Ilford - new reciprocity failure compensation factors

[Michael R]

As you may have noticed, the reciprocity failure compensation graphs in Ilford's film literature are generic. A few years ago I had a discussion with Harman tech service about how frankly lousy Ilford's and Kodak's low intensity reciprocity failure (LIRF) compensation charts were/are. After some back and forth they decided to carry out new, film-specific LIRF testing. I followed along as Harman went through this process and the revised factors have now been publicly released. Notice most of the factors are substantially different than the old chart indicated.

https://www.ilfordphoto.com/wp/wp-content/uploads/2017/06/Reciprocity-Failure-Compensation.pdf

[Neal Chaves]

This doesn't seem to work for exposure times of one second or less. After my own tests, I never applied corrections at times of 1/4, 1/2, 1 sec but the old literature suggested doing so and many good negatives were spoiled as a result.

[Pawlowski6132]

Wow. Cool.

Good job Michael.

[IanBarber]

Good job Michael, can you work on Kodak now :-)

[Pere Casals]

Great to know it !

[Pere Casals]

After reading it, IMHO it is also good they point those important factors:


"For very long exposures at very low light levels then
some other variables come in to play such as the
accuracy of the light measurement. This means that
some trial and error may be required.

You may also find that the contrast is increased with
long exposures. This is because of the light level
difference in light levels between highlights and
shadows in the image in effect giving different
reciprocity failure within the image. If this occurs, then
pulling the development may be required (reducing
development time) but will depend on the range of light
levels in the image."

The "some other variables ...such..." wording disclaimer is important. It is not mentioned, but I guess that also "other variables" as film batch and film aging may play a role. About metering, it can also be really challenging, for separate zones, and including flare from highlights to the shadows...

Perhaps because that complexity... manufacturers were not giving precise factors to encourage practical trials, rather than encouraging the counter... this is the easy way.

So IMHO this document is the right way, giving accurate factors, but still warning about the practical challenges a photographer may find.

[Pere Casals]

Good job Michael, can you work on Kodak now :-)

Kodak gives separate LIRF corrections for each film, but not the factor. In general Kodak shows excellent technical documentation, I like that.

Ilford is prone to give more "photographer friendly" information, IMHO, also not a bad thing.


Anyway I like the LIRF specs from Acros :)

Sadly they are going to kill LF Acros. To me this is a big mistake coming from earlier big mistakes...

[baro-nite]

Thanks very much indeed. Interesting to compare Ilford's new LIRF compensation factors with the work Howard Bond did in 2003. He was trying to retain density in Zone III, and what he found for HP5+ is less compensation than these new factors indicate. But they're in the same ballpark, which can't be said for the old Ilford graph (which is still in the film data sheets). I have added tables based on the new factors to my film notebook.

[devb]

The "some other variables ...such..." wording disclaimer is important. It is not mentioned, but I guess that also "other variables" as film batch and film aging may play a role. About metering, it can also be really challenging, for separate zones, and including flare from highlights to the shadows...


Could the other variables include environmental factors like the spectral qualities of the light being captured?

[tgtaylor]

I'd take the new reciprocity factors with a heavy grain of salt. I have had excellent results using Ilford's published reciprocity graph for Delta 100. For example the negative for this salt print http://spiritsofsilver.com/yahoo_site_admin/assets/images/Port-of-San-Francisco.169105649_large.jpg was metered at 30 seconds which translated to 160 seconds on the graph. Important exposure considerations were the light on the water, the clock, and the office lights. Plugging 30 seconds into the new equation gives an exposure of 73 seconds - almost half that of the old. If I had cut the exposure by 1/2 I would not have gotten the print that I ended up with which is exactly as I visualized it when I took it.

Thomas

[Pere Casals]

Could the other variables include environmental factors like the spectral qualities of the light being captured?

Yes, of course, as film spectral sensitivity is not flat. SPD (spectral power distribution) of light that our silver crystalls receive depends on the illumination SPD and on the spectral reflectiveness our subject has, and our filters. So at the end we have light with particular SPD reaching our silver crystals. Is SPD peak hits a valley in the film spectral sensitivity curve then we need longer exposure, with greater LIRF correction (Low intensity reciprocity failure).


I may be like the way exposure correction for a particular color filter depends on the light source, see here different corrections for same filter (for TMX) depending on if daylight or tungsten, page 20 : http://www.kodak.com/global/en/professional/support/techPubs/f4016/f4016.pdf;jsessionid=145M2SXDAJGWRQHIO3JXWJI


Also a great variation (Alaska -30ºC vs Death Valley +45ºC) of temperature will substantially change LIRF, it is lower with cold, as astronomers saw in 1930s, they were using "dry ice" cold backs.

[Pere Casals]

I'd take the new reciprocity factors with a heavy grain of salt. I have had excellent results using Ilford's published reciprocity graph for Delta 100. For example the negative for this salt print http://spiritsofsilver.com/yahoo_site_admin/assets/images/Port-of-San-Francisco.169105649_large.jpg was metered at 30 seconds which translated to 160 seconds on the graph. Important exposure considerations were the light on the water, the clock, and the office lights. Plugging 30 seconds into the new equation gives an exposure of 73 seconds - almost half that of the old. If I had cut the exposure by 1/2 I would not have gotten the print that I ended up with which is exactly as I visualized it when I took it.

Thomas

I'd add that beyond any LIRF calculation it is a suitable practice giving an extra stop and then making a N-1 compression, because LIRF works different in the shadows than in the lights, as Ilford document says, thus increasing contrast, so it is easy to get too much contrast in night photography.


Best LIRF calculation is Acros calculation: no calculation, just an easy rule, and good negatives.

Sadly Fuji nasty managers have destroyed LF Acros market and we'll attend a funeral, R.I.P.

