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Showing posts with label latent. Show all posts
Showing posts with label latent. Show all posts

Friday 4 December 2015

Redeveloping the negative.


You will at some point in your developing career, come across a negative(s) that has so much contrast that no matter what you do, you cannot get a decent print. There is a method you can use to retrieve the situation by redeveloping the negative(s).

To start with you will need to make up a solution of halogenizing bleach as follows:

  • 10 grams of Potassium permanganate.
  • 10 grams of Potassium Bromide.
  • 1 litre of cool water.
  • Stir this until all is dissolved in the water.

This can be carried out in a normally lit area so you can see the change in the negative. It takes about 5-7 minutes for the black silver on the film to be converted to a yellowish precipitate. You can remove the film from the bleach when the strongest high lights have gone a pale grey and wash well in running water. Now place in a soft compensating developer. When the highlights return to a greyish yellow remove the film and place in an acid stop bath for 30 seconds. Then fix, wash and dry as you would normally. This should produce a softer easier negative to print.

It is probably better to use a farmers reducer which subtracts the density from a
processed negative.They come ready mixed, you only add the right amount of water. This process can be repeated as many times as needed to get the right density; it's not a one shot approach. Allowing you to do a test print at each stage. There are three to types:

  • Kodak R-4a is best used for over exposed negatives and is easy to control. Acts on shadows first, then mid-range and then highlights. Mainly used for clearing fog from film and reducing prints.
  • Kodak R-4b is best for over developed negatives; it removes equal amounts of deposited silver from the highlight and shadow areas.
  • Kodak R-15 This is a super reducer, striping the highlights and not the shadows. For seriously over developed negatives and is the most difficult to control.

This is just a basic outline on the subject and will require further reading.

Friday 6 January 2012

Film storage.


Out of date colour film.
Upto four years on some
boxes
The recent receipt of ten rolls of out of date colour negative film from a friend has prompted me to share my experience with issues around the storage and freshness of film.



How do you define fresh? A film that has a long expiry date, one that has been kept refrigerated most of its life or even in the deep freeze. It is true to say that film used before the manufactures expiry date, which by the way is a conservative indication of when it should be used by, will yield the best results provided that it has been kept properly. The manufacturers suggest that  normal conditions are temperatures of no greater than 24 degrees C (75 F) and a relative humidity of 40% to as much as 60% in some cases. At temperatures and humanities greater than this will cause the emulsions to age far quicker. Normal conditions also refer to the fact that the film should only be removed from, in the case of 35mm from its plastic container and roll film from its foil wrapper just prier to use. Once the film has been exposed the rate of deterioration increases so you should not leave it to long after the roll is finished, to develop the latent image. It is reasonable to say that  monochrome film is more robust relatively speaking to colour film which has a greater number of   delicate layers for the atmosphere to attack and if stored badly will increase the likely hood of a colour shift.
Fg 1
Film 35mm, FP4, developed in ID11.
Printed on Ilford MGr paper 

Freezing is an extreme method of slowing the ageing process and can cause  problems with condensation and ice particles. Refrigeration is the most popular with film photographers but should be treated with care and common sense. At one time I used this method but not any more as it is not suitable with the way I work. Instead I use a floor standing Cabernet that is out of direct sunlight and away from direct heat. I have used this method for years with no ill affects. I also pay little attention to expiry dates as experience has shown me that it has had little affect on my results thus far.

FG 2
Same as above.
A couple of years ago I was sorting out some boxes of darkroom kit when I came across some containers of FP4 that was about twenty years out of date. I say twenty but on thinking back it's probably closer to thirty years or longer. The pictures (fg1 & fg2) are the results from one of those rolls of FP4 which was mistakenly exposed at ISO 400. Half the film was developed in ID11 and timed for HP5 and the other was developed in Rolie R3 developer and timed  for 400 iso. With results like this it makes me wonder whether refrigeration is necessary for monochrome emulsion if stored with care.

 It would seem that all film users over estimate how quickly film deteriorates. Each person needs to look at the way they use film and what sort of climate they live in, then take the appropriate action to comply with normal conditions. 


Related Posts:

Colour film out of date

Sunday 18 December 2011

What next for PMK Pyro?


This year I decided to push the boundaries of my black and white film photography with a bit of dangerous living; well, flamboyant then!!. By using three makes of film I have not tried before: Agfa's relaunched APX 100 35mm, Adox CHS 100 35mm and 120, Fuji neopane 400 35mm. All of whom are going to be finessed with PMK Pyro staining developer in to reveling their latent images.
The first of these to receive Pyro's tender kiss is Agfa's APX. I have had a quick look at Digital truth massive dev chart ( thanks guys) and have discovered that the data they hold could be out dated as it is for the original film emulsion. A quick film test (quick! just joking) as described in another post, to check the time and if needed adjust it. I'll be using the suggested dilution formula of 1+2+100 and the 13 minutes as the normal process time for comparison.
It is a fine bright warm day just right to choose a subject and take pictures for the test. Wow! that's the fastest 22 frames I've taken in a long time! So as not to waste the rest of the film I took a walk round the local area to use up the other frames. Film is becoming expensive. Now all I have to do is find the time to process the film.

Friday 9 December 2011

Checking development times?


How do you know that the negatives you are looking at are correctly developed and not under or over exposed. The only way to be sure is to do a test. What follows is a method to help you achieve this:
   Choose a subject like a view or still life to take a series of photographs.
   First you will need to determine what the correct exposure should be.
   Then set the camera settings to two stops under and take the picture.
   Follow this by setting it to one stop under and take another picture.
   Now enter the correct exposure settings and press the shutter.
   Next, one stop over and two stops over respectively.
   Once you have done this wind the film on two frames and repeat the procedure, once done do the same again with a two frame separation so you now have three test strips.
Once back in the darkroom cut the film into three strips. Give the first section of film half the recommended development time the second set twice the time and the third group the suggested process time. Then compare the combined results of exposure and development and you will be able to clearly see which was developed correctly. It's worth the cost of a film to know that your films have been correctly developed.

Friday 2 December 2011

What does developer do?


The function of the developer is to bring out the latent image held in the emulsion. This is achieved by a chemical reaction, acting on the silver, producing dark areas where it is light and bright areas where there is shadow. The negative is reversed later with the print. The two most important things to keep at the front of your mind are: the development time and the temperature. It is these two factors that ensure the ultimate image quality you later produce in the print. Too short a development time will produce too thin a negative, like wise too long a process time will make the negative too dence, leading to very short and very long print times.