Re: Dumb question re: processing 4x5

"Ken Hart" <kwhart@[EMAIL PROTECTED]
> wrote in message 
news:ffgtrm$ovo$1@[EMAIL PROTECTED]
>
> "Richard Knoppow" <dickburk@[EMAIL PROTECTED]
> wrote in 
> message news:13hnhtoo4m2pf18@[EMAIL PROTECTED]
>>
> snip
>>     I also use Unicolor and Besler print drums for sheet 
>> film. I have found that I can get "bromide streaks" on 
>> occasion if the drums are rotated using the Unicolor 
>> motor base unless they are taken off several times during 
>> development and agitated sideways. Evidently there is not 
>> enough turbulance in the flow of the developer to move 
>> the reaction products away from the development sites in 
>> the long direction of the drum. I've had this problem 
>> specifically with Rodinal. Its likely it may not happen 
>> with other developers but its worth beign aware of.
>>     The streaks show up as lines of lighter density on 
>> either side of dense highlights on the negative in the 
>> direction of rotation.
>>
>>
> What if the base were tilted just a couple of degrees? Of 
> course this could make the streaks slightly diagonal, but 
> as the developer 'runs into' the end of the tank perhaps 
> it would agitate it sufficiently to prevent the streaks. 
> I'd try it myself, but I've never experienced the problem. 
> Maybe because I can't seem to level the motor base! (I use 
> either HC-110 or C-41)
    I don't think this would work. The problem seem to be 
that there is not enough sideways agitation to dissipate the 
developer reaction products so they are dragged back and 
forth across the point where they are being produced. For 
medium densities there doesn't seem to be much effect but 
where one has a quite high density the effect is quite 
noticable. I noticed this first on a cityscape where there 
were direct reflections of a low sun in some windows. Those 
windows have streak which show up on both print and 
negative.
    Some developer reaction products, bromide and iodide for 
instance, inhibit development, some accelerate it. I am 
pretty sure that the negatives I first noticed the effect on 
were developed with Rodinal. The active ingredient in 
Rodinal is para aminophenol, related to Metol, which is 
sensitive to bromide and produces restraining reaction 
products.
    In normal use for developing color prints the effect is 
probably not noticable because prints are developed to the 
maximum density possible rather than partial development as 
is the case for film. This probably masks any small 
uneveness in development.
    In any case agitating sideways several times during 
development seems to cure the problem.


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Richard Knoppow
Los Angeles, CA, USA
dickburk@[EMAIL PROTECTED]