[tgtaylor]

I'd add that beyond any LIRF calculation it is a suitable practice giving an extra stop and then making a N-1 compression, because LIRF works different in the shadows than in the lights, as Ilford document says, thus increasing contrast, so it is easy to get too much contrast in night photography.


Best LIRF calculation is Acros calculation: no calculation, just an easy rule, and good negatives.

Sadly Fuji nasty managers have destroyed LF Acros market and we'll attend a funeral, R.I.P.

While overexposing by 1-stop and developing N-1 might work for night photography with Delta, I needed all the density the film could deliver for printing as a salt print. That meant over developing the negative to the max. Acros, of course, would have required a 30 second exposure but I wonder if the water would have appeared as smooth as it does in the Delta. At the time the Bay had a strong current running and I was looking for the silver light reflecting off the black bay water under a black sky. No fog was present but ripples or waves would have resulted in a different look.

Thomas

[Pere Casals]

While overexposing by 1-stop and developing N-1 might work for night photography with Delta, I needed all the density the film could deliver for printing as a salt print. That meant over developing the negative to the max. Acros, of course, would have required a 30 second exposure but I wonder if the water would have appeared as smooth as it does in the Delta. At the time the Bay had a strong current running and I was looking for the silver light reflecting off the black bay water under a black sky. No fog was present but ripples or waves would have resulted in a different look.

Thomas

Hello Thomas,

Of course I've no doubt Delta is a superb film that will work perfect with the right process, and I ignore the intrinsics of the amazing Salt Printing, one day I'll try it !!! Now I'm very busy with dry plates...

Anyway, if you want 2min exposure with Acros it is also possible, by stopping diafragm or ND filter... IMHO the advantage Acros (still) has is that it not increases contrast much with long exposures. A film with LIRF has more LIRF for the shadows, as the the Ilford doc points. So in reality one has to make a LIRF correction calculation for the shadows and another one for the lights, and then one knows in what zones of the negative each zone of the scene will end, and if resulting contrast will we printable without troubles.

The disadvantage Acros has is that infame Fuji managers are to discontinue it for LF... and this is a major disadvantage !

Another aproach I'm considering for night photography is minimal agitation with Pyrocat HD as Steve Sherman teaches it

Regards

[paulbarden]

I'd take the new reciprocity factors with a heavy grain of salt. I have had excellent results using Ilford's published reciprocity graph for Delta 100. For example the negative for this salt print http://spiritsofsilver.com/yahoo_site_admin/assets/images/Port-of-San-Francisco.169105649_large.jpg was metered at 30 seconds which translated to 160 seconds on the graph. Important exposure considerations were the light on the water, the clock, and the office lights. Plugging 30 seconds into the new equation gives an exposure of 73 seconds - almost half that of the old. If I had cut the exposure by 1/2 I would not have gotten the print that I ended up with which is exactly as I visualized it when I took it.

Thomas

That is an exquisite salt print, Thomas. :-)

[David Karp]

Has anyone put the new Ilford reciprocity correction factors to the test in the field? I would be interested to hear your experiences.

[Pere Casals]

Has anyone put the new Ilford reciprocity correction factors to the test in the field? I would be interested to hear your experiences.

Yes... I shot at night with HP5

David, the newly Ilford published correction factors are accurate, but only useful for very careful spot metering en each zone. The former graph in datasheets contains a safety factor of aprox 2/3 stop (for 15s base at least), and it is a good advice for an starting point.

The right correction factors are very sensitive to the way we meter, and to the other factors, so IMHO the old good graph recommends a good starting point.

For example, the graph says that 15s base has to be corrected to 50s, while the new factors say 35s for HP5 and 30s for FP4.

Principal problem with correction factors is that the shadows have more failure than mids and highlights, so one thing is correcting for the scene average illumination and another one is correcting for the shadows.

IMHO if we have a low contrast dull scene the new factors can be used, but with a contrasty scene (urban night) we should apply an additional correction if we want some shadow detail, and in this case the old graph included a lot of wisdom to get our starting point.


Lower correction factors were published by Howard Bond 5 years ago: http://phototechmag.com/kodak-ilford-black-white-films-2013/

One has to be careful when comparing LIRF features of different film manufacturers, because ilford used a generous safety margin for good practical results.

Anyway, if one want to do the thng perfect one should calibrate LIRF, this is making contact prints of the Stouffer wedge with known lux, and using also long exposures (15, 30, 60s , 120 for example) and different N+/-. With that information one can guess very well what density he will obtain in the negative for each scene metered spot. I made some informal tests in this way, enough to see that full calibration it's interesting for night shots.


Let me repeat, IMHO new factors are useful for accurate metering, if one wants to use spot metering in the shadows to know in what density it will end a "zone" in the negative, but better make calibrations with the Stouffer. If it's not the case, better to start with the old graph, because that safety margin is benefical to conserve shadows.

[Ulophot]

Math challenges me. I looked up factors and looked at Ilford's explanation, including the mention of the x-superscript-y button on calculators. I get different results if I multiply a given time by 1.31 (HP5+ factor) or use that time, then press the x-super-y button on Windows calculator, and then 1.3. Which is correct, and why?

Thank you.

[Tin Can]

Math challenges me. I looked up factors and looked at Ilford's explanation, including the mention of the x-superscript-y button on calculators. I get different results if I multiply a given time by 1.31 (HP5+ factor) or use that time, then press the x-super-y button on Windows calculator, and then 1.3. Which is correct, and why?

Thank you.

Since we are both lousy at math I tried the same thing you did. I plugged in 10 sec and 100 sec for meter times. Then did it the WRONG WAY by simply multiplying the P factor times my 10, of 100 seconds.

