The authoritative answer on Kentmere 400 vs HP5 please!

[Augustus Caesar]

They also incorporate other anti-halation tools - besides that base.
The layer diagrams I have only deal with the colour negative films - and Kodak ones at that - but those show AH layer between the bottom light sensitive emulsion layers and the subbing layer that sits directly on the base.

That's color film, not B&W. No B&W films have such a layer, so far as I know.

 

[Lachlan Young]

That's color film, not B&W. No B&W films have such a layer, so far as I know.

Many B&W films incorporate both anti-halation layers, and other absorber dyes to prevent internal reflection problems between layers etc. Kentmere 400 doesn't seem to have as strong a level of internal reflection prevention (which is fine if you are not expecting to give it generous exposure and curtailed processing) as something like HP5+ - this should not be a surprise as these components are potentially immensely costly custom organic chemicals. Making assumptions about today's emulsion coating structures on the basis of assertions of popular writers from the 50s/ 60s is a major error.

 

[relistan]

His charts are no longer available (deleted account?), but @aparat had done pretty extensive testing on a bunch of films and the spectral sensitivity and response curve of the Kentmere films was pretty much identical to the Delta films (which are not the same as HP5+ at all). So close that we can assume that a large part of the chemistry is shared.

The general assessment is that Kentmere/Kentmere PAN films are:

• Same substrate as Ilford films
• Identical hardness to Ilford Delta films
• Sensitivity and response curves identical to Delta films
• Lower silver content than FP4+/HP5+/Delta films
• Slightly less anti-halation protection - although this only very slightly different in my experience
• Finer grain than FP4+/HP5+ but not as fine as Delta films
• Not provided with documentation of any of the above because they are not aimed at a professional market (if there remains much of a thing like that)

The result of the silver and grain differences is slightly lower resolution. However, you pretty much get the beautiful spectral sensitivity and response curves of Delta.

Hope it helps

 

[koraks]

His charts are no longer available (deleted account?)

Not a deleted account, but @aparat has chosen to remove most of his test charts from public view on flickr. This has been the case for quite a while already, so many of his posts now involve dead links. Maybe if @aparat comes by and we ask him kindly, he might be willing to share the Kentmere vs. Ilford film comparisons once more.

The general assessment is that Kentmere/Kentmere PAN films are:

Several of these assessments are impossible to substantiate with the kind of information the likes of us have access to. I'm referring to the degree of hardening, silver content and anti-halation measures (qualitative and quantitative). Other factors are often assessed on the basis of very shaky empirical testing and interpretation of the outcome of such tests.

The result of the silver and grain differences is slightly lower resolution.

I don't see any theoretical or physical basis for this claim. It also ignores the (by contrast) highly relevant difference in grain structure/aspect ratio.

 

[relistan]

Several of these assessments are impossible to substantiate with the kind of information the likes of us have access to. I'm referring to the degree of hardening, silver content and anti-halation measures (qualitative and quantitative). Other factors are often assessed on the basis of very shaky empirical testing and interpretation of the outcome of such tests.

Without a lab or the inclination to do the extensive testing, I can only surmise from observations. Observations on my part and others are that the emulsion behaves in reversal similarly to Ilford Delta films in terms of how softened it is by permanganate bleaches or damaged by peroxide bleaches (i.e. indicative of hardening) and how it does not build density in reversal to the same level as Delta (indicative of silver content).

Both of the above match with many observations by others in other areas. I have not tracked links and am not inclined now to go find them all. Without Harman providing the technical details, we can only make a general assessment.

Nobody has to take my word for it, but from all the reading I have done an my own testing, that's the general assessment.

I don't see any theoretical or physical basis for this claim. It also ignores the (by contrast) highly relevant difference in grain structure/aspect ratio.

I was covering the amount and structure of the differences in the silver halide crystals as "silver and grain differences". I am happy to accept your more precise wording.

For the record, I like and use both Kentmere 100 and 400 PAN films and will continue to do so.

 

[koraks]

in terms of how softened it is by permanganate bleaches or damaged by peroxide bleaches

This says mostly something about the quality of the subbing procedure and thus the adhesion of the emulsion to the film base. It's not really indicative of the hardening of the emulsion as such. Subbing approaches have improved dramatically at the main manufacturers (Kodak, Fuji, Harman) even since the 1990s. Smaller manufacturers may still lag behind on this.

I'm somewhat allergic to the 'silver content' argument because it generally isn't rooted in factual information on how silver load affects imaging behavior, and all too often involves implied normative judgement on the desirability of high silver content. Such an advantage has never been demonstrated to exist.

For the record, I like and use both Kentmere 100 and 400 PAN films and will continue to do so.

