sábado, 5 de Abril de 2014

What is behind temperature in C41 process?

For many years my hobby has been B&W photography and I used brand chemicals to develop my films and prints. I never supposed it possible to develop color at home, even professional photographers were sending the films to more sofisticated laboratories to process clients requests.

For more or less one year, or more, I started developing C41 films. OK, first I baught a kit from Tetenal and studied what each thing does. The great handicap for many of us, by processing C41 is that the developer should be mantained at 38,5ºC, continuos agitation and last 3' 15''. This is only possible with a automatic film processor.

But many purists follow exactly those steps in order to achieve the best of their photos. I am not a purist and very distracted, I could give 16'' instead of 15'', eheheheh!

By chance I discovered Dignan's 2-bath developer, which is safe against idiots and distracted people, don't need temperature and don't need exact timing. I have read that article several times and one detail called my attention shortly: original Dignan's 2-bath developer used as second bath Potassium Carbonate whose pH is greater than that of Sodium Carbonate.

But in the Tetenal kit one of the bottles contained just Sodium Carbonate.

Dignan's 2-bath is OK, gives some color shift but in some cases makes the picture look very artistic. But as photographs that intend to reproduce exactly the objects, it is not advisable.

So, when I developed one of my last color films, I decided to use Sodium Carbonate but at more or less the recommended temperature, about 40ºC. But I measured the temperature and the pH of the bath. Aha! The solution of Sodium Carbonate had a pH of 12,6 when at 20 ºC the pH is said to be 11,6.

Then I came to the supposition that the temperature was needed to rise the pH of the bath. To be sure of that, I prepared a 1% solution of sodium Hydroxide with pH at 13,4 cold and used it as the second bath. The result is that the pictures came with much more color saturation.

Full color

I had to dessaturate them to achieve a more acceptable color picture:

Full color

Next time I will prepare a buffer solution with pH = 12,8 to be used at room temperature and hope to get the right degree of color saturation.

sábado, 29 de Março de 2014

Dignan's 2-bath developer

I have been using Dignan's 2-bath developer with some success. The pictures are quite different from a normal C-41 process, but nice. See, for instance, this one:

Dignan's 2-bath at room temperature

As is known, color photography works with 3 sensitive layers, each of them sensible to one the main colors Red, Green, Blue, from which a color image is done. Yhe red sensitive layer will give the color Cyan in the negative film, the green sensitive laer will give Magenta and the Blue sensitive will give yellow. Cyan, Magenta and Yellow are considered the inverted colors of Red, Green, Blue. So, the negative color image should have only diffrent amounts of Cyan, Magenta and Yellow and when positivated give a normal RGB positive image.

Dignan's 2-bath developer consists in soaking the fim in a solution of CD-4. the dye developer and then let it work in the second bath of Potassium or Sodium Carbonate.

My pictures, developed with this developer at room temperature present color shifts, what means that the dyes didn't get their CMY values. For instance the shift to Magenta instead of red means that the Cyan dye coupler became greenish. And so on.

What is the main difference between normal C41 process and Dignan's? The temperature! So, we must assume that the temperature will calibrate the CMY dyes in the film.

So I decided to use temperature in the second bath, around 40ºC. The results became more satisfactory, what colors shift are concerned. Look at this example, with no color correction via software:

Dignan's 2-bath using temperature

terça-feira, 25 de Março de 2014

Orange juice pure

With more or less the same philosophy I followed for Coffee Black, a only coffee developer with 20g/l of coffee and pH=11,4, I tried to make the same with Vit.C. The first time I diluted some 10g/l Vit.C and tried to rise its pH to 12 what I succeeded using sodium hydroxide. The second time I found out that I was very lucky in the first time. It is not that easy to achieve pH=12, it will be more or less than 12. Back to internet pool searching for other's experiences with Vit C. And here I found the solution to my problem: Patrick Gainer. Patrick advices us to join Vit.C in the buffer solution and not the contrary.

