Ilford FP4+ Characteristic Curve

[Adrian Bacon]

Stephen, I had Adrian mark (in red) the ASA parameters for 125 film, plus the ‘10x’ point. Then for Zone System he took Ralph’s (I think) densities for Zone V and Zone VIII. (Close enough to Ansel Adams’ suggestions to work for me). He extrapolated the other Zones. We took the Zone Reference 0.1 speed point and shifted it to the right 0.05 (an arbitrary guess) from ISO 125 speed point to reflect where I think the lesser development for Zone System N may move it.

The result is a red ISO Reference and a green Zone System Reference for N.

Then his characteristic curve is yellow and we put the interpolated 0.1 on the Zone I mark. The yellow dots are his data points.

I think it’s perfect and could only be better if we find the absolute speed point shift due to Zone N development. For now 0.05 is my best guess.

The zone system reference marks are from Way beyond monochrome, 2nd Ed. I’d have to go grab my copy and find the page it’s on, but there’s a full reference table in 3rd stop increments, and Ralph has posted iit here on photrio a few times. I used the full stop marks in the table starting at zone 1.

 

[Bill Burk]

Way Beyond Monochrome is a good reference.

I think Stephen means the ASA parameters are only relevant if you meet them. Toe at 0.1 and then hit +/- 0.05 of the top red dot. Really calling the 0.1 speed point out at -2.2 lux seconds is “putting the cart before the horse”. For you first have to meet the parameters, then you find the lux seconds at that point and if it happens to be -2.2 then you can call the speed 125.

I always work backwards but recognize I am going about it backwards.

It’s like the study that found being a Scout makes you more likely to be trustworthy, loyal, helpful, friendly...

 

[Adrian Bacon]

Really calling the 0.1 speed point out at -2.2 lux seconds is “putting the cart before the horse”. For you first have to meet the parameters, then you find the lux seconds at that point and if it happens to be -2.2 then you can call the speed 125.

True, but the way I see it, gotta pick something. Might as well pick the speed you’re testing for (if you’re doing that). The way I set it up in the spreadsheet is only the ISO lux seconds is set, and the surrounding lux seconds are calculated from that, so if you find that you need to change it, just change the one cell and the rest of the table automatically updates. Makes the lux seconds on the bottom of the chart kind of like a sliding ruler.

 

[Stephen Benskin]

Adrian, at first I was confused why you were using the ISO contrast parameters the way you were, until I saw Bill's post that one of the curve examples had the reference drawn to steeply. So, it appears that you've taken the contrast parameters presented in the ISO black and white film speed standard and extrapolated an average gradient or 0.61 from the Δ1.30 log-H and Δ0.80 density conditions and are using it as some kind of aim / reference curve. While at first glance it seems logical to assume the ISO parameters are a guideline to correct film contrast and that film speed is then determined from there. This actually isn't the case.

1. The black and white film speed standard doesn't deal with Normal development or development for statistically average scenes. It's only about how to determine ISO film speed.
2. Average gradient shouldn't be extrapolate from the ISO film contrast parameters. In the case with the ISO film speed standard, it's strictly about the two ranges, Δ1.30 over and Δ0.80 up and hitting those two points. Short toed films will generally have close to a 0.61 average gradient when they match the parameters, but long toed films require a slightly higher average gradient to match.
3. In practice, the average gradient for a film shooting a statistically average scene and printing on a grade 2 paper with a diffusion enlarger is around 0.56 to 0.58. So there's no correlation between the two.
4. The contrast parameters are part of the Delta-X Criterion and Δ0.80 (ΔD) is a variable in one of it's equations (see the illustration).
5. The Delta-X Criterion is a method that calculates the Fractional Gradient point using a fixed density point of 0.10 over Fb+f. When the parameters are met, the Fractional Gradient point will fall 0.29 log-H to the left of the 0.10 fixed density point, but only when the parameters are met. Otherwise, the value of ΔD needs to be entered into an equation. Using the the film speed equation of 0.80 / Hm, as stated in the ISO standard, is only accurate under the ISO parameters.

Because of the specific nature of sensitometry, concepts that once seemed to make sense start to become problematic when moving up to plotting curves. Especially when attempting to justify Zone System methodology with tone reproduction theory. Based on your questions, I believe you are starting to realize this. There are a number of other issues here for possible discussion, but I'm going to end this post before it becomes too long and overwhelming.

