What is film latitude?

Oranges

A
Oranges

  • 3
  • 0
  • 71
Charging Station

A
Charging Station

  • 0
  • 0
  • 65
Paintin' growth

D
Paintin' growth

  • 3
  • 0
  • 58
Spain

A
Spain

  • 5
  • 0
  • 67

Forum statistics

Threads
198,114
Messages
2,769,824
Members
99,563
Latest member
WalSto
Recent bookmarks
0

fidget

Member
Joined
Nov 13, 2006
Messages
62
Location
North West E
Format
Medium Format
Hi, a sort of newbie question, I guess, but one that has puzzled me for a long while.
When looking at B&W film, some (say FP4+ for example) is credited with having a larger degree of "latitude" than others, (say a Delta type). This is claimed to make the film more forgiving of exposure errors. Does this mean to say that this film is able to capture a wider range of tones than others, or is it a feature of its development?

Regards, Dave......
 

Jim Jones

Subscriber
Joined
Jan 16, 2006
Messages
3,740
Location
Chillicothe MO
Format
Multi Format
It's a characteristic of some films. Development also alters latitude of an image. Delta films might not work as well for latitude adjustment in the development as traditional films like FP4.
 

Michel Hardy-Vallée

Membership Council
Subscriber
Joined
Apr 2, 2005
Messages
4,793
Location
Montréal, QC
Format
Multi Format
Generally speaking, it means a long straight line on the characteristic curve, so that overexposure will not bring the highlights near the shoulder part of the curve, at which point they would all look the same (being "compressed") and you would lose details.

I am not exactly sure however whether a short and abrupt or a slow and gradual toe would mean more underexposure latitude. Anyone?
 

Roger Hicks

Member
Joined
May 17, 2006
Messages
4,895
Location
Northern Aqu
Format
35mm RF
Dear Dave,

Basically, it's tolerance for under- or over-exposure without excessive loss of quality (loss of shadow or highlight detail, oversize grain, loss of sharpness). When monosize emulsions first came out (T-grain, Delta, etc) they were much more critical than traditional cubic-crystal films (FP4, HP5, Tri-X...). They also had smaller developer repertoires (couldn't be used successfully with as many developers) and were much more critical when it came to development regimes (worse effects, faster, from over- and under-development). The gap has since narrowed -- some will say it has vanished -- but others remain convinced that traditional emulsions are more tolerant and give better tonality.

Cheers,

R.
 

wfwhitaker

Member
Joined
Feb 6, 2004
Messages
565
Location
Lobsta
Format
Multi Format
People in northwest England require film of higher latitude than, say, London, or more southern climes. It's quite simple, really...

:smile:
 

OldBikerPete

Member
Joined
Aug 29, 2005
Messages
386
Location
Melbourne, A
Format
4x5 Format
It's a myth. Film can render bright objects through to dark objects. If the scene you are photographing contains objects at both limits of the film's capability to render then your margin for error is zero - ie your 'latitude' is zero. If your scene has less contrast then you may have margin for error - ie 'latitude'.( EG in the first, contrasty scene there is 11 stops difference between the darkest and lightest object you want to clearly render and the film you are using has the ability to render in that range, then you've used up all the film's capability and you've got no margin for error. In the second case the contrast of the scene is 6 stops then you can probably make an exposure error of two stops or so and yet still be able to produce an acceptable print. BTW good luck in trying to make a print from the first scene - you would have difficulty getting all taht tonal range to render on paper)
 
Joined
Dec 30, 2005
Messages
7,175
Location
Milton, DE USA
Format
Analog
Yeah, typically your black and white negative films have the most film latitude before whites get whiter and darks stay darker, about 7 stops. Color negative films generally chime in about 5 stops. Color reversal (slide) films step in at about three-four stops. Closer to three.
 