I've shot both Kentmere 400 (branded as Rollei RPX back then) and HP5+. I found the differences subtle to the advantage of the latter in terms of retention of shadow detail and graininess. It's been ages since I shot any Delta, so I couldn't comment. I wouldn't on the basis of my qualitative observations dare draw any conclusion in terms of hard criteria such as resolution.

 

[Ben Hutcherson]

I'm somewhat allergic to the 'silver content' argument because it generally isn't rooted in factual information on how silver load affects imaging behavior, and all too often involves implied normative judgement on the desirability of high silver content. Such an advantage has never been demonstrated to exist.

Even back years ago, when we could still get Efke films, I remember a lot of the web verbiage describing them as "Old style high silver thin emulsions."

I used and liked Efke films(actually was just looking at a B&H invoice from 2007 where I'd bought a bunch at $3.50 a roll-that was attractive to a broke college student especially when the Plus-X on the same invoice was $4.50)

With that said, they certainly had their quirks, and high tech emulsions they were not. I can remember even seeing emulsions described as "high silver" or "low silver" and I never really saw any particular correlation in properties amongst emulsions described one way or another.

My impression then and now, right or wrong, was that the amount of silver present was less important than how the manufacturer was able to use it.

Tabular grain films, per my understanding, are able to use grain shape to their advantage to get more surface area for a given grain size(that may be a poor explanation or lack a good understanding of the full picture) but basically the end result is that they may need less silver for a given sensitivity than a conventional grain film. The lower amount of silver is then, in turn, by design and turns into smaller apparent grains for a given sensitivity.

I really want to take some time to dig into Making Kodak Film, which I was fortunate last fall to be able to buy a comb-bound copy of from @laser . I'd intended to spend some time over my Christmas break doing that, but unfortunately real life often gets in the way. I was extremely grateful to be able to get any copy of it, but two thick comb-bound books inspire a bit less confidence reading anywhere other than at a table/desk than I might read a more conventionally bound book. I'm really curious now to pull it out today(in between trying to process a bunch of film and polish off my syllabi for classes starting tomorrow) and if nothing else look at the micrographs of films shown.

 

[relistan]

This says mostly something about the quality of the subbing procedure and thus the adhesion of the emulsion to the film base. It's not really indicative of the hardening of the emulsion as such. Subbing approaches have improved dramatically at the main manufacturers (Kodak, Fuji, Harman) even since the 1990s. Smaller manufacturers may still lag behind on this.

This may be one of the aspects that affects permanganate, but peroxide bleach generates bubbles which have to pass out through the emulsion. In my experience the films aimed at reversal, which I surmise to be more hardened, fair worse in peroxide because rather than allowing the bubbles to release, they tear out through the gelatin. I found this to be true for Fomapan R100 and for ADOX Scala 160 and for old Agfa Scala 200. By contrast, most other films are not as damaged by peroxide bleaches. Films considered to be "soft" like Fomapan 400 and 200 do quite well in peroxide reversal. Does it prove anything definitively? No. But it's aligned with my other experience and what I've seen from other people.

I'm somewhat allergic to the 'silver content' argument because it generally isn't rooted in factual information on how silver load affects imaging behavior, and all too often involves implied normative judgement on the desirability of high silver content. Such an advantage has never been demonstrated to exist.

"High silver content" either implies a thicker emulsion layer, finer grained crystals such that less space is "wasted" in between them in the same thickness of gelatin, or a different crystalline structure that allows them to be packed more tightly. I think we can safely assume that any of those affect the image output. None of that implies that you will get a definitively "better" output from higher silver conten. But in any of those cases, the ability to catch more of the light in the same surface area is going to be improved. Whether or not those image centers are reachable by developer is another story.

I've shot both Kentmere 400 (branded as Rollei RPX back then) and HP5+. I found the differences subtle to the advantage of the latter in terms of retention of shadow detail and graininess. It's been ages since I shot any Delta, so I couldn't comment. I wouldn't on the basis of my qualitative observations dare draw any conclusion in terms of hard criteria such as resolution.

Maybe @Henning Serger has numbers for Kentmere 400 to match his numbers here: https://www.photrio.com/forum/threads/rollei-rpx-25-grain-and-resolution.115244/post-1523223

 

[koraks]

peroxide bleach generates bubbles which have to pass out through the emulsion

I have severe doubts about the correctness of this technical assessment of the failure mode you're seeing with certain reversal processes. There are many ways in which a gelatin layer can disintegrate and/or peel away from the base it's adhered to.

"High silver content" either implies a thicker emulsion layer

Gelatin layer thickness is yet another parameter. We do agree that crystal geometry and orientation have an effect, and tabular grain emulsions exploit this property. It's one of several factors that breaks the correlation between silver content and imaging properties. Silver content as such says nothing.

 

[pentaxuser]

Good luck with that!

