PhotoStudio13 discontinuing Scala process

Raghu Kuvempunagar · Apr 21, 2022

flavio81 said:
However if the slides are to be scanned, this is not a requisite, and in fact perhaps the dynamic range should be reduce to better match the scanner's capability.

Actually, low DMax slides make more sense for the purpose of enlarging the slides in the darkroom (to make reversal prints).

Klaus Wehner · Apr 21, 2022

There is a lot to say about the last statements. I will try to do this very briefly.

The well-known standard reversal process does not give really satisfactory results with all films.

To get better results, you have to change the chemistry. It is generally known from technology that the effort is much higher if you want to increase a yield from 90% to 95%, for example, than perhaps from 65% to 70%.
That is the case here: an improvement can be realised with a high effort.
Of course, an additional bath also means additional watering. That is banal. But it is additional work that has to be done.

Digital photography and analogue photography are two different media. One should not play them off against each other. Of course, digital processing has completely different possibilities than a purely analogue process.
But whether a digital projection or the projection of a good black and white slide achieves the highest dynamics, I don't know for sure.

My aim was to create the best conditions for a high-quality analogue projection of a black-and-white slide.

Best regards
Klaus

Raghu Kuvempunagar · Apr 21, 2022

Klaus Wehner said:
effort is much higher if you want to increase a yield from 90% to 95%, for example, than perhaps from 65% to 70%.

What is the metric? DMax?

AgX · Apr 21, 2022

I read this as general remark on technological processes.

Klaus Wehner · Apr 21, 2022

It was a general comment on technical processes.
The reference for a good black and white slide is generally the maximum density. But of course there are others like a "pure white" in the highlights, good differentiation of the grey levels and so on.

Best regards
Klaus

flavio81 · Apr 21, 2022

Klaus Wehner said:
Digital photography and analogue photography are two different media. One should not play them off against each other. Of course, digital processing has completely different possibilities than a purely analogue process.
But whether a digital projection or the projection of a good black and white slide achieves the highest dynamics, I don't know for sure.

There is a misunderstanding. I never mentioned scanning for digital projection of b&w slides... Which, in my opinion, would be a silly thing to do, and I would guess we both think the same about digital projection.

flavio81 · Apr 21, 2022

AgX said:
What about proposing Klaus to sell digital cameras instead?

I would have expected a better comment from you.

AgX · Apr 21, 2022

Well, people have certain ideas in mind when offering services or products.

Klaus Wehner, from all I know from or about him, is devoted to black and white slide projection and to yield "best" results (whatever this means, he explained above). Proposing to him to adapt his process for film to be scanned seems ridiculous to me. And thus I thought my comment cheap but appropriate.

As you know from other posts of mine I am sensitive to proposals of going digital or adapt to digital. Which of course does not exclude that I myself from my engineering perspective am able to question long standindg standards of analog processes seen the new market situation. But questiong not necessarily leads to adaptation.
I would say who still is in the photographic analog world and has not adapted yet, has made up his mind and got his reasons.

AgX · Apr 21, 2022

I would like to get back to the original topic of this thread:

What happened to Photostudio 13, I mean, how did the takeover by a local competitor went along?

"The reason for the cancellation of Scala processing is that Photo Studio 13 has been sold.
The new owner, who already runs a photolab at same city, does not want to take over the Scala processing." (AgX)

Can someone give an update, has got experiences in their offer? Have they really cancelled Scala processing?

flavio81 · Apr 21, 2022

AgX said:
Well, people have certain ideas in mind when offering services or products.

Klaus Wehner, from all I know from or about him, is devoted to black and white slide projection and to yield "best" results (whatever this means, he explained above). Proposing to him to adapt his process for film to be scanned seems ridiculous to me. And thus I thought my comment cheap but appropriate.

I never suggested such a thing. This is a non-sequitur fallacy.

Raghu Kuvempunagar · Apr 22, 2022

Is the optimal DMax for best viewing experience different for B&W slide vs B&W motion picture? I checked the data sheet of KODAK TRI-X Reversal Film 7266 and the recommended DMax seems to be around 2.6 as ascertained from this graph:

Klaus Wehner · Apr 22, 2022

flavio81 said:
There is a misunderstanding. I never mentioned scanning for digital projection of b&w slides... Which, in my opinion, would be a silly thing to do, and I would guess we both think the same about digital projection.

I probably misunderstood you then.
If you consider the projection of black and white slides to be a photographic medium with a very high potential, then we are in agreement.

I am trying to improve the results of the slides for production. To do this, it is necessary to change the chemistry of the reversal process a little.
Some films need a more complex processing. The necessary quality cannot be achieved with the standard chemistry.