Then I did what Ilford clearly says to do. When we use the P factor with the special key Xy we get far different numbers that in no way are direct multiples of our wrong way attempts.

Just follow the instructions, splaining won't get us anywhere. It's calculus factorial. Never any fun.

[Drew Wiley]

Do they state what their specific light source was (K)? Even if threshold exposures are matched, significantly different colors of filtration cannot just be corrected with a filter factor, because the contrast gamma also significantly diverges at long exposures, and is inconsistent from one film to another, and even with the same film at different lengths of exposure. You're back to square one, realistically needing to test in advance with analogous parameters.

[ic-racer]

I like it when they keep this stuff a secret. The easier it is to do low-light photography, the less "wow" and "how did he do that" factor there is in Large Format low light photography. :)

[Tin Can]

Do they state what their specific light source was (K)? Even if threshold exposures are matched, significantly different colors of filtration cannot just be corrected with a filter factor, because the contrast gamma also significantly diverges at long exposures, and is inconsistent from one film to another, and even with the same film at different lengths of exposure. You're back to square one, realistically needing to test in advance with analogous parameters.

You could click on the Ilford link...

[Michael R]

Yes... I shot at night with HP5

David, the newly Ilford published correction factors are accurate, but only useful for very careful spot metering en each zone. The former graph in datasheets contains a safety factor of aprox 2/3 stop (for 15s base at least), and it is a good advice for an starting point.

The right correction factors are very sensitive to the way we meter, and to the other factors, so IMHO the old good graph recommends a good starting point.

For example, the graph says that 15s base has to be corrected to 50s, while the new factors say 35s for HP5 and 30s for FP4.

Principal problem with correction factors is that the shadows have more failure than mids and highlights, so one thing is correcting for the scene average illumination and another one is correcting for the shadows.

IMHO if we have a low contrast dull scene the new factors can be used, but with a contrasty scene (urban night) we should apply an additional correction if we want some shadow detail, and in this case the old graph included a lot of wisdom to get our starting point.


Lower correction factors were published by Howard Bond 5 years ago: http://phototechmag.com/kodak-ilford-black-white-films-2013/

One has to be careful when comparing LIRF features of different film manufacturers, because ilford used a generous safety margin for good practical results.

Anyway, if one want to do the thng perfect one should calibrate LIRF, this is making contact prints of the Stouffer wedge with known lux, and using also long exposures (15, 30, 60s , 120 for example) and different N+/-. With that information one can guess very well what density he will obtain in the negative for each scene metered spot. I made some informal tests in this way, enough to see that full calibration it's interesting for night shots.


Let me repeat, IMHO new factors are useful for accurate metering, if one wants to use spot metering in the shadows to know in what density it will end a "zone" in the negative, but better make calibrations with the Stouffer. If it's not the case, better to start with the old graph, because that safety margin is benefical to conserve shadows.

Pere,

Ilford used a fixed density criterion (0.1 above Fb+fog) to determine these t-factors. As you know, the speed point under ISO conditions is the exposure Hm where density is 0.1 above Fb+fog. Using this as a reference point, they then plotted characteristic curves for successively longer exposures and measured the speed losses relative to Hm, by finding the exposure in each case that produced a density of 0.1 above Fb+fog.

Said another way, the equation gives you the adjusted time so that the density 3 1/3 stops below the metered exposure is always 0.1.

From a Zone System perspective (for those who use it), the equation can be said to give you a constant density at Zone I 2/3.

This is a little more conservative than Howard Bond's tests which targeted a constant density at Zone III.

Hope this helps.

[Pere Casals]

Pere,

Ilford used a fixed density criterion (0.1 above FB+fog) to determine these t-factors.

Hello Michael,

The ilford technical notice https://www.ilfordphoto.com/wp/wp-content/uploads/2017/06/Reciprocity-Failure-Compensation.pdf speaks about "effective speed", not about ISO speed.

I understand what you say, giving a correction factor for the speed point it is not the same than for the meter point that has exactly x10 (3 1/3 stops) more light intensity...

IMHO a key factor in this discussion is if the new ilford correction is for the speed point or not. If it was for the speed point IMHO new factors would be higher than the old curve (I guess), but it's the counter.

Still, do you know for sure that the new values are based in the fixed density criterion (0.1 above FB+fog) ? Or factors are for "the effective speed" ? What is the "effective speed" ?

Regards

[Michael R]

ISO speed point is the reference point, and the t-factors are based on the loss of effective speed relative to the ISO speed point.

Effective speed is based on finding the exposure that produces a density of 0.1 above Fb+fog under LIRF conditions. It is called effective speed because it is based on a fixed density criterion (ISO contrast conditions do not apply under LIRF conditions due to the inherent contrast increase).

Another way of saying this is that the correction is for the speed point (using your words).

This is the most logical way of doing it. It isn't very complicated, just time consuming to test without the right equipment.

The old curves were generic and also were not film-specific.

[Tin Can]

When you guys get done, will you please give a summation and succinct advice on actually using Ilford's new guideline.

Must be comprehensible to a 5th-grade level.

And very short.

Carry on, we can wait.:)

[Michael R]

1) Look up the P factor for the film you are using in the Ilford table

2) Whatever your exposure time is (in seconds), put that number to the power of the P factor (the P factor is the exponent), and this is your new exposure time.

Example - you're using Delta 100 and your meter tells you to expose for 10 seconds:

1) Use a P factor of 1.26 from the Ilford table

2) Metered time(P factor)=Adjusted time so 101.26=18.2 (round to 18 seconds)

[Tin Can]

1) Look up the P factor for the film you are using in the Ilford table

2) Whatever your exposure time is (in seconds), put that number to the power of the P factor (the P factor is the exponent), and this is your new exposure time.

