HP5+ over exposed by 4 stops, will my recovery plan work ?

[PeterB]

Thank you again Bill and Michael. Thanks also to Thomas, David, Matt and Jnanian.
My plan is to slightly reduce my dev time. I still think differently about the effect of development on the shoulder and will write more about that later.

regards
Peter

 

[PeterB]

This example shows HP5P 135 developed to a CI of 0.56 in Xtol. The graph on the left shows normal exposure with a resulting negative density range of 1.06. The graph on the right shows a three stop "over" exposure with a resulting negative density range of 1.02.

Stephen, thanks for those curves. It shows that for a 3 stop overexposure , highlights (up to Zone VIII ?) will remain uncompressed. However in my process when I consider one more highlight zone than you do plus one more stop of over exposure, my theoretical max neg density will be 2.1 which is right at the limit of Ilford's curve and beyond that I assume it begins flattening out. There appears to be very little published data available for the shoulder sections of characteristic curves across all the development times. My next post will talk more about the shoulder sections.

 

[PeterB]

If possible I would like to make a very general statement about a film's shoulder (reached due to overexposure). Is it true that in general the following set of curves will represent the relationship in the shoulder area to increasing development times ? Note dev times might get too short to achieve Dmax as I show in the lowest curve.

If my graph is not general enough, then what generalisation could we make about the way a curve's shoulder is affected by increasing dev times ?? (you must ensure sufficient over exposure is given to define all of the shoulder right out to Dmax)

 

[markbarendt]

To your generalization. No.

In general, as development is increased the curve gets steeper.

It can be said that each emulsion/developer/technique combo creates a unique set of curves.

It can be said that some films will shoulder off as you have shown, but its not a general truth. For example, TXP reaches 2.8ish with almost no bend and gets well over 3 with just a little, the shoulder is still really steep though.



DR5 claims a D-max of about 3.3 for HP-5 chromes.
http://www.dr5.com/blackandwhiteslide/hp5dev-1.html

So where do we start bumping D-max for a given film? Where do we start shouldering? I don't know.

 

[PeterB]

OK Mark, so I had assumed that we keep every other variable fixed except development time. Surely we can say something about each successive shoulder for increasing dev times. How about "As we increase dev time, the shoulder of the curve will begin earlier and reach Dmax sooner".

regards
Peter

 

[Bill Burk]

This example shows HP5P 135 developed to a CI of 0.56 in Xtol. The graph on the left shows normal exposure with a resulting negative density range of 1.06. The graph on the right shows a three stop "over" exposure with a resulting negative density range of 1.02.

View attachment 69433

Nice to see your program coming to the aid of a forum discussion!

PeterB, The reason our curves end abruptly on the right, is that "we" try to catch the toe in our tests and haven't done studies of gross overexposure... All it would take to see how far out the straight line extends... would be to remove a ND filter from the well of the sensitometer, pop a test, and develop and measure it. I believe there is a great long straight line ahead.

 

[PeterB]

Nice to see your program coming to the aid of a forum discussion!

PeterB, The reason our curves end abruptly on the right, is that "we" try to catch the toe in our tests and haven't done studies of gross overexposure... All it would take to see how far out the straight line extends... would be to remove a ND filter from the well of the sensitometer, pop a test, and develop and measure it. I believe there is a great long straight line ahead.

Thanks Bill. I'm curious as to why films are rated with so much latitude for over exposure but virtually none for under exposure ?

regards
Peter

 

[markbarendt]

The curves for TXP aren't showing it reaching D-max so, no to that part at least.

TMY can hold about 14 stops on the straight line IIRC, so if you had used TMY instead of HP5 for the shots that started this thread you could have exposed another three stops (7 stops up total) before you even got to the shoulder let alone finding D-max. So again no, the generalization doesn't work.

 

[markbarendt]

Thanks Bill. I'm curious as to why films are rated with so much latitude for over exposure but virtually none for under exposure ?

regards
Peter

Shutter speed is my bet.

 

[Bill Burk]

You'll soon find out first-hand when you print your negatives. I think you will find you would have preferred them to be less dense. There will be some, uh, qualities that will make your prints different from your usual. The most significant degradation (and it is a graceful degradation) will probably be some "halation", reduced clarity and some excess grain.

