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  #11  
Old March 5th 09, 07:50 AM posted to rec.photo.equipment.35mm
Colin.D
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Posts: 217
Default Film Q.

David Nebenzahl wrote:
On 3/3/2009 12:31 PM Michael Benveniste spake thus:

"Annika1980" wrote in message
...

Remind me again .....

I just got a few rolls of Kodak Ektar 100.
Everything I read says to rate it at either 50 or 64 instead
of 100.


If Johnny tells you to jump off a cliff ... (I'd rate it
at 80 myself).


Doesn't the difference between ISO 50 and 64 fall well under the
tolerance for inaccuracy in most camera's light meters? In other words,
won't make any visible difference.

For me, ISO 50 and 64 can be treated as identical for all practical
purposes. Even 50 and 80 are pretty dang close (1 stop vs. ~2/3 stop
difference).


Calibration may be out a bit with any given meter, but the repeatability
should be pretty accurate. You should always test a film against your
meter to find the best setting for your camera, after which the meter
should be as accurate as you want.

Professional meters like the Sekonic range for example are guaranteed
accurate to within 1/10 of a stop, provided it is used intelligently.

Colin D.
  #12  
Old March 5th 09, 08:11 AM posted to rec.photo.equipment.35mm
David Nebenzahl
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Posts: 1,353
Default Film Q.

On 3/4/2009 9:17 PM Peter Irwin spake thus:

Michael Benveniste wrote:

On Thu, 5 Mar 2009 01:51:17 +0000 (UTC), Peter Irwin
wrote:

It is going to take more than the listed results from filmscan.ru
to convince me that Kodak is rating their films inaccurately.


Then pick up some old film shootouts from the various photo magazines,
or go shoot some and ask your lab to measure the densities for you, or
talk to people who rate their own film, and see if they use the same
EI for all films with the same ISO rating.


That's another question entirely. What is optimum to use is a different
question from whether or not films are rated accurately. Film
manufacturers always tell users to find their own optimum EI by testing,
and say the ISO rating is only a starting point.


This whole exchange you two are having is very enlightening (what parts
of it aren't whizzing over my head). Please don't stop.


--
Made From Pears: Pretty good chance that the product is at least
mostly pears.
Made With Pears: Pretty good chance that pears will be detectable in
the product.
Contains Pears: One pear seed per multiple tons of product.

(with apologies to Dorothy L. Sayers)
  #13  
Old March 5th 09, 03:18 PM posted to rec.photo.equipment.35mm
Michael Benveniste[_2_]
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Posts: 229
Default Film Q.

"Peter Irwin" wrote"

That's another question entirely. What is optimum to use is a different
question from whether or not films are rated accurately. Film
manufacturers always tell users to find their own optimum EI by testing,
and say the ISO rating is only a starting point.


If ISO is as accurate as you claim, such tests would result
in the same EI for all films of a given ISO. They don't.

Cine negative film speeds are covered by a different ISO standard than
still negative films. Both will be rated to the nearest standard value
to the measured speed.


And that standard is? For the 250D movie film, Kodak states:
"Use these indexes with incident- or reflected-light exposure
meters and cameras marked for ISO or ASA speeds or exposure
indexes."
So from this statement, we see that ISO for movie photography
should equate to ASA, which covered both markets. You claim
that ASA and ISO for still camera film are also equivalent. If
A=B and B=C, then why doesn't A=C?

One uses the same exposure meters and settings for movie or
still photography. I haven't shot 250D in a film camera, but I
have shot Fuji Eterna 500T. The "grain" was about the same as
Fuji NPZ, but I found it was true to its 500 speed badging.

I bet that difference is to gain more contrast on the Portra by
putting more of the exposure off the toe.


When I'm using a film like 160S, I'm not interested in gaining
contrast.

Within 1/6th of a stop for _all_ existing films? Not very likely.

From _Photographic_Sensitometry_ by Todd and Zakia (1974 ed) p.162


You're confusing precision and accuracy. ASA defined one method
of measurement, specifying a precision of 1/3rd of a stop. Yet
under those methods, original Tri-X was marketed at either two or
three different speeds. ISO also specifies a precision of 1/3rd
of a stop, but requires different measurements. Both specs had
and have plenty of slop.

Neither B&H nor Adorama make film. I haven't seen anything actually
from Kodak which claims 3200 as the ISO speed.


