Metering with film

[RobC]

And halation is caused air/surface boundaries and reflection from film backing plate which has been utilised by infra red film manufacturers to get that characteristic bloom in IR film shots. They didn't use antihalation dyes in their films. Normal films have it though. I guess its like a lens coating for films. They've improved too, so much so that they can get film resolution of 200 lp/mm (ignoring the massive numbers claimed by some specialist films like 800 lp/mm).

Just to emphasize this point. If you have a high level of IR in your subject then you can get this IR blooming effect even if your film has anti-halation dyes in it. Where that dye is makes a difference too. If its on the back of the film it won't be as effective as if its between film support and emulsion (which makes it more difficult to wash out when processing).
And if your film is not in good contact with the backing plate then blooming will be worse if there is a lot of IR. Film which has been left in camera tightly wound around roller is often not flat when advanced so that there is wave in the film which sits across a frame top to bottom. So there are circumstances when you can see some IR blooming. And different backing/pressure plates will reflect differeing amounts of IR back into the film.
And if film is not pressed up against film gate firmly you will get diffraction and IR bloom around edges of frame as IR and visible light bounces between film and inside of film gate.

And if you are using some cheap films their anti-halation dyes may or may not exist or be less good than other films and the film sensitivity may extend further into the IR region than is desirable for a non IR film.

So in short, what is causing film lighting bloom is dependant on various factors and can not be assumed to light tunneling through emulsion and or film backing purely because of high contrast boundaries. It may be more noticeable there but not at all necessarily due to the boundary. Far more likely due to IR blooming IMO.

Buy good qualiy film and you're less likely to experience it IMO.

 

[pentaxuser]

. For info on ideal exposure check pp. 68 (depends on the edition) to see the complete picture. .

I checked my download of the book between pages 67 and 70 and I think that you are referring to the paragraph on OPTIMUM EXPOSURE which is on pages 66-67 in my download. I cannot see a reference to increasing box speed by half a stop to improve things but it does say that exposure should be the minimum commensurate with good shadow details. This of course is true and is really a truism but doesn't necessarily lead to the conclusion that an increase in box speed will improve the negative in terms of printing nor do the authors suggest this as a course of action that I can see.

It may of course work for you but as a general rule in photography it may well not have universal application

pentaxuser

 

[Ian Grant]

I checked my download of the book between pages 67 and 70 and I think that you are referring to the paragraph on OPTIMUM EXPOSURE which is on pages 66-67 in my download. I cannot see a reference to increasing box speed by half a stop to improve things but it does say that exposure should be the minimum commensurate with good shadow details. This of course is true and is really a truism but doesn't necessarily lead to the conclusion that an increase in box speed will improve the negative in terms of printing nor do the authors suggest this as a course of action that I can see.

It may of course work for you but as a general rule in photography it may well not have universal application

pentaxuser

The reality is hat to obtain optimum exposure and development negatives usually have to be processed individually, two methods are the Zone System and BTZ. People were doing this though long before Adams and Minor White caame ip with the Zone system. That's fine for sheet film and occasionally for 35mm &b 120 were the whole film has been shot under similar lighting conditions.

In practice we compromise slightly with 35mm & 120 films to cope with slight variations in contrasts. It's far more important to do some very basic tests to determine one's own personal EI and development time with a film/developer combination whether it's for darkroom prints or scanning.

Jacobson's book Developing is one of the best on the subject and well worth reading, he was at the cutting edge in his field, I learnt all the basics reading this book and its companion Printing in the late 1960's and I've never seen any better books.

Ian

 

[Arvee]

I checked my download of the book between pages 67 and 70 and I think that you are referring to the paragraph on OPTIMUM EXPOSURE which is on pages 66-67 in my download. I cannot see a reference to increasing box speed by half a stop to improve things but it does say that exposure should be the minimum commensurate with good shadow details. This of course is true and is really a truism but doesn't necessarily lead to the conclusion that an increase in box speed will improve the negative in terms of printing nor do the authors suggest this as a course of action that I can see.

It may of course work for you but as a general rule in photography it may well not have universal application

pentaxuser

You found the information I was talking about.

Jacobson's recommendations are right on the money and will get you in the ballpark for optimal print quality. Jacobson's explanations of the physics of photography are the necessary facts one needs to know so one is able to make informed decisions about how one wants to capture his/her images and what trade-offs one may have to accept in the process.

If you have done any research on the workflow/techniques practiced by many of the well known photographers, you'll find they vary all over the map. Each of them has their own perception of what the final print should look like and they adjust their practices to achieve that end. For example, Gene Smith's methods are completely different from Ralph Gibson's methods; Jerry Uelsmann's practices are completely different from Ansel Adams' techniques. For example, when Lee Friedlander came to Tucson to photograph the AZ desert, he overexposed/overdeveloped the negs to create final images that represented the 'searing, white hot Arizona desert.' I don't think I have ever read of any notable photographer that follows the baseline recommendations to the letter; there are always some deviations, some wildly so! I personally tend to shoot higher than box speed (note that a lot of film manufacturers/MDC recommendations are box speed to 2X box speed with normal development) because that gets me the results I want. I tried shooting at numbers below box speed and I never liked the results; they were always flat/lifeless and took a lot of time in the darkroom to inject some life into them and they never seemed to represent what I originally observed. They seemed to always have an artificial/contrived/unnatural look.

The point: virtually no one complies exactly with the baseline recommendations set forth in Jacobson. Everyone has their own vision and it usually involves devising methods/practices to fit the end result. That is why you so often encounter the advice that exposure/development recommendations are only a starting point; you need to experiment and find the numbers that produce the results you desire.