Kino

Subscriber
Joined
Jan 20, 2006
Messages
7,685
Location
Orange, Virginia
Format
Multi Format
It's a myth. Film can render bright objects through to dark objects. If the scene you are photographing contains objects at both limits of the film's capability to render then your margin for error is zero - ie your 'latitude' is zero. If your scene has less contrast then you may have margin for error - ie 'latitude'.( EG in the first, contrasty scene there is 11 stops difference between the darkest and lightest object you want to clearly render and the film you are using has the ability to render in that range, then you've used up all the film's capability and you've got no margin for error. In the second case the contrast of the scene is 6 stops then you can probably make an exposure error of two stops or so and yet still be able to produce an acceptable print. BTW good luck in trying to make a print from the first scene - you would have difficulty getting all taht tonal range to render on paper)

Well, I agree to a certain extent, but you can't say that is true with a lith film Vs. a film intended for field photography.

I would think it still valid as a generic term describing the relative reproductive qualities of an emulsion; why not?
 

Sirius Glass

Subscriber
Joined
Jan 18, 2007
Messages
50,262
Location
Southern California
Format
Multi Format
It's a myth. Film can render bright objects through to dark objects. If the scene you are photographing contains objects at both limits of the film's capability to render then your margin for error is zero - ie your 'latitude' is zero. If your scene has less contrast then you may have margin for error - ie 'latitude'.( EG in the first, contrasty scene there is 11 stops difference between the darkest and lightest object you want to clearly render and the film you are using has the ability to render in that range, then you've used up all the film's capability and you've got no margin for error. In the second case the contrast of the scene is 6 stops then you can probably make an exposure error of two stops or so and yet still be able to produce an acceptable print. BTW good luck in trying to make a print from the first scene - you would have difficulty getting all taht tonal range to render on paper)

Not quite. The latitude of the film is the latitude of the film => some number of f/stops. Whether or not the particular scene uses all the latitude is another question.

Steve
 

cowanw

Member
Joined
Aug 29, 2006
Messages
2,229
Location
Hamilton, On
Format
Large Format
Yeah, typically your black and white negative films have the most film latitude before whites get whiter and darks stay darker, about 7 stops. Color negative films generally chime in about 5 stops. Color reversal (slide) films step in at about three-four stops. Closer to three.

I have been puzzled for ages why then slide film is said to have a greater density range. Does not all film go from clear (black) to opaque (white)?
Bill
 

Roger Hicks

Member
Joined
May 17, 2006
Messages
4,895
Location
Northern Aqu
Format
35mm RF
Does not all film go from clear (black) to opaque (white)?
Bill

Dear Bill,

Re-read what you just wrote. Clear blacks and opaque whites... I think I know what you meant but it's hardly what you said!

The clearest clear Dmin in a tranny, representing 'blown' white, has a density including fb+f of maybe 0.1. In a neg, representing 'blocked' shadows, it is typically 0.3 or so including fb+f.

The blackest black Dmax in a tranny, representing 'blocked' shadows, can exceed 4.0. It rarely exceeds 3.0 for a neg, where it represents the brightest highlights.

The usable density range in a neg to print on grade 2 paper is about 1.2 (depending on paper, developer and enlarger/lens flare); the usable density range on a tranny for projection can exceed 4.0.

Cheers,

R.
 
Last edited by a moderator:

cowanw

Member
Joined
Aug 29, 2006
Messages
2,229
Location
Hamilton, On
Format
Large Format
Dear Bill,

Re-read what you just wrote. Clear blacks and opaque whites... I think I know what you meant but it's hardly what you said!

The clearest clear Dmin in a tranny, representing 'blown' white, has a density including fb+f of maybe 0.1. In a neg, representing 'blocked' shadows, it is typically 0.3 or so including fb+f.

The blackest black Dmax in a tranny, representing 'blocked' shadows, can exceed 4.0. It rarely exceeds 3.0 for a neg, where it represents the brightest highlights.

The usable density range in a neg to print on grade 2 paper is about 1.2 (depending on paper, developer and enlarger/lens flare); the usable density range on a tranny for projection can exceed 4.0.

Cheers,

R.
Firstly,I approve of your insistence on clear English which comes across in your posts and in your writing.
I shortened what I was trying to say.
clear negative (black positive) to opaque negative (white positive).
But I remain puzzled. How does a negative with a density range of .3 to 3 end up with a greater latitude of 7 stops; whereas a tranny with a density range of .1 to 4 end up with a latitude of 3-4 stops.
I suspect I just do not understand the definition of a range of density and a range of f-stops.
I would appreciate a more descriptive explanation if you would be so kind .
Double Cheers
Bill
 
OP
OP

fidget

Member
Joined
Nov 13, 2006
Messages
62
Location
North West E
Format
Medium Format
Hi, many thanks for your help. I am still puzzled, and have consulted the Ilfordpro web site to see the "characteristic" curves for FP4+ and Delta100.