 

[Adrian Bacon]

Adrian, at first I was confused why you were using the ISO contrast parameters the way you were, until I saw Bill's post that one of the curve examples had the reference drawn to steeply. So, it appears that you've taken the contrast parameters presented in the ISO black and white film speed standard and extrapolated an average gradient or 0.61 from the Δ1.30 log-H and Δ0.80 density conditions and are using it as some kind of aim / reference curve. While at first glance it seems logical to assume the ISO parameters are a guideline to correct film contrast and that film speed is then determined from there. This actually isn't the case.

1. The black and white film speed standard doesn't deal with Normal development or development for statistically average scenes. It's only about how to determine ISO film speed.
2. Average gradient shouldn't be extrapolate from the ISO film contrast parameters. In the case with the ISO film speed standard, it's strictly about the two ranges, Δ1.30 over and Δ0.80 up and hitting those two points. Short toed films will generally have close to a 0.61 average gradient when they match the parameters, but long toed films require a slightly higher average gradient to match.
3. In practice, the average gradient for a film shooting a statistically average scene and printing on a grade 2 paper with a diffusion enlarger is around 0.56 to 0.58. So there's no correlation between the two.
4. The contrast parameters are part of the Delta-X Criterion and Δ0.80 (ΔD) is a variable in one of it's equations (see the illustration).
5. The Delta-X Criterion is a method that calculates the Fractional Gradient point using a fixed density point of 0.10 over Fb+f. When the parameters are met, the Fractional Gradient point will fall 0.29 log-H to the left of the 0.10 fixed density point, but only when the parameters are met. Otherwise, the value of ΔD needs to be entered into an equation. Using the the film speed equation of 0.80 / Hm, as stated in the ISO standard, is only accurate under the ISO parameters.

Because of the specific nature of sensitometry, concepts that once seemed to make sense start to become problematic when moving up to plotting curves. Especially when attempting to justify Zone System methodology with tone reproduction theory. Based on your questions, I believe you are starting to realize this. There are a number of other issues here for possible discussion, but I'm going to end this post before it becomes too long and overwhelming.

View attachment 224894

Stephen,

Thank you. This is all very useful information, and I'm grateful that people that know more about this than me are willing to share. The whole reason why I'm even doing any of this is multi-fold. I recently opened up a film lab and started processing film for other people. My standard black and white development regime is replenished XTOL at 24C in a JOBO. Kodak's J-109 is a wonderful document, but doesn't cover all films available, and so if I want to process everything in replenished XTOL, I needed to come up with a way to see what a film was doing for a given development time. This is why there's the red ISO line and the green zone line. If a film at a certain time has more contrast than the red ISO line (this is why it's red), I need to pull my development time in. If it it has less contrast than the green line, I need to add development time. Ideally, it should be as close as possible to the zone line (this is why it's green). Let me show a couple of preliminary examples.

Below is Fomapan 100. 6 minutes is clearly waaaayyy too much time.

Along the way, this has allowed some insight into other things. Below is Bergger Pancro 400

I originally made the exposures metering at ISO 400, however didn't break 0.1 at -4 down. -3 down did, which tells me that this is not really a true 400 speed film. Based on the data points I have so far, it looks like 15 minutes will give ISO contrast, or close enough to it, which is not what I want, so I'm planning to do another round at ISO 200 and pull the time in by 25% to see where that puts it.

So what do I do if somebody sends me something that I haven't worked out a time for yet? This all goes by the wayside and if I can get a data sheet for the film, I'll try to use the recommended developer, temperature, and agitation in the tech sheet. What this usually means is I'll pour 300-600ml of D-76, put the roll in a Paterson tank and run it at 68F with inversions for whatever time is in the tech sheet. If I can't get a tech sheet, then I try to go by massive dev chart for D-76.

If it's a film that is currently in production that I can buy easily enough, then I put it on my list of emulsions to work out a replenished XTOL time for.

Along the way, it occurred to me that I'm not the only guy out there running film in a JOBO and using replenished Xtol, and that this might be useful to other people, which leads us to this thread.

