Tmax Reciprocity Calculation Tmax 400

[timbo10ca]

When adjusting for reciprocity, is there a quick calculation you can do to determine the adjusted time for Tmax 400 (for example, I read once that for FP4+ and HP5+ you can take the metered time and raise it to the exponent of 1.48 to get the new time)?

Tim

 

[Lee L]

Here's what I'd do with TMY: (there was a url link here which no longer exists)

If you read through that thread, you'll find other methods, especially Gainer's, which is simpler math and gives effectively identical results within any practical range. Also search on "reciprocity misbehavior" for a (much) longer APUG thread on methodology with lots of neat graphs and charts.

Lee

 

[Shawn Dougherty]

Kodak has data on their website, T-max has much less failure than most films. If you're shooting long exposures at night you may want to switch to Tmax100 as it's failure is even less and becomes fast than 400 after a couple minutes. Sorry, I don't have my data handy. All the best. Shawn

 

[timbo10ca]

Thanks to you both- Lee, I tried using the calculation from Gainer's post, and the numbers are bang- on. Mind you I had to remember to convert to seconds first, then back to minutes after the calculation! Do you think this would work for Tmax 100 as well? I thought you wanted to take advantage of reciprocity failure in these types of photos, to get the effect. Or do you want to use minimal reciprocity so you don't introduse too much contrast and blow out your highlights? I was under the impression that Tmax 400 was the film to use for these types of shots...?

Tim

 

[Konical]

Good Evening, Tim,

The developer choice, instead of the film, becomes a significant factor in contrast control with the kind of exposures where reciprocity adjustments are necessary. I concur with the advice above: use T-100 for the long exposures. You're already in tripod territory, so you might as well have the advantage of T-100's somewhat finer grain. Try Technidol or some other soft-working developer to minimize contrast problems.

Konical

 

[Lee L]

Howard Bond did extensive tests that included TMX and TMY in 2003, reported in the July/Aug issue of Photo Techniques (Vol. 24, No.4) . He found TMY to fail less rapidly than TMX. TMY with indicated exposure of 240 seconds required 540 seconds to reach expected densities. TMX at indicated exposure of 240 seconds required 770 seconds to reach expected densities.

He also found that contrast didn't increase with TMY and 240 seconds adjusted to 540 seconds. Zone VIII placement density still fell on Zone VIII. On TMX, Zone VIII rose about 2/3 of a 'zone', which I take to mean than N-2/3 development would give you a normal contrast negative or a normally processed negative would require about 1 grade lower paper.

So Bond's findings with these films are counter to what was commonly considered 'typical' behavior among older films. I obviously can't post the whole article, or quote long passages here, but his work was meticulous, and I'd rely on it more than the mfgrs typical chart and disclaimer that you need to test for your own conditions. Bond doesn't mention the developer used. He tested the new Tri-X, HP5+, Delta 100, TMX, and TMY. He contact exposed a step tablet over film inside a 4x5 camera to light from blue photofloods bounced off a white surface. He took a month to do the testing and used 300 sheets of film.

Back issues are available if you want the entire article.

If you use the equation in the post I referred to earlier in this thread, you should set p=0.872 for TMY and p=0.825 for TMX to get essentially identical adjustments to those found by Bond in his article. Then with TMX, give N-2/3 development, which you'll need to figure out using your chosen developer and procedures.

Lee

 

[CBG]

Major film manufacturor's exposure recommendations are usually pretty well thought out and researched. They have a great deal to lose if they steer people wrong.

Best,

C

 

[Lee L]

Bond points out that in the case of Tri-X, Kodak has not revised its early 1970's recommendations to change times of 1, 10, and 100 seconds to 2, 50 and 1200 seconds respectively, with accompanying reductions of development by 10%, 20%, and 30%. Bond finds that in testing the 2003 Tri-X he needed no reduction in development (i.e. the film's contrast did not increase) and that the times for 1, 10, and 100 seconds should be adjusted to 1.5, 17, and 311 seconds. The film has been reformulated for improvement and manufacturing reasons at least twice in those nearly 40 years, and it stands to reason that reciprocity behavior has changed. You'd also expect the contrast increase to go away to a great degree as reciprocity failure lessens, in line with what individuals testing films have found. So why is the data unchanged if Kodak is staying right on top of this?