To use the full potential in projection, a sufficient maximum density is necessary. This should be around 4.00 (+/-) (depending on the projection conditions).

Achieving this is not always easy. But one should make an effort.

Thank you for your critical enquiries!

Best regards
Klaus

Klaus Wehner · Apr 22, 2022

Raghu Kuvempunagar said:
Unterscheidet sich die optimale DMax für das beste Seherlebnis für Schwarzweiß-Dias von Schwarzweiß-Filmen? Ich habe das Datenblatt des KODAK TRI-X Reversal Film 7266 überprüft und die empfohlene DMax scheint bei etwa 2,6 zu liegen, wie aus dieser Grafik hervorgeht:

View attachment 303536

You have to distinguish between the "maximum density" (2.7) that can be achieved with the standard process
and the actual "optimal density" (4.00) in the projection.

This can be a very big difference!

Best regards
Klaus

Klaus Wehner · Apr 22, 2022

What is the required maximum density for an optimal black and white slide?
That is the central question.

The maximum density is the essential quality criterion for a black and white slide.
I have already given a short answer in my post #79.

Which maximum density is necessary, everyone can easily find out for themselves with their own means.

One has to find out the density that one's own projector at home can just about shine through.
For projection you need a good slide frame (with a metal mask from Gepe, for example).

In the slide frame you clamp grey films of different density (for example the leader of a slide film).
Higher densities can be achieved by placing several layers on top of each other.

Through such experiments one finds out that the limit for transilluminating a slide is approximately 4.00.
This is the usable density interval for a good black and white slide. Otherwise you give away quality.

An analogy:
anyone who makes enlargements themselves in the darkroom knows how faint a photo looks that has been printed on an overlaid photographic paper.
Here, too, quality is given away. An overlaid paper may achieve an interval of 0.5 to 1.80 (fresh paper: 0.1 to 2.00).

Nobody would accept such an old, overlaid paper in the darkroom.
The same should apply to black and white slides. An adjusted density interval of approx. 4.00 guarantees the best quality.

Best regards
Klaus

Raghu Kuvempunagar · Apr 22, 2022

Klaus Wehner said:
You have to distinguish between the "maximum density" (2.7) that can be achieved with the standard process
and the actual "optimal density" (4.00) in the projection.

This can be a very big difference!

Makes me wonder why B&W motion picture makers never tried to optimize their processes to get as high DMax as 4.00 if such a high DMax indeed gave a huge improvement in viewing experience. Their target DMax has been between 2.5-2.75 and there must be good reasons for that. One of the technical books on the subject mentions that flare is a factor that makes densities higher than 2.75 not so useful for projection.

AgX · Apr 22, 2022

Klaus Wehner said:
An analogy:
anyone who makes enlargements themselves in the darkroom knows how faint a photo looks that has been printed on an overlaid photographic paper.
Here, too, quality is given away. An overlaid paper may achieve an interval of 0.5 to 1.80 (fresh paper: 0.1 to 2.00).

Nobody would accept such an old, overlaid paper in the darkroom.

With "overlaid" you mean paper stored too long, no longer yielding its intended character.

Lachlan Young · Apr 22, 2022

Raghu Kuvempunagar said:
Makes me wonder why B&W motion picture makers never tried to optimize their processes to get as high DMax as 4.00 if such a high DMax indeed gave a huge improvement in viewing experience. Their target DMax has been between 2.5-2.75 and there must be good reasons for that. One of the technical books on the subject mentions that flare is a factor that makes densities higher than 2.75 not so useful for projection.

B&W motion picture at the non-amateur level uses neg-pos, not direct reversal. Take a look at the Dmax of 2302 in D-97 - and while you're there, do consider that what is needed for cinema projection is going to be different from a light table presentation or a domestic slide projector.

Raghu Kuvempunagar · Apr 22, 2022

Lachlan Young said:
B&W motion picture at the non-amateur level uses neg-pos, not direct reversal. Take a look at the Dmax of 2302 in D-97 - and while you're there, do consider that what is needed for cinema projection is going to be different from a light table presentation or a domestic slide projector.

You're right - Kodak 2302 has very high theoretical DMax (~4.0). However, in a neg-pos system where this film is used, to achieve the theoretical DMax of 4.0 in the positive, the density range of the negative needs to be > 2.0. Is the negative film in the neg-pos system developed to this high density range?

