https://en.wikipedia.org/wiki/Raw_image_formatI shoot RAW, the camera does ZERO processing in camera. I do RAW conversion with Lightroom, and the only processing it does is what I instruct it to do. The values of Brightness and Contrast are my own standard settings that I had chosen which results in an appearance which I had experimentally determined to provide what my own film-experienced shooting expected to see as a result. My standard settings would reproduce the Macbeth Colorchecker chart with a faithful brightness and contrast and subjectively faithful reproduction of hues (saturation and vibrance). It is possible to derive a profile with measured objectively faithful reproduction of hues, but I have not needed that for my now-enthusiast level of photography...I haven't shot any textiles or fashions since my film days.
So while the derivation of ISO rating is different from film to digital, I am ultimately a pragmatist and not a theory driven sensitometrist measuring density values on film. I seek black blacks and white whites and 18% midtones in between those two extremes, regardless of my medium, and I find my incident meter to give me the right tonal values in combination with my standardized settings during RAW conversion with my digital, just as it allowed faithful placement of midtones on slide transparency.
The point I am making is that digital is different.
Sometimes very different. Once the analysis has been done digitally, the analysis will need to be repeated on film. So why bother with digital in the first place other than to just play with it?
There certainly are very many possible algorithm for defining film speed.... If Mr. ASA chooses to take a certain low density point as "speed point" he does it for some technical reason but not because he has Zone System in mind...
Perhaps both of you can enlighten us all with specifics of how 'digital is different' and behaves in a manner inconsistent with film. BTW, reciprocity does not count among the differences.
wiltw, to clarify what Mark means regarding speed point, I suggest you read Kodak document H-740, "Basic Photographic Sensitometry Workbook", which explain the basics of sensitometry, and I certainly won't go a centimetre past that document as far as complexity is concerned
What Mark means is a well-known property of B&W negatives: by altering the developing time you alter much more the highlights than the shadows. One can imagine the characteristic curve as "pivoting" around a shadow point, on the left of the graph, where there is minimum density. The more the exposure, the higher the density, by a "law" which is defined by the ISO speed of the film but also by the development time (or agitation, or temperature). The curve can "pivot" around that shadow point at different kind of development and while the different development raises somehow all the curve, the effect will be more relevant to the highlights.
That leads to the "zone system" by Adams. By developing negatives one by one, you can alter the contrast and the highlight renditions of the image. That's because the development can alter the highlights much more than the shadows. So you control the shadows with the exposure, and you "control" the highlights with the development. In this manner you can obtain a negative which is more contrasted, or less contrasted, than the original scene, and always print on the same gradation of paper with the intended result.
This is all very esoteric, very sophisticated photography. The Zone System applies only in Black & White, in sheet film (because you develop each shot individually), and is as far as I know quite a complication in a world of variable contrast papers. But that's only what I heard through the grapevine, I use slides, and I would like to go back to it.
[My example of the digital ETTR was intended to mean that it is a technique that uses a "non ISO" exposure to reach a certain result. It's not meant to be taken literally and transported in the analogue world].
Before we talk slides, we should talk very simple sensitometry. For a complete ignorant of the matter like yours truly, you can define a speed scale either by choosing a certain arbitrary density on film, and then measuring how much exposure it takes to arrive to that density (the higher the exposure, the lower the speed) OR by choosing a certain arbitrary exposure on film, and then measuring how much density that produces on film (the higher the density, the higher the speed).
There certainly are very many possible algorithm for defining film speed. The most famous are ASA/ISO, and DIN. There used to be others, created in the United Kingdom, in Eastern Europe, in Russia. Now the world set on the ISO standard which is basically the ASA standard.
If I were Mr. ISO I would define a certain density on film "around the middle" and measure how much exposure it takes to arrive there. Mr. ASA did things very differently. He chose a certain point at the near transparent end of the characteristic curve of the negative, and from the density of that point, he derived a certain speed, assuming, I suppose, that the rest of the curve was basically linear and the ASA number would describe the "entire curve" (or line) of the film even if it was calculating by extrapolating the very initial part.
As a completely ignorant person of the subject, I can infer that Mr ASA chose to measure density near the extreme left because that minimizes the differences in development. Even though the ISO standard certainly stipulates a certain "standard" treatment defined by the manufacturer, measuring on the left of the curve takes some complexity out of the tests, takes away some head-scratching.
Conceptually, though, given a standard well-known development, Mr. ASA could have chosen any density, and is possible that Mr. DIN did something completely different than Mr. ASA, considering that certain films (Vericolor III if memory serves) have a "different" speed rating in the ASA and DIN systems (meaning: they employ two different algorithms). (The difference was 1/3 of a stop but is relevant for what I am saying). And the aim of Mr ASA, just as the aim for Mr. DIN, is to actually show the behaviour of the film around the middle part of the curve. If Mr. ASA chooses to take a certain low density point as "speed point" he does it for some technical reason but not because he has Zone System in mind, so to speak! Mr. ASA does not think that the user will develop for the highlights, or use sheet film. He means to tell you the speed of the film all along its linear part of the curve so that Aunt Sue will get the holiday pictures with the same tones that she saw during her trip to that most beautiful wonder which is Rome (shameless plug).
