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  #1  
Old March 3rd 09, 09:31 PM posted to rec.photo.equipment.35mm
Michael Benveniste[_2_]
external usenet poster
 
Posts: 229
Default Film Q.

"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).

That means I set my camera's ISO to 64. OK, so far.


Now when I have the film developed do I have the lab develop it
normally as if it was shot at ISO 100?


Yes.

What is the difference between doing this and shooting at +2/3
Exposure Compensation?


Unless you're using some sort of data recording, the main
advantage is convenience.

--
Michael Benveniste -- (Clarification required)
Legalize Updoc.

  #2  
Old March 4th 09, 12:01 AM posted to rec.photo.equipment.35mm
David Nebenzahl
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Posts: 1,353
Default Film Q.

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).


--
Any system of knowledge that is capable of listing films in order
of use of the word "****" is incapable of writing a good summary
and analysis of the Philippine-American War. And vice-versa.
This is an inviolable rule.

- Matthew White, referring to Wikipedia on his WikiWatch site
(http://users.erols.com/mwhite28/wikiwoo.htm)
  #3  
Old March 4th 09, 01:17 AM posted to rec.photo.equipment.35mm
Peter Irwin
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Posts: 352
Default Film Q.

David Nebenzahl wrote:

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).


It's true that shutters and light meters are often less accurate
than we would like them to be, but I think the idea is to have
a bias in favour of a generous exposure.

Aiming towards a generous exposure of C-41 negative does three
things for you.

1) It improves shadow detail.
2) It reduces apparent graininess.
3) It makes the film's latitude more useful. C-41 film has plenty of
overexposure latitude, but little if any underexposure latitude.

Peter.
--


  #4  
Old March 4th 09, 01:42 AM posted to rec.photo.equipment.35mm
David Nebenzahl
external usenet poster
 
Posts: 1,353
Default Film Q.

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

David Nebenzahl wrote:

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).


It's true that shutters and light meters are often less accurate
than we would like them to be, but I think the idea is to have
a bias in favour of a generous exposure.

Aiming towards a generous exposure of C-41 negative does three
things for you.

1) It improves shadow detail.
2) It reduces apparent graininess.
3) It makes the film's latitude more useful. C-41 film has plenty of
overexposure latitude, but little if any underexposure latitude.


Yes. I routinely overexpose color negative film by 2/3 stop and seem to
see all the benefits you listed.

--
Any system of knowledge that is capable of listing films in order
of use of the word "****" is incapable of writing a good summary
and analysis of the Philippine-American War. And vice-versa.
This is an inviolable rule.

- Matthew White, referring to Wikipedia on his WikiWatch site
(http://users.erols.com/mwhite28/wikiwoo.htm)
  #5  
Old March 4th 09, 02:31 PM posted to rec.photo.equipment.35mm
Michael Benveniste[_2_]
external usenet poster
 
Posts: 229
Default Film Q.

"Peter Irwin" wrote:

Aiming towards a generous exposure of C-41 negative does three
things for you.

1) It improves shadow detail.
2) It reduces apparent graininess.
3) It makes the film's latitude more useful. C-41 film has plenty of
overexposure latitude, but little if any underexposure latitude.


The third point depends strictly on the manufacturers nominal
rating as compared to physical response of the actual emulsion.
There's no technical reason why a C-41 film exposed at the
box rating couldn't have lots of underexposure latitude and
only a little overexposure latitude.

What is clear from looking at the curves of the Ektar 100
datasheet is that overexposure will tend to emphasize blues,
contributing to an overall cooler exposure. That's why I
suggest that people don't rely on generalizations and rate their
own film to their own preference.

After my own test roll (which included bouncing my F100 off a
sidewalk), I found that 80 was the best compromise with my Nikon
gear.

--
Michael Benveniste -- (Clarification required)
Legalize Updoc.

  #6  
Old March 4th 09, 05:09 PM posted to rec.photo.equipment.35mm
Peter Irwin
external usenet poster
 
Posts: 352
Default Film Q.

