with you. Read: "on the plus side"; obviously, he
> thinks that with smaller formfactor he will have larger depth of
> field. (This is only true if he would use the same f-stop; but when
> you convert to a more open f-stop needed to get the same diffraction
> [measured in the subject space, i.e., in angular units], one gets
> exactly the same DoF...)
>
> Yours,
> Ilya

Yes - but he also gets increased DOF at the same f-stop , same FOV, and
same shutter speed. For sure a big drawback for large format is slow
shutter speeds, as although you can use a tripod, you can't stop things
from moving in the frame.
Ultimately you are of course correct - but it may mean that you can't
take a photo with even a moving snail in the frame
 
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