Camera system format wars

I've never developed film or been much interested in it, but found this today:

It clearly shows a relationship between 'ISO' and development time for a given exposure, so yes.

However, don't stretch the analogy too far. Increasing development time for film increases density, but also increases grain size. Increasing digital ISO does not, of itself, increase noise in digital images.

Hi,

Again, let us look at the beginning. That'd be Kodak with their buying of Nikon and Canon film cameras and attaching digital backs.

They need an ISO for the sensor to then set the ISO dial so that the camera meter would expose somewhere near correctly.

That, then carried over to the first offerings directly from Nikon and Canon which were still originally film cameras with better integrated digital halves. And so, the same ISO settings came along.

These days, I leave the ISO at whatever the maker tells me is the base ISO for the model. Then just pull up the exposure in post processing of the raw file. This, unless there is a clear separate gain stage in play for a given sensor at a higher ISO. Then I may go there.

Stan

I never thought that it did, although some people don't realize that the ISO setting does not directly determine the Exposure Value.

Clearly the longer one leaves a film in the developer - the more density in the negative. However, the ISO of a film is determined the exposure when Zone 1 shows density above fog and Zone 2 shows the appearance of shadow detail. Zone 5 here is middle gray. In general one needs a densitometer to determine ISO. ISO has nothing to do with anything but base sensitivity of the film - the minimal amount of light that is detectable by the film. ISO in B&W film is very much dependent on

1) Developer used
2) Dilution of the developer
3) Agitation protocol
4) Special development techniques such as water bath development
5) Type of developer.

Color development is fixed and ISO of color film is fixed.

In the Zone System, the first thing one does is measure the ISO of their film in their normal workflow of development. If I were to use HC 110 dilution A, I rated Tri X sheet film at ISO 400. If I were using HC 110 dilution B - I used much longer development and rated the same Tri X at ISO 200. With Rodinal which I used often with 4x5 Tri X, again the dilution and agitation protocol determined the ISO. The key is the ISO was calibrated to all the above factors.

Once the ISO is determined then it does determine the exposure value since it is the base sensitivity of the film to light based on how it will be developed. So if one considers the "exposure triangle" one vertex is fixed in stone in film and the exposure is determined uniquely by the amount of light on the film which is determined by how long the shutter is open at the set aperture.

To increase the DR of film, one uses a more dilute or weaker developer, e.g., HC110 Dilution B will increase the DR of TriX. Dilute Rodinal can be used to increase the DR of Tril X even more. Water bath development when the film is put into the developer solution for 15 to 30 seconds and then in to a tank of water for a couple minutes to cook, with the process repeated multiple can result 15 or more stops of DR on Tri X.

Grain size is determined more by the type of developer. Developers with silver solvents such as sodium sulfite (e.g., Microdol-X, D76, FG7) produce small grain and developers without silver solvents (e.g. Rodinal, HC110), produce larger grains. More dilute solutions of such developers produce larger grain. On the other hand silver solvent developers produce images with less sharpness as the sharp edges are rounded.

None of that applies to digital. ISO in digital simply tells the camera how much digital amplification to apply the the image to provide sufficient brightness to the out of camera JPEG and/or the jpeg to use for the EVF/display to make the picture look normal. Turning the ISO up to 400 is equivalent is to two stops less light than taking at a base ISO of 100. The noise profile of the raw is the same with setting the ISO 100 and cranking in -2 stops of EC and exposing the same scene normally at ISO 400. With my Nikon Z8 with its dual gain on sensor amplifier, it really has to base ISO. That is if you don't shoot at 62 to 125 you are better off to set the ISO to 500. The DR from about 125 up to 500 is less that that at 500. That is pretty much my guide with that camera.

As someone who spent years developing B&W film and who used the Zone system, I agree with almost all the above. The other developing variable that needs to be included is the temperature. While it is listed on the graph, it needs more discussion. Every darkroom I worked in had graphs on the wall where film development time was shown as a variable that could be changed, to some extent, by developing at a different temperature.

By 'ISO' in single quotes I was trying to imply digital ISO setting not the ISO/ASA rating of a film, pardon the lack of clarity.

For anyone interested here is an excellent article by Richard Butler at DPreview titled:

"The ins and outs of ISO: What is ISO?"

www.dpreview.com/articles/9698391814/the-ins-and-outs-of-iso-what-is-iso

A better explanation might be: 'ISO' in a digital sense is the calibration of mid grey for certain exposure values.

In the Zone System ISO is really the set point of the minimum amount of light that produces the first measurable density in the negative. If you look at the graph then you notice that increasing development time has a proportional effect. Areas that have a low exposure, or minimum density, are not really affected by increased development, not by any amount that is significant. Therefore under the Zone System ISO becomes a fixed value, a measure of base film sensitivity rather than a calibration of mid grey against development time. the curves, once known, are fixed points. What A Adams did was to map the Log Exposure scale to camera stops and map that against film density. Thus allowing spot meter readings to be related to finished print values against various development times.

The important part is that if you calibrate film performance then you find that ISO, as defined by base sensitivity in the Zone System, is effectively a fixed value, the shadow exposure remains a constant. It is the highlight values and DR that are affected by development time.