Example - you're using Delta 100 and your meter tells you to expose for 10 seconds:

1) Use a P factor of 1.26 from the Ilford table

2) Metered time(P factor)=Adjusted time so 101.26=18.2 (round to 18 seconds)

Not bad, that's exactly what I wrote.

[Pere Casals]

ISO speed point is the reference point, and the t-factors are based on the loss of effective speed relative to the ISO speed point.

Effective speed is based on finding the exposure that produces a density of 0.1 above Fb+fog under LIRF conditions. It is called effective speed because it is based on a fixed density criterion (ISO contrast conditions do not apply under LIRF conditions due to the inherent contrast increase).

Another way of saying this is that the correction is for the speed point (using your words).

This is the most logical way of doing it. It isn't very complicated, just time consuming to test without the right equipment.

The old curves were generic and also were not film-specific.

Thanks for the explanation

[Drew Wiley]

Still would be more intuitive in graph form. Most of us carry a limited number of films at any given time, maybe only one. Alas, I'm down to my last three sheets of 8x10 Acros.

[Drew Wiley]

I should point out that what Ilford objectively regards as a speed point tends to be well below realistic shadow separation, because it's still on the toe.

[David Karp]

Thanks everyone. I have been using a table I created based on the one provided by Steve Simmons in his view camera book. If I recall properly, he gave one set of times for all Ilford films, which, as noted above, is problematic due to the real differences in the films. I am thinking that I can make a new table using the formula. Another alternative is to use a spreadsheet on my phone to automate the calculations. I know that there are apps out there, but they are based on different approaches to the reciprocity problem. This discussion is helpful.

Michael, Let's say I meter off of a subject that I want to place on Zone VI. That means that I would take my meter reading and adjust one stop to place it on Zone VI, just as always. We would normally expect that 3 1/3 stops below that will fall on Zone 2 2/3. The exposure will register as .1 above Fb+fog if we follow the time determined by using Ilford's factor/formula. Am I understanding properly / making sense?

I should say that most of the situations when I am photographing something under low light conditions and dealing with reciprocity, I look for something I want to register at Zone V and meter that. In that case, the 3 1/3 drop would be zone 1 2/3, which in most scenes would be just fine registering at .1 above Fb+fog. Let it go black!

[David Schaller]

You didn't ask me, but you should meter for the low value, then apply the reciprocity correction, then divide to get the corrected exposure time. I meter Zone III and then divide the corrected time by 4 to get the right exposure. If you do the reciprocity correction on Zone V, your shadows will be underexposed.

[Pere Casals]

You didn't ask me, but you should meter for the low value, then apply the reciprocity correction, then divide to get the corrected exposure time. I meter Zone III and then divide the corrected time by 4 to get the right exposure. If you do the reciprocity correction on Zone V, your shadows will be underexposed.

This is a choice, but something else can be done... in LIRF conditions costrast may rise too much, so rather than dividing the corrected time by 4... an N-2 development may be better. Just another choice...

[Michael R]

Thanks everyone. I have been using a table I created based on the one provided by Steve Simmons in his view camera book. If I recall properly, he gave one set of times for all Ilford films, which, as noted above, is problematic due to the real differences in the films. I am thinking that I can make a new table using the formula. Another alternative is to use a spreadsheet on my phone to automate the calculations. I know that there are apps out there, but they are based on different approaches to the reciprocity problem. This discussion is helpful.

Michael, Let's say I meter off of a subject that I want to place on Zone VI. That means that I would take my meter reading and adjust one stop to place it on Zone VI, just as always. We would normally expect that 3 1/3 stops below that will fall on Zone 2 2/3. The exposure will register as .1 above Fb+fog if we follow the time determined by using Ilford's factor/formula. Am I understanding properly / making sense?

I should say that most of the situations when I am photographing something under low light conditions and dealing with reciprocity, I look for something I want to register at Zone V and meter that. In that case, the 3 1/3 drop would be zone 1 2/3, which in most scenes would be just fine registering at .1 above Fb+fog. Let it go black!

David,

I'm not sure I completely understand the question, but I don't think your second paragraph is correct. Assume you set your meter to the film's ISO speed. Further assume there is no flare. If you meter something in the scene and place it on Zone V, whatever falls on Zone I 2/3 should have a density of 0.1 above Fb+fog in the negative. The Ilford factors should ensure that remains the case when exposures are long. If you instead decide to place the metered object on Zone VI, whatever falls on Zone 0 2/3 should have a density of 0.1 above Fb+fog in the negative. Again, the Ilford factors would ensure that remains the case when exposures are long.

The Ilford factors are designed to maintain a density of 0.1, 3 1/3 stops below the metered exposure.

Don't get too caught up in the underlying theory. The important thing is the Ilford factors ensure that when exposures are long, shadow densities stay the same as they would when exposures are short. Consider the Zone System separately. Figure out your exposure, then apply the Ilford factors.

[David Karp]

. . . Figure out your exposure, then apply the Ilford factors.

Ahhhhh. That makes sense. Thank you.

I am going to give these a whirl. Interesting how the factors for FP4+ and Delta 100 are the same, while HP5+ is actually a little better than Delta 400. My wife (an Excel wizard) made a spreadsheet for me that allows me to select the film, input the metered time, and automatically calculate the "corrected time." I transferred the file to my phone, so as long as I have battery power I will be able to use it to make photos.

[Tin Can]

There it is, to quote the essential Michael R, '...figure out your exposure, then apply the Ilford factors.'

Sorry, I am a simple guy.

