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film vs digital

D&A

Well-known member
I happen to have an Ansel Adams print purchased from him directly in the 1960s.
I use it for reference.
Mostly I would say that I can come almost as close as I want to those as far as print quality is concerned. The biggest issue is getting a DMax close enough to Silver Bromide so that under identical lighting conditions the reflectance range can be matched. Of course, there is the issue of selenium toning which imparts a rather rich color to the blacks which can be mimicked in PS but it depends a bit on the ink-set used.
I would have said it was "pretty close" with Harman FB AL, but that surface is distracting. Exhibition Fiber is perhaps the closest I have seen.
Of course I am viewing both prints in a lighting booth so it is a fair comparison.
I would say also that when we shoot digital, and expose to the right, that in those cases where the camera's DR is bigger than the subject, we tend to be placing blacks on the straight-line part of the curve. Zone System processing very carefully exposes for the blacks (or near blacks) and then adjusts the curve to get the beginnings of gentle roll-off in the highlights.
When processing digital to get the best film-mimic look, I would say that exposure is very important, and that exposing a bit less that ETTR would imply is necessary, perhaps 1/3-2/3 stop but no less.
Digital gets into trouble mostly because it is very hard to do the equivalent to N-1 processing without losing something. N+1 is easy.
-bob
Interesting observations and valuable thoughts Bob!

Dave (D&A)
 

Leigh

New member
You're just comparing two digital images, to no obvious purpose.

Once an image is digitized it is by definition a digital image, regardless of how it started.

The only valid comparison of technologies would be to put a digital print on a wall next to a real film/wet lab print and compare them under identical lighting conditions.

The obvious difference in the technologies is that film/wet lab prints can capture an infinite number of gray tones; digital modes cannot.

- Leigh
 

D&A

Well-known member
You're just comparing two digital images, to no obvious purpose.

Once an image is digitized it is by definition a digital image, regardless of how it started.

The only valid comparison of technologies would be to put a digital print on a wall next to a real film/wet lab print and compare them under identical lighting conditions.

The obvious difference in the technologies is that film/wet lab prints can capture an infinite number of gray tones; digital modes cannot.

- Leigh
Exactly what I thought (and stated) but if you provide the digital file and negative to 10 different individuals to print each via ink jet and wet darkroom respectfully, the results will be considerably different with each pairing. Having each use the same papers, printers, chemicals and so forth, will narrow down these differences to a degree. A while back I partook in both judging and participating in such an exercise and the results were quite revealing, to say the least.

It's now come down to different mediums, where each is quite capable of achieving remarkable results but where output to print reveals strinking differences. Unfortunately web sized images tends to equalize a great many things.

Dave (D&A)
 

Leigh

New member
A while back I partook in both judging and participating in such an exercise and the results were quite revealing, to say the least.
So what were the results of that comparison?

There certainly is a wide range of results attainable from either technology.

- Leigh
 

Bob

Administrator
Staff member
Actually, I have, and infinite is well beyond what you can see and besides not what that technology will yield given the quantization of exposed silver halide crystals. Rather it is a dithering result that you see, softened by diffusion of enclosing gelatin. At RIT, it seems like a hundred years ago, we tried to figure out how many "bits equivalent" in digital terms we have with film. It turns out that is is somewhere between 12-14.
I will agree that if the print is examined under a loupe, you will see two different dithers. Digital printers tend to dither in a regular array, digital prints tend to lay down a pseudo-random dither with rather less sharp dots.
-bob


You're just comparing two digital images, to no obvious purpose.

Once an image is digitized it is by definition a digital image, regardless of how it started.

The only valid comparison of technologies would be to put a digital print on a wall next to a real film/wet lab print and compare them under identical lighting conditions.

The obvious difference in the technologies is that film/wet lab prints can capture an infinite number of gray tones; digital modes cannot.

- Leigh
 

D&A

Well-known member
So what were the results of that comparison?

There certainly is a wide range of results attainable from either technology.

- Leigh
Your statement reflects the essence of what was observed. In one instance (test) where each participant was allowed free range of choice of papers, film, chemicals, but the ink jet printer, enlarger w/lens was kept constant as was the lens used on both the film based and DSLR camera, each matched pair of prints were fairly divergent in their look and the consensus was the conventional wet print was far more impressive in terms of dynamic range and gradations in tonal transitions among many other attributes. Most favored was the darkroom/film generated print.

In instances where we tried matching as closely as possible the use of papers in both technologies...various Baryta ink jet papers were employed with the digital generated file, while fiber or RC Variable contrast papers were used in the darkroom. Both types are commonly used in these sorts of comparisons. Film type and developers (for film and papers) were kept constant as were other components outlined in 1st test (above).

The results were closer this time around, but differences were still obvious, especially for those who knew what to look for. Reproduction of blacks were "still" different as was the perceived detail in textual components. Of course this could be somewhat manipulated in post processing with the digital file. Some of the differences I previously outlined in the 1st test were also evident. As for those examining each pair of prints, the feeling was it was often subject dependent which technology was preferred. Industrial and landscape type images were often preferable in the digital realm while portraits were more evenly split between the two technologies with most leaning towards the film/wet darkroom generated print. I was surprised about the landscape results, expecting more favoring conventional film and print.

What I presented here of course is an over simplification of the results and opinions of the participants and a very lively discussion took place as to the merits and strengths of each process. I'm not sure there was a clear cut winner, nor did most others who participated.