All this discussion about folks worrying over ½ stop in exposure or a ¼ stop loss in shadow detail or your meter is calibrated 2.7% higher than mine is a colossal waste of bandwidth. It matters not unless you aren't getting the result you desire; ultimately, you necessarily alter the parameters until you get your desired result and it is most often a compromise of sorts.

And, folks who espouse the 'my way or the highway' attitude are merely howling into the wind.

 

[removed account4]

If you have done any research on the workflow/techniques practiced by many of the well known photographers, you'll find they vary all over the map.

exactly!

that is hey discussions on these forums can be so much fun!
everyone has their own ideas of what a good exposure/print &c is
and what not so good is, including technique and everything inbetween.

 

[Arvee]

Speaking of which, what's with the title of this thread? You can't actually meter with film as far as I know. You have to meter with a meter.

Good call, Michael!!

 

[DREW WILEY]

Fred pretty much bagged the gist of it yesterday. That's because he seems to be from a mountainous area and understands contrast. Me too; and
where I'm from, there are cats big enough to skin people. And that's why I'm very choosy about the shape of the film curve, especially the toe. Yeah,
you can develop film in such a manner that overall contrast is reduced, yet at the expense of well defined gradations in between. For example, last
Saturday I was running some tests on roll film backs near the beach. It was a clear day, but with just enough mist in the air to turn Pan F into sheer
magic. Well, that's a film with a pronounced S-curve with a very brief straight line, in other words, not something I would routinely use in the desert
or mountains unless falling snow or rain diffused the light, like at the beach. I'd want something capable of digging way down into the shadows like
TMY for large format, or at least FP4 or ACROS in roll film, as a compromise. The old school method was to take Tri-X sheet film and overexpose it
to go way up onto the straight line, and end up with a "thick" dense negative. That might have been acceptable for contact printers on Azo paper,
but distinctly risks blowing out the highlights on typical enlarging papers. I really don't care what famous so and so did, or does it, that way. There
are really better ways unless you are absolutely married to a single film choice.

 

[Arvee]

John knows I'm just fooling, but I pictured using a strip of film to meter a scene and had to make the comment.

So did I!

 

[removed account4]

Speaking of which, what's with the title of this thread? You can't actually meter with film as far as I know. You have to meter with a meter.

John knows I'm just fooling, but I pictured using a strip of film to meter a scene and had to make the comment.

i thought it had to do with 39 inch actinometer ...

 

[Luckless]

John knows I'm just fooling, but I pictured using a strip of film to meter a scene and had to make the comment.

Actually not all that far off from some of the earliest examples of light metering tools I've seen. Almost like litmus strips, and not as crazy as it first sounds really.

 

[Stephen Benskin]

Just an FYI. Below are four graphs. The first two are comparisons of exposure vs image quality. The graph on the top has three situations: contact print, 10x enlargement, and a 10x enlargement of a negative with extended development. The other two graphs are on density and graininess.

 

[markbarendt]

Thanks Stephen.

12-3 is interesting.

 

[Diapositivo]

Thanks Stephen. From the third graph I infer that grain doesn't appear "more evident" in the high-midtones. There actually is more grain to be seen. What is the reason for this behaviour? Is it the fact that the "grains" overlap, with increasing density, thus somehow hiding each other or assuming a more coherent appearance?

 

[baachitraka]

3a is obvious. Less the exposure is more the grain not taking the developer and printing into account.

But I don't understand 3b though,.

 

[Diapositivo]

3a is obvious. Less the exposure is more the grain not taking the developer and printing into account.

If I get it right, 3 (or 3a) means same light under which you look at the microscope the developed negative when you "count" the grain (which is expressed as a numeric value on the vertical axis). That exemplifies what the enlarger (or the human eye, or the scanner) sees when you look at a certain negative, which has regions of different density. The grain is more present in that interval of density. In denser areas there actually is less grain.

3b (or 4) illustrates the case of placing the same scene in two different regions of the film curve, in two different shots with different exposure. The enlarger has to throw more light at the denser negative in order to obtain the same print (the same light passing through it) and the denser negative gives a grainier print.

(yes the description counts the grain that reaches "the eye" not the paper, that's probably counted with a microscope).

 

[markbarendt]

The perception or subjective sense of grain ("graininess") in a print is supposed to peak at reflection densities around 0.4.

So 0.4 means that it's in the highlight half of the curve, so probably one reason people complain about grainy skies more than grainy lakes.

So is this specific effect more about the paper's response or the negative's higher density at the corresponding spot there.

Granularity (the objective measure of graininess) in a silver negative increases with increasing density.

In figure 12-4 that Stephen provided above the grain is measured with a variable light source, given that we don't print that way (where the light reaching the paper/eye would be the same and produce a one tone print) I don't understand the practical value of that test. Is this the objective measure of graininess you speak of? Does this really translate into a difference in the print?

 

[RobC]

fig IX.4 doesn't tell us anything becasue it doesn't tell us how much neg exposure produces optimal quality. Is it ISO standard exposure for a particular film type or is it some other exposure value. Or to put it another way, does ISO standard expsoure mean optimal negative quality or does it mean film speed which may not be optimal quality.

fig 13.3 is just saying human visual resolution decreases with a constrast decrease.
fig 12.4 is just saying human visual resolution increases with a contrast increase.

 

[Stephen Benskin]

Fig IX 4 is just a simplified version of the first graph (from the paper Safety Factors in Camera Exposures). It appeared in Todd & Zakia Photographic Sensitometry. I wanted to include it because it used easy to understand + and - stops from the optimum exposure. It's not necessary to know what optimum is in order for the graph to make its point.

fig 12.3 and 12.4 are from Photographic Materials and Processes. Figure 12.3 is about physical graininess and 12.4 perceptual. As the text explains 0.30 corresponds to a transmittance of 1/2, which represents equal amounts of clear and opaque areas.