[Doremus Scudder]

... Assume you set your meter to the film's ISO speed. Further assume there is no flare. If you meter something in the scene and place it on Zone V, whatever falls on Zone I 2/3 should have a density of 0.1 above Fb+fog in the negative. The Ilford factors should ensure that remains the case when exposures are long. If you instead decide to place the metered object on Zone VI, whatever falls on Zone 0 2/3 should have a density of 0.1 above Fb+fog in the negative. Again, the Ilford factors would ensure that remains the case when exposures are long.
... The Ilford factors are designed to maintain a density of 0.1, 3 1/3 stops below the metered exposure.

Michael,

Let me chime in here (late) with an observation/request for clarification.

As I see it, when I "place" something in Zone III or Zone VI or whatever, it's because I want a particular area of the scene to be rendered differently than "normal," i.e., Zone V. Now regardless of what I'm basing my exposure on, there's a hypothetical Zone V implied. The speed point Ilford is working with is 3 1/3-stops below this; not 3 1/3-stops below whatever I'm placing.

In the example above, "placing" a value in Zone VI would imply overexposing it one stop from Zone V, for whatever reason, but a clear and conscious choice to ensure that area of the scene gets more than Zone V exposure. So... if I'm figuring correctly here, the Ilford speed point is still going to be at Zone I 2/3. The same thing should happen if I base my exposure on Zone II, III or VI (where I'm intentionally underexposing from a Zone V meter reading).

So, do correct me if I'm wrong, because I can't seem to figure this out the way you have.

Change of subject:

One problem with LIRF that gets lost in talk of preserving shadow detail is the contrast expansion that happens with really long exposures due to the proportional nature of reciprocity failure. If one meters and places a value on Zone VI and then gives a really long corrected exposure (say upwards of 4x the metered exposure) and then develops normally, that Zone VI density is going to be way higher on the negative than a "normal" Zone VI density. In essence (if the Ilford factors work as they should), we've produced proper density at the speed point, but now have a really contrasty negative to deal with, one in which our target density (Zone VI) is significantly denser than we wanted. Of course, the obvious solution is to adjust development. However, since the amount of development adjustment likely varies from film-to-film (just as the LIRF factors do), testing this for many films is a lot of work. I'm not even sure that the exposure correction is linear. Add to this Howard Bond's suggestion that no development adjustment is necessary and the subject becomes even more complicated (BTW, I'm fairly sure Bond is wrong here, especially for very long exposures). Kodak used to publish development adjustments in their reciprocity tables.

I've empirically figured out what to do to get negatives that are in the ballpark and can be printed halfway easily with very long exposures for the two films I use most, but have no real quantifiable data. If Ilford wants another project, they could test how to maintain the speed point and a Zone VIII density and publish the exposure and development adjustments for very long exposures. :)

Best,

Doremus

[Drew Wiley]

Perhaps for "street jargon" purposes, the "speed point" could be equated to the transition between Zone 0 and 1 ? I realize this is hardly an ideal explanation. But there is very little pintable value down there.

[Pere Casals]

Perhaps for "street jargon" purposes, the "speed point" could be equated to the transition between Zone 0 and 1 ? I realize this is hardly an ideal explanation. But there is very little pintable value down there.

Drew, speed point is exactly 3 1/3 underexposure from box speed so it should be in the Zone I to the to the Zone II transition.

Before the ISO speed change in 1960 ISO the speed point was in the Z-0 to the Z-I transition, but after 1960 it's only 3 1/3 stops underexposure from what meter says. Books edited before 1960 use the criterion you say, since 1960 things moved one stop.

[Drew Wiley]

That's helpful. These films differ with regard to shadow placement, but nominal Z2 usually works for FP4, a film I use often enough to be correct with long exp thru sheer experience. But another thing which needs to be differentiated is night exposures which probably don't involve filtrstion, and long daylight exp due to a combo of dense contrast filters and small f-stops. Deep blue filters significantly depress the gamma of most films at long exp and require longer or plus dev. Red and green can differ in this respect between different films. Only Kodak TMax films were engineered with symmetry in this respect, though TMY needs a bit of tweaking for green as I recall (the actual plots are in the lab). Most people don't carry deep blue filters, but I'm tempted to throw one in the pack today.

[Pere Casals]

Another factor is film toe, the now defunct LF Acros had excellent LIRF factors, but it was short toe, while TXP is longer toe. This may be important in some situations.

Another think to consider at night is EMA...

[Drew Wiley]

Both TMax have very short toe, less than FP4 or TX. Pity the only "straight line" left on the market is Fomapan 200, which has horrible long exp characteristics. Wish ole Super XX were still around, or even Bergger 200.

[David Karp]

OK, so now I am thinking about it some more. After reading Doremus's post and thinking about my photography, ignoring where zones fall does not make sense. It may be that there is nothing we can do about it (except perhaps adjust development), but the zones have to fall somewhere based on what decisions we make when metering. If I absolutely place an important zone that absolutely has to look a certain way in my final photo, then there are consequences. Things are going to go darker higher up the scale than if I placed that part of the scene lower. Of course, we normally meter to ensure adequate detail in the shadows, but sometimes make judgments about what to sacrifice based on the needs of the desired photo. Not worrying about zone placement would imply that we just take an incident reading or place zones based on keeping zone 1 2/3 at .1 above Fb+fog.

As I keep thinking around this, I am back wondering if I can follow my normal procedures for low light landscapes or whether I need to make an adjustment if I want to use Ilford's formula, etc.

[Drew Wiley]

If it is OK to give a bit of advice, I'd say keep it simple and stick with one particular film in this respect. Among Ilford films, the most predictable straight line is FP4. The only "silver bullet" out there is Fuji ACROSS. I still keep a reserve box of that in 4X5 in the freezer for some special project, and it can still be readily acquired for roll film backs. It also exposes and develops very similarly to FP4, though different in its pan response. Second to ACROS for long exp would be both TMax films from Kodak. But since this is an Ilford thread, you have my two cents worth with FP4.