 

[PeterB]

The curves for TXP aren't showing it reaching D-max so, no to that part at least.

TMY can hold about 14 stops on the straight line IIRC, so if you had used TMY instead of HP5 for the shots that started this thread you could have exposed another three stops (7 stops up total) before you even got to the shoulder let alone finding D-max. So again no, the generalization doesn't work.

Hi Mark. I think you are missing my point. Here is how I would conduct the experiment so that a generalisation can be made about the curve shoulders for at least a few popular films and developer combinations:

1. Pick one of the 5 most popular B&W panchromatic films.​

2. Pick one of the 5 most popular film developers.​

3. Expose the film to a step tablet with sufficient intensity that causes Dmax to be reached and entered into by at least 1 stop (this guarantees you WILL eventually traverse the shoulder even if you can't find it in the published curves) when it is developed.​

4. Develop the roll for some minimum time which ensures a CI beginning at say 0.3 and that Dmax is reached because it was overexposed so much in step 3.​

5. Repeat the above steps, increasing the dev time to give increases in CI of reasonable steps (say 0.1 or 0.2) until you reach a CI of say 1.0.​

6. Plot all HD curves for that combo on one page.​

7. Repeat all above steps for a few more film+dev combos.​

8. Make a general statement about what you observe in the shoulder areas of all the curve sets.​

regards
Peter

 

[markbarendt]

Peter,

I understand your idea.

I do think you have your work cut out for you to make it real; first in finding, then in mapping the shoulders.

Personally I doubt that you find a clear cut shape or threshold that defines shoulders in general in a meaningful way.

Consider D3200, it has a long arc of a shoulder, depending on the CI you might consider "normal" the shoulder can even make up most of the curve. XP2's curve is similar in shape. Like the energizer bunny they just keep going and going.

 

[sun of sand]

I wouldn't suggest that. Soft working developers and/or reduced agitation can make the film shoulder earlier. That's exactly what Peter doesn't want.

Edit: this is a response to post #23.

I was trying to reduce effective film speed not rescue a 4 stop overexposure with mathematics and theory
I'm beginning to wonder if there is any roll of film
losing film speed would be my first action before heading into all this graphing of whatever you're doing
if you use xtol at 400 you can use 250 with rodinal
add in restrainer and you could use 200
maybe add in enough and you could have a film speed drop from 400 to 100
more? don't know. At some point you wouldn't develop that latent image at all or so I've read

with that much restrainer you'd likely have to reduce development to tame the contrast from its addition


drop film speed enough and print on azo or alternative process



I'll include a pic of 3 4x5 negatives taken on badly fogged film. I was trying to reduce fog through restrainers
all exposed at ASA10 in Rodinal 1:20
upper neg had some restrainer
right neg had more
left had even more

as you can see the fog nearly disappeared and it seems the effective film speed was dropped probably from 40-50 at foggiest/most dense to about what I shot it at 10

i'll take a quick pic of the straight print using no filter "Grade 2"
detail from slightly smaller than 20x24 print

 

[PeterB]

Whenever I have tested films/developers I have always tested including the shoulder region because it is important in my work. I've done this with several films and developers - over and over. There are quite a few variables to consider and both the shape of the shoulder and where it begins are subject to manipulation. The only rough generalization I would make is that the films I've tested tend to exhibit their longest straight lines when developed to an approximately normal CI. Underdevelopment tends to shorten the straight line due to increasing compression on both ends, and gross overdevelopment moves the shoulder to the left for obvious reasons. On the underdevelopment side, different developers and techniques can have some effect on the curve shape.

I would suggest you simply move on from your overexposure error.

I have done the deed. Developed at N-0.5, and............ they look very printable ! I will measure the max density when negs are dry tomorrow but it looks to be between about 1.7 and 1.9 which is roughly what I predicted given my process and kept me away from the theorised shoulder section at 2.1.

Thanks for your generalisation Michael. One day I might plot the HD curves for HP5 out past the shoulder as I am still convinced that for a given overexposure scenario it is possible to avoid a small encroachment into the shoulder (from the straight line region) by reducing dev time by one "N step".