Dave (D&A)
 
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Shashin

Well-known member
If I am printing a 3' x 16' panorama, I would not want to do that optically in a wet darkroom.
 

Leigh

New member
Thanks, Dave. That's pretty much what I expected.

It's awfully difficult to separate preconceptions from actual observations in such a test.

- Leigh
 

Shashin

Well-known member
12 bits is only 4096 gray levels. That can easily be disproved by examination.
Well, since you only need about 200 levels of gray to create a visually stepless gradient from black to white, I would say you could never see a 12 bit gradient as anything but stepless.
 

Bob

Administrator
Staff member
I'm sorry, Bob, but that suggests flawed methodology.

12 bits is only 4096 gray levels. That can easily be disproved by examination.

- Leigh
Actually this is a trick question...
Ok, how would you examine it?
How many silver halide crystals are there per square micron?
Fine grain films have a crystal size that is approximately one micron in diameter. Each crystal is actually a binary sensor. It is either exposed enough to reach its threshold to develop, but when it does it is developed completely. There is no grey, only black or white. If course these grains often do not cover 100% of the area but occasionally can approach 100% coverage. Lets say they do, and lets say we take a sample of 10 microns on a side. That sample will only contain roughly 100 crystals and can have only 100 different levels of transmission.
So actually, depending on the subtended area, the levels possible to be represented by silver halide emulsions is limited by the number of grains that exist in the sample.
-bob
 

Leigh

New member
Well, since you only need about 200 levels of gray to create a visually stepless gradient from black to white, I would say you could never see a 12 bit gradient as anything but stepless.
So the reason for using 16 bits or more for gray scale and 48 bits or more for RGB is what?

Those standards place a significant burden on storage and processing power.
You would have us believe that no benefit is derived from that???

- Leigh
 

Shashin

Well-known member
Bob, don't forget covering power also plays into that equation. I am sure that is an M&P question.
 

Shashin

Well-known member
So the reason for using 16 bits or more for gray scale and 48 bits or more for RGB is what?

Those standards place a significant burden on storage and processing power.
You would have us believe that no benefit is derived from that???

- Leigh
Processing and data. Both valid. But visual perception of an image is something else, I only need 200 levels to create the illusion.
 

Leigh

New member
There is no grey, only black or white. If course these grains often do not cover 100% of the area but occasionally can approach 100% coverage. Lets say they do, and lets say we take a sample of 10 microns on a side. That sample will only contain roughly 100 crystals and can have only 100 different levels of transmission.
Invalid assumptions.

You're neglecting the depth of the emulsion and the orientation of the grains.
Both factors can dramatically increases the number of possibilities.

I went through an exhaustive study of this effect on a product that I designed a few years ago.
It counted microscopic particles in a fluid, which flowed through a sensor array.

The methodology was quite simple for low densities of particles, but became much more complex when the concentration exceeded about 10% of the presumed maximum, which itself was not nearly full saturation.

- Leigh
 

Bob

Administrator
Staff member
So the reason for using 16 bits or more for gray scale and 48 bits or more for RGB is what?

Those standards place a significant burden on storage and processing power.
You would have us believe that no benefit is derived from that???

- Leigh
16 bit units are so much easier to use than 12 or 14. Most digital sensors barely get much beyond noise in the 13th or 14th bit.
Folks like "malleable" files that can be pushed or pulled a bit. Each stop of push uses one of those bits. In the darks, when most of the most significant bits are zero anyway, you are left with precious few bits of actual information.
IMO 16 bits is a nice tradeoff of space vs processing requirements.
To extract 14 bits say from a contiguously encoded format requires for most machines a load, a variable length shift and and "and" operation to mask the extraneous bits.
-bob
 

Bob

Administrator
Staff member
Invalid assumptions.

You're neglecting the depth of the emulsion and the orientation of the grains.
Both factors can dramatically increases the number of possibilities.

I went through an exhaustive study of this effect on a product that I designed a few years ago.
It counted microscopic particles in a fluid, which flowed through a sensor array.

The methodology was quite simple for low densities of particles, but became much more complex when the concentration exceeded about 10% of the presumed maximum, which itself was not nearly full saturation.

- Leigh
I counted crystal grains in dry photographic emulsions. Only rarely did we find dried films that had significantly overlapping crystals although we did find some that had almost complete coverage.
Here is a link to some electron microscope images of a few representative films http://www.optics.rochester.edu/workgroups/cml/opt307/spr04/jidong/
Of course, if the film area considered is large enough and there is a potential, say for detection of even one grain more or less, then given a large enough sample of film, an arbitrarily large number of "levels" might be encoded.
-bob
 

Leigh

New member
I counted crystal grains in dry photographic emulsions. Only rarely did we find dried films that had significantly overlapping crystals although we did find some that had almost complete coverage.
Here is a link to some electron microscope images of a few representative films Photographic Film
I'm sorry, Bob, but you did not measure grains "in dry photographic emulsions".

From the Background Information section on the linked page:
"Therefore, if we take image directly with the unprocessed photographic film samples, what could be seen is just the situation on the very top of the gelatin/silver halide particle mixture. This means very poor image quality and sparsely distributed silver halide particles, which is of course not desirable. Taken these into account, some special sample preparation is necessary: to remove silver halide particles from film base and then redisperse them on SEM sample stub."

Since the grains were completely removed from the film, centrifuged, then re-deposited on a sample carrier in an intentionally thin layer, the results do not correlate with measurements taken in situ.

The methodology quite specifically precludes evaluation of grain overlap in an actual emulsion.


- Leigh
 
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