EDIT: I forgot to add one other thing: This plotting what a film is doing at a given time also allows me to do a better job of scanning the film, as it lets me make a tone curve that matches the film for a chosen time. I know there's a lot of old school guys here on Photrio who print on paper via an enlarger and don't really scan, and whole workflow and methodology is based on making analog prints, however, the reality of a lab environment today is that people want scans. They don't have a darkroom, and don't know or care about how much contrast a film has. They want a scan that doesn't look terrible. A top rate scan is in many ways the new paper because those images will likely never make it onto actual paper. An analog print is great, and if I can develop a film so that it works for that AND I can scan it, that's even better, but sometimes, I have to make compromises. Bergger Pancro 400 is a prime example. People are going to shoot it as a 400 speed film and send it in and expect an awesome set of scans that doesn't look like they under exposed it by a full stop. So, what to do? Add development time until I have enough unique tone values between -4 and -5 that I can make a tone curve for it and linearize that section in the scan. This means that the rest of the characteristic curve is going to be pretty high contrast, but since we're making a tone curve for it to linearize it anyway, that's less of a big deal. You'll have more grain than you otherwise would have, but the scan will have relatively reasonable -3 to -4 and -4 to -5 detail. It'll look way better than if I developed it for zone system and told the client they should have shot it at 200.

 

[Stephen Benskin]

Stephen,

Thank you. This is all very useful information, and I'm grateful that people that know more about this than me are willing to share. The whole reason why I'm even doing any of this is multi-fold. I recently opened up a film lab and started processing film for other people. My standard black and white development regime is replenished XTOL at 24C in a JOBO. Kodak's J-109 is a wonderful document, but doesn't cover all films available, and so if I want to process everything in replenished XTOL, I needed to come up with a way to see what a film was doing for a given development time. This is why there's the red ISO line and the green zone line. If a film at a certain time has more contrast than the red ISO line (this is why it's red), I need to pull my development time in. If it it has less contrast than the green line, I need to add development time. Ideally, it should be as close as possible to the zone line (this is why it's green). Let me show a couple of preliminary examples.

Below is Fomapan 100. 6 minutes is clearly waaaayyy too much time.

View attachment 224909

Along the way, this has allowed some insight into other things. Below is Bergger Pancro 400

View attachment 224910

I originally made the exposures metering at ISO 400, however didn't break 0.1 at -4 down. -3 down did, which tells me that this is not really a true 400 speed film. Based on the data points I have so far, it looks like 15 minutes will give ISO contrast, or close enough to it, which is not what I want, so I'm planning to do another round at ISO 200 and pull the time in by 25% to see where that puts it.

So what do I do if somebody sends me something that I haven't worked out a time for yet? This all goes by the wayside and if I can get a data sheet for the film, I'll try to use the recommended developer, temperature, and agitation in the tech sheet. What this usually means is I'll pour 300-600ml of D-76, put the roll in a Paterson tank and run it at 68F with inversions for whatever time is in the tech sheet. If I can't get a tech sheet, then I try to go by massive dev chart for D-76.

If it's a film that is currently in production that I can buy easily enough, then I put it on my list of emulsions to work out a replenished XTOL time for.

Along the way, it occurred to me that I'm not the only guy out there running film in a JOBO and using replenished Xtol, and that this might be useful to other people, which leads us to this thread.

I can relate. Back in the day, I was the B&W film supervisor for a number of labs in Los Angeles. Ran replenished Xtol in two of them. Both of them Refremas and one a customized 75 gallon Olympic. I used a calibrated EG&G sensitometer for film testing and process control. I can tell you most of the films came close to or at the ISO speeds. At home, I only use fresh Xtol in my Jobo. Does Kodak still sell control strips? A control strip will let you know the state of the replenished developer.

Under the circumstances, it looks like you've put together a system that will get you basically to where you want to go, at least for film contrast. I've uploaded a paper I wrote on determining a developmental model. Maybe you will find it of use.

Are you aware Zone System speed testing assumes a different ratio between the metered exposure point and the speed point then the ISO standard? This difference is 2/3 stop. In my opinion, unless you know the exact lxs hitting the film with film speed testing, it's really not worth doing. Why not just ball park it? Following somebody's home brewed testing method (this includes Zone System) will only create a false sense of control. Think about it. There's a 2/3 stop difference in the methodology of the speed testing between the Zone System and ISO standard (or basically how exposure really works), yet people confidently claimed the Zone System testing found the "true" film speed, or that the film manufacturers lied about their results and other such conspiracy theories. The near universal results film speeds 1/2 to 1 stop slower than the ISO rating indicate the potential experimental error in such methods. Actually given all the possibilities for errors, I find the range to be rather tight. Perhaps some of the errors cancel each other out rather than being accumulative.

