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PaulJohn

Dev times look wrong

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Massive dev chart:

 

Delta 100 @100 in ID-11 1+1 = 11 mins

Delta 400 @400 in ID-11 1+1 = 14 mins

 

Looks right as I am used to seeing longer dev times on faster films

 
But
 
Delta 100 @100 in Rodinal 1+25 = 9 mins
Delta 400 @400 in Rodinal 1+25 = 9 mins
 
So Delta 400 takes longer to dev than Delta 100 in ID-11 but takes the same time as Delta 100 in Rodinal. 
 
Why might that be?

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Doug A is quite correct - the MDC is suggestions from a great many different photographers, and therefore their tastes in what makes a "good negative" (more density, more contrast, less density, less contrast) may result in times that don't necessarily track with one another.

 

However - it is not actually accurate to assume a high-ISO film requires more development time than a lower-ISO film. Delta 400 is not simply Delta 100 developed for a longer time - it has its own characteristics. Photo chemistry is not that straightforward and simplistic.

 

Kodak's own times for their films in TMax developer (20°C) are

 

TMX 100 - 8 minutes

TMY 400 - 7 minutes

TX400 (Tri-X) - 6 minutes

 

Fuji's times for ACROS 100 and their now-defunct 1600-ISO film (D-76 stock @ 20°C)

 

Neopan ACROS 100 @ ISO 100 - 7.25 minutes

Neopan 1600 @ ISO 1600 - 7.5 minutes

 

The development of film is a complex dance involving 4-8 chemicals in the developer (or less, if you count "caffeinol"

), and various proportions of silver and gelatin compounds in any given film, not just "developer + silver halide = silver + hydrogen halide (waste)" in a 1-to-1 reaction. The various developer "parts" can restrain or accelerate the reaction; the by-products of the developing process (which can be affected by the film itself) can restrain or accelerate the process (and react with each other as well as the film to produce even more by-products), the thickness of the gelatin can extend the developing time as the liquid developer percolates down to the deepest silver crystals, etc.

 

Part of the "speed" of the film, in both ISO and developing time required, may be built right into the film itself, thus allowing a higher-ISO film to develop in less time than a lower ISO film, other things being equal.

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All I can say is I never had luck with MDC.  I find Kodak and Ilford times perfect for their respective films their own developers printed with diffusion enlarger,  condenser enlarger subtract 10%.  Changing paper grades is not the same.

 

Bergger 400 is also spot on.  

 

MDC is at best a poor starting point.  Some water PH varies,  some thermometers are off,   some agitation schemes are different.  Times need to be developed using laboratory controls, i.e. everything perfect.  

 

Make your own chart.  Six exposures is 12" of film   ,  cut off a run a test. 

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Note all the above - read, mark, learn and inwardly digest. Then do you own well organized tests. That is the only way to know for sure.

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