Ilford Delta 100 Reciprocity Departure Chart (approximated)

[CreativeMJP]

Greetings,

I'm not sure if this is going to be useful to anyone else. But I took a detailed look at Ilford's reciprocity chart for Delta 100 and came up with the numbers seen on the attached graphic. I apologize if this post is somehow unnecessary or redundant. I'm new to APUG and film shooting in general.

Respectfully,

Mike Peters
Minneapolis, MN
View attachment Ilford_Delta100_Reciprocity.pdf

 

[andrew.roos]

Hi Mike

Welcome to APUG and thanks for posting this.

However note that the reciprocity failure chart that Ilford provides in the Delta 100 data sheet is not accurate. An indication of the problem is that the reciprocity failure graphs given by Ilford for FP4+, HP5+, Delta 100 and Delta 400 are identical. It is extremely unlikely that these films (which include both conventional and CCG emulsions) have identical reciprocity failure characteristics, so I expect it is sloppiness on Ilford's part copying and pasting the graphs rather than actually performing the measurements.

Both Howard Bond and I have done independent measurements and our results are quite similar, but quite different to Ilford's data! See my post on this at (there was a url link here which no longer exists). There is a pointer to Howard's results in one of the replies to my post.

My "rule of thumb" based on these measurements is that no correction is required for exposure times up to 4 seconds. For exposures longer than 4 seconds, add an additional 1/3 stop of reciprocity failure correction for each stop of (metered) exposure over 4 seconds.

Regards
Andrew

 

[CreativeMJP]

Hey Andrew,

Thanks for the correction and explanation. I will put your suggestion to good use.

Mike

 

[Richard S. (rich815)]

Anytime I have to worry about reciprocity with Delta 100 I use Fuji Acros instead.

 

[CreativeMJP]

Rich815,

I hear that Fuji Acros is wonderful film. But, how does that song go . . . "If I were a rich man . . ."

;-)

Mike

 

[Richard S. (rich815)]

Rich815,

I hear that Fuji Acros is wonderful film. But, how does that song go . . . "If I were a rich man . . ."

;-)

Mike

Ah yes. For 35mm and 120 not so bad, but 4x5 quite a price difference, you're right.

 

[Rudolf Karachun]

Thanks for information.

 

[pentaxuser]

Hi Mike

Welcome to APUG and thanks for posting this.

However note that the reciprocity failure chart that Ilford provides in the Delta 100 data sheet is not accurate. It is extremely unlikely that these films (which include both conventional and CCG emulsions) have identical reciprocity failure characteristics, so I expect it is sloppiness on Ilford's part copying and pasting the graphs rather than actually performing the measurements.

My "rule of thumb" based on these measurements is that no correction is required for exposure times up to 4 seconds. For exposures longer than 4 seconds, add an additional 1/3 stop of reciprocity failure correction for each stop of (metered) exposure over 4 seconds.

Regards
Andrew

So you are suggesting, I think: 1.The OP's findings are clearly and substantially wrong
2. Ilford has been incredibly lazy over reciprocity testing.

I have no idea how difficult such things are to ascertain but given that Ilford tries to meet customers' requirements to an extent that other manufacturers do not, it seems quite incredible that Ilford hasn't bothered to check on these matters when it is within individuals ability such as Howard Bond to ascertain reciprocity. Why not be as lazy with development times and simply cut and paste ID11 times for say HP5+ for all its films and all its developers? I don't think we are suggesting that Ilford has done this

Might it be that the methodology used was different?

Maybe Simon Galley will respond. I would if my company were accused of cutting and pasting our of laziness

pentaxuser

 

[johnnywalker]

I questioned their reciprocity charts a few years ago (because I couldn't understand why the charts were basically the same for 4 films, and the reply from Ilford was that "they stood by their charts".

 

[Ian Grant]

I questioned their reciprocity charts a few years ago (because I couldn't understand why the charts were basically the same for 4 films, and the reply from Ilford was that "they stood by their charts".

The issue with reciprocity charts is that the reciprocity failure of films differs depending on the lighting conditions the film's being used for.