Here's one such flyer:
http://wwwca.kodak.com/HK/zh/consume...ireworks.shtml

I haven't used Ektar 100 yet. I don't doubt that you saw what you
describe. I do doubt that it had anything to do with overexposure.


So inaccurate recording of color doesn't qualify as overexposure
by your definition? Then we should agree to disagree.

Then please feel free to provide your own data or test shots rather
than stating generalities.

My three generalities were useful, and were things I did not
know when staring out.


The site I referred to provided data from actual tests, which
you claim are not meaningful. So please provide meaningful
data to support your generalities.

--
Michael Benveniste -- (Clarification required)
Nid wif yn y swyddfa ar hyn o bryd. Anfonwch ar unrhyw waith i'w
gyfieithu.


  #14  
Old March 5th 09, 10:22 PM posted to rec.photo.equipment.35mm
Doug Jewell[_3_]
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Posts: 426
Default Film Q.

Peter Irwin wrote:
Michael Benveniste wrote:


You're right on Kodak's spec sheets, although they've been less
precise in consumer ads.

In their specifications tab B&H lists both TMAX-3200 and Delta 3200 as
ISO 3200 films. Adorama does the same.


Neither B&H nor Adorama make film. I haven't seen anything actually
from Kodak which claims 3200 as the ISO speed.

Just grabbed a box out of the fridge - here is what it says:
Front:
Kodak Professional
T-MAX P3200 FILM
P3200TMAX
Black & White Negative Film
Film Negatif Noir Et Blanc
Schwarzweiss Negativ Film
Pelicula Negativa En Blanco Y Negro

End:
Kodak Professional
T-MAX P3200 FILM
P3200 TMAX
Black & White Negative Film
Film Negatif Noir Et Blanc
135-36 P3200TMZ

The other end is the same except in foreign language.

Top
Kodak Olympic Sponsor Symbol.
T-Max P3200 Film
P3200TMAX

Bottom
36 EXP
24x36mm
CAT 151 6798
Made In USA
Finished in Mexico for
EASTMAN KODAK COMPANY
Rochester NY 14650
www.kodak.com/go/professional

Back:
Limitation of Liability: blah blah blah
Expiry Date...

EXPIRY 05/2007... FLAMIN HELL!!!
I bought a pack just before my youngest kid was born to do
some nice grainy baby photos. He's now 2-1/2, and the pack
is untouched. Time to get some batteries for the film camera
and start snapping I think. I hope my developer and fixer
are still good.

In answer to the original discussion, there is nothing on
the box that actuall says "ISO 3200", although it is
certainly inferred by the repeated use of "P3200". The DX
coding on the film is 3200, if that means anything. I've
always shot it at 3200, because I like the look that it
gives at that speed. I don't know and don't care what the
true ISO rating of the film is - 3200 gives results that I
like. If I didn't want the look that P3200 gives at 3200,
I'd shoot something else.
  #15  
Old March 9th 09, 03:28 AM posted to rec.photo.equipment.35mm
Alan Browne
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Posts: 12,640
Default Film Q.

Peter Irwin wrote:
Michael Benveniste wrote:


In their specifications tab B&H lists both TMAX-3200 and Delta 3200 as
ISO 3200 films. Adorama does the same.


Neither B&H nor Adorama make film. I haven't seen anything actually
from Kodak which claims 3200 as the ISO speed.


As responsible vendors B&H and Adorama do post the specifications of the
products they sell, which was Michael's point, I'm sure.

As to 3200 ISO, yes indeed, Kodak make that too.
  #16  
Old March 9th 09, 04:37 AM posted to rec.photo.equipment.35mm
Peter Irwin
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Posts: 352
Default Film Q.

Michael Benveniste wrote:
"Peter Irwin" wrote"

That's another question entirely. What is optimum to use is a different
question from whether or not films are rated accurately. Film
manufacturers always tell users to find their own optimum EI by testing,
and say the ISO rating is only a starting point.


If ISO is as accurate as you claim, such tests would result
in the same EI for all films of a given ISO. They don't.


There seem to be several issues packed together here.
- Are ISO ratings the nearest standard value to what the film
actually was tested at? (Yes)
- Are the ISO ratings of negative films a valid indicator of
the useful response of the film in the toe, so that two films
of the same rating will have about equal shadow detail for
the same exposure? (I think yes)
- Do the two points above mean that you can determine the exposure
which will get the results you want entirely from the ISO speed
rating? (No)

Cine negative film speeds are covered by a different ISO standard than
still negative films. Both will be rated to the nearest standard value
to the measured speed.