Coming to the effect of flare in projection, here is a discussion that suggests that densities higher than 2.3 log D in the positive are generally not useful:

"Motion picture print film has a density range of 4.0 log D. From this one could expect to have a luminance ratio of 104:1 or 10000:1 in the projected image, which would exceed the recorded scene contrast. But the actual screen contrast is reduced by stray projector light and from light that first reflects of the projection screen to surfaces in the room and than reflects back to the screen. Both effects are summarized as viewing flare, which is 0.5% to 1% of the maximum screen luminance for good projection rooms. 0.5% seems to be a small number but flare reduces the contrast in the projected image from 10000:1 (4 log D) to 200:1 (2.3 log D). Therefore, the motion picture system has to squeeze a scene contrast of 500:1 or more into a screen contrast of 200:1."

Is it realistic to assume that in the case of a domestic slide projector at home, flare will be significantly lower than 0.5%?

Lachlan Young · Apr 22, 2022

Raghu Kuvempunagar said:
However, in a neg-pos system where this film is used, to achieve the theoretical DMax of 4.0 in the positive, the density range of the negative needs to be > 2.0. Is the negative film in the neg-pos system developed to this high density range?

No. Put together a tone reproduction diagram with 5222 developed to something in the 'normal' aim gamma range of 0.66-0.7 in D-96 and 2302 in D-97 and it all becomes clear. You will reproduce the straight line of the camera neg as you should, and shadows will run out to 2.5-2.75 - but the huge Dmax is to ensure that you get a real 'black', even with the immense power of cinema projectors trying to punch through. As I said, it's designed to do a specific job. Start from the position that Kodak/ Agfa/ Ilford etc's work was always tied back to perceptual and sensitometric reality - and that if perception had demanded they take the route that various ultra-Dmax claimants have re-trodden until extremely muddy, they would have done. Then ask yourself why they didn't. Hint: tone-curve. Specifically, amount of straight-line. Which matters immensely if you are using the transparency for any form of subsequent reproduction method.

Raghu Kuvempunagar · Apr 22, 2022

Klaus Wehner said:
Which maximum density is necessary, everyone can easily find out for themselves with their own means.

One has to find out the density that one's own projector at home can just about shine through.
...
Through such experiments one finds out that the limit for transilluminating a slide is approximately 4.00.
This is the usable density interval for a good black and white slide.

It seems to me that there a methodological flaw in this argument - it uses a slide of very low contrast but high uniform density to do perceptual evaluation of the projected image. Flare has little effect on the projected image when the contrast is low. It's effect, that of reducing the contrast, is noticed when the slide has high contrast. See the page whose link I shared in my previous post for a technical discussion of flare and its effect on projection.

Raghu Kuvempunagar · Apr 23, 2022

I am certainly no expert on this subject, but IMHO the following is a better methodology:

1. Choose a slide that has clear highlights, good midtones and deep shadows going into DMax territory of 4.0 log D.
2. Identify a reference highlight patch in the slide. Measure its density using a densitometer.
2. Identify a few patches in the slide with densities in the range 2.00 - 4.0. Ideally, the chosen patches will have density throughout this range.
3. Measure the densities of these high density patches using a densitometer.
4. Project the slide in your normal viewing environment.
5. Measure the luminance of the reference highlight patch as well as the high density patches from the projection.
6. Compute the luminance ratio of the reference highlight patch with each of the high density patches.
7. Compare these ratios with that obtained from the densitometric measurements of the slide.
8. Due to flare, the two sets of ratios will not be identical. The amount of flare in the viewing environment determines at which density the ratios start diverging. With a flare of 0.5% you should see divergence at density 2.75 and above.

Klaus Wehner · Apr 23, 2022

Raghu Kuvempunagar said:
I am certainly no expert on this subject, but IMHO the following is a better methodology:

1. Choose a slide that has clear highlights, good midtones and deep shadows going into DMax territory of 4.0 log D.
2. Identify a reference highlight patch in the slide. Measure its density using a densitometer.
2. Identify a few patches in the slide with densities in the range 2.00 - 4.0. Ideally, the chosen patches will have density throughout this range.
3. Measure the densities of these high density patches using a densitometer.
4. Project the slide in your normal viewing environment.
5. Measure the luminance of the reference highlight patch as well as the high density patches from the projection.
6. Compute the luminance ratio of the reference highlight patch with each of the high density patches.
7. Compare these ratios with that obtained from the densitometric measurements of the slide.
8. Due to flare, the two sets of ratios will not be identical. The amount of flare in the viewing environment determines at which density the ratios start diverging. With a flare of 0.5% you should see divergence at density 2.75 and above.

Dear colleagues,

I am very pleased about the well-founded discussion. Thank you for the wise contributions.

The measurement method that Raghu suggests here can show that stray light can have a big impact on the contrast of a projected slide.
But this fact is undisputed!

