Methinks me also smells some BS based on selective use of the variables. Color and b&w deliver an impression of sharpness in different manners,
and in either case it's contrast related. Even the concept of sharpness versus acutance can turn this game into nonsense if you are merely
crunching numbers. How you develop and print the film if a significant factor too. But overall, comparing apples to oranges is a waste of time.
Contrast is one of the components of perceived sharpness. With colour, perceived sharpness may be affected subjectively by the level of colour saturation.
Originally Posted by didjiman
The Portra films are designed to be excellent for skin tones. They exhibit moderate contrast and saturation. So they exhibit lower perceived sharpness unless you adjust them for higher contrast and saturation.
Originally Posted by DREW WILEY
It's not bullshit. I am aware of the other factors and that the idea of sharpnes is a subjective one to begin with. Those numbers are a useful means to understanding why color slides or negatives may appear to have less resolved detail than black and white films. I used to shoot Kodachrome long ago and was disappointed when I scanned them a couple years ago on an Imacon scanner and found their resolved details were
No match for most of my Black and white negatives. There is something to the fact that light has to travel to three layers, not counting the filter layer in color film. The MTF is useful for understanding the maximum capabilities of a film like we may know a digital cameras resolution, of course the lens resolving on that film determines how much can be revealed. There is no number crunching at all, just simple comparing of numbers to try to understand some of the different properties.
Acutance of the film during processing is different than the actual resolved detail as it can alter the contrast between resolved details and the perception of sharpness can be very high. If the details are not recorded however, no amount of processing can create them, which is why I mentioned this problem of resolution/sharpness arises mostly from printing very large or scanning very high resolution and realizing the film doesn't have incredible detail after a certain size. Of course you don't take the numbers to heart and say "well crap, I'll never shoot color again now" because that's just stupid.
All the numbers say is that under the specified conditions, the film can resolve up to this amount of detail at this percentage of contrast. The maximum a film can resolve is at a very low contrast at the end of the curve. Likely P3200 using the developer stated is able to resolve what it can because at around 70 Lp/mm the perceived contrast Is still high enough likely due to the large grain size but the finer the recorded details go the grains become too large to differentiate anymore. T-Max 400 may not be as grainy but may have reduced ability to resolve more than P3200 due to its heavy use of tabular grain and dye.
Originally Posted by pentaxuser
I am not saying this is why, I am just trying to reason this out. The fact exists that this film did record this detail under the set conditions although it likely wont record that much if used normally in a real world situation.
Nikanon first I think we are comparing apples to oranges. Color and black-and-white films present their detail differently.
Second comparing scans introduces way too many variables to allow any meaningful conclusions outside of your house or mine.
Fair enough, I don't work with color enough anyway to really examine the theory I am describing.
Originally Posted by markbarendt
I guess I am just saying that I miss Kodachrome 64 :-/
Of course it's BS. Throw away your calculator and actually print all these film for forty years like I have! The graphs are useful, but only when
the playing field is perfectly level; and the whole name of the game in the darkroom is to skew the variables. A particular black and white neg
which might appear sharper in a 16x20 print versus its color counterpart might see the apparent result switched in a 30x40 magnification, for
example. There are all kinds of ways of tweaking these things, and I'm not referring to digital manipulation. Sometimes a grainier film appears
sharper than a fine-grained one, sometimes it doesn't. It can even depend on which dye layer of a color film is predominantly exposed. We could talk for hours and hours about this. Those of us who cut our teeth on Kodachrome 25 thought the 64 version stunk. It's all relative.
But if detail is a priority in color, take a look at Ektar. Otherwise, shoot a larger format (I do both).
You are right in the practical applications, but its still not bullshit. The facts are what they are and knowing them can be useful, although it isn't necessary as many successful photographers can attest to. The science and math is supplementary, but shouldn't restrict the way that you work. When im out photographing, im not thinking of all that nonsense, and quite often im not when im printing or developing either, its just useful to understand the process and how your materials function in order to deconstruct the mysteries of it at times.
Thanks for all the comments. I was hoping someone else who uses all 3 types of the films can make some generalized statements, but I will just chalk it up as apples vs. oranges.
There are not only whole different categories of film, but within each of these different categories many different specific products, each with
more than one way of using them. A color neg film primarily marketed for portrait use, like Portra 160, will be engineered with fine grain but
low contrast. That can be altered to some extent by how you print it; but it behaves differently than something like Ektar, which has been
engineered for a different range of potential applications, even though it belongs to the same general family by the same manufacturer. You
can take a black and white film like HP5, develop it in pyro, and it will look like utter mush under a high-powered loupe, if you compare it to
TMax 100. But when you print both of them at, say a 5X magnification, the HP5 will actually seem crisper or apparently sharper. Change the
developer or make significantly greater scale enlargement, the effect will be different. There are just way way too many variables to make