If you go to Ilford's web site and check their film data, you'll find the same chart for reciprocity time adjustments to Pan F+, FP4+, Delta 100, and Delta 400 (and perhaps others, I got tired of checking). If you read any test data in books or other forms from astrophotographers and other people who use long exposures and who have actually tested the films, you'll find that these films have widely varying reciprocity behavior. (see http://www.robertreeves.com/b&w.htm for examples) It's also widely accepted that T and Delta grain films have much less reciprocity failure than older style films. So why are the same charts used for both types of Ilford films?

Film manufacturers and consumers alike have always accepted that this use of film is beyond any performance guarantee made by the mfgr, and that photographers must test for specific conditions and methods to find their own parameters for reciprocity corrections. Bond and many others that have done so using standard sensitometric methods have found the manufacturers data to be out of date, and only the very roughest of guides. There is also no incentive for Kodak to invest any funds in trying to test film performance outside of typical usage. It won't sell film.

No one contends that this is deliberately misleading the consumer, it's just a recognition that those who do this kind of work routinely will do their own testing, and are a tiny percentage of users that doesn't drive the market. When was the last time Fuji took out an ad in Pop Photo selling Acros as having cornered the reciprocity failure market? The people concerned with this aspect of film either already know this about Acros or will find out through other means, and Fuji knows it's not cost effective to promote it that way.

In the mean time, I'll choose to use the results of Bond's 2003 tests, Michael Covington's results, and Robert Reeves' tests (all of which are in close agreement) combined with my own results, not Ilford's generic, non-film-specific guidelines or Kodak's unchanging numbers for 1968 vintage Tri-X.

Lee

(BTW, you should pass along your take on steering people wrong on product performance to Steve Ballmer.)

 

[eddie gunks]

hello,
i use this http://www.pinhole.cz/en/pinholedesigner/
it is great. you can put in Tmax100 and it will calculate the exposure including reciprocity. it is made for pinhole cameras but works well on lenses also. just put in F22 as your aperture. then if you shoot at other apertures you will have to modify for that. i have used this with great results. Tmax100 and Across are the "fastest" B&W films with regard to reciprocity. i find most of the color C41 and E6 to be equally fast.

eddie

 

[Lee L]

Pinhole Designer is a very nice program. Its reciprocity data, however, is calculated to match the manufacturers' data sheets, and so has the same problems with being out of date that I mentioned in my earlier post.

Lee

 

[timbo10ca]

I appreciate the advice- I tried some exposures this weekend using the only film I had on hand (FP4+), and can see why a) you want a good reciprocity response, and b) why a faster film (ISO 400) may be preferred: at dusk, the light EV changes so fast, you want to somewhat limit the length of the exposure or you're just guessing on time. FP4+ is crap for reciprocity (e.g. a 30 sec exposure becomes 2 1/2 min and a 1 min exposure becomes 7 min), so I found that if I was doing anything beyond a 5 minute exposure *max*, my light level had changed so much, I was adding minutes, or opening the aperature a bit "for good measure", based on continous EV readings and rough guestimations in my head (my solar calculater battery wasn't helpful for long!). I was going to use HC-110 at dilution H for development at about minus 20% - would this be considered a "dilute" developer to control highlight contrast?

I really can't see how these photographers know how to expose for the times they do when it's running into many minutes or hours, other than through alot of trial and error. This weekend was trial number 1 for me.....

Tim

 

[Lee L]

I really can't see how these photographers know how to expose for the times they do when it's running into many minutes or hours, other than through alot of trial and error. This weekend was trial number 1 for me.....