Here: http://www.ilfordphoto.com/Webfiles/2006216115141521.pdf
and here: http://www.ilfordphoto.com/Webfiles/20061301938422338.pdf
(but you knew where they were anyway....)

Is my understanding here on the correct lines?:
The curve for FP4+ starts its ascent earlier than Delta100. This represents low exposure values (shadows)?
At the other end of these curves the FP4+ curve levels out as it approaches d2.0 and I guess that further exposure yields no further increase in density. Delta100 is still very linear at this point and stops abruptly so, although it must be possible to expose further, no data is given for its performance, so I assume that no usable extra density is possible?
Does this amount to a larger range in practical terms? This is the particular puzzle, if this film gave a couple of stops MORE exposure range, nobody would be using anything else, would they?

Regards, Dave...
 

Roger Hicks

Member
Joined
May 17, 2006
Messages
4,895
Location
Northern Aqu
Format
35mm RF
Firstly,I approve of your insistence on clear English which comes across in your posts and in your writing.
I shortened what I was trying to say.
clear negative (black positive) to opaque negative (white positive).
But I remain puzzled. How does a negative with a density range of .3 to 3 end up with a greater latitude of 7 stops; whereas a tranny with a density range of .1 to 4 end up with a latitude of 3-4 stops.
I suspect I just do not understand the definition of a range of density and a range of f-stops.
I would appreciate a more descriptive explanation if you would be so kind .
Double Cheers
Bill

Dear Bill,

We all do it!

Film density is not necessarily related to the brightness range captured. If the ratio were constant, e.g. 1:1 (gamma = 1) then (assuming a zero flare factor) a density range of 4.0 would relate to a subject brightness range (SBR) of 4.0 also, i.e. 13-1/2 stops.

But if you change the contrast to 1:2 (gamma = 0.5), then a density range of only 3.0 can capture an SBR of 6.0, i.e. 20 stops (6 divided by 0.3).

Hope this clarifies matters.

Cheers,

R.
 

cowanw

Member
Joined
Aug 29, 2006
Messages
2,229
Location
Hamilton, On
Format
Large Format
Dear Bill,

We all do it!

Film density is not necessarily related to the brightness range captured. If the ratio were constant, e.g. 1:1 (gamma = 1) then (assuming a zero flare factor) a density range of 4.0 would relate to a subject brightness range (SBR) of 4.0 also, i.e. 13-1/2 stops.

But if you change the contrast to 1:2 (gamma = 0.5), then a density range of only 3.0 can capture an SBR of 6.0, i.e. 20 stops (6 divided by 0.3).

Hope this clarifies matters.

Cheers,

R.
To restate you (perhaps), the more the sbr is compressed to match the capture medium, the greater is the contrast. I understand the capture side of things
I am still puzzled by the output side of things.
Of course a tranny is both, compressing the sbr to 3-4 stops of range and outputting that information as those very same 3-4 stops, from black to white. But when printed must show even less range.
While negative film, printed on paper, compresses and outputs the sbr to a wider range but still from black to white.
Is the tranny's black blacker or the white whiter? Or is there just more of each because of the compression of the sbr?
As Fidget asks-
Does this amount to a larger range in practical terms? This is the particular puzzle, if this film gave a couple of stops MORE exposure range, nobody would be using anything else, would they?

Why do photographers choose trannies over negative film when so much light information is lost?

Any more cheers and I will be drunk.
Bill
 

Roger Hicks

Member
Joined
May 17, 2006
Messages
4,895
Location
Northern Aqu
Format
35mm RF
Dear Bill,

It's expanded again at the printing stage. To take some easy figures, a log SBR of 2.1 might be reduced to an image brightness log range of 1.8 by a flare ratio 2 -- high but not impossible, though a good LF camera with MC lens can approach unity.

At a gamma of 0.7 this image brightness range is recorded as a density range 1.26. Now allow for another flare factor of 2 at the enlarging stage and the
projected image on the enlarging easel will be 0.96 -- about right for grade 2.