Most questions I have submitted to this community have resulted in a considerable amount of noise and conflicting opinions. It may be that I did get one or two authoritative answers, but it was hard to identify those among all the noise.

I think one reason there are so many conflicting opinions is because everyone exposes different, develops different, and likes different results. If two opinions conflict with each other, it doesn't necessarily mean one is right and the other is wrong. Opinions are not facts. When it comes to opinions, there is no authoritative answer.

Conflicting opinions on Photrio? Surely not?

pentaxuser

 

[pentaxuser]

So which of your questions have we been able to answer in a more satisfactory/reliable way than the range of opinion "out there"

Are you closer to a decision on which film to use for what scenes based on what has been said here ?

Thanks

pentaxuser

 

[Lachlan Young]

@relistan @koraks there is evidence from some Agfa patent materials etc that they added further gelatin tanning agents to subbing layers etc in materials that were potentially going to be subjected to processes like B&W reversal (and added both gelatin swell agents and gelatin swell control components in their first developer) - which can (in their more modern forms) probably subject emulsions to greater stresses than C-41 or E-6. That cost would only be worth the expenditure by Harman (or Kodak for that matter) if a much more significant amount of their emulsions were being subjected to prolonged bleach baths in B&W reversal.

It's also probably not impossible that the genesis of the Kentmere films relates to the newer rapid-mixing emulsion plant built for Delta etc (and which the paper emulsions have moved to) - it will be able to manufacture whatever crystal form you need for a particular emulsion outcome, but may have a greater familial resemblance to aspects of Delta than the FP/HP family (more tightly controlled monodispersity of each discrete emulsion probably being a significant part of it). The same plant probably also allows for a greater degree of cost control & estimation of what certain performance boosting components would have relative to cost/ performance. They were probably particularly interested in how readily FP/HP type emulsions could be translated to the new plant.

 

[relistan]

I have severe doubts about the correctness of this technical assessment of the failure mode you're seeing with certain reversal processes. There are many ways in which a gelatin layer can disintegrate and/or peel away from the base it's adhered to.

There are patents showing it as background information about why the proposed peroxide bleach was unique. Not for this film, and I don't have them at my fingertips, but I read through tens of these patents a few years back when working on the peroxide/citric acid/EDTA bleach I published, and this failure mode is a fairly-well-researched fact. The gelatin is torn to a lesser or greater extent by the formation of bubbles inside it. It is not torn off of the substrate.

Gelatin layer thickness is yet another parameter. We do agree that crystal geometry and orientation have an effect, and tabular grain emulsions exploit this property. It's one of several factors that breaks the correlation between silver content and imaging properties. Silver content as such says nothing.

Ok, I am not sure what we're discussing at this point, honestly. The OP asked how they differed. If you'd like to characterize some of that differently, please feel fee to contribute how you would practically characterize it for someone wanting to shoot these films. Having more than one opinion of stated summary is certainly not unhelpful.

@relistan @koraks there is evidence from some Agfa patent materials etc that they added further gelatin tanning agents to subbing layers etc in materials that were potentially going to be subjected to processes like B&W reversal (and added both gelatin swell agents and gelatin swell control components in their first developer) - which can (in their more modern forms) probably subject emulsions to greater stresses than C-41 or E-6. That cost would only be worth the expenditure by Harman (or Kodak for that matter) if a much more significant amount of their emulsions were being subjected to prolonged bleach baths in B&W reversal.

It's also probably not impossible that the genesis of the Kentmere films relates to the newer rapid-mixing emulsion plant built for Delta etc (and which the paper emulsions have moved to) - it will be able to manufacture whatever crystal form you need for a particular emulsion outcome, but may have a greater familial resemblance to aspects of Delta than the FP/HP family (more tightly controlled monodispersity of each discrete emulsion probably being a significant part of it). The same plant probably also allows for a greater degree of cost control & estimation of what certain performance boosting components would have relative to cost/ performance. They were probably particularly interested in how readily FP/HP type emulsions could be translated to the new plant.

Both of those make sense to me @Lachlan Young

 

[koraks]

If you'd like to characterize some of that differently

Subjectively, not in terms of quasi-objective, pseudo-scientific terms. That's the main issue I have with qualifications that go off into the woods of terminology use that's not warranted by the empirical evidence provided.

 

[albireo]

However, you pretty much get the beautiful spectral sensitivity and response curves of Delta.

Hope it helps

What's the source of this information please? Firstly, which Delta are we talking about? The spectral sensitivity of Delta 400 is different from that of Delta 100.

Can I assume you're suggesting Kentmere 400 has the spectral sensitivity of Delta 400? If so, that doesn't match my experience. Delta 400 is noticeably more red sensitive than Kentmere 400. Kentmere 400 has a very standard panchromatic profile, very similar to TriX.