[Pere Casals]

In fact, the rigth way to deal with LIRF (if one needs it) is calibration. In the same way we calibrate a film by plotting a family of sesitometric curves from N-3 to N+3 unsing a 1s (typical) exposure we can also plot a graph for each useful exposure, say for 15s, 30s, 60s, 2', 5' exposures,

With those graphs in the hand (or in the smartphone...) all mistery disapears, we just will guess a resulting density for every important scene spot, so we can decide what exposure and what development having positive knowledge.

The other way was using Acros, and near no LIRF correction. Sadly Fuji burned that extraordinary product time ago.

I would be happy if Ilford would make a low LIRF film.

[Pere Casals]

The only "silver bullet" out there is Fuji ACROSS.

Not exactly a silver bullet, but we still have a choice: hypering.

I was considering accumulating some acros, but I decided to experiment with hypering, more fun.

Here there is an interesting text: http://adsbit.harvard.edu//full/1988JBAA...98..249D/0000254.000.html

[David Karp]

Drew, I do use FP4+ and HP5+ even more. I never used FP4+ for low light situations, but I am going to do so now, having learned that it has the better low light characteristics based on the Ilford-derived factor and having seen your comment. I never cared for the TMax films. I tried to like them, but prefer all of the Ilford films over them, including Delta 100 and 400.

Mostly, my low light photos have been successful using my old chart, but sometimes they were not and it was hard to determine why. Next time I am in that situation I will make some exposures with the new calculator and the old chart and see how things come out.

[Drew Wiley]

Excuse my personal preferences, but a Smartphone or calculator is just one more battery-dependent item I don't want in a pack, esp on a long trek where pack space is at a premium and there's no cell reception anyway, in case of emergency. That kind of thing is best done in a trial run and then either jotted down or memorized per representative times. Working with large format in a snowstorm or downpour already has enough steps and gadgets to keep track of without adding yet another.

[interneg]

Reading this thread makes you wonder how on earth generations of photographers made extraordinary night images without voluminous pages of theorising, correction tables and the arcane practices of specialist astronomical photographers...

Apologies for the sarcasm above, but there are some people who could do with a lot less huffing and puffing about zones and reciprocity and the essentiality of one particular (discontinued) film & instead just get on with making images...

[LabRat]

FWIW, I do a lot of night work with different B/W films, and the films have different LIRF, but in practice, the supplied charts usually work fine (for me)... I meter so that the darkest part of the scene that I want start to render is 3 stops under zone V, to have some detail is 2 stops under V, and full detail 1 stop...

The long exposure time covers up most of the minor differences allowing some "fudge factor", so not a problem...

What's annoying to me now is the only sheet film I can afford these days is (Foma) EDU100, and not unusual for an 8 min (or much) longer exposure (a still life I was doing was properly exposed in an hour!!!), so sit back, and get comfortable...

Steve K

[Drew Wiley]

Actually there was a tremendous amt of technical info avail to night photographers if they needed. TMax astro glass plates were still avail maybe 25 yrs ago, and other plates well before. But like many others, I'd just test bracket some 35mm frames of a promising film before using sheets. And that low tech method still works extremely well.

[David Karp]

Reading this thread makes you wonder how on earth generations of photographers made extraordinary night images without voluminous pages of theorising, correction tables and the arcane practices of specialist astronomical photographers...

Apologies for the sarcasm above, but there are some people who could do with a lot less huffing and puffing about zones and reciprocity and the essentiality of one particular (discontinued) film & instead just get on with making images...

Good idea. Who needs good technical information? And why stop there? Why not stop using light meters too? A good photographer should be able to guess at the proper exposure. (I have heard that one more than once over the years.) Why would we use test data derived by the film manufacturer? Even better, why would we even try to make sure we understand that data and its implications?

Now that I got that out of my system, please accept my apology for my sarcasm above. I have made plenty of long exposures in low light situations. Most of them are fine. Some did not work out. This new data may or may not impact my success rate. I think in zones when I photograph. I am trying to understand how the new information can be put to use effectively and put it in the context of my photography. You may not need the information or input from others. Great. I find much of the information in this thread to be interesting and helpful to me precisely because of the fact that there are others who are more technically oriented than I am. I appreciate others taking the time to contribute something. Maybe I will make a better photograph as a result of their contributions.

[Tin Can]

Yes, David, however I for one need definition of terms somewhere.

It wasn't until miles into this thread that LIRF was defined.

Now I know it's not the acronym for LIRF - Rome Fiumicino Leonardo da Vinci (https://acukwik.com/Airport-Info/LIRF), an Italian airport!

[David Karp]

I know Randy. Sometimes we get lost in our own jargon. LIRF, however, was mentioned in the very first post.

Like you, I prefer a simple explanation of what to do and how to do it. I also like the detailed technical explanation, which sometimes I can understand and sometimes not. I am far from the most technically oriented. I don't have a densitometer to measure my negs. I eyeball things. I always use a two bath developer even when I am going to print in the darkroom even though I have been assured my results will be better if I developed in a single bath developer by time and temperature. Ridiculing the more technically oriented among us and denigrating their contributions, which you never do, doesn't move anyone forward. I have found so much help on this forum and the home page on so many topics. The range of expertise of the contributors is amazing. I am a better photographer because of what I have learned here.

[Tin Can]

I know Randy. Sometimes we get lost in our own jargon. LIRF, however, was mentioned in the very first post.

Like you, I prefer a simple explanation of what to do and how to do it. I also like the explanation, which sometimes I can understand and sometimes not. I am far from the most technically oriented. I don't have a densitometer to measure my negs. I eyeball things. I always use a two bath developer even when I am going to print in the darkroom even though I have been assured my results will be better if I developed in a single bath developer by time and temperature. Ridiculing the more technically oriented among us and denigrating their contributions, which you never do, doesn't move anyone forward. I have found so much help on this forum and the home page on so many topics. The range of expertise of the contributors is amazing. I am a better photographer because of what I have learned here.