Michael Benveniste wrote:
"Peter Irwin" wrote:
3) It makes the film's latitude more useful. C-41 film has plenty of
overexposure latitude, but little if any underexposure latitude.


The third point depends strictly on the manufacturers nominal
rating as compared to physical response of the actual emulsion.
There's no technical reason why a C-41 film exposed at the
box rating couldn't have lots of underexposure latitude and
only a little overexposure latitude.


Manufacturers rate the sensitivity of colour negative film
according to the ISO standard. The speed of negative films
is based on shadow sensitivity. All colour negative films
of the same rating have the same shadow sensitivity within
1/3 of a stop (plus or minus 1/6 of a stop from nominal rating).

There are few cases where Kodak gives a box speed which does
not conform to the ISO standard, but when they do this they
are careful to print EI rather than ISO. When Kodak says the
speed is ISO then it is.

All modern colour negative films have considerable overexposure
latitude. Compare the H&D graphs for a 100 speed c-41 film and
a 100 speed e-6 film and you will invariably find that the
c-41 film stays reasonably linear to the right of the point where
the e-6 film goes completely clear.


What is clear from looking at the curves of the Ektar 100
datasheet is that overexposure will tend to emphasize blues,
contributing to an overall cooler exposure.


The three colours seldom (or never) track as perfectly as
one might wish, but the overall balance in a colour print
is always adjusted when printing. You do realise that each
1/3 of a stop increase in exposure is a shift of 0.1 units
to the right on the graph.

That's why I
suggest that people don't rely on generalizations and rate their
own film to their own preference.


Absolutely. You should always do your own experimentation to
see what works best for you.

I will have to buy some Ektar 100 soon. The claimed Print Grain
Index figures are especially impressive. If you look at the decade
old figures for Vericolor III 160, you will notice that the claimed
performance from 35mm Ektar 100 is comparable to the claims for
6x6 format vericolor III. Remarkable.

Peter.
--



  #7  
Old March 5th 09, 01:45 AM posted to rec.photo.equipment.35mm
Michael Benveniste[_2_]
external usenet poster
 
Posts: 229
Default Film Q.

On Wed, 4 Mar 2009 16:09:27 +0000 (UTC), Peter Irwin
wrote:

Manufacturers rate the sensitivity of colour negative film
according to the ISO standard. The speed of negative films
is based on shadow sensitivity. All colour negative films
of the same rating have the same shadow sensitivity within
1/3 of a stop (plus or minus 1/6 of a stop from nominal rating).


Take a look at the test results at this website and see if you still
believe that:
http://www.cacreeks.com/films.htm

The 1987 ISO standard does not define speed by shadow sensitivity per
se. It establishes density criteria instead. The standard merely
codified existing practice -- as far as I know not a single color
negative films had to be reformulated or rebadged in order to meet the
1987 standard.

There are few cases where Kodak gives a box speed which does
not conform to the ISO standard, but when they do this they
are careful to print EI rather than ISO. When Kodak says the
speed is ISO then it is.


On a box of TMax-3200, what's the designation? Certainly in spec
sheets, it's listed as an ISO-3200/36 film. They can get away with
that because of the "recommended processing" loophole in the ISO
specs.

All modern colour negative films have considerable overexposure
latitude.


Again, the site I mentioned above disagrees. They give Ektar 100 only
2 stops of overexposure latitude, which means that if you expose it at
an EI of 64 you'll have less overexposure latitude than underexposure.
Superia 100 they rate at +2/-2.

I will have to buy some Ektar 100 soon. The claimed Print Grain
Index figures are especially impressive. If you look at the decade
old figures for Vericolor III 160, you will notice that the claimed
performance from 35mm Ektar 100 is comparable to the claims for
6x6 format vericolor III. Remarkable.


Actually, I still have some frozen Vericolor III in 70mm. Assuming I
can find anyone who can still process the stuff, I'd like to revisit
it someday.