So, I started by making a buffer solution of pH=12 with sodium carbonate only (50g/l is enough). Then I joined Vit C until I see that the pH will strat to drop from 12. Stop! 10 g Vit. C. I may resume then the recipe as follows:

700ml water
50g Sodium Carbonate
5g Vit. C
Water to make 1 liter

It is a one-shot developer like others I described here. Development time is also 60 minutes and gives no fog and little grain. The film will not have deep blacks, looks much less contrasty than Coffee Black and shows that Vit. C can work together with coffee to make general purpose developers.

terça-feira, 18 de Março de 2014

Caffenol Solo or Caffenol Alone or Black Caffenol

In a recent discussion in Flickr, someone wanted to give up from caffenol because he only got dense negatives, hard to extract an image. I entered the discussion later and started a seiries of experiments using just coffee as developing agent and just Sodium Hydroxide as alkali.

The results are very nice, no fog, no stain, completely nice developed negatives using only 2 components. This is, maybe, not so often, I only remenber a developer using 2 components, the Kodak 23, which formula is:

7,5 g metol
100 g Sodium Sulfite
Water to make 1 liter

This new developer I prepared by the scientific method (trial-and-error), may be prepared as follows:

750 ml water
15 g soluble coffee
Sodium Hydroxide (or Carbonate) q.b. to achieve pH=11,4
Water to make 1 liter
Properties of the developer: it is important that pH=11,4 or maybe a little higher. Too high pH will produce fog, too little will take too long and below 11 no development takes place. It is a one-shot developer. Reuse gave bad result even with pH=11,4. You may put more coffee and more alkali to accelerate the process but keep pH=11.4. I needed 60 minutes with the above formula.

And here are some photos made with my Minolta Maxxum 7000 using Polypan F film:

segunda-feira, 17 de Março de 2014

I have been absent so long...

I am sorry, time is not enough for Facebook, Flickr, Ipernity and making photos and developing and scanning and posting and also write about the work done.

So, if nothing new has been tested or experimented, normaly the blog stays without changes.

But you are lucky that I have made more advances and I have a B&W developer recipe, very simple, and lots of photos to show, both B&W and color. In color I want to start a series of experiments around the Dignan's 2-bath developer in order to establish a chart of parameters like pH and temperature and what we may obtain of it.

I have a technical problem to solve but maybe someone knows how it works. I want to classify the color negatives I produce according to their state of development, if they are weak or strong and the color shift, etc. Is there a software that combined with the scanner cann measure a color negative?

terça-feira, 10 de Dezembro de 2013

Artistic color pictures manipulations

The last two months I have been shooting mainly digital. Admittedly digital photography is much easier and failures are less probable than with film. The digital pictures I took were very impressiv, thought they were made with a compact camera I bought recently, a Sony DSC HX-300 with 20 MP and a Carl Zeiss lens capable of 50 times zoom. Fantastic but I still miss the film photography, which enables much more challenge, both by shooting and processing.

I decided to test a FED 5-B camera with a Industar-22 lens. I charged the camera with an Agfa Plus 100 and went through the villages around my town. It was a clear Autumn day, camera speed at 125 and aperture around f / 8 for most of the captures.

The film was developed with Dignan's two bath method, using as bleach Iodopovidone (Betadine) and fixer of Ammonium Thiosulfate. The scanner was my Epson V500 and finally I treated the scans with the free software Photoscape, that allows you, among other possibilities, to transform your pictures in nice watercolors.

segunda-feira, 21 de Outubro de 2013

The problem of white spots in caffenol

It is a well known problem when using caffenol, any of the recipes of caffenol.
If you are using a coffee based developer, you might have had this problem too, on your B&W pictures. It may depend on the film used, but with Ilford HP5 for instance it is a very annoying thing, look to the following picture, scanned at 1200 dpi:

You can make the picture more presentable via software. I used the GIMP filter 'despeckle' and I've got the following:

It is said that if the film is very well washed after the developer, the spots will be tolerable, but I washed very well after the developer and it was still untolerable.

On my modest opinion, coffee developers are not compatible with the Ammonium Thiosulfate fixer. If coffee is a must for you, as it is for me, then better use another fixer. Sodium Thiosulfate is the best alternative, or even Ammonia. Sodium Thiosulfate may be prepared by boiling a solution of Sodium Sulfite with Sulphur.

The next I will be using Sodium Thiosulfate that takes longer to fix but, I hope, will give clean negatives. The spots look like silver grains and I make no idea why they precipitate on the film developed with coffee. The same fixer was used with Parodinal and no spots were produced.