Sorry I missed LIRF in the first post. I read all day long and tend to skim very fast. I learned nearly everything I know about photography on this site. I have written several times here about how this forum saved my life, by enabling my goals. I was sick and down. Now I wake up each day happy for the challenge. I needed and still need this forum. So many acronyms, so little time. :)

[David Karp]

So, I will do some testing to find out, but after puzzling over whether or not to worry about zone placement, as I posted above, I think I am back where I was right after Michael posted.

I am leaning toward thinking that the answer is not to worry any more than normal. Zone placement is unavoidable no matter how we think about our photography. The zones will fall around whatever point we decide upon to expose our photograph. We set the meter and what we decide to read will play on through the reciprocity corrections. The dark zones will be dark, because that is what happens. We might lose detail in the lowest values, but if we place things higher, we are probably intentionally saving something else we need in the photo. We know from the Ilford data what the values are going to be 3 1/3 stops below our chosen light measurement and that below that things are going to disappear into the blackness. Is that what Michael was driving at?

[David Karp]

Excuse my personal preferences, but a Smartphone or calculator is just one more battery-dependent item I don't want in a pack, esp on a long trek where pack space is at a premium and there's no cell reception anyway, in case of emergency. That kind of thing is best done in a trial run and then either jotted down or memorized per representative times. Working with large format in a snowstorm or downpour already has enough steps and gadgets to keep track of without adding yet another.

Drew, one alternative, which I have used, is to print the information on an Avery 5388 index cards. They come in an 8.5 x 11 sheet and are easy to punch out. There are three 3" x 5" cards per sheet. You can put the information into an Excel table and then drop them into Word. Avery has templates that you can download and use to print out the tables. You can carry the tables with you in your backpack. I have cards for filter corrections, measured shutter speeds for my lenses, selecting the f/stop for near/far focus, and reciprocity. I will have one with the new Ilford reciprocity information on it. Avery also makes some adhesive backed laminating sheets that I use to stiffen up the cards and protect them. Works great for me anyway.

[Pere Casals]

Reading this thread makes you wonder how on earth generations of photographers made extraordinary night images without voluminous pages of theorising, correction tables and the arcane practices of specialist astronomical photographers...

Apologies for the sarcasm above, but there are some people who could do with a lot less huffing and puffing about zones and reciprocity and the essentiality of one particular (discontinued) film & instead just get on with making images...

Of course, a highly compensating development does the trick. And with Acros it was even simpler...

[Michael R]

Doremus,

It's just place and fall. I think we're saying the same thing but my wording was probably unclear. If you meter something and place it on Zone V, something else in the scene falls on Zone I 2/3 and should register as a density of 0.1 in the negative. All I meant was that if you instead give an extra stop of exposure, everything moves up the curve - what previously fell on Zone 0 2/3 now falls on Zone I 2/3 and should register as 0.1 in the negative.

On the subject of contrast under LIRF conditions, yes contrast increases so development adjustments may be required (or print at lower contrast). I think the reason Bond found the contrast increase to be inconsequential in his tests is that he targeted a constant density for Zone III (ie higher on the curve).

David and everyone else,

Again, I would say don't overcomplicate this by mixing the Zone System in with LIRF adjustments. I probably shouldn't have even brought up Zones in my initial response to Pere. What matters is that the Ilford factors are designed to preserve shadow values. Figure out your exposure first, using the Zone System or whatever other method you use, then adjust using the Ilford factors. The longer the exposure, the more of a contrast increase one would expect.

LIRF in the field is not an exact science (actually, even regular exposures in the field are an inexact science).

[David Karp]

Thanks Michael.

[Drew Wiley]

The Zone System, despite its limitations, is still the best common denominator jargon for sheet film users that I'm aware of; so I often use that terminology on forums even though as an exposure model it now exists only in my rear-view mirror.

[Pere Casals]

The Zone System, despite its limitations, is still the best common denominator jargon for sheet film users that I'm aware of; so I often use that terminology on forums even though as an exposure model it now exists only in my rear-view mirror.

Drew, I'd say more:

What limitation? Any limitation?

> It is also visualization system.

> It is based in spot metering interesting spots in the scene

> It says what density we will obtain in the negative for each scene spot depending on the exposure.

> For reciprocity failure, calculations should also be based on the ZS, knowing where zones in the scene will end in the negative zones...

Where is it the flaw ??? We just need to know well our film, what toe and shoulder we have, but this is with any metering strategy.

Anyway (of course) we can use any other metering strategy we want, and also we can further use other advanced techniques like scim on it, but if ZS+BTZS is not complete, I'd ask that somebody explains it to me why !!!

The single alternative (IMHO) is incident metering, for what it's worth...








https://www.alanrossphotography.com/category/tech/zonesystemandmetering/
https://www.alanrossphotography.com/wp-content/uploads/Ansel-Adams-zone-system-1.png

[Drew Wiley]

It's just a shorthand method for pigeonholing exp placement and development. It's all some people need. More of a teaching tool.

[Drew Wiley]

I use spotmeters for everything except lab work. But the ZS is quite clumsy for color film work, and is no substitute for real sensitometry under special conditions, like extreme lighting or matched b&w color separations. If you like to work with a variety of films, formats, and developers, you almost need a different zone system for each. It relies too much on contraction to handle high-contrast, at the expense of micotonality In other words, it's a good starting point, but certainly no silver bullet.

[Pere Casals]

If you like to work with a variety of films, formats, and developers, you almost need a different zone system for each.

