DMax and Markings along B&W Film

[bernhard]

When scanning, one primary goal is to capture the entire density

range. The clear base of B&W film can be used as a reference point for

the lower end of the density range, but what about the upper end?

I wondered if the imprinted marks that tell you the name of the film

etc. could be used for that. In other words, are the imprints that run

along the top and bottom of a roll ALWAYS the densest part of a B&W

negative, regardless of how you developed?

How are these imprints made? If it were by exposure to bright light it

would be pretty safe to assume that they would correspond to the DMax

of the

film.

 

Thanks

 

Bernhard

[wickedmartini]

The edge markings on films is exposed onto the film during manufacturing. While it can be used as a general processing indicator I would not recommend using it as a measurable source of information. The method and intensity by which these markings are exposed onto the film can change at any time.

 

I hope that helps.

 

Michael D. D'Avignon

[m0002a]

No they can't. The density varies from film to film and from batch to batch. My older Ilford negatives have fairly dense markings, but my newer negatives have sparse markings. My Kodak negatives are just the reverse (older sparse, newer dense markings). But I have not used any of the brand new Kodak films from the new plant.

[bernhard]

Mark,

 

just to make sure, you say that on films with sparse markings there are areas with higher densities in the frame than the markings. is this correct?

[richard_cochran]

<cite>are the imprints that run along the top and bottom of a roll ALWAYS the densest part of a B&W negative, regardless of how you developed?

</cite>

<p>

Reminds me of a test question I received in school.

True or false? Every T/F question containing the word

"always" is always false.

<p>

No, the edge markings

aren't always exposed sufficiently to reach DMax. Yes,

the markings are made by exposure to light, but

they usually aren't exposed deeply enough to

completely saturate the film. A specular highlight

can often be more dense.

<p>

I've found that, if I load my film in subdued light,

even my leader isn't ALWAYS at the maximum density, though

it's usually pretty close.

<p>

The actual observed density will vary from one negative

to the next, depending on subject matter and exposure.

Are you wanting to capture the entire density range of

one particular negative, or the entire theoretical density range of

an emulsion/developer combo? If the former, you can usually

check your histogram to be sure it isn't bunching up too much at

the high end. If the latter, expose the leader to direct

sunlight for a minute and use that for calibration.

<p>

But I'm not sure you always want to capture the full

density range. An ordinary B&W print usually clips off the most dense

portions of a negative, printing them as pure white. Often,

I'd want to do the same in scanning, to get better separation

of the middle values.

[bernhard]

Richard

 

thanks for the answer, I think the question is settled now.

 

Thanks again

[m0002a]

Yes, sometimes there are areas of the image that have higher density than the markings. The edge markings seem to vary considerably from film to film, and batch to batch. Sometimes the markings are exposed at a high density, but many times not.

[ken_burns1]

Even if the imprints were DMax, thry would be mostly useless as a reference point in scanning. Most, if not all, of today's B&W films have the ability to produce a DMax much greater than is workable in either conventional B&W printing or digital scanning. I don't really have a good suggestiion for another approach, but whatever is done, the target point would have to fall within the limited range that digital imaging can handle. DMax of B&W films is far outside that range.

[andy_piper2]

Bernhard: To get a "DMax" measurement (at least with 35mm film) - take the fogged end of the B&W film roll (where the leader stuck out of the casette into the daylight) and use that - it will definitely always be the densest part of the film (unless you load your cameras at superman speed or in total darkness!)

 

As to whether it's "useful" or not: For each of my commonly-used film/developer combos I have a slide mount that contains a chip from the leader right at the point where it transitions from fogged leader to clear film base (the mounted pice is half fogged and half clear).

 

Before I scan a negative or slide, I run the appropriate mounted piece of leader through the scanner and let the NikonScan plugin set exposure for these densities (DMax and film-base-plus-fog) - and peg those to 255 and 0 (or 0 and 255 for slides).

 

Then I TURN OFF NikonScan's autoexposure and do my preview and scan of the actual picture - that way I know that ANY film density other than DMax or FB+F will register as a usable tone (something between 0 and 255) instead of being clipped.

 

If I happen to have a thin negative it may preview as rather dark and flat (since the highest density in the image is well below the fully-fogged Dmax)

 

- but I can then set the 'white point' manually in NikonScan's histogram/curve graph before doing the final scan to just touch the highest (or with slides, the lowest) actual density, insuring a full-scale scan that captures every faint variation in tone within the actual picture.

 

The whole process is roughly (emphasize 'roughly') comparable to doing Zone system tests for print exposure - setting enlarger time to just barely produce a black from the thin areas of the neg and just barely produce white from the densest areas.

[pete_andrews]

<i>"DMax of B&W films is far outside that range."</i> - No it isn't. Or at least it shouldn't be!<p>I keep hearing this statement, that B&W negs have a Dmax that's outside the range of any scanner, and it's utter rubbish. Presumably it comes from people who've never bothered to take a density reading from a properly exposed and developed B&W neg.<br>They certainly can't ever have tried printing from a neg that exceeds the density range of a filmscanner.<p>The fully fogged leaders of my 35mm films generally give a density reading of between 2.2D and 3.2D, depending on the film type and the developer used. Those negatives print and scan easily, since even 3.2D should be well within the range of even the cheapest scanner.<p>The maximum density found in the actual picture content is well below the fully-fogged Dmax of those negs. Usually something like 1.8 to 2.1D, occasionally going up as far as 2.4D from an exceptionally bright highlight.<p>If anyone's regularly getting B&W negs that exceed the density range of the average filmscanner, then they need to cut their developing times considerably. Because those negs will be far too dense and contrasty to print on a normal grade of photographic paper too!