Thanks to everybody else for your suggestions.

regards
Peter

 

[zsas]

Peter - Congrats! I am a mere mortal and don't get all this N-x talk, though, I do know AA's texts contain the whole explanation, however, in an effort to make this thread something mortals can follow, would you mind "101'ing" it? Like real brief, for eg, I over exposed by x stops and to compensate I developed in this manner..... Nothing fancy, just like "for those following along at home who might not be Zone folks I used D76 and agitated...."

That way many can use your real world issue and kind of back into what was theorized and eventually seen. Books are great but real world examples and discussions are even better (sometimes)....

 

[markbarendt]

So Michael, per chance have you done plots on HP 5?

 

[markbarendt]

No sweat Michael. Google can't find much either.

 

[cliveh]

Hi folks,

I was rather annoyed at myself to discover that I over exposed a 120 roll of HP5+ by a whopping 4 stops ! The good news is that I think my highlights will not be compressed at all but I wanted to run my solution past you.

The SBR was 7 stops from Zone II to VIII inclusive which would have otherwise lead to Normal (N) development time. In short I plan on reducing the film development time to be that for N-1 which in my process will lower the gamma from 0.5 to 0.4

Below you can see my analysis, but I am amazed that I can still keep my scene in the straight line portion of the curve by forcing a minor reduction to its CI/gamma/slope. I will just print using 1 grade harder MG filter. What am I going to lose out on here ? This seems too easy to recover from.

** warning that a bit more theory and maths will now follow... **

I have analysed the HD/characteristic curve of HP5+ and it is linear out to at least a density of 2.1 log units which has basically been my saving grace here. Normally a neg exposed for N development in my process would result in a density ranging between 0.3 and 1.35 on the neg. [gamma=(1.35-0.3)/(7x0.3)=0.5]. 1.35 is nowhere near 2.1 but 4 stops over exposing would put the density right on 2.1, however if I reduce the gamma to 0.4 and calculate the range for Zone II to IX, you will see it comfortably makes it in. I am calculating from zone II up to Zone IX (i.e. an 8 stop range) as I want to include even the last nuance of detail in my highlights. So here is the formula:

Gamma=0.4=(D_zone_IX_end - D_zone_II_start)/((4+8)x0.3)
0.4=(D_zone_IX_end - 0.3)/((4+8)x0.3)
D_zone_IX_end = 1.74.​

Now because D_zone_IX_end<2.1 , I should be OK. In fact because I still have a bit of wiggle room I could develop to N-0.5 which would give D_zone_IX_end = 1.92 Developing for N would put D_zone_IX_end right at a density of 2.1 and permit no room for any error in dev time/temperature/age/minor film exposure variations etc.


regards
Peter

Forgive me for being devil’s advocate here, but if you are over exposing by 4 stops, isn't the rest of your post irrelevant, as you should concentrate on exposing correctly.

 

[markbarendt]

Forgive me for being devil’s advocate here, but if you are over exposing by 4 stops, isn't the rest of your post irrelevant, as you should concentrate on exposing correctly.

Oh Clive. You're so silly.

 

[cliveh]

I sincerely hope the silliness of cliveh's posts is intentional.

Probably not, but perhaps I'm misreading the original post. Perhaps you can please explain.

 

[markbarendt]

Probably not, but perhaps I'm misreading the original post. Perhaps you can please explain.

Have you ever screwed up something important, figured it out too late, and not known how to fix it?

 

[cliveh]

Have you ever screwed up something important

Yes, but have tried not to repeat it.

 

[markbarendt]

Yes, but have tried not to repeat it.

I think Peter will endeavor not to repeat his mistake too and he learned things he didn't know and has new questions to answer.

 

[cliveh]

I think Peter will endeavor not to repeat his mistake too and he learned things he didn't know and has new questions to answer.

So why is it silly to highlight the cause rather than the effect?

 

[markbarendt]

One thing that I thought about bringing up earlier but forgot to was that what Peter did by accident is something that Kodak, Fuji, and Ilford have been encouraging for many, many years on an industrial scale.

http://ilfordphoto.com/products/product.asp?n=77&t=ILFORD+CAMERAS
http://www.kodak.com/ek/US/en/Single_Use_Cameras.htm
http://www.fujifilm.com/products/film_camera/quicksnap/

The latitude of the film is what makes single use cameras workable.