SBRs are normally recorded as very much smaller log density ranges on the film, but by varying the gamma, you can vary the film density range that is recorded for a given SBR. Or you can use a different paper grade. If you have a very long film density range, you use a softer grade; with a very short film density range, a harder grade.

Why do people use trannies? Historically, because they looked gorgeous when projected; were usually sharper than colournegs; and (for professional repro) were easily judged as camera originals without an additional, time-consuming, expensive printing stage. I still find them easier to file, sort and judge than negs, though given that most of my work is scanned for repro, neg might make more sense. At that point, though, high-end digi looks good from a professional colour viewpoint.

Hope this helps (and indeed that it makes sense: it might not, when I'm this tired). It's getting late and I'm off to bed. You might find it interesting to read the subject brightness range module in the Photo School at www.rogerandfrances.com.

Cheers,

R.
 

Doyle Thomas

Member
Joined
Oct 28, 2006
Messages
276
Location
VANCOUVER, W
Format
8x10 Format
Film latitude is the available range of light energy that the film can record. For any given lighting situation as it falls on the film there is a correct combination of f/stop, shutter speed, and ISO that will control how much light energy is allowed to strike the film. This is the "exposure". Within that exposure which is an average, there is a range of brightness levels, That is, there may be areas that are in dark shadow and areas that are in bright sunlight. The simple light meter assumes that everything is gray and will report the correct exposure as the average of the bright and dark areas to strike the film with the amount of energy to develop to film to be gray (center of the curve). Because the subject is not gray and contains a range of brightness levels detail is recorded on the film. The film can only be so dark(Dmax) and so light (Dmin=film base + fog), these are points at the ends of the curve with gray in the center. The film can only record the details of light energy within the curve.
--------------------------------------------------------------------------
Yeah, typically your black and white negative films have the most film latitude before whites get whiter and darks stay darker, about 7 stops. Color negative films generally chime in about 5 stops. Color reversal (slide) films step in at about three-four stops. Closer to three.
--------------------------------------------------------------------------

Using a spot meter or getting very close with an averaging meter and measuring the darkest area and the lightest area where you want detail will tell you the total range of brightness on the subject in stops. If that total range of brightness is greater than the total range of brightness the film can record (latitude) then you will reach Dmax and or Dmin too soon and block up shadow detail or blow out hi-light detail. This is all just a part of what the "zone system" of film exposure is about. You "place" your exposure and development to optimize the recorded detail.

Doyle
 

aldevo

Member
Joined
Oct 4, 2004
Messages
949
Location
Cambridge, M
Format
Multi Format
Here's how I would define "Film Latitude" with a strong B&W bias....

It's the Log H value (which is exposure, and can be translated to f-stops) over which the exposure of a given subject can vary without "critical" loss of available tonal separation in the low or high values.

In other words, it's "what you can get away, exposure-wise with for a specific subject".

Now for the explanation:

- "Critical" certainly would certainly vary by photographer. A LF landscape photographer practicing the Zone System or BTZS would likely be striving to avoid shadow compression. A street photographer shooting a 35mm Rangefinder can probably live with some loss of spearation in the shadows.
- The "loss of availble tonal separation" is often characterized by the "toe" region (low values) and "shoulder" (high values) on the D&H curve.

Practically speaking, most of us only see the "film shoulder" for one of two reasons:

a) Gross error in over-exposure (rare)
b) Specular or polarized reflections (common)

So we either reach the film shoulder by accident or we simply can't help it(*). In my mind, this makes the shoulder far less significant than the toe when discussing latitude.

As a result, I believe many people would consider "Film Latitude" to be - more or less - the length (in F-stops) of the film's toe region.

This definition is also at the root of the wide-spread belief (and, in my mind, a true one) that a film like Kodak TMY can be said to have little film latitude. Yes, a short toe means you can have nice shadow separation - but if the exposure of subject elements in deep shadows falls below a critical Log H threshold - then that detail is irrevocably lost and unprintable.

You'll notice a sudden switch in my terminology from "low values" to "deep shadows". That's intentional. "Deep shadows" are the "low values" on the density range that your negative uses. And it's important to realize that this is a relative concern. It's not what your eye interprets as "dark" that constitutes a shadow - it's a region of the negative that receives little exposure because the corresponding region of the subject exhibited low luminance resulting in less exposure relative to other regions in the negative.