Tim

Few people have the patience to work at calibrating extended exposures and development. You're finding out why. Now think about testing accurately with multiple 500 or 2000 second exposures with multiple films and exposures to be tested in multiple developers. Long tedious work. It took Bond over a month to get his data in 1/3 stop increments for just five films, and only one developer as far as I can determine. This is why people mostly go with manufacturers recommendations and then bracket a bit. A one stop increase in exposure time with a film with poor reciprocity characteristics gets you into a lot of standing around and thumb twiddling.

HC-110 at dilution H would act as you describe, especially with reduced agitation. However, HC-110 isn't going to get you the highest effective film speed compared to some other developers. Early editions of Adams' The Negative suggest just this with agitation of 15 seconds every three or four minutes, what's commonly referred to these days as reduced agitation (and sometimes semi-stand, although most people seem to reserve the semi-stand term for agitation only at the beginning and midpoint of developing time.)

Let us know what you learn.

Lee

 

[DWThomas]

Pinhole Designer is a very nice program. Its reciprocity data, however, is calculated to match the manufacturers' data sheets, and so has the same problems with being out of date that I mentioned in my earlier post.

Yes, I used Pinhole Designer with Delta 100 on Worldwide Pinhole Photography Day and got the distinct impression that it over compensated. Of course, I also get the impression that we may tend to split too many hairs, considering that at some pinhole exposures, two or three minutes is barely one stop.

Purportedly there are possible configuration updates for PD on the website, but I didn't find any. It would be truly cool if you could create some sort of user input file to reconfigure or add new films on the fly. (Oh well! )

DaveT

 

[Lee L]

Of course, I also get the impression that we may tend to split too many hairs, considering that at some pinhole exposures, two or three minutes is barely one stop.

DaveT

Very true that the differences appear larger when you look at the pure numbers, especially when expressed in seconds, and they can easily be overstated. I've also gotten overexposure going with mfgrs reciprocity recommendations as given in pinhole designer. It's often only a stop or two, which you can just print through if the highlights don't get away from you. But it's also nice to get a better handle on things with other peoples' real world tests, and I don't see the point in spending the extra time making the exposure and dealing with the extra grain and density in printing. Why work longer and harder for a lesser image?

I run linux, and Pinhole Designer works there under Wine (Wine Is Not and Emulator), but I haven't tried to look at where it gets data or how to change it. I just use spreadsheets and print out either a table or graph of compensation times for the films I use and stick it in my camera bag. I use data from Bond and the astrophotographers I mentioned.

Both Covington and Reeves calculate a Schwarzschild factor from the exposure length compensation needed for a 128 second exposure (one shot at 1/125th with no filter and then a series of time exposures with a 3.0 ND filter, 10 stops or a factor of 1000) to see exactly what time is needed for equal densities where the time _should_ be 128 seconds without reciprocity failure. Bond did a lot more work over a wider range of exposures.

Lee

 

[timbo10ca]

Few people have the patience to work at calibrating extended exposures and development. You're finding out why. Now think about testing accurately with multiple 500 or 2000 second exposures with multiple films and exposures to be tested in multiple developers. Long tedious work. It took Bond over a month to get his data in 1/3 stop increments for just five films, and only one developer as far as I can determine. This is why people mostly go with manufacturers recommendations and then bracket a bit. A one stop increase in exposure time with a film with poor reciprocity characteristics gets you into a lot of standing around and thumb twiddling.

HC-110 at dilution H would act as you describe, especially with reduced agitation. However, HC-110 isn't going to get you the highest effective film speed compared to some other developers. Early editions of Adams' The Negative suggest just this with agitation of 15 seconds every three or four minutes, what's commonly referred to these days as reduced agitation (and sometimes semi-stand, although most people seem to reserve the semi-stand term for agitation only at the beginning and midpoint of developing time.)

Let us know what you learn.

Lee

Yes- long and tedious work! Alot of work assuming your light level is remaining constant, mind numbing work when you take into account exposures of different lengths and decreasing light levels at dusk! I'd love to be able to sit down with Michael Levin and David Burdney and say "OK guys- tell me how you do it"! Then I'd at least have some workable parameters to jump off from.

