Sunday, April 22, 2012

Designing a developer part 4. Testing and evaluation.

Testing the developer.
Time has come to test the developer to see if it performs like it is supposed to.

To test this developer I shot a short strip of Kodak Imagelink HQ film in a Flexaret Va TLR camera with 35mm insert.

According to information on the net, the correct EI for this fil is about EI 25.
Set your meter to 25 ISO/ASA and your meter will tell you correct exposure.

I mixed the developer according to the formula with a small change.

10g Sodium Sulfite
0.25g Hydroquinone
0.35g Phenidone
4g Borax
1g Boric Acid.
0.01g Potassium Iodide.
1g Fotoplex-2 AKA Etidronic acid

 Since I had Dimezone-S at hand, I used this instead of Phenidone. Since it has a slightly higher mol weight and has a slightly slower working, I multiplied the amount of Phenidone by 1.4.
This is the accepted multiplier to use when using Dimezone-S instead Phenidone.

The measured pH was 8.6. This is a bit more than the design and calculation goal, pH 8.2.
I am investigating why is is a bit off the target, but initial hints are that the Fotoplex-2 doesn't inflict on the pH as much as the calculation shows.
This will be investigated further.

Anyway, the pH is lower than the pH where the hydroquinone is activated, so I went ahead and made a clip-test.
The exposed fil leader clip was blackend in 3 minutes.
This indicates a development time of about 12 minutes.
Well, I put the film into the tank and developed for 12 minutes@21c.
The difference between 20c and 21c is insignificant, but if you want to correct for it, just develop for 12:30 minutes.

Constant agitation for the first minute, then for 5 seconds each minute.
Water was used as stop bath. 3 tankfuls in one minute.

Normal fixing and drying.

The film came out quite well. Good deep blacks in the highlights and details in the shadows. Absolutely no fogging.

Sample images:
Imagelink HQ @EI25. Im my opinion, the contrast is a bit on the low side.
That may make it possible to shoot at EI50 and develop for  17 minutes.
This isn't tested, so if you do so, you are on your own.

Imagelink HQ @EI25. In my opinion, the contrast is a bit on the low side.
That may make it possible to shoot at EI50 and develop for  17 minutes.
This isn't tested, so if you do so, you are on your own.
This image also shows the downside of this film. It is easily scratched. This scratches is from the film transport in the camera.

 Triplet image shot with the Imagelink HQ film.
First one is according to meter, second is -1EV, third is +1EV.
In reality, the one shot at -1EV looks best, meaning that EI-50 is more correct for this film and development time.

 I also souped a PolyPan-F film exposed at EI-100 in the developer. This is a film with normal contrast, not a high contrast film like the Imagelink HQ or the Technical Pan.

It was developed for 15 minutes@21c. 
The result was just like expected. A bit low contrast indicating it may be developed for a slightly longer time. This will bring out more details in the shadows, enabling it to be shot at a even higher EI without blocking up the highlights in the developer.

Sample images:
Polypan-F at EI-100.
15 minutes@21c. 
The image has a bit low contrast.
The image is shot in bright sunlight.

Same image with increased contrast and a bit of unsharp mask to counter for the loss of sharpness in the scanning process. This image looks a bit better.

Another image that shows a bit low contrast.
The image is shot in bright sunlight.

Same image. Contrast adjusted a bit and some unsharp mask.

100% crop from another image on the PolyPan-F film.
Extremely fine grain.

Even if the pH is a bit higher than calculated, the developer works as planned.

The developing agents are calculated to be enough for more than 10 films, but I won't specify that you can develop more then 10 films in one liter of this developer.
Since Phenidone and it's derivative, the Dimezone-S is very little affected by bromide ions in the developer, the accumulated bromide in the developer will not slow down the activity much. In addition to this, selecting Potassium iodide as restrainer works against increased time because some of it is lost when developing a film, and some bromide is gained. 
The combination of Phenidone and Hydroquinone is also a factor. The Phenidone in this PQ developer is regenerated more effectively than Metol in a MQ developer by the Hydroquinone. This means that the level of Phenidone is fairly stable in the developer.
The net result is a fairly stable developer where almost no correction in development time is needed.

Because of that, I will not present a table of development times for each consecutive film.
Just use the same time and correct it only if the developer shows signs of slowing down.

Shelf life.
This is a PQ developer. PQ developers are a bit more stable than MQ developers like D76. You can expect this developer to last as long as a bottle of D76, if not longer.
Since it isn't an ascorbic developer, it can't suffer from the sudden death syndrome that seems to hit randomly at ascorbic developers.
It even contains a chelating agent to protect it from oxidation accelrated by metal particles from the water or impurities in the chemicals.
Stored correctly, this will last at least six months.
If you don't develop 10 films in six months, try to store it in a cool dark place. This will slow down oxidation.

The phenomena with pH being a bit higher than expected is under investigation.
It doesn't matter for this developer, but it is interesting to know why the calculation and pH meter shows different values.

Lets summarize the design goals:

  1. Low contrast developer for document films.
  2. Fine grain developer.
  3. Working solution, reuseable developer.
  4. Shelf life og more than three months.
The design goals seems to be met.
It is a low contrast developer suitable for document films.
It is a fine grain developer for said films.
It is a working solution developer. No need to mix anything when you need to develop a film.
It is reuseable for up to 10 films for a liter.
Shelf life should be no less than other PQ developers with sulfite as a preservative. It even contains an additional chemical to increase shelf life. There is no reason to belive this developer to have shorter shelf life than D76 or ID-11. They have a shelf life of six months or more.

It's a wrap!

1 comment:

  1. Where did you get your fotoplex-2? I have searched many places and was not able to find a place selling it.