--
Mike Benveniste -- (Clarification Required)
Cogito eggo sum -- I'm thinking toaster waffles for breakfast.
  #8  
Old March 5th 09, 02:51 AM posted to rec.photo.equipment.35mm
Peter Irwin
external usenet poster
 
Posts: 352
Default Film Q.

Michael Benveniste wrote:

Take a look at the test results at this website and see if you still
believe that:
http://www.cacreeks.com/films.htm


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

The 1987 ISO standard does not define speed by shadow sensitivity per
se. It establishes density criteria instead. The standard merely
codified existing practice -- as far as I know not a single color
negative films had to be reformulated or rebadged in order to meet the
1987 standard.


The first ASA standard for colour negative films came out
in 1965. The method of averaging the colour layers and the
definition of the speed point have been rejigged since then
but the changes were intended to be neutral for the majority
of films. In other words, I would expect the results of the current
method and the 1965 method to be very close in most cases.


On a box of TMax-3200, what's the designation?


From memory, it doesn't say anything about ISO on the box.
I don't have a roll right now to check.

Certainly in spec
sheets, it's listed as an ISO-3200/36 film.


I just checked. The PDF spec sheets say ISO 1000 in Tmax developer,
and ISO 800 in D-76 and most other developers. Show me which
spec sheets say ISO 3200.

They can get away with
that because of the "recommended processing" loophole in the ISO
specs.


Um, no. They can get away with saying ISO 1000 in Tmax developer,
because the B&W standard no longer specifies a developer. It would be
likely ASA 800 in the formerly specified developer.

All modern colour negative films have considerable overexposure
latitude.


Again, the site I mentioned above disagrees. They give Ektar 100 only
2 stops of overexposure latitude, which means that if you expose it at
an EI of 64 you'll have less overexposure latitude than underexposure.
Superia 100 they rate at +2/-2.


Take the negative film of your choice, either colour or black and white,
do a series of exposures one stop apart until you get to ridiculous
overexposures. See how many stops you have to go over before you get
any actual highlight compression or other obvious overexposure faults.

On the other hand, shadow detail will start to go with any level
of underexposure. One stop over (derating by half) will almost
always allow you to see details in the shadow areas better without
causing any problems with the highlights. Increasing exposure will
cause an increase in apparent contrast because you are moving
the exposure off the toe. This may be undesirable in some cases
especially if you are unable to reduce printing contrast slightly
to compensate.

I do not believe that the listed latitude ratings are meaningful.

Peter.
--


  #9  
Old March 5th 09, 04:57 AM posted to rec.photo.equipment.35mm
Michael Benveniste[_2_]
external usenet poster
 
Posts: 229
Default Film Q.

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.

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.

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.

In other words, I would expect the results of the current
method and the 1965 method to be very close in most cases.


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

On a box of TMax-3200, what's the designation?

From memory, it doesn't say anything about ISO on the box.
I don't have a roll right now to check.
Certainly in spec
sheets, it's listed as an ISO-3200/36 film.


I just checked. The PDF spec sheets say ISO 1000 in Tmax developer,
and ISO 800 in D-76 and most other developers. Show me which
spec sheets say ISO 3200.


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.
http://www.bhphotovideo.com/c/produc...ecific ations
http://www.bhphotovideo.com/c/produc...specifications

Take the negative film of your choice, either colour or black and white,
do a series of exposures one stop apart until you get to ridiculous
overexposures. See how many stops you have to go over before you get
any actual highlight compression or other obvious overexposure faults.


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 do not believe that the listed latitude ratings are meaningful.


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

--
Mike Benveniste -- (Clarification Required)
Cogito eggo sum -- I'm thinking toaster waffles for breakfast.
  #10  
Old March 5th 09, 06:17 AM posted to rec.photo.equipment.35mm
Peter Irwin
external usenet poster
 
Posts: 352
Default Film Q.

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.
--



 




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