Exposure latitude in film

[AlanG]

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And while a traditional sheet of paper may have a greater DR than the best scanner, the software can selectively change all the tones in between so even your 4 or 6 stop under exposed examples may become 'acceptable'.

 

 

In traditional printing you can always use a longer exposure time to print from a dense negative. And you can burn in highlight detail if necessary. If a scanner can handle the D-max of the negative you can do the same via scanning. If not you can't. Of course one has more selective control in digital scanning and digital post production than with film.

 

If you study the characteristic curve of a particular film/developing combo you will get a pretty good idea of how far you can overexpose it and still pull out detail. You simply have to look at how long the sloped part of the curve goes before it becomes a flatter "shoulder." On some films a double coating of a low speed and a faster speed emulsion is used. This would extend the straight line part of the curve quite far allowing for more "over exposure."

 

A glossy print might have a brightness range between the white and black of 100:1 whereas a negative can have a range of more than 1000:1. A color slide has a range of around 1000:1 and sometimes more. A scene can have a brightness range up to 1,000,000:1 but is typically way less than that. If your scene is very flat you will have a lot more latitude in exposure than if your scene has a wide brightness range that you are trying to compress. So the concept of exposure comes down to where you place your scene's brightness range onto this curve.

 

As for underexposure that is always going to be limited as the toe of the curve is pretty much dictated by the need to stay within a specific shape to have an ISO rating rather than an exposure index. So as you cut the exposure too far you get down to very little information being recorded and there is nothing you can do about that.

 

This publication is a good introductory guide to film sensitometry.

 

http://motion.kodak.com/motion/uploadedFiles/US_plugins_acrobat_en_motion_education_sensitometry_workbook.pdf

[Guest]

Aaaanyway, trying to stay on-topic, a well exposed frame is more important than the latitude, particularly for scanning.

Also, if you're developing yourself you could try stand development. Here's an interesting article about it.

 

Cheers

Philip

 

"I think I should point that out, using stand development might not always give you the best negative, but the trade off is flexibility and reliability" (Quote from Jesse Hildebrand's article.)

 

Thank you Philip for a very interesting link. All his tutorials are very interesting upon scrolling and I am looking forward to "reading more" of them all. Did you try stand development yourself? No tank inversion??

[Michael Geschlecht]

Hello Adam,

 

As per your original question in Post #1 of this Thread: An answer from a slightly different perspective.

 

There is another way:

 

With the advent of more accurate electronically timed shutters 30 or so years ago, camera makers wanted to take advantage of this greater accuracy.

 

Film makers accomodated camera makers by putting various types of information on each film cassette which film readers in cameras, such as the film reader in an M7, would be able to understand. That information is contained in those little black & white squares that are on each film cassette.

 

That is:

 

1. The film speed written on the box & on the film cartridge. This is the speed YOU see on the camera display which has been put there by the film reader in the camera.

 

2. The actual speed of the film in that individual cartridge with normal development. This can be different than the speed in the display. This is the speed the CAMERA actually uses to determine exposure. You can't see the actual speed in the display if it is different than the speed on the box. You only get to see the speed written on the box.

 

3. The latitude of the film.

 

4. The minimum number of exposures on that individual roll.

 

In their June 1983 issue Modern Photography (magazine) printed an explanation of that code on page 8 of that issue. Unfortunately I don't know enough about computers to put a copy of it on this screen.

 

If you put a picture of that part of your film cartridge in this Thread I will be glad to tell you what you have as per above. You have to include the little nubbin that sticks out at 1 end of the cartridge.

 

Not the brand. Not whether it is B&W or color. Not if it is a negative film or a transparency film. Just what is above.

 

Best Regards,

 

Michael

[giordano]

1. The film speed written on the box & on the film cartridge. This is the speed YOU see on the camera display which has been put there by the film reader in the camera.

 

2. The actual speed of the film in that individual cartridge with normal development. This can be different than the speed in the display. This is the speed the CAMERA actually uses to determine exposure. You can't see the actual speed in the display if it is different than the speed on the box. You only get to see the speed written on the box.

 

This bit I don't understand. You're saying that the "checkerboard" on the cassette encodes two film speeds, the nominal speed and the actual speed of that production batch of film. But none of the online sources I've found (e.g. the Wikipedia article on DX encoding) mention this, and the descriptions of the coding show that all the available "bits" - silver or black squares - are used to encode the nominal ISO speed, exposure tolerance (which is not quite the same thing as latitude) and number of exposures.

 

There are ten bits available (two rows of six squares, but two of the squares are always silver as the "ground" connection). Five of them are needed to encode the 24 ISO speeds between 25 and 5000. Two are used to encode 4 tolerance values, and three to encode 7 possible numbers of (full frame) exposures (12, 20, 24, 36, 48, 60, 72).