I'll try your suggestion of reduced agitation as well, to tone down the highlights, and will let you know how things go. A question though- I'm not sure I understand why HC-110 may not give me good film speed- what does this matter if I'm going so far into the effects of reciprocity? Is it going to cause the exposures to look underexposed if I base it on my current personal EI and N time? Should I be rating my film slower whe using such long exposures (I'm currently trying out a suggestion to place the highlights on zone 8 and let the shadows take care of themselves)? I thought HC-110 was kinda all-purpose, quite good for any film speed (but not the *best* for any of them). I'm still working on my personal EI with FP4+ and N development time (which doesn't help my current "project"), but I'm getting close- I rate the 120 and sheet film at ISO 100, and I think dilution H for 10 minutes is about right for N development. I was going to develop this roll of long exposures I just shot for 8 min, and I'll try agitation once at the halfway mark.

Tim

 

[thebanana]

Tim, save yourself a lot of aggravation and try some Fuji Acros 100. Almost no reciprocity to deal with at all. Cheers,

John

 

[MikeK]

I have found the work that Gainer did a few years back is pretty accurate and yes both TMX and TMY have very low reciprocity loss.

A bunch of us ran the numbers for the factors that Gainer arrived at and I have the results posted here Dead Link Removed

You can download the tables or the Exel worksheet.

There are a couple of other films with good reciprocity characteristics, namely Across 100 and Iford XP2.

Mike

 

[Lee L]

A question though- I'm not sure I understand why HC-110 may not give me good film speed- what does this matter if I'm going so far into the effects of reciprocity? Is it going to cause the exposures to look underexposed if I base it on my current personal EI and N time? Should I be rating my film slower whe using such long exposures (I'm currently trying out a suggestion to place the highlights on zone 8 and let the shadows take care of themselves)?

Tim

Tim,

HC-110 with normal agitation at the most commonly used dilutions is similar to D-76 in that it most often results in lower than box speed for shooters who do zone system style film speed tests. So I'm speaking about HC-110 relative to other developers that routinely produce higher EIs across films. However, with reduced agitation and longer development times, the shadows get more time to develop and film speed (based on shadow exposure and retention) tends to rise back toward box speed. Obviously this varies with particular films and personal developing techniques. If you work off your already established EI with HC-110 and TMY, I'd expect you to be in great shape as far as film speed.

I can't see your earlier posts from this editing page, so to be complete, I'll add that you'll need to extend development time with reduced agitation, and greater dilution will also require an increase in development time. This will obviously involve some guesswork/estimation on your part for the first run, and likely a trial or two after that to nail down contrast and perhaps revise your EI a little. If it helps with estimating, Don Cardwell (df cardwell here on APUG; not active lately, and I really miss his input) has recommended approximately doubling your development times when dropping agitation from once each minute to once every five minutes. Keep in mind, when thinking about reduced development to control contrast increase due to reciprocity failure, that Bond found Zone VIII to rise only 2/3 of a Zone with TMY and normal development.

Hope this helps.

Lee

 

[timbo10ca]

Thanks Lee- I'll give it a whirl and see what happens. Thanks also John and Mike- I'll try some Acros as well.

Tim

 

[eddie gunks]

Pinhole Designer is a very nice program. Its reciprocity data, however, is calculated to match the manufacturers' data sheets, and so has the same problems with being out of date that I mentioned in my earlier post.

Lee

seems to work very well for me. maybe my metering technique fits well with PD. i get fine results. again, i shoot lots of pinhole images so maybe that has an effect. as for developing foma100 i use hc110 at dil g (1:119) for 18 min at 20C. agitation for the first 30 sec and then every 3 min. awesome stuff. for fp4 i use dil h (1:63) times from the massive dev. chart, i double the dil b times, and agitate every 2nd min. hope this helps.

eddie