Chemical temps.

[zauhar]

Gabor, thanks - I think 'usable' is the key word. Most of the frames from my Efke roll are definitely usable, even if the contrast on some is low for my taste. Maybe I cam improve the interesting ones upon printing (that's the next thing I am learning!)

Mike. thanks also for the helpful suggestion about rinsing.

Randy

 

[Fotohuis]

Especially for Efke films you have to take care to develop the whole process on the same temperature. The film can reticulate (shrinking of the emulsion), easily.
The film has also a pretty strong correction in reciprocity (Schwarzschild) up from > 0,5 seconds exposure time.

Efke single layer films feel most OK in high acutance developers:
Rodinal, Tetenal Neofin Blue, Beutler, FX-1 etc.

 

[zauhar]

Especially for Efke films you have to take care to develop the whole process on the same temperature. The film can reticulate (shrinking of the emulsion), easily.
The film has also a pretty strong correction in reciprocity (Schwarzschild) up from > 0,5 seconds exposure time.

Efke single layer films feel most OK in high acutance developers:
Rodinal, Tetenal Neofin Blue, Beutler, FX-1 etc.

Thanks for these details . Some of my exposures were around 1 sec, so reciprocity failure could factor in, but at the same time my meter was not very usable at the low light I had.

Developer was d76, maybe not the best? My temp was consistent however, even if too high (all chemicals in same water bath).

Randy

 

[Fotohuis]

Some important things when working with Efke films:

For best results choose a high acutance developer.
Never over-expose the Efke Single layer films a lot.
Never touch the wet emulsion of Efke films.
Never develop Efke films over 24C.
Keep the whole processing baths within 2C deviation for this film.
Make the right reciproke correction over 1/2S
For sheet film development you have to consider a hardener (when not in reel).

Here an example of Efke 25 in Beutler 1+1+10 7:00 minutes at 20C
M7+Summarit 2,5/75mm.

 

[Fotohuis]

and what I forgot:
Efke 25 and Efke 50 are Orthopan films so not very sensitive for RED.

Which also means in artificial light the effective iso rate will be about 1/2 as expected.
But due to this feature the resolution is higher then a panchromatic film and because it's single layer technology it looks very sharp.

Beutler and FX-1 gives a small speed boost: About +0,5F stop. So depending on the situation you can expose Efke 25 between E.I. 25 and E.I. 32-40. Same with Efke 50.

The only Orthopan film in an iso 100 range is the new Rollei Retro 100 TONAL. Also very nice in landscape photography.

Rollei Retro 100 TONAL E.I. 80 in AM74. C.V. Bessa III 667.

 

[semilog]

The problem with equations like that, and with the Ilford time-compensation chart that someone posted earlier, is that every chemical formulation has a different time/temp curve. In other words, the amount of compensation for a temperature change varies from one developer to the next. The generalized equation makes a good starting point if you do not have more exact info for the developer/film combination you are using, but I know from experience that using it on important pictures without prior testing can be risky :bang:

Note also that the manufacturers' data guides for films and developers typically list a times for bunch of film/dev/dilution combinations, and different temperatures. These are of course curve-specific.

For example:

XTOL datasheet.

TMAX datasheet.

Fujifilm Professional Data Guide.