 

So it's for impossible the DX code to include two ISO speeds. Even storing the difference between the actual and nominal speed (three values, -1/3, 0, +1/3 stops, would be enough) would require two more bits.

 

So either your memory is misleading you or Modern Photography got it wrong.

 

PS: has anyone ever seen or heard of a factory-filled 35mm cassette with 48 or 60 exposures? I've seen all the others, but never these.

[Michael Geschlecht]

Hello John,

 

Thank you for your reply.

 

I have a copy of this chart in front of me as I write. It works quite well as I described it. I have been using it with no problems since I got it in 1983.

 

One of the unfilled spaces for numbers of exposures was for 27 exposures. A number of exposures which was popular for a while.

 

The other MIGHT have been 72. Alternatively: The other might never have been asssigned.

 

There were some emulsions available in 72 exposure rolls coated on thin Estar film base for a while. They fit into a standard cartridge.

 

Best Regards,

 

Michael

[chris_livsey]

The issue here is that the code is not read just by the camera it is read by the processing machine.

The conflict I think is arising because the DX code is an ANSI standard but there is the possibility of the maker adding an enhanced code. Primarily for use in the processing machine:-

 

"If the film when purchased included the price of processing and printing. This information would be read out and provided to the billing computer.

If any special services were included with the film purchase, such as Photofile bonus prints, or the like.

If the order requires a special print format such as a panoramic or a half frame print.

If the film cartridge is from a single use camera.

If a free enlargement of one or more image frames or other promotions are included with the order."

Patent US5761558 - Expanded film cartridge bar code - Google Patents

 

It may be the article referred to was discussing data that could be added at the makers discretion and for a professional film the actual film speed could have been coded. This is speculation but the coding under the ANSI standard is as stated.

[pico]

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Besides stand development, there are two-part (or divided) developing solutions. Divided development might serve well with negatives to be scanned because they are less susceptible to over-development. In use, one develops in solution A, then in solution B. In the A step the film's emulsion is saturated with potential developer and in B, actual development takes place.

 

Some two-part developers also 'stain' the negative which helps to suppress blocked highlights.

 

There are claims of 'edge development' in stand development which is supposed to give greater acutance, but in forty years I have never found it in my own processing.

 

I can suggest more specifics if you wish.

[Michael Geschlecht]

Hello Everybody,

 

Another thing is that cameras of the 1980's began having a "Program" mode.

 

Under certain circumstances: After reading the parameters listed above many cameras can display the nominal ISO for the photographer while they (the camera) separately fine tune the ISO's & exposure (shutter speed/lens opening) as a factor of what is contained on the individual film cartridge.

 

This might have something to with why the electronic shutter of the M7 (as is also the case with many electronically controlled shutters from many other manufacturers) is sometimes thought of as producing more consistent results & more accurately exposed negatives/transparencies than the purely mechanical shutter of the MP.

 

As far as I know the MP & the M7 share the same meter cell.

 

Best Regards,

 

Michael

[chris_livsey]

Whilst no one is questioning the M7 shutter and its "A" mode you should note that with a manual Leica in most light conditions you will shoot above 1/30th at a given middling aperture that leaves you five speeds to choose from. I don't think you need a very sophisticated computer to have a go at that

Bring this back OT given the five speeds and a "reasonable" aperture you have the film latitude on your side, particularly on B/W.

I'm convinced that this fad for colour film will pass, just as digital capture will, given time

[xalo]

I'm convinced that this fad for colour film will pass, just as digital capture will, given time

 

ROFL. Yes, eventually. Thanks, Chris, for putting things back into a sound perspective.

Reminds me of E. O. Wilson, who stated that even the current great biological extinction spasm will doubtlessly be overcome by the planet's resilience. Not that this would happen in any period of time meaningful to humanity.

 

In the meantime let's try to leave beautifully exposed b&w film with looong lifespans, showing what we want to keep for a couple of generations, accessible to our eyes w/o a computer. ...I'm trying hard, but can't get back on topic... ah, yes, I bought 30,5m of Delta 400 to roll my own cartridges. Besides fearing now to overexpose the Delta (well, not really), I'm wondering about getting some fashionable colour film to roll it myself, too. Any experiences with labs not properly developing, refusing or not returning home-filled cartridges w/o codes, especially films with less latitude like slides?

 

Cheers,

 

Alexander

[250swb]

Some two-part developers also 'stain' the negative which helps to suppress blocked highlights.

 

You make a good point about staining/tanning developers which I think have come around full circle and now have an important role to play with negatives that are going to be scanned. They can be much more effective than the 'use Rodinal' advice for stand development with all of the upsides and none of the downsides if the right one is chosen.