You've asked what the film density should be at the metered exposure point. As this point is Δ10 log-H to the right of the fixed density point of 0.10, you just need to find the resulting density at that point.

If your chemistry is in good shape and the contrast is around Normal, then the film speed will be at or close to the ISO rating. My advice, keep the focus on contrast.

Stephen

 

[Adrian Bacon]

I can relate. Back in the day, I was the B&W film supervisor for a number of labs in Los Angeles. Ran replenished Xtol in two of them. Both of them Refremas and one a customized 75 gallon Olympic. I used a calibrated EG&G sensitometer for film testing and process control. I can tell you most of the films came close to or at the ISO speeds. At home, I only use fresh Xtol in my Jobo. Does Kodak still sell control strips? A control strip will let you know the state of the replenished developer.

Under the circumstances, it looks like you've put together a system that will get you basically to where you want to go, at least for film contrast. I've uploaded a paper I wrote on determining a developmental model. Maybe you will find it of use.

Are you aware Zone System speed testing assumes a different ratio between the metered exposure point and the speed point then the ISO standard? This difference is 2/3 stop. In my opinion, unless you know the exact lxs hitting the film with film speed testing, it's really not worth doing. Why not just ball park it? Following somebody's home brewed testing method (this includes Zone System) will only create a false sense of control. Think about it. There's a 2/3 stop difference in the methodology of the speed testing between the Zone System and ISO standard (or basically how exposure really works), yet people confidently claimed the Zone System testing found the "true" film speed, or that the film manufacturers lied about their results and other such conspiracy theories. The near universal results film speeds 1/2 to 1 stop slower than the ISO rating indicate the potential experimental error in such methods. Actually given all the possibilities for errors, I find the range to be rather tight. Perhaps some of the errors cancel each other out rather than being accumulative.

You've asked what the film density should be at the metered exposure point. As this point is Δ10 log-H to the right of the fixed density point of 0.10, you just need to find the resulting density at that point.

If your chemistry is in good shape and the contrast is around Normal, then the film speed will be at or close to the ISO rating. My advice, keep the focus on contrast.

Stephen

Again, many thanks. This is quite a lot to munch on. See my edit to the post you quoted. For black and white film, Ilford sells control strips. It’s FP4+.

 

[Stephen Benskin]

Bergger Pancro 400 is a prime example. People are going to shoot it as a 400 speed film and send it in and expect an awesome set of scans that doesn't look like they under exposed it by a full stop.

If an exposure four stops down from the metered point is above 0.10 over Fb+f, it doesn't indicate a lower EI than the metered speed. It either indicates an experimental error or the EI is faster than the metered speed. If the effective film speed is higher than the metered speed, the metered exposure point will fall higher on the curve (further to the right). If the difference between the EI and metered speed is one stop, your shadow exposure will fall 0.30 log-H to the right of where you would expect it to.

BTW, have you though of using a step tablet?

Looking at the graphs again, I noticed the dev temperature is rather high, while the developmental times mostly fall around what I'd expect from a lower temperature. The Bergger Pancro 400 hitting Normal dev at 24C at 15:00 seems a little unusual though. I'm not familiar with this film, but if the stated results are correct, maybe the time it takes to reach normal in Xtol accounts for the speed difference you've noticed.

For me APX 25 was a film that didn't respond well in Xtol. The contrast barely changed with development time. The CI / Time curve was almost flat. Interesting story, the revision to the ISO speed standard in the 90s was due to the T-Max films poor film speed response to the standard's developer.

 

[Stephen Benskin]

Again, many thanks. This is quite a lot to munch on. See my edit to the post you quoted. For black and white film, Ilford sells control strips. It’s FP4+.

It's for process control. Plotting the results can show trending with replenishment. Using one film type isn't perfect. Kodak uses / used? TMX for their control strip. I'd frequently run a sensitometic strip of TMX and two other films along with it. I found that on occasion, the control strip and my sensitometric TMX strip were the same as the day before, but one or both of the other strips had shifted.

Xtol is unprecedented. It can be replenished indefinitely and is extremely clean. D-76 would reach a point where the contrast would shoot up, and T-Max RS was extremely dirty. I would have to pump the developer out of the tank and do a systems clean more often than I'd like to remember. Never had to with Xtol.