Now, back to slides. Slides matter because all this talk about exposing for the shadows, developing for the highlights, compensating in print does not stick with slides and does not stick with aunt Sue. I insist: slides can be developed only in one correct way, and can be seen only in one way, there's no print and there's no "recover" of details, no dodging, no burning, the bunny must come out of the hat at first attempt.
With slides, a light meter must work exactly and very precisely as intended. And it does! So - I insist - there is, even "implicitly" in the ISO speed determination, a way to make the middle grey (and all surrounding tones of all colours) fall exactly where they are perceptually faithful. Yes the extremes of the dynamic range will not be rendered, or will be rendered with some faults. But the tones around the average MUST be perceptually precise on slides, and they are. So lightmeters are actually devices that allow us to know where the middle tone will fall, and they show that to us every day. And they must be calibrated for a certain, unknown but certainly determined by the manufacturer, shade of middle tone. And I would be very, very surprised if this middle tone wouldn't fall exactly where the human eye sees middle tone, and where the "world at large", as shown by a research conducted by Kodak and mentioned by Ralph, shows middle tone. That's 18%.
So let's keep the reasoning alive because there is a lot to be understood more precisely (I have got a couple of huge doubts that I will try to clarify with your help) by keeping slide film in mind. Let's forget B&W negatives for the time being.
Well, while they both accept input of light through a lens, they use very different subsets of the rules of physics from there forward.Perhaps both of you can enlighten us all with specifics of how 'digital is different' and behaves in a manner inconsistent with film. BTW, reciprocity does not count among the differences.
Well, while they both accept input of light through a lens, they use very different subsets of the rules of physics from there forward.
Chemical/Physical processes, like how certain wavelengths of radiation affects the silver in a film and how that silver behaves when dipped in certain chemicals, are constrained by rules we can't change.
Digital processes can't break the rules of physics either but the rules that define a digital image are fully contrived at the whim of man. If a software engineer were to pick middle gray to hinge all adjustments on there's no reason they couldn't. Film can't do that.
So a "Roebuck's Extra Fast Dry Plate" would get a speed of H&D 200 (something like ASA 10).
All of these threads have been interesting, but this is truly the bottom line. Especially if "and learn how to use the meter(s) correctly" is added.if you stop trying to compare incident meters with reflection meter, throw your grey card in the bin, then all your problems and worries about exposure will disappear. You will learn to interpret your meter reading and adjust accordingly as an instinctive action.
On the other hand, if you are a perfectly able bodied person who thinks they need a crutch to walk with combined with two measuring sticks one of which is slightly longer (or is it shorter?) than the other and you can't see why they never quite match each other, then you are destined to be a pathetic paraplegic for the rest of your life by your own choice. That is not an intelligent choice to make. So is that you just so we know?
When film is exposed, it is inherently more contasty than Digital...
I often wonder why ISO standardization wizards didn't think of using a different naming and numbering nomenclature. I understand being backward compatible but if the are different they ought to be different.
No.
Neither has an inherent contrast defined by the rules of physics.
Digital and Analog do though each have their own separate ISO standard for determining the sensitivity/exposure speed they can claim and that standard has certain rules that specify contrast.
In the wild though no one/no company is bound to use the ISO standards for contrast.
Digital and analog require different standards because they don't work the same.
Mark, I don't think there is a standard for contrast.
The Standard Output Sensitivity (SOS) technique, also new in the 2006 version of the standard, effectively specifies that the average level in the sRGB image must be 18% gray plus or minus 1/3 stop when the exposure is controlled by an automatic exposure control system calibrated per ISO 2721 and set to the EI with no exposure compensation. Because the output level is measured in the sRGB output from the camera, it is only applicable to sRGB images—typicallyJPEG—and not to output files in raw image format.
if you stop trying to compare incident meters with reflection meter, throw your grey card in the bin, then all your problems and worries about exposure will disappear. You will learn to interpret your meter reading and adjust accordingly as an instinctive action.
On the other hand, if you are a perfectly able bodied person who thinks they need a crutch to walk with combined with two measuring sticks one of which is slightly longer (or is it shorter?) than the other and you can't see why they never quite match each other, then you are destined to be a pathetic paraplegic for the rest of your life by your own choice. That is not an intelligent choice to make. Is that you, just so we know?
I can say without a doubt that digital colour correction moves are identical to enlarger colour correction moves. a 5 yellow change is the same if you are using an all digital platform vs an colour enlarger.Perhaps both of you can enlighten us all with specifics of how 'digital is different' and behaves in a manner inconsistent with film. BTW, reciprocity does not count among the differences.
No.
Neither has an inherent contrast defined by the rules of physics.
Digital and Analog do though each have their own separate ISO standard for determining the sensitivity/exposure speed they can claim and that standard has certain rules that specify contrast.
In the wild though no one/no company is bound to use the ISO standards for contrast.
Digital and analog require different standards because they don't work the same.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?