I think there is a misunderstanding here.

The fact that only a lower contrast (2.75) is measurable on the projection screen only speaks for the fact that the slide should have the highest possible contrast (4.00).
On a slide with an optimal maximum density of about 4.00, the deep shadows (zone I...III) are perhaps in the range 3.6...2.8.

Even with the influence of stray light, one can expect optimal differentiation here. Of course, all mid-tones and also the highlights benefit from a higher contrast.

The fact is that a black and white slide should have as high a contrast as possible (4.00). This is the only way to achieve maximum sharpness (the high contrast makes fine details appear) and better differentiation of all grey values (the gradation curve is as long as possible).

Both the linked literature in #168 (http://dicomp.arri.de/digital/digital_systems/DIcompanion/ch02.html) Figure 2.8 und 2.9 and the information on the Kodak 2302 as well as my own practical experiments confirm that a maximum density of about 4.00 is a practicable and desirable value for a black and white slide. The fact that this high contrast cannot be fully utilised on the screen is unfortunately technically unavoidable.

Thank you and best regards
Klaus

Raghu Kuvempunagar · Apr 23, 2022

Klaus Wehner said:
On a slide with an optimal maximum density of about 4.00, the deep shadows (zone I...III) are perhaps in the range 3.6...2.8.

Even with the influence of stray light, one can expect optimal differentiation here. Of course, all mid-tones and also the highlights benefit from a higher contrast.

This is not true IMHO. Assuming a flare of 0.5%, the deep shadow range of density 2.8 log D .. 3.6 log D in your slide gets mapped to the range 2.18 log D .. 2.28 log D in the projection. What this means is that there is not much effective shadow separation in the projection despite the high densities in your slide. This is also obvious from Figure 2.9 of this page on the effect of flare.

Ironical it might seem, but if your deep shadow was in the range 1.7 log D .. 2.3 log D, you would get better shadow separation: 1.60 log D .. 2.0 log D. So for best shadow separation in the slide, it makes sense to aim for a slide DMax that is a little above the DMax of the projection for the expected flare factor. For 0.5% flare this is ~2.5 log D.

As you can see there is definitely a tradeoff between midtone contrast and shadow separation in the projection due to the presence of flare. Optimizing the slides for midtone contrast alone comes at the expense of poorer shadow separation. Optimizing the slides for best shadow separation results in poorer midtone contrast. As @Lachlan Young opined earlier, none of this would have eluded the thought process of the scientists/engineers who were in the forefront of film design and processing. I believe typical DMax of 2.75 log D - 3.2 log D for slides must have been a consequence of trying to achieve a reasonable tradeoff between midtone contrast and shadow separation.

Klaus Wehner · Apr 23, 2022

Thank you for the quick reply.
I think we are misunderstanding each other.

I understand you to be recommending that black and white slides should have a maximum density of 2.75? Is that right? Is that your opinion?
I cannot understand that.

Let's look together at figure 2.9 http://dicomp.arri.de/digital/digital_systems/DIcompanion/printcurve.html

The maximum density is almost 4.00 (which I think is right).
Here, obviously, a maximum density of almost 4.00 is assumed to be ideal. And that is exactly my recommendation.

Do you see any problem with the density of 4.00? Do you think this density is too high?

The stray light reduces the contrast. This is due to technical reasons and can hardly be prevented.
For me, the consequence is to keep the stray light as low as possible.

I see in Figure 2.8 and 2.9 that a maximum density of about 4.00 is always assumed here. I consider this density to be reasonable.
I have also determined this density as a practicable maximum density in my own experiments.

I hope that we can somehow clarify this misunderstanding.

Thank you!
Kind regards
Klaus

Raghu Kuvempunagar · Apr 24, 2022

Take a look at the portion of the curves inside the red oval below. The black line is the density curve and the gray line is density after taking into account 0.5% flare on the projected image. You can see that the high densities corresponding to the deep shadows in your slides (2.75 log D .. 3.6 log D) get mapped to very narrow density range (2.2 log D .. 2.3 log D) in the projection due to flare. Though there is substantial shadow separation in the slide (0.8 log D), there is very little in the projection (~0.1 log D). So high densities in the slides don't mean much as far as shadow separation in the projection is concerned. This is what I tried to explain in my previous post. Hope it's now more clear.

It's not too difficult to see from the above graph so see the tradeoff between midtone contrast and shadow separation in the projection. The steeper the black curve gets in the shadow region, the flatter the corresponding part of the grey curve will be. Increasing the contrast of the slide does increase the midtone contrast of the projection but at the expense of poorer shadow separation.

PhotoStudio13 discontinuing Scala process

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