 

[Adrian Bacon]

If an exposure four stops down from the metered point is above 0.10 over Fb+f, it doesn't indicate a lower EI than the metered speed. It either indicates an experimental error or the EI is faster than the metered speed. If the effective film speed is higher than the metered speed, the metered exposure point will fall higher on the curve (further to the right). If the difference between the EI and metered speed is one stop, your shadow exposure will fall 0.30 log-H to the right of where you would expect it to.

BTW, have you though of using a step tablet?

Looking at the graphs again, I noticed the dev temperature is rather high, while the developmental times mostly fall around what I'd expect from a lower temperature. The Bergger Pancro 400 hitting Normal dev at 24C at 15:00 seems a little unusual though. I'm not familiar with this film, but if the stated results are correct, maybe the time it takes to reach normal in Xtol accounts for the speed difference you've noticed.

For me APX 25 was a film that didn't respond well in Xtol. The contrast barely changed with development time. The CI / Time curve was almost flat. Interesting story, the changes to the ISO speed standard in the 90s were due to the T-Max films poor response to the standard's developer.

View attachment 224912

The reason why I pointed Pancro 400 out is that I metered the fp4+ at 125, not 80. At 125 I have a whole pile of discrete tone values between -3 to -4, and -4 to -5, and a fair amount from -5 to -6 with -6 basically indistinguishable from film base plus fog. This is with zone contrast to boot. With pancro 400, same exact setup, but metered for 400, with close to ISO contrast, I have a lot of discrete tone values between -3 to -4, with -4 to -5 showing a density difference of 0.01 and no difference from -5 to -6. They both look like film base plus fog, -4 is barely distinguishable from film base plus fog. That’s quite a disparity. Most films I’ve done this with show discrete tone values down to at least zone 0 metered at their box speed, just like fp4 does. I’ve repeated this with pancro multiple times, it’s not an error on my part. Fomapan 400 is another one. 200 speed shows similar to FP4, 400 speed shows similar to pancro in terms of shadow detail.

Yes, I’ve thought of using a step wedge. My dark room is dark enough for paper, but not for film. I use a changing bag. I’m renting an office space in an area zoned for industrial uses and am limited in what changes I can make to the space I’m renting, so unless I can come up with a way to expose a step tablet in a camera, it’s easier to do it the way I’m doing it now.

Re: time/temperature 24C is my standard temperature. It’s hard to maintain cooler temps during the summer. Pancro 400, delta 3200, and JCH streetpan are relatively insensitive to xtol. You have to run them forever.

 

[Stephen Benskin]

The reason why I pointed Pancro 400 out is that I metered the fp4+ at 125, not 80. At 125 I have a whole pile of discrete tone values between -3 to -4, and -4 to -5, and a fair amount from -5 to -6 with -6 basically indistinguishable from film base plus fog. This is with zone contrast to boot. With pancro 400, same exact setup, but metered for 400, with close to ISO contrast, I have a lot of discrete tone values between -3 to -4, with -4 to -5 showing a density difference of 0.01 and no difference from -5 to -6. They both look like film base plus fog, -4 is barely distinguishable from film base plus fog. That’s quite a disparity. Most films I’ve done this with show discrete tone values down to at least zone 0 metered at their box speed, just like fp4 does. I’ve repeated this with pancro multiple times, it’s not an error on my part. Fomapan 400 is another one. 200 speed shows similar to FP4, 400 speed shows similar to pancro in terms of shadow detail.

Yes, I’ve thought of using a step wedge. My dark room is dark enough for paper, but not for film. I use a changing bag. I’m renting an office space in an area zoned for industrial uses and am limited in what changes I can make to the space I’m renting, so unless I can come up with a way to expose a step tablet in a camera, it’s easier to do it the way I’m doing it now.

Re: time/temperature 24C is my standard temperature. It’s hard to maintain cooler temps during the summer. Pancro 400, delta 3200, and JCH streetpan are relatively insensitive to xtol. You have to run them forever.

Sorry, that one's on me. I misread the plots.

 

[Tom Kershaw]

Re: time/temperature 24C is my standard temperature. It’s hard to maintain cooler temps during the summer. Pancro 400, delta 3200, and JCH streetpan are relatively insensitive to xtol. You have to run them forever.

I use XTOL replenished in a Jobo. Have you managed to get good results from either Pancro 400 or Delta 3200? - I've not tried the Bergger film in XTOL, but Delta 3200 I've found works fine in Microphen / ID-68 whereas I haven't yet worked out a time in XTOL.

