Definitely not. You don't have to know anything about characteristic curves either, but some of us find them interesting and useful.
Do I have to learn calculus to shoot a picture?
Do I have to learn calculus to shoot a picture?
@aparat,
I have digitized (with suitable freeware) your curve for Delta100 in Xtol 8min, as shown in your post #210 above. Using basic software LibreOffice Calc) I have plotted
View attachment 328734
- all digitized points : small blue dots
- points selected by me as representative of the "straight-line portion"; choice did not seem critical or problematic
- a least-squares fit of a linear relation to the above-mentioned "straight-line portion", and the corresponding equation
Rounding up by 0.002, the gamma results as 0.70. Not 0.56. And identifying the straight-line portion is not problematic, as one can see at a glance from the near-perfect agreement between the fit line and the red crosses.
I don't know what is (what might be) a statistically derived value of gamma, when there is one data set to work with.
A separate point. In my opinion, CI and G-bar were not created because the straight-line portion of the D-logE curve was difficult to identify. But rather because in actual use for pictorial photography, the scene values are not generally placed entirely in the straight-line portion (except maybe for reproduction work). But rather with some shadow values in the toe; so that for the purpose of translating scene brightness range to density range, CI or G-bar are more useful.
Might sound like I'm nagging at your valuable work. Not so. You have provided lots of excellent and useful data. My remarks aim to help you correct what I perceive as errors.
No! You are doing the right thing asking a lot of questions. Do not stop! I really enjoy reading your questions because they are insightful. It's a very simple thing that never occurred to me: do I need to learn calculus to understand the characteristic curve? Of course not, and I am very sorry that you got that impression. The idea is to make this kind of analysis as easy to digest as possible. I am not there yet, and maybe I never will, but I appreciate your insight very much.Just making a nuisance of myself.
Do I have to learn calculus to shoot a picture?
And you definitely need to learn a lot of math - including calculus - and have a lot of computer knowledge in order to become a trade certified auto mechanic.Alan - you have to learn about calculus if you're a dental assistant.
For example, taking the derivative of the lines plotted in the H&D charts gives the contrast index at any point on the line - a very useful thing to know.There are actually some benefits to learning calculus when it comes to photography. The calculus is, among many other things, a method of constructing mathematical analogues of real world phenomena that enable us to examine the characteristics of those phenomena and predict other phenomena.
Well Matt, I've had two close friends who were super math whiz types. One is a famous astrophysicist and the other got bored working at NASA and retired young. Neither can tie their shoelaces correctly.
Well Matt, I've had two close friends who were super math whiz types. One is a famous astrophysicist and the other got bored working at NASA and retired young. Neither can tie their shoelaces correctly.
I was going through my backlog of negatives and I found a 120 negative, including a test exposure in my sensitometer. The film is Fujifilm Acros 100, the older version, now discontinued. I decided to run the analysis, and here are the results.
Please, do not put too much stock into this result, as this is only one curve, and the ISO value is computed based on a hypothetical curve. Still, I thought this was a really interesting result, especially compared to the current version.
acros by Nick Mazur, on Flickr
That is interesting! I looked on your Flickr stream but didn’t see if you have a curve for Acros II in D-76 1+1. Wonder if the developer is important in the difference.
I was going through my backlog of negatives and I found a 120 negative, including a test exposure in my sensitometer. The film is Fujifilm Acros 100, the older version, now discontinued. I decided to run the analysis, and here are the results.
Please, do not put too much stock into this result, as this is only one curve, and the ISO value is computed based on a hypothetical curve. Still, I thought this was a really interesting result, especially compared to the current version.
the old Acros was a wonderful film, it worked great in Rodinal and DDX
No worries, no pressure from me! Appreciate everything you have done already.I'm still working on it. I am re-testing Acros II, in D-76, because other people got a higher speed in their tests than I did in mine. It's going to be at least a couple of weeks. Acros II is such a popular film, I need to be sure I get it right so it can be a useful test for other photographers.
Only time I ever played with Acros II was to try it in a pinhole, where its low reciprocity failure should have been a big advantage. The results came out fine, I didn't see anything special about the film (it was a roll of 120 in a curved-plane 6x17 camera). Of course, a random pinhole isn't exactly a fair shake for that film to shine. I know it has a large fanbase.
I guess I'm just happy enough with Delta 100 that I can comfortably sit up on my high horse and continue my low-key boycott of Fuji without worrying too much about what I might be missing out on with Acros II
One other thing I want to mention is that a hypo-clearing agent can reduce the amount of the pinkish cast from the film base pretty effectively, in my experience. In fact, after washing the tabular grain films, my Kodak Hypo Clearing Agent has turned a nice shade of pink.
I found an interesting quote in Woods (Zone System Craftbook, 1993) regarding pushing and pulling t-grain films: "This variable zone placement must be used with care and only when the T-Max developers are used. When some conventional developers are used, the extreme high values produced by overexposure will "shoulder" quickly," and later "I again stress the need to use the special developers designed for this film to achieve the maximum benefits from it."
I wonder if statements such as this bear out in your experience. In my tests, the Kodak t-grain films do not shoulder particularly easily with XTOL or D-76, but perhaps they do in your experience? Do we really need to use the T-MAX Developer with tabular grain films? Or was that just a marketing ploy to make sure we buy those special developers?
Nicholas - Tech Pan was pathetic at trying to mimic 4X5 results. Not only was it incapable of handling highlights and shadows anywhere near as well as ordinary film, even using special developers, but if enlarged directly from 35mm much, exhibited enlarged little dots in the sky too. I had a backpacking pal addicted to it, who used very expensive Zeiss 6x6 lenses. Sharp, yup, but with that proverbial "soot and chalk" look which AA derided, and lots of tiny sky blemishes. He eventually got frustrated and switched to FP4, and while it was still availlable used Efke 25 roll film on my recommendation, which gave him something super-fine grained, but without TP's headaches.
The edge effect of Tech Pan was abominably mediocre. So yeah, doing the very best that could be done using 35mm TP, and comparing the resultant print side by side to the worst that can be done using actual 4X5, by some klutz with a warped film back, dumpy lens, and the grainiest film he can find, devoid of a focus loupe, and that old BS Kodak ad sorta, vaguely, remotely rings true. But I've got 8x10 Tech Pan film on hand - so that must be equivalent to traditional film ten feet across if you want to believe Kodak's old marketing ploy!
My biggest complaint with TMX100 is its own disappointing edge effect despite very fine grain and otherwise exceptional detail capacity over a very long contrast scale. That's why I develop small sizes of it (including 120 roll film shots) using Perceptol 1:3, which gives me a very nice boost in edge effect, yet only a minimal increase in graininess. TMY400 has very good edge effect, so in its case, all kinds of developers work well, though I lean toward PMK pyro as my standard option. Sometimes, like for portraiture, I actually prefer to keep the softer-edged look of TMX100 as-is. Note that this has nothing to do with overall detail capacity or the reproduction of subtle microtonality, but just the Mackie line edge effect itself.
Perceived sharpness is based upon both resolution and boundary contrast.
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