And that standard is?


I was wrong about this. There is no ISO speed for cine negative films.
There seems not to be a standard on purpose. (The standard for reversal
films covers both still and cine films, but the standards for negative
films specify still films only.) Kodak's cine negative films all carry
an EI rating in their datasheets. I haven't been able to find out what
Kodak's rules are for rating cine negatives, but they seem generally
to be 2/3 of a stop under what the ISO speed rating would be if they
were still films. Thus Plus-X cine negative is rated at EI 80, but is
the same speed (though not exactly the same film) as Plus-x 125 for
35mm still cameras. The EI 250 cine films seem to be about the speed
of ISO 400 still negative films.

For the 250D movie film, Kodak states:
"Use these indexes with incident- or reflected-light exposure
meters and cameras marked for ISO or ASA speeds or exposure
indexes."
So from this statement, we see that ISO for movie photography
should equate to ASA, which covered both markets. You claim
that ASA and ISO for still camera film are also equivalent. If
A=B and B=C, then why doesn't A=C?


The meters are the same. Exposing cine negatives at the rating
system used for still negative camera films would give you
degraded blacks. You have probably noticed that reversal films
of a given speed rating tend to be much better at picking up
shadow detail. Kodachrome 64 will give you a bit better shadow detail
at box speed than ISO 100 colour negative film shot at EI64.
If you are going to make a transparency for projection from
negative film shot at the ISO speed rating, you will probably
find the film underexposed for that purpose. ISO speed for negative
films is supposed to be the minimum exposure required to produce
a reflection print rated as excellent. The same exposure is probably
inadequate for making a transparency for projection.

One uses the same exposure meters and settings for movie or
still photography. I haven't shot 250D in a film camera, but I
have shot Fuji Eterna 500T. The "grain" was about the same as
Fuji NPZ, but I found it was true to its 500 speed badging.


Interesting, how did you do the subjective comparison?
If my belief is correct about cine films being rated
conservatively then Eterna 500T should be more than
1 stop faster than NPZ+80A conversion filter. If it is
only equal to ISO 500 then it should be less than one
stop faster than ISO 800 speed negative plus an 80A filter.

Note that if you are shooting tungsten balanced negative film
or daylight film plus an 80A then you need a little extra
exposure with 2800K household incandescents to get enough blue
on the film.

Neither B&H nor Adorama make film. I haven't seen anything actually
from Kodak which claims 3200 as the ISO speed.


Here's one such flyer:
http://wwwca.kodak.com/HK/zh/consume...ireworks.shtml


It does seem that Kodak got it wrong on a Chinese language webpage.
Thanks for pointing that out. It would seem to indicate that it is
something that Kodak promotional material very rarely gets wrong.

Peter.
--

  #17  
Old March 10th 09, 12:26 AM posted to rec.photo.equipment.35mm
Michael Benveniste[_2_]
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Posts: 229
Default Film Q.

"Peter Irwin" wrote:

There seem to be several issues packed together here.
- Are ISO ratings the nearest standard value to what the film
actually was tested at? (Yes)


I'm not sure what you're saying here. The ISO rating is a
summary statistic of a test, but that doesn't speak to the
accuracy of that test.

- Are the ISO ratings of negative films a valid indicator of
the useful response of the film in the toe, so that two films
of the same rating will have about equal shadow detail for
the same exposure? (I think yes)


The ISO standard says nothing about the shape of the curve, and
the ASA measurement specifically ignored the toe when rating
a film.

But to test your claim, compare the curves for Fuji Reala 100
and Fuji Superia 100. The manufacturer, exposure and methods
and resulting ISO ratings are the same; the toes are markedly
different.
http://www.fujifilm.com/products/con..._datasheet.pdf
http://www.fujifilm.com/products/con..._datasheet.pdf

Thus Plus-X cine negative is rated at EI 80, but is
the same speed (though not exactly the same film) as Plus-x 125 for
35mm still cameras. The EI 250 cine films seem to be about the speed
of ISO 400 still negative films.


Ah, Plus-X. Initially marketed as an ASA 80 film, it then changed
to an ASA 160 film, and finally settled in at 125. But Kodak 5231/
7231 and PXP are the same stuff -- only the aerial stuff is different.
If you're willing to load it yourself in a changing bag or darkroom,
you can often buy "short ends" of Kodak 5231 for under $0.20 a foot.
Then shoot and process normally.