And, as many have pointed out, ultimately you have a finite density range to work with in your negative that can be translated to the available exposure range for the printing paper. Venture beyond that and you'll be (minimally) burning and/or dodging.

Obviously, exposure is governed by the EI we choose for our exposure. To discuss this in terms of Kodak TMY, 400TX, and TXP:

- When shooting TMY in constrasty light, many of us feel compelled to shoot it at (at least!) an EI of one stop below its rated ISO speed. This, in effect, is a decision based on the need for an exposure "safety factor" rather than achieving high shadow separation.
- When shooting TXP in contrasty light, many of us feel compelled to shoot it at an EI of about one stop below its rated ISO speed. But the reasoning here is different than for TMY. TXP is a very long-toed film and the decision to give it greater exposure often reflects a desire to achieve greater shadow separation by lifting the density range in the negative off of the film toe.
- When shooting 400TX in flat light, lots of photographer wouldn't think twice about shooting the film at EI 400 (box speed) or even higher! In flat lighting a bit of shadow compression can give a somewhat "richer" appearance to the negative.

For my part, here's how I expose the afore-mentioned films...

TMY: EI 160-200 (depending on developer). I never use TMY in anything in other contrasty light and never use it when I know an exposure could be rushed; I feel it's a poor choice for street photography. I don't use it that much, really, and when I do its for landscape/architecture shots where I want good shadow separation.

400TX: Anywhere from EI 200-640 depending on lighting. I use it merrily in all sorts of lighting conditions for all sorts of subjects. Depending on the subject and lighting, strong shadow separation may be desired. Or not.

320TXP: I've never used it in flat light but would shoot it at EI 125-160 in contrasty light. I don't often use it. I use it under the same lighting/subject conditions as TMY. So, again, good shadow separation is important to me.

(*) Alternative process photographers who do contract printing with UV light often need a very dense and contrasty negative. They are the exception, and Kodak TMY is a very popular emulsion with these folks because the film does not shoulder off until very high densities.
 
Last edited by a moderator:

Sirius Glass

Subscriber
Joined
Jan 18, 2007
Messages
50,262
Location
Southern California
Format
Multi Format
Here's how I would define "Film Latitude"....

... <snip>...

with these folks because the film does not shoulder off until very high densities.

Well said. Thank you,
Steve
 

Helen B

Member
Joined
Jul 1, 2004
Messages
1,590
Location
Hell's Kitch
Format
Multi Format
Roger:
"Basically, it's tolerance for under- or over-exposure..."

Pete:
"If your scene has less contrast then you may have margin for error - ie 'latitude'."

Steve:
"The latitude of the film is the latitude of the film => some number of f/stops. Whether or not the particular scene uses all the latitude is another question."

Doyle:
"Film latitude is the available range of light energy that the film can record."

Aldevo:
"It's the Log H value (which is exposure, and can be translated to f-stops) over which the exposure of a given subject can vary without "critical" loss of available tonal separation in the low or high values." (my emphasis)

Exactly. I agree with everyone, unequivocally. Without saying that anyone is right or wrong, the quantitative meaning of 'latitude' appears to be understood in two different ways*, and so it seems to be sensible to acknowledge the lack of a universally-accepted definition.

Best,
Helen
*This reminds me of The Navy Lark, a vaguely navigated comedy on BBC radio.

PS I think of film latitude as the approximate acceptable wiggle room in a particular situation - conceptually like the dynamic range of the film less the subject brightness range .
 
Last edited by a moderator:

film_guy

Member
Joined
Jan 10, 2007
Messages
258
Location
Canada
Format
35mm
Wow, lots of information to read over. I have a question about film lattitude. Does traditional iso400 B&W film have more lattitude than the newer chromogenics like XP2 Super?
 
Photrio.com contains affiliate links to products. We may receive a commission for purchases made through these links.
To read our full affiliate disclosure statement please click Here.

PHOTRIO PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Ilford ADOX Freestyle Photographic Stearman Press Weldon Color Lab Blue Moon Camera & Machine
Top Bottom