Dynamic Range, Contrast, latitude
Can someone speak on the relationship between dynamic range, latitude, and contrast?
Does a high dynamic range always allow for more contrast? I tend to have a preference for contrasty photos. That said, I also love Michael Kenna and sometimes I think his photos often have very little contrast (some have lots of contrast).
Just attempting to learn more (and continue to tweak what films I prefer).
From what I understand, dynamic range refers to the dmin, dmax and ALL of the tones in between. Typically dynamic range comes up a lot with digtial, but its applicable to film also. You would preferably meter, expose the film, develop and print etc to acheive the most "information" in each step. A high contrast image on the other hand would have very high dmax areas and very low dimin areas, but very few of the tones in between.
Latitude means "how sloppy can I get and still get away with something?". It is a factor engineered into
amateur color neg films in particular, but seems to be an attractive concept to anyone allergic to using a light meter. Contrast is determined both by the slope of the specific film and its development regimen. Dynamic range is the usable part of the film curve if you do correctly meter and develop it.
Some films have more range than others. Lazy photographers convert this into "latitude" mentality,
but dyanamic range is far more useful is you understand its endpoints and how to meter for them in
specific given situations. Most black and white films can be developed in all kinds of manners per overall contrast, microtonality in middle, etc. Just depends on exactly what you are trying to achieve.
Trying to answer this qualitatively, not quantitatively - my experiential 2cents .
Latitude and contrast, I think, go hand in hand. If an emulsion has a lot of latitude, then it needs a relatively greater difference in exposure to yield a difference in tonal density (which is why it is forgiving), which is, in principle, a low(er) contrast condition. If contrasty, then small changes in exposure yield larger changes in density (like a high contrast filter or paper), so less forgiving in exposure, but necessary for higher contrast results from whatever the original is (light through a neg if printing, light values striking the film if shooting).
But these two are independent of dynamic range, which is the total range of values an emulsion (or "output device") is capable, which is usually quantified with densities, etc. The contrast of an image is obviously affected by the total range of the emulsion, but I think, at least for me, this attribute needs to be kept separate from the other two. It seems to me that contrast is independent of dynamic range, but relative to it.
Good question - I'm interested to see what others think.
Oops - Drew and I answered simultaneously without seeing each other's - it's interesting already.
I can't speak to "Latitude" other than it is a sort of jargon for dynamic range. Dynamic Range is fairly precise in definition and is best understood by examining sensitometric curves. Such a curve is just a plot of scene EV value range vs the resulting density range of the developed negative. As Drew implies above, the dynamic range is the number of visible density steps that can be recorded between Dmin and D max. For example a dynamic range that goes from log .05 to log 2.4 (8 stops at log 0.3 per stop) could be considered to have a high dynamic range. Contrast is the slope of the sensitometric plot. Both the dynamic range and contrast are wholly controlled by the exposure and development conditions through the use a zone system approach or something equivalent.
Nate Potter, Austin TX.
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The definitions depend on whether one is talking about the subject, the film, the negative or the print.
Low dynamic range = high contrast.
Originally Posted by mporter012
High dynamic range = low contrast.
Unless we're talking about compensation.
3 stops stretched over the image display range (whether it's printing or otherwise) in a normal fashion is much higher contrast than 10 stops stretched out over the same display range.
Which is why I recommend treating colour neg the same as slide when it comes to beaches and sunsets/sunrises etc.. reverse grad ND to reduce the dynamic range of the scene, and bring the average of the sky and land closer together.
Obviously can't do that with more complex distribution rather than just a split bright/dark horizon line.
Often have thought about making a 'transition lens' to stick in a view camera just near where the film holder goes in, or part of the film holder, double dark slide, one for transition lens, one for film etc, in a custom setup.
Pre-expose the transition lens for a while with a slightly different focus (ala local contrast mask), then quickly expose the scene image though that onto the film.
Last edited by Athiril; 03-25-2013 at 08:32 PM. Click to view previous post history.
Cool - thanks for the feedback. I'll continue to explore this further.
and download (and read) the Basic Photographic Sensitometry Workbook
It will explain things for you
Yes, but the classic, and less ambiguous, term from the halide world is: DENSITY RANGE
Originally Posted by edcculus