[rollei_list] Re: JOBO development tips

  • From: CarlosMFreaza <cmfreaza@xxxxxxxxx>
  • To: "rollei_list@xxxxxxxxxxxxx" <rollei_list@xxxxxxxxxxxxx>
  • Date: Tue, 17 Dec 2013 07:08:52 -0200

Thor:
           The standard density for a negative to be print with a
condenser enlarger and normal paper is Gamma 65, you could measure a
neg density using a densitometer; there are other practical methods
like a densities wedge to measure a negative, I think Richard could
explain them better than me. Anyway, Richard's previous post last
paragragraph describes some different criteria to define "standard" .
If you don't like to experiment, film and developer manufacturers
developing times )according the processing method used) for a given
gamma are good guides to start

Carlos

2013/12/17 Thor Legvold <tlegvold@xxxxxx>:
> Ok,
>
> let me ask in a different way.
>
> How do I know if my negatives are over or under processed?
>
> I had taken 10 frames of a grey wall, just to check exposure (loosely 
> following the zone methodology). Since I didn’t focus carefully, nor were 
> there any clear features on the wall, the test roll didn’t tell me a whole 
> lot.
>
> I did get 10 frames of differing density and two of the clear base, but can’t 
> be sure if the actual eposure, acutance and all the rest is appropriate.
>
> I’m sure there must be a standard way to test this to find correct 
> development times, right?
>
> Thanks,
> Thor
>
> On 17. des. 2013, at 01:06, Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
>
>>
>> ----- Original Message ----- From: "CarlosMFreaza" <cmfreaza@xxxxxxxxx>
>> To: <rollei_list@xxxxxxxxxxxxx>
>> Sent: Monday, December 16, 2013 8:17 AM
>> Subject: [rollei_list] Re: JOBO development tips
>>
>>
>> Thor:
>>         I couldn't share my experience with you because I do manual
>> B&W film processing and never used an ATL 1500 nor prewash;anyway
>> developing times have to do with the negative contrast, I think you
>> need to find the best neg contrast for your purposes, f.e. print via
>> condenser (flatter negatives) or diffuser enlargers ( higher
>> contrast); it looks like a contrast for a diffuser enlarger is better
>> to scan negs for digital prints. BTW, variable contrast papers and
>> their filters help very much to compensate the negative features and
>> the differences Condenser vs Diffuser enlargers are not so
>> significant.
>>
>> Carlos
>>
>>    The presoak affects the take up time for the developer so it has some 
>> effect on total development time for a given contrast.  The effect depends 
>> on everything, film, temperature, developer, and must be determined by 
>> experiment.  Kodak used to recommend a pre-soak for processing sheet film by 
>> hand to prevent the sheets from sticking together when first introduced to 
>> the developer. I think JOBO recommends a pre-soak to slow the penetration of 
>> the developer when it is poured into the tank so as to eliminate streaks due 
>> to uneven development.
>>    To add to what Carlos says above, Kodak philosophy was to standardize 
>> development contrast based on the expected type of printer with an aim gamma 
>> to match "normal" grade paper and then chosing contrast grade to correct as 
>> necessary.  This is as opposed to zone system processing where development 
>> is adjusted to obtain a fixed negative contrast based on the scene contrast, 
>> again so that all print on "normal" grade paper.  The problem is that the 
>> reproduced contrast of a scene may be considerably distorted from the 
>> original contrast even though the entire range of brightness will be 
>> reproduced as shades of gray.  the Kodak method gives you essentially 1 to 1 
>> brightness reproduction for some selected range of scene brightness.  The 
>> eye likes to have mid-gray tones reproduced 1:1 even if shadows and 
>> highlights are compressed or clipped, otherwise the scene may look grayed 
>> out or overly contrasty.
>>   Development charts vary with manufacturer:  Kodak charts used to be based 
>> on suitable contrast index for diffusion printing sources, about one paper 
>> grade more contrasty than ideal for a typical semi-diffusing condenser 
>> source while Ilford uses a compromise value.  In any case,  as Carlos points 
>> out, with variable contrast paper this is of little significance since the 
>> print contrast can be adjusted for best visual effect from any reasonable 
>> negative.
>>
>>
>> --
>> Richard Knoppow
>> Los Angeles
>> WB6KBL
>> dickburk@xxxxxxxxxxxxx
>>
>>
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