Here's the Naked Photographer's observation on the matter. My findings agree with his

Image below: Kentmere 400 left, TriX right. Quite comparable rendition, with minor differences probably being due to non contrast matched development

Image below: Delta 400 left, Trix right. Notice the lighter 'red' box (first column, second row) in the Delta 400 screen.

 

[retina_restoration]

So, it appears that "Camerarabbit", who posted the question, isn't paying any attention to this discussion, so bear that in mind.

 

[relistan]

What's the source of this information please? Firstly, which Delta are we talking about? The spectral sensitivity of Delta 400 is different from that of Delta 100.

This was from the charts I referred to from @aparat in my first post.

I was trying to help the OP identify the difference here to HP5+. But this discussion has now taken more time than I have.

 

[pentaxuser]

So, it appears that "Camerarabbit", who posted the question, isn't paying any attention to this discussion, so bear that in mind.

The problem being from what I see in the case of many of this category of questions is that we may not have uppermost in our minds this question , namely: What does the OP want to know and does what we are discussing have a bearing on what he wants to know and if it does have a bearing, how do we make this clear to him in terms that make sense to him which one of relistan's comments appears to make reference to above?

If he is no longer paying any attention and that may be the case then we need to ask ourselves why if the prime purpose of the forum is to provide answers to questions asked and answers that are commensurate with the OP's level of knowledge

pentaxuser

 

[Andrew O'Neill]

The big difference is when it comes to anti-halation. Kentmere's isn't as good as HP5's.
I made a video a while back on this issue:

 

[MattKing]

If he is no longer paying any attention and that may be the case then we need to ask ourselves why if the prime purpose of the forum is to provide answers to questions asked and answers that are commensurate with the OP's level of knowledge

The purpose of the forum is to provide a place for discussion relating to photography.
There is a side purpose as well - it provides a forum for sharing some photography.
And for some, there is a marketplace add-on.
A lot of things get learned. A lot of questions are answered. And a lot of discussion happens.
We try to keep threads to the general subject raised when the thread is started, but thread expansion or "drilling down" happens.
Otherwise we wouldn't get the benefit of the rather wonderfully vague

It's also probably not impossible

Thanks to Lachlan for that - it made me smile!

 

[Lachlan Young]

Can I assume you're suggesting Kentmere 400 has the spectral sensitivity of Delta 400

More in the sense of some aspects of perceptual image structure behaviour than colour sensitivity. I'm not volunteering to do matched sets of 30x enlargements (nor X-ray microdensitometry or feeding emulsion samples through an SEM) to demonstrate though. Just so that this is clear, even Delta 3200 is perceptibly sharper at low frequencies than K400 (as is HP5+) - it's more as the frequencies go up where some of the characteristics look more Delta derived than HP/FP - which does not necessarily translate into ultimate resolution either.

Lower silver content than FP4+/HP5+/Delta films

This is something that should be reiterated - K400 has been designed to fulfil the range of 'normal' contrast indices required for diffusion & condenser enlargers and not really go beyond that. 'Old' emulsions that only ever got to the same CI maximums (but which might reverse better) were simply much less efficent/ efficiently sensitisable and thus needed much more silver/m2 in them to even get to that point.

 

[albireo]

More in the sense of some aspects of perceptual image structure behaviour than colour sensitivity.

Thanks. Can I bother you to explain for me the idea of 'perceptual image structure'?

 

[pentaxuser]

The purpose of the forum is to provide a place for discussion relating to photography.
There is a side purpose as well - it provides a forum for sharing some photography.
And for some, there is a marketplace add-on.
A lot of things get learned. A lot of questions are answered. And a lot of discussion happens.
We try to keep threads to the general subject raised when the thread is started, but thread expansion or "drilling down" happens.
Otherwise we wouldn't get the benefit of the rather wonderfully vague

Thanks Matt, that was largely the answer I was expecting. Just a pity that at times we don't drill down a little more into what the OP might want or need to know first

pentaxuser

 

[koraks]

Just a pity that at times we don't drill down a little more into what the OP might want or need to know first

"We" do, though. Often, OP comes back and asks follow-up questions.
What generally doesn't work is if someone comes in, we barrage them with probing questions and they have to go through some kind of inquisition before any useful information is being imparted to them. That's when people tend to walk away or simply get angry. If you want examples, there are forums I can point you to where this has happened a lot, and I can tell you, it wasn't nice.

 

[Milpool]

Thanks Matt, that was largely the answer I was expecting. Just a pity that at times we don't drill down a little more into what the OP might want or need to know first

pentaxuser

I think the OP’s questions were clear enough. The problem is in this case (as in many others) an authoritative answer is elusive unless one is inside the company. OP was confused by all the opinions and noise “out there”, and Photrio really isn’t different than “out there” (the first response OP got was a link to a YouTuber, and so on).