help understanding ISO settings?

[Nicholas Lindan]

The film is tested in lab conditions, and under those conditions the negative will yield sufficient shadow detail and excellent tonal rendition all the way to the highlights and without blocking up the highlights. Basically, a 'technically' perfect negative. This is when the Exposure Index (EI) is the same as the box speed, or ISO rating.

Agreed.

The longer I work in photography and the more I refine my technique the more I find the manufacturer's numbers for ASA/ISO/EI/AotW and development are indeed the optimum values.

Changing film speed to compensate for technique is, IMO, doing things backwards. Changing technique to get the published film speed is the right way round.

Once you can get the 'technically perfect negative' with standard values for exposure and processing then it is time to look at variations to achieve the effects you want - time to pick up the zone system, as it were.

My experience, in customer support for Darkroom Automation products, is that people who jump straight into the zone system as their first effort in photography quickly get lost on the most basic principles. Once they get the zone system out of their heads things move smoothly.

As someone posted in another thread:

"When learning to play the piano, the first task is not rebuilding the Stienway."

On the subject of people preferring a stop or so overexposure - well, it's their preference, there is no arguing with it. I find it really gets in the way of highlight detail. The general FotM, however, is shadow detail. This came about with a 50-70's fixation on getting high film speed - outrageous claims were made for developers - and as a result the shadow detail in photographs of that era was zilch. The pendulum has swung the other way on the subject of exposure, perhaps a bit too far, as it always does, and now lowering film speed is chic. It is only for an instant in the middle of the swing of the Zeitgeist pendulum that things are 'perfect'.

Go and see master prints in a gallery and you will find that what makes a print sing, what makes your eyes open wide, are the highlights and not the shadows.

***

AotW = Acronym of the Week
FotM = Fixation of the Month

 

[Stephen Benskin]

The math was to make a tangible relationship to the theory. Theory remains in the ether until you get down to the nitty-gritty. Someone can now actually apply it and see for themselves. Plus, everyone here isn't a beginner.

One of the points I was trying to make is how so much about exposure is misunderstood. I would say 90% or more of general photographers (non photographic scientists) who have studied the B&W ISO speed standard, have wrongfully interpreted it. There's the very concept of speed point not actually being the exposure aim point but a point to calculate speed from. Transparencies use 10/Hm. They used to use 8/Hm. That's a difference of 1/3 stop, but Hm remains at the same point. Then there's the influence of flare in the shadows. I frequently attempt to demonstrate how precise shadow exposure is impossible because of flare. In order to make claims that are different from the mass perception, you need proof. That's were the quotes and math help.

I was also wanting to demonstrate what film speed actually is. I tend to make a distinction between making a usable exposure (which I have repeated state that a disposable camera can produce an acceptable image most of the time), and defining film speed and exposure (you know, theory stuff). I frequently make statements on how the Zone System testing is flawed and will produce incorrect film speeds, but it will still produce quality images. There's not much really to talk about if all you want to accomplish is acceptable images. My grandmother can do that with a disposable camera from Walgreens and no training (except which way to point the thing). If someone wants to know the why of it, isn't that why they would take the time to come to a photography forum?

 

[Ian David]

I think that what somebody wants to know from a photography forum, and in what detail, is best judged from the questions they ask. I reckon most people here would agree that very fine images can be accomplished without getting into too much mathematics.

 

[Nicholas Lindan]

very fine images can be accomplished without getting into too much mathematics.

No argument.

But, some of us like mathematics and find it gives insight. And very fine images can be accomplished with mathematics. Everything around you is filled with mathematics - I mean, you are sitting at a high speed computer, no?

A danger with detail of this level is that someone just starting out thinks 'Oh, this is the way it is really supposed to be done,' and promptly has a mathematics exam panic attack. Starting out with the information printed on the inside of the film box is where to start.

The depth of information people are interested in on this forum is all over the map. The questions of the OP are the starting points in a discussion. The original question is sometimes not even answered per se.

If one isn't mathematically inclined then just skip the stuff. Same as tuning to another station when the Hungarian Talk Hour comes on the radio.

Although the Darkroom Automation system has been seen as overly mathematical, it's purpose is to reduce the mathematics needed in photography from it's already low level. Much of the published information shows the math behind it, none of this is required to use it. Same with this discussion.

 

[Stephen Benskin]

Some people say that the Zone System is too technical and gets in the way of shooting. Some say it's Beyond the Zone System that's too technical. My grandmother has problems with a disposable camera. It's all a matter of taste, desire, interest, and ability.

 

[Nicholas Lindan]

It's all a matter of taste.

De Gustibus non est disputandum.