It's often forgotten for instance that films have an ISO speed for Daylight and a different speed for Tungsten light and reciprocity failure is also affected by the type of light. So take 3 extremes a lens stopped down to f45 in sunlight perhaps with an ND filter and an exposure time of 10 seconds, a low light evening shot at f4 @ 10 seconds and a poorly lit tungsten light shot of say f11 @10 seconds.

There's important differences in the spectral components of those 3 conditions and also the contrasts, so any reciprocity ajustment will be different as will any necessary tweaking (B&W) to get the best contrast range. So this is why Ilford use a single generous reciprocity chart.

Foma's figures for reciprocity are way different to the figures I found from testing under the conditions I shoot their films.

Rather than relying on manufacturers charts it's far more importnat to do some tests (or barcket) to find the best exposure adjustment for the conditions you'll be shooting in.

Ian

 

[steven_e007]

This has been discussed many times before and I think the consensus is that the reciprocity chart produced by Ilford is of little value with the Delta films....

I have said it before - Ilford are missing a trick because low level light shooters, astronomers, anyone using film for long exposure purposes is likely to consider Acros first as they boast about it's excellent reciprocity characteristics.

Delta is probably just as good - It is just that far few people seem to know this :confused:

 

[Shawn Dougherty]

Check out THIS link to an article by Howard Bond. Do an APUG search for reciprocity data and you will find some charts (including Delta 100) that were made from Howard Bond's data. They have served me well. Good luck!

 

[andrew.roos]

So you are suggesting, I think: 1.The OP's findings are clearly and substantially wrong
2. Ilford has been incredibly lazy over reciprocity testing.

I have no idea how difficult such things are to ascertain but given that Ilford tries to meet customers' requirements to an extent that other manufacturers do not, it seems quite incredible that Ilford hasn't bothered to check on these matters when it is within individuals ability such as Howard Bond to ascertain reciprocity. Why not be as lazy with development times and simply cut and paste ID11 times for say HP5+ for all its films and all its developers? I don't think we are suggesting that Ilford has done this

Might it be that the methodology used was different?

Maybe Simon Galley will respond. I would if my company were accused of cutting and pasting our of laziness

pentaxuser

1. The OP did not make any "findings". He simply converted Ilford's graph into a table for easier and more accurate reference. I was simply pointing out that the data he was using, which he reasonably assumed to be accurate as it came from Ilford, was in fact questionable.

2. In Ilford's defence I note that the graph they publish does not claim to be measured reciprocity failure for Delta 100. It simply claims to be the adjustment one should make when making long exposures. Since the Ilford data suggests a longer exposure (by up to 2 stops) than was found to be necessary according to the measurements that Howard Bond and I made, and because Delta 100 is quite tolerant of over-exposure, exposing according to the Ilford graph would result in usable, although dense, negatives for scenes with a normal contrast range. (This would not necessarily be the case for scenes with a wide contrast range where one needs to place highlights and shadows accurately to retain detail in both, or for anyone needing to go beyond a metered exposure time of 30 seconds). But yes, I do still think it is lazy of them not to publish actual measured reciprocity data for their films.

3. As for Ilford's customer responsiveness - I agree and have complimented them on this in several posts. I use Ilford's products exclusively and would not have taken the time and trouble to make the measurements I have if I did not think they were the best products for my purposes. However that does not - and should not - prevent me from pointing out areas where I believe that the published data is potentially misleading and is not confirmed by measurements. Your analogy with film development times is spurious since they don't actually suggest the same development times for all their films and I would be equally suspicious if they did. Nevertheless for my own interest I also measured the characteristic curve of Delta 100 in ID-11 (see (there was a url link here which no longer exists)) and found the time for "normal" development at 20 deg. given in the Ilford data sheet to be correct.

4. I do not believe that the differences can be ascribed to testing methodology since it is extremely unlikely that any methodology would come up with identical figures for five films that have two different emulsion types (conventional and CCG) and three different ISO speeds (50, 100 and 400).

Andrew