Once again we find that in other markets, Kodak does refer to 5231/7231
as an ISO 80 film:
http://motion.kodak.com/DE/de/motion...ilms/index.htm

But here the difference in recommended shooting speeds is easily
explained. Kodak recommends EI 80 for D-96 developer. D-96 has less
metol and hydroquinone than D-76, so it isn't surprising that the
output is different. There's no such discrepency between ECN-II and
C-41 chemistry.

The Aerecon version has extended red sensitivity and gets yet a
different rating (200) on yet a different ISO scale (ISO-A) for
a different developer. I've never tried it, and with a minimum order
of 500' in 70mm I'm not likely to. But I have tried Agfa Aviphot
N400, which is a C-41 film. That film was rated at 400 via both the
ISO-A and ISO methods, and did well in my Pentax 645 at rated speed.
I certainly wouldn't rate it any lower.

The meters are the same. Exposing cine negatives at the rating
system used for still negative camera films would give you
degraded blacks.


By "degraded blacks," do you mean loss of shadow detail?
Underexposing would make the blacks even blacker.

In the past, several labs offered a service to create slides
as well as negatives from C-41 film. Dale labs still does.
While such slides suffer from the usual "2nd generation" issues,
loss of shadow detail was not a significant problem.

Nor does the difference in workflow explain the difference
in recommendations. When movies shifted from using optical
intermediate films to a digital intermediate process, the
EI of camera films didn't change at all.

One uses the same exposure meters and settings for movie or
still photography. I haven't shot 250D in a film camera, but I
have shot Fuji Eterna 500T. The "grain" was about the same as
Fuji NPZ, but I found it was true to its 500 speed badging.


Interesting, how did you do the subjective comparison?


I compared grain by scanning both films with a Canon FS4000US.
I determined exposure by bracketing and verifying incident
light with a Minolta V light meter.

The grain comparison was against NPZ shot in daylight -- I
gave up on trying to use 80A filters long ago.

I've shot the 500T under 3200K photofloods, stage lighting,
and room lighting. It's a bit warm under room lighting, as
expected. I've still got about 100' left of the stuff in
the freezer, so I can spool up some more if you want to give
it a try.

--
Michael Benveniste -- (Clarification required)
Nid wif yn y swyddfa ar hyn o bryd. Anfonwch ar unrhyw waith i'w
gyfieithu.

  #18  
Old March 10th 09, 05:29 PM
Harold Gough Harold Gough is offline
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First recorded activity by PhotoBanter: Mar 2008
Posts: 31
Default

In the pre-digital days the rule of thumb was to slightly under-expose reversal film and to slightly over-expose print film. To me, that would mean 1/3 to 1/2 stop and no more.

Quote:
Originally Posted by Peter Irwin View Post
Michael Benveniste wrote:
On Thu, 5 Mar 2009 01:51:17 +0000 (UTC), Peter Irwin

wrote:

It is going to take more than the listed results from filmscan.ru
to convince me that Kodak is rating their films inaccurately.


Then pick up some old film shootouts from the various photo magazines,
or go shoot some and ask your lab to measure the densities for you, or
talk to people who rate their own film, and see if they use the same
EI for all films with the same ISO rating.


That's another question entirely. What is optimum to use is a different
question from whether or not films are rated accurately. Film
manufacturers always tell users to find their own optimum EI by testing,
and say the ISO rating is only a starting point.


Kodak isn't rating films inaccurately -- the spec is simply loose
enough to permit them to choose the nominal rating. Don't believe me?
Compare the characteristic curve of Kodak 400NC to that for Kodak
Vision2 250D.


Cine negative film speeds are covered by a different ISO standard than
still negative films. Both will be rated to the nearest standard value
to the measured speed.

My own experience with 400UC and 400NC show them to be at 2/3rds
of a stop apart. Similarly, I rate Fuji 160S at either 125 or 160,
but I typically rated Portra 160 at 100.


I bet that difference is to gain more contrast on the Portra by putting
more of the exposure off the toe.

Within 1/6th of a stop for _all_ existing films? Not very likely.