 

[Adrian Bacon]

I use XTOL replenished in a Jobo. Have you managed to get good results from either Pancro 400 or Delta 3200? - I've not tried the Bergger film in XTOL, but Delta 3200 I've found works fine in Microphen / ID-68 whereas I haven't yet worked out a time in XTOL.

15 minutes at 24C gives pretty close to ISO contrast for pancro. I’ve not yet done another cycle to try to get zone contrast, but I suspect that it’ll be right in the 12-13 minute range. If you expose at 400 and do zone contrast you’re going to be disappointed. It needs more exposure than than that. I’ve not yet worked out a “push” time for exposing at 400 where you’ll have *something* in terms of density for -4 to -5, however, whatever that time is, it’s gonna be longer than 15 minutes. Bergger’s tech sheet gives times that result in more than ISO contrast for the developers they have listed and they quote an average gradient of 0.70, so they’re effectively push processing out of the box. They say it’s ISO 400, but don’t say what developer they used to get that speed, or whether they actually followed ISO parameters. At least Ilford says they didn’t follow ISO parameters and instead did a practical evaluation of film speed in their tech sheets.

For delta 3200, I don’t have an official charted time, but have a quick time based on the average gradient between +3 and -3 at 3200. That time is 23 minutes. I suspect that an official time will likely be right in that ballpark. You could try 23 minutes and see what that looks like for you.

 

[Tom Kershaw]

My impression of the Pancro in ID-68 from the results, was that I was "pushing" it at 400 speed, agreeing with your comments. I wonder why Bergger put '400' in the film's name. I'm sure I would have got better results at 200.

Rather oddly, for XTOL stock ILFORD give a time of 7 1/2 minutes for Delta 3200, which is significantly too short. I wonder how they came up with this time?

 

[Adrian Bacon]

My impression of the Pancro in ID-68 from the results, was that I was "pushing" it at 400 speed, agreeing with your comments. I wonder why Bergger put '400' in the film's name. I'm sure I would have got better results at 200.

Rather oddly, for XTOL stock ILFORD give a time of 7 1/2 minutes for Delta 3200, which is significantly too short. I wonder how they came up with this time?

I wish I knew. It’s *a lot* better at 200, though a bit too grainy for my taste in 35mm. In 120 shooting people though... wow. I haven’t shot any in 4x5 yet, but I expect it’ll be even more wow there.

For Ilford’s delta 3200 I suspect that it’s the time for ISO 800 or 1000, but haven’t done anything to prove/disprove it.

 

[Tom Kershaw]

Um, I've been processing at 21ºC, using times under 10 minutes, but I see you're using 24ºC.

 

[Adrian Bacon]

Um, I've been processing at 21ºC, using times under 10 minutes, but I see you're using 24ºC.

Yes. I have a hard time keeping times less than 24 during the summer, so rather than have multiple development times for different times of the year, I just standardized on 24 for everything. The jobo bath sits at 24.5, and I pre-heat the tank in the bath for 3 minutes. I keep the developer and other liquids in a separate temperature controlled bath heated to 25. The developer goes in at 25 and comes out at 23.5 I don’t do a pre-soak. That’s during the winter. During the summer, the jobo bath won’t go below 25. The developer gets put in the fridge for 10-15 minutes to get it down below 24, and the developer bath is set to 23, but it usually hovers around 24.5. I do no tank pre-heat in the jobo bath, take the developer out of the fridge, put it in the developer bath and wait for the temperature to hit 23.5. Once it does it goes into the tank and onto the jobo. It comes out of the tank at 24.5.

Kodak lists 24C times in J109, so I’m OK with that.

 

[Stephen Benskin]

they quote an average gradient of 0.70

Bergger is probably using Gamma. A Gamma of 0.70 usually equals around 0.58 or Normal when measured as CI or average gradient.
70

 

[Adrian Bacon]

Bergger is probably using Gamma. A Gamma of 0.70 usually equals around 0.58 or Normal when measured as CI or average gradient.

Here’s their tech sheet if you want to look at it: https://bergger.com/media/wysiwyg/Fiches_techniques/BERGGER_PANCRO_400_DATASHEET_01_2017.pdf

The curve they post is relative log exposure, so it’s hard to tell what they actually exposed it at.

 

[Stephen Benskin]

Here’s their tech sheet if you want to look at it: https://bergger.com/media/wysiwyg/Fiches_techniques/BERGGER_PANCRO_400_DATASHEET_01_2017.pdf

The curve they post is relative log exposure, so it’s hard to tell what they actually exposed it at.