Yup, temperature is critical. The old Kodak temperature wheel - that give equivalent times for the 68 deg F default development temp was always close at hand. When I move to FL, one of the issues faced was the water temp seldom got cool cool enough to keep developer at 68 deg F. When I live in more moderate zones, one could use a water bath to bring and keep temps in the proper range. When tap water starts out at 75, difficult to do as you need a refrigeration system for a water bath! I always liked using dilute developer and longer development times with one minute agitation intervals. So when I moved to FL, Rodinal became my standard for 4x5 and 6x7. I normally used PanX 120 and TriX sheet film. With 35 mm B&W I took it to a custom lab for development.

I think the key to film is ISO is determined by the point the density appears above fog. In B&W film the Zone System was the result of "expose for the shadows and develop for the highlights." In digital, the concept is "expose for the highlights and pray for the shadows." 🤪

By coincidence, I became interested recently in Kodak's 'Steps' versus Adams/Archer's 'Zones' ...

Interesting that the logarithmic mean of Kodak's equivalent Step 3 (by description) to Zone V is not middle gray (18%), unlike that of Zone V.

Please note that the density column refers to Kodak's step-wedge testing - not that of any particular film.

Sounds like the ISO/CIPA method "Standard Output Sensitivity" aka SOS where the Standard Output is indeed sRGB mid-gray 118/255.

One of the reason Archer and Adams developed the Zone systems was what they saw the failure of the film makers to provide the data they needed to capture their vision. Kodak, Agfa, Ilford, etc. had the tendency to inflate their film sensitivity (ASA which was changed to ISO) because film was slow and people wanted faster film. So why not call film with true sensitivity of 200, 400 to show progress to a fast film? Minor White said as much to Kodak when he came to the University of Rochester after working with Archer and Adams as the developed the Zone System. My advisor in art school worked under White after he got out of the Navy at Rochester. Richard said, while White worked with Kodak closely - he did not mince his worlds about their inflating their recommendations to underexpose and over develop their films. Kodak seems to listen somewhat as the changed there ISO ratings on TRX Professional in sheet film - although it was the same old Tri X as far as I can see. That is it calibrated out to ISO 200 for most.

Developing 35 mm roll film is different than sheet film. Developing 35 mm roll film is a compromise while each shot takes place under differing lighting, they have to under go the same development. So in reality it might make sense to underexpose by a stop and over develop with a concentrate developer. Medium format roll film (120 and 220) is somewhat different since most medium format cameras took interchangeable backs so different backs could be used for different shots. Most of Kodak's data was targeted to the development of 35mm. Kodak got away with it since because of the S-curve of film - there was a lot of margin for highlight recovery since unlike digital film does not saturate and if you are good with darkroom work, highlights can be burned in. However, I had to work in the dark room longer printing a 35mm negative than a 4x5 (inch) negative simply because the 35 mm development was a compromise for the entire roll while each sheet had its own unique development based on proper exposure at the calibrated ISO.

To some extent using exposure bracketing on my Q2M -2 stops normal +2 stops I can mostly accomplish in a short time what it took much longer and a lot of pre-metering with my 1 degree spot meter back in the film days. At my advanced age I don't seem to have the patients for darkroom work these days. I guess I'm getting lazy.

Obvious now that you say it but I never fully realized that until now!

I've never done darkroom work but, as I read more about it, I'm very glad that K-Mart processed my snaps back then and not me ...

Amen to all that. Our bathroom was more a dedicated darkroom that could also be used for having a shower if absolutely necessary.
Any discussion on Zone system process also needs more discussion of printing and paper grading. Exposure, film developing and printing were all part of the same process. What you did at any one stage was done with knowledge of what could and would be done in the other stages to get the outcome planned. IMNHO, it was (and still is) the difference between a photographer and a snapshooter. I'm not using snapshooter in a derisory way. A photographer had control; of the entire image making process and took photos knowing how they would be processed for a preconceived print. A snapshooter, took photos and hoped the processing done by others would be more or less OK.

That is why a few years back I decided to take full control of making my prints.

I built a darkroom in three different houses. When we moved into our current house, my wife put her foot down - telling me I was not going to "steal" the basement for yet another darkroom 😂. New news scanner technology was coming along as was digital editing capability. It did not take long until I realized it was a lot easier to use a computer to edit than to stand in front of the sink and enlarger. It took awhile for printer technology to catch up - especially for B&W. That all changed about 15 years ago as great strides were made in fine arts B&W printing and papers. Yes you are right the integral part of the Zone System was to know what your print would look like before you ever snapped the shutter. That required you think out the whole process in advance. Then meter the scene and tailor your exposure and development to realize your vision. I carried a small notebook and with my large format and medium format would document each shot so I would have the information available - metering and exposure, etc. - when I got back to the darkroom. For that very reason, the Zone System was more useful for large and medium format. With sheet film each sheet can be processed independently. Most medium format cameras use interchangeable film backs. Some people tried to apply the Zone System to 35 mm by carrying multiple cameras. However, the my 35 mm was relegated to "street" for which it is the proper tool simply because street is a "snap shooter" genre.