From _Photographic_Sensitometry_ by Todd and Zakia (1974 ed) p.162
"Manufacturers' published speed values necessarily include some
tolerance. Thus an ASA Speed value of 64 represents in fact a range
of speed values. The present standard permits a total range, at the
time of testing, of 1/3 of a stop, so that a film rated at 64 could
have a tested speed between 57 and 71."
"Beyond this tolerance, any given sample of film will, by reason
of its age and usually unknown storage conditions, have an effective
speed perhaps considerably different from the value obtained when
it was tested."

You're right on Kodak's spec sheets, although they've been less
precise in consumer ads.

In their specifications tab B&H lists both TMAX-3200 and Delta 3200 as
ISO 3200 films. Adorama does the same.


Neither B&H nor Adorama make film. I haven't seen anything actually
from Kodak which claims 3200 as the ISO speed.


Specifically with Ektar 100, I found an overexposure of about 2 stops
was sufficient to blow out the blues, resulting in the dreaded C-41
cyan sky. And you?


I haven't used Ektar 100 yet. I don't doubt that you saw what you
describe. I do doubt that it had anything to do with overexposure.
I think it highly probable that this is a side effect of moving
the shadow values up off the toe thus increasing the overall
contrast with the result that the same printing contrast didn't
give enough room on the paper for the highlights.

Then please feel free to provide your own data or test shots rather
than stating generalities.


My three generalities were useful, and were things I did not
know when staring out.

With colour negative film
- a small increase in exposure gives better detail in the shadows
- a small increase in exposure results in a decrease in apparent grain
- a small increase in exposure reduces the risk of underexposure
and that the risk of underexposing negative films is greater than
the risk of overexposure thus giving more useful latitude.

I should also have noted that increasing exposure increases the
contrast in the shadows which can sometimes have undesirable
consequences and that increased exposure also makes film very
slightly less sharp, although this is scarcely noticeable unless
you go seriously overboard.

Peter.
--
  #19  
Old March 11th 09, 01:57 AM posted to rec.photo.equipment.35mm
Alan Browne
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Posts: 12,640
Default Film Q.

Harold Gough wrote:
In the pre-digital days the rule of thumb was to slightly under-expose
reversal film and to slightly over-expose print film. To me, that would
mean 1/3 to 1/2 stop and no more.


Slightly under-exp reversal means 1/3 to 1/2 stop.

Slightly over-exp negative means 1/2 to 1 stop.

Don't top post. Do trim attribution to what's relevant.



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  #20  
Old March 11th 09, 02:45 AM posted to rec.photo.equipment.35mm
Michael Benveniste[_2_]
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Posts: 229
Default Film Q.

On Tue, 10 Mar 2009 09:47:29 -0700 (PDT), Annika1980
wrote:

And therein lies the main difference between film and digital!
The digital shooters want high Megapixels, low noise, and anything
else that will give them the best shot.
The film shooters worry about the shape of the toes on the film
curves.


Digital shooters get to worry instead about birefringence in micro
lenses, sensor bloom, light-angle induced falloff, banding and a whole
set of different issues. They also have to worry about paying for
that latest and greatest camera every 2 years or so. Been there,
still doing that.

The funny thing is that I _don't_ worry about curves, toes, and the
rest except in one rare circumstance. Once or twice a year, I'll
shoot slow black-and-white film outdoors in medium or large format and
do the quasi-zone system thing. Otherwise, I just grab the film I
want, set the EI to my preferred value, load up and go.

Yeah, once in a great while, I have to *gasp* go out and shoot a test
roll to rate a new film, or at least one new to me. Such a burden!

In most typical shooting situations, you can shoot at the
manufacturer's suggested speed and get reasonably good results. You
make decide you like the "look" of a different EI, but that's purely a
subjective call. Don't let anyone else make it for you, whether you
crank that difference in via EI or exposure compensation.

But when the lighting gets both interesting and challenging, whether
you are shooting digital or analog, you're going to have to make some
tough choices. If you have the luxury of a static subject, a sturdy
support, and sufficient shooting time, you can use HDR techniques. If
you're not that lucky, then there isn't a generality in the world that
can help you.

My point in this thread is that the manufacturer's speed ratings on
film, even when marked as an ISO rating, is a compromise between the
engineers and the marketeers for a particular market. It doesn't tell
you anything about exposure latitude, contrast, color shifts or any of
the other non-linear response characteristics you see when you push
the envelope.

--
Mike Benveniste -- (Clarification Required)
Amo conventum instituti. -- Artifex Hannibal
 




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