It's Gamma. The curve looks steep because the density and log expose scales are not in a 1:1 ratio. It's more of a 1:2.3 ratio (3.0 up and 7.0 over).

Your processing time is way off compared to their chart. Perhaps seasoned Xtol isn't a good combination. Have you tried processing it in fresh Xtol or maybe change to another developer altogether like D-76?

 

[Tom Kershaw]

For reference, I used the recommended time for Berspeed when developing Pancro 400 with ID-68 as these developers appear to be extremely similar. My results appeared to be "correct" assuming a 400 speed film rating, although I agree with Adrian that a 200 speed rating would have given better results - at '400' the Pancro film is surprisingly grainy as a 9 1/2" x 12" print from a 67 medium format negative. The Bergger film also appears to require disproportionately long times in XTOL compared to other developers, when compared with other films from ILFORD and Kodak.

Metering in this context was / is with a Pentax Digital Spotmeter, metering shadows and placing on "zone 3" for want of a better term...

 

[Adrian Bacon]

Your processing time is way off compared to their chart. Perhaps seasoned Xtol isn't a good combination. Have you tried processing it in fresh Xtol or maybe change to another developer altogether like D-76?

They don’t post a time for replenished xtol and 24C with continuous agitation. However, in my experience so far with other films, my replenished xtol at 24 with continuous agitation time more often than not ends up pretty close to the xtol 1:1 time with inversions. Bergger does have an xtol 1:1 time at 24 which is 13 minutes, and I did predict earlier that pulling the time in from 15 minutes to 12-13 minutes would likely result in zone system contrast. I haven’t done it yet, but there’s a pretty high likelihood that 13 minutes at 24C with replenished xtol and constant agitation is the normal zone contrast.

EDIT: I did run it in D-76 when it first came out to see what it looked like, and do currently run it in D-76 when someone sends a roll in. Replenished xtol looks better in terms of grain structure in my humble opinion,

 

[Paul Howell]

Yes, I’ve thought of using a step wedge. My dark room is dark enough for paper, but not for film. I use a changing bag. I’m renting an office space in an area zoned for industrial uses and am limited in what changes I can make to the space I’m renting, so unless I can come up with a way to expose a step tablet in a camera, it’s easier to do it the way I’m doing it now.

You might to find a copy of John Schaefer's The Ansel Adams Guide Basic Techniques of Photography Book 2. He provides a method of using a step wedge with a 4X5 film holder, also a method for 35mm, but if you darkroom is not dark enough for film and you shoot 4X5 you can give the 4X5 method a try as you can use a changing bag to load the film and step wedge. Not sure why you use black out cloth to total light seal your darkroom.

 

[Adrian Bacon]

You might to find a copy of John Schaefer's The Ansel Adams Guide Basic Techniques of Photography Book 2. He provides a method of using a step wedge with a 4X5 film holder, also a method for 35mm, but if you darkroom is not dark enough for film and you shoot 4X5 you can give the 4X5 method a try as you can use a changing bag to load the film and step wedge. Not sure why you use black out cloth to total light seal your darkroom.

I’ll look it up.

The darkroom is sealed except the doors. The main suite door has a window in it and a healthy gap between the door and floor. The darkroom is one of the offices in the suite, and it also has a healthy gap between the door and floor as well as it leaks like a sieve around the rest if the door. I can’t change the doors, and I can’t kill the building lights outside my suite. I discovered that the reason why the doors have such a healthy gap under the door is for ventilation. The buildings main air return is in the main hallway, and each suite has a duct dumping air into the suite. It goes under the door to get out of the suite. I’ve covered the main window with a blackout curtain, and have a curtain covering the door, but can’t completely block it or I get no airflow, so it still leaks a little, so I make do. There’s not a lot of space in my area with the right zoning that also has water and sewer in the suite, and the space I’m renting now is the one most suited to make a darkroom out of all the spaces I originally looked at. It’s all a compromise.

 

[Stephen Benskin]

There have been discussions about Schaefer's testing method from time to time over the years. At some point I did an analysis of it. The speeds resulting from the test conform to the results from traditional Zone System testing methodology. This means there is an inherent 2/3 of a stop difference in speed between his method and the ISO speed rating.

Apart from what the camera exposure should be, there's off axis light fall off. In other words, the tablet probably won't be evenly illuminated.