Ok, Drew... but speaking about BW, ISO box speed is always 3 1/3 stops under meter reading (because ISO definition of speed point), so with standard development always it works similar.

If we use a development that is not the standard one then we just need to know the effective speed resulting for that process, and then ZS works the same again with the new speed... does not ?

Of course film toe, and higlight latitude knowledge (shoulder and DMax) is also an important thing, but this is just knowing the nature of the film we use...

So I'd say that with ZS we guess the resulting densities in the negative, and depending on toe/shoulder nature we can guess or not having some deatil in Z-I and how highlights are to be blown beyond Z-VIII. Do we need something else ?

[Michael R]

If we use a development that is not the standard one then we just need to know the effective speed resulting for that process, and then ZS works the same again with the new speed... does not ?

Underlying the ISO method is the Delta-X fractional gradient estimation. Delta-X tells us that speed doesn't decrease as much as the Zone System says it does, when contrast is reduced, and that speed doesn't increase as much as the Zone System says it does, when contrast is increased. The Zone System overestimates the change in speed because it relies on a fixed density speed criterion.


So I'd say that with ZS we guess the resulting densities in the negative, and depending on toe/shoulder nature we can guess or not having some deatil in Z-I and how highlights are to be blown beyond Z-VIII. Do we need something else ?

Zone System expansion/contraction is based on "fitting" the negative to a paper grade. Strictly speaking this is not based on print quality.

Many people also come away from studying the Zone System (and/or related systems) with a false impression of the level of precision one can achieve (or needs to achieve) in making negatives. In reality "place" and "fall" are approximate due to metering technique, flare, etc.

I think the best feature of the Zone System is that it gives us a language.

[Pere Casals]

Underlying the ISO method is the Delta-X fractional gradient estimation. Delta-X tells us that speed doesn't decrease as much as the Zone System says it does, when contrast is reduced, and that speed doesn't increase as much as the Zone System says it does, when contrast is increased. The Zone System overestimates the change in speed because it relies on a fixed density speed criterion.

IMHO ZS does not speak about speed change, to me it says expose for the shadows and adjust development to not have a excessive (or to low) density in the highlights.

Beyond exposing to have detail enough in the shadows, and cooking to have a desired density in the highlights... can we do something else ?



Zone System expansion/contraction is based on "fitting" the negative to a paper grade. Strictly speaking this is not based on print quality.

Many people also come away from studying the Zone System (and/or related systems) with a false impression of the level of precision one can achieve (or needs to achieve) in making negatives. In reality "place" and "fall" are approximate due to metering technique, flare, etc.

I think the best feature of the Zone System is that it gives us a language.

The metering technique has to include flare, or even better, one has to remove flare, this is prety easy, if we have a 500mm image circle in a 8x10 camera, then 80% of light bounces in the bellows, a front hub solves that.

Let me reiterate... if we expose to have detail enough in the shadows, and then we develop to have a desired density in the lights... what else can we do ?


Well... we can use film toe/shoulder to compress highlights and shadows to leave what we want for the mids, or we can take a linear capture and do it in the printing process...

[faberryman]

Let me reiterate... if we expose to have detail enough in the shadows, and then we develop to have a desired density in the lights... what else can we do?
You have to make it more complicated than that or else it doesn't qualify as alchemy.

[faberryman]

Let me reiterate... if we expose to have detail enough in the shadows, and then we develop to have a desired density in the lights... what else can we do?
You have to make it more complicated than that or else it doesn't qualify as alchemy. You have to waive your hands a couple of times at least.

[Michael R]

Beyond exposing to have detail enough in the shadows, and cooking to have a desired density in the highlights... can we do something else ?

I think the Zone System is fine for that. Things can be simplified though.

[Pere Casals]

You have to make it more complicated than that or else it doesn't qualify as alchemy. You have to waive your hands a couple of times at least.

:) ... but true alchemy is my DIY emulsion making for dry plates... you never know when the pot is to burst !



I think the Zone System is fine for that. Things can be simplified though.

Of course, IMHO for some scenes it can be simplified, incident metering is a way. Another way is a compensating development, with diafine or EMA. Another way is just using the Nikon F5 matrix metering of the scene, one has to insert a cassette of the same film for DX code reading so the F5 knows the latitude, it knows if it is like velvia or like tmax: it won't fail, never, same exposure will work in the view camera after bellows draw compensation.

But anyway for some jobs an accurate mettering is required, a contrasty night scene with LIRF requires thinking well in what one is doing...

[Drew Wiley]

I'm frequently in situations where I need to be very conscious of the specific character of the toe of the film. Neither the Zone System nor speed point nor box speed do that. You need to understand the full characteristic curve with respect to a particular film and development regimen. At this point in my life, it's almost a subconscious process. I rarely botch an exposure unless I try to read the meter in dimlight without a magnifier; and with roll film, there's inevitably going to be a frame or two with different contrast than the others. A lot of things get instinctive and easy with experience.

[Drew Wiley]

I almost never rely on alleged latitude or compensating development. There's a trade-off or penalty to both.

[Michael R]

But anyway for some jobs an accurate mettering is required, a contrasty night scene with LIRF requires thinking well in what one is doing...

This describes most of the photography I do, which is under extreme contrast, low light conditions. It used to be complicated but after I learnt about exposure theory etc. I was able to simplify my approach to making negatives.

[interneg]

Many people also come away from studying the Zone System (and/or related systems) with a false impression of the level of precision one can achieve (or needs to achieve) in making negatives.

Bang on the money.

Most of the rest is about being/ hiring a competent printer.

[Drew Wiley]

The object is to exp & dev specifically enough to obtain your own idea of a target, but still end up with a versatile negative because paper choices do change, and we often change our own minds in the course of printing about what looks best.