 

As Pico has said the catechol and pyro based staining developers work by slowing then blocking further development of the highlights while allowing the shadows to play catch-up. It is a marvellous way to control contrast. They can be used as stand/semi stand developers (probably at their best) or conventional agitate on the minute developers. The other advantage is that for many the development time is the same for nearly all films, and that time is considerably less than using ultra dilutions of Rodinal, bringing them into the realm of everyday usability and avoiding the possibility of streaking in the process. So you may have a 12min development time rather than a one hour Rodinal time. And even Delta 100 can be over exposed!

 

I scan my negatives now so use three types of staining developer for nearly all my work.

 

The first is Barry Thornton's DiXactol, either a two part developer or a one part. I use it as a one part developer and everything from Pan F to Tri-X is 8:20 semi stand. It is very sharp in its edge effects, but has prominent grain, not noticeable in MF upwards, but shows up a lot in 35mm.

 

The second needs mixing up yourself and it is 510 Pyro. Actually a good friend mixes mine because he enjoyed chemistry at school, but I am assured it is easy. Getting the chemicals is the harder part. 510 Pyro is a very even smooth toned gentle developer, very fine grain, and gives a very classic look, mid-tones are its playground. Again all the films I use are 7:00 plus or minus 30 seconds as a final tweak in consideration of the exposure.

 

Third is Jay DeFehr's 'Obsidian Aqua' (sharp water), a wonderful catechol based developer. It gives less stain than the previous two but is equally as good for slowing/stopping highlight development. Grain is very small and very sharp, making it very good for 35mm. In fact to my mind the grain isn't so far off Rodinal in character but just a bit finer. All films are 12:00. But it has to be mixed at home, although it lasts incredibly well and is amazingly cheap. You can make litre's of the stock solution (of which you use very little for each film) for almost nothing (in the scheme of things).

 

There are many formula's for staining developers available on the internet, and some like DiXactol can be purchased ready mixed, they are well worth a look.

 

I am sure Pico can add more.

 

Steve

[xalo]

Thanks a lot for these developer suggestions, pico and Steve.

Steve, the gorgeous images on your flickr page are strong samples, not only for your chemistry. I hope to do some landscape 6x7 b&w this summer and your work is very inspiring.

Alexander

[Guest]

I can suggest more specifics if you wish

Donno what php stands for, I typed 3 yellow smileys, as for yes! Pico, please do.

[pico]

Donno what php stands for, I typed 3 yellow smileys, as for yes! Pico, please do.

 

I cannot add anything that Steve mentioned a bit earlier has.

[mdarnton]

I'm just going to duck in here with a short comment: the supposed 10-stop range of film is, I think, mainly an artifact of Ansel Adams' personal method, not the reality of the materials themselves. Film has a much greater range than that, and the main rule is that it has no tolerance for underexposure: you can't print what's not on the film, no matter what kind of darkroom or Photoshop wizard you are. The other downside of underexposure is increased grain. Consequently, in order to fully realize the shadow detail I want in a picture, and minimize grain I have always shot Tri-X at 250 or lower, thanks to a workshop I took in the 70s with David Vestal where, among other things, we examined the range and real speed of film.

 

This is a shot with an actual metered range of 16 stops, from the black of the desk cubbyholes to the bright-lit wall outside: Julian Hersh | Flickr - Photo Sharing!

 

It would be a bear to print in silver, but capturing the full range and printing it digitally is a cinch, and it's easily within the range of the film (Tri-X). The tonal range of a B&W film negative is not nearly as wide as that of a color slide (and remember that total the range on the film isn't wide at all in comparison to the original scene), so the scanner won't have any problems picking it up and giving it to you to work with, but I don't use a scanner: Scanning film with a digital camera | Flickr - Photo Sharing!

 

Anyway, bottom line is you have lots of overhead to play with, but no basement. When the lighting is flat (doesn't cover a wide range as in my picture) you have even more room for overexposure before something goes bad. But no room at all for undereposure before you get nothing but clear film, assuming you are shooting at normal ISO ratings and exposing conventionally.

[250swb]

The tonal range of a B&W film negative is not nearly as wide as that of a color slide

 

Would you like to expand upon that?

 

Steve

[Guest]

I'm just going to duck in here with a short comment: the supposed 10-stop range of film is, I think, mainly an artifact of Ansel Adams' personal method, not the reality of the materials themselves. Film has a much greater range than that, and the main rule is that it has no tolerance for underexposure: you can't print what's not on the film, no matter what kind of darkroom or Photoshop wizard you are. The other downside of underexposure is increased grain. Consequently, in order to fully realize the shadow detail I want in a picture, and minimize grain I have always shot Tri-X at 250 or lower, thanks to a workshop I took in the 70s with David Vestal where, among other things, we examined the range and real speed of film.

 

This is a shot with an actual metered range of 16 stops, from the black of the desk cubbyholes to the bright-lit wall outside: Julian Hersh | Flickr - Photo Sharing!

 

It would be a bear to print in silver, but capturing the full range and printing it digitally is a cinch, and it's easily within the range of the film (Tri-X). The tonal range of a B&W film negative is not nearly as wide as that of a color slide (and remember that total the range on the film isn't wide at all in comparison to the original scene), so the scanner won't have any problems picking it up and giving it to you to work with, but I don't use a scanner: Scanning film with a digital camera | Flickr - Photo Sharing!

 

Anyway, bottom line is you have lots of overhead to play with, but no basement. When the lighting is flat (doesn't cover a wide range as in my picture) you have even more room for overexposure before something goes bad. But no room at all for undereposure before you get nothing but clear film, assuming you are shooting at normal ISO ratings and exposing conventionally.

 

Wellcome Michael!

 

 

Best regards,

Simon

[mdarnton]

Would you like to expand upon that?

 

Steve

 

Sure. When I talk about camera scanning people often get confused and think back to the original scene's dynamic range, not the subject at hand, which is the film. Scanning is a reset on the problem of range, and the original scene and what was captured on film isn't the issue--it's the tonal range in the film medium, itself, the no-silver to max-silver range, which is a lot smaller than what was in the original subject matter.

 

On the film, the negative of my partner in his office (which had a 16-stop range in life) has a range of about six stops or so from clear film to the densest silver. Copied to the camera, it covers around 2/3 of the camera's histogram. A color slide goes from a clearer white to a much more opaque black--a wider tonal range, even though the range of the original scene captured by the slide film was much less, it still takes up nearly the whole histogram in the camera because the black is so much denser than the B&W neg can ever achieve. As a subject, the slide has a much greater tonal range than a black and white neg.

 

By the way, people who do camera scans talk about the problem of devising a strange curve to correct the results when the neg is inverted in Photoshop. You can avoid a lot of that by exposing "to the right" as they say, in the camera--moving the whole histogram towards overexposure. There's certainly room to do that, and having it centered turns out not to be the best exposure for the best results, in this job.

 

Of course, as you're probably thinking, the slide represents a much narrower range of the original subject, and that's true, but the problem for scanning isn't the original range, it's the density range of the film itself, which has become the new subject matter of the scanning "shot".

 

For me, this is the main advantage of a hybrid workflow--the ability to, still, capture much more range on film than any digital camera can capture, then convert it and work with it in the digital realm where it's easier to bring it all out than it was in the darkroom. Even with the Nikon D800, and it's almost-14-stop dynamic range, the picture of my partner would have had the background blown out, but not so with film.

 

By the way, people who camera scan talk about having to devise strange curves to correct the odd tonality that results when a neg is inverted in Photoshop. That can be cured by exposing "to the right"--going much farther towards overexposure in the digital camera. It turns out that a centered histogram of the neg in the digital camera doesn't work particularly well in this application.

 

Simon--thanks.

[mdarnton]

Sorry about that repeat paragraph--enough time to edit to make things wrong, but not enough to make them right again? :-)

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Hallo,

Look here: Interesting Leica gear

[250swb]

A color slide goes from a clearer white to a much more opaque black--a wider tonal range, even though the range of the original scene captured by the slide film was much less, it still takes up nearly the whole histogram in the camera because the black is so much denser than the B&W neg can ever achieve. As a subject, the slide has a much greater tonal range than a black and white neg.

 

It may be the case the way you work, but black is black whether a slide or a negative and I can assure you that photographers have managed to achieve 'black' from negatives throughout history. If only he was alive you could try telling Ansel Adams that he can't get a good black.

 

The assertion that the slide has a wider dynamic range than a negative is fundamentally flawed. The dynamic range of slide film is set in the characteristic's of the film, it can only deal with a limited range dictated by the emulsion and the E6 processing which can't be adjusted. So a scene that goes from intense highlight to the deepest shadow will be truncated at one end of the range or another, and is the reason that slide film is generally recommended to be slightly under exposed. The fact that you see the deep black that you like is because the film has given up as much as it can, it has fallen off the cliff. B&W negative film on the other hand (if we forget for one moment your assertion it has a smaller range) can be exposed with the development pre-planned to mimic the tonal range of the same high range scene, or to compress the tonal range. The 'black' that you seem to see as a definition of a wide dynamic range is a very tiny proportion of a typical landscape scene for instance, intense black does not normally appear in nature, yet I will agree with you that it does often appear as a characteristic of slide film, because it has a limited dynamic range, not because it has a wide dynamic range.

 

Steve