Re: Bergger Versus Forte/ PMK testing.

Gregory,

The speed of different batches of these films can vary significantly,
and this will impact maximum density for a given exposure by far more
than 20%.

You observe a difference of about +20% density for BPF. In my own
tests the maximum Dmax of BPF was actually slightly lower than that
of Fortepan 200, but slightly higher than JancC. But the curves were
absolutely identical when adjusted for time.

As for the fact that there was more stain, one would expect more
stain with higher density. I suspect that you would also find a
slightly higher B+f.

Sandy

>Thanks Sandy;
>
>I can agree with the Classic versus the Forte 200
>as I am positive beyond doubt those are the same
>beast (knowing the histories and who sells them).
>
>The Bergger versus Forte based on what I am
>seeing merits some additional testing perhaps using various developers.
>I will heed and consider what your say, as I value your input.
>
>I am again saying at this point; that I was extimating 20% so it could
>be more. The Bergger rated at 200 is clearly better.
>The Forte lacks density as has been my experience,
>I intially anticipated no difference so the results come
>as some surprise.
>
>My secondary question based on your statement, is this;
>if they are the same film (Forte & Bergger) would not the stain
>in the base non image areas match, they do not,
>Bergger again has alot more stain.
>
>
>on 5/3/04 1:43 AM, Sandy King at sanking@clemson.edu wrote:
>
>> I have also tested the three films produced at the plant in Hungary
>> (Bergger BPF 200, JandC Classic 200, and Fortepan 200) and in my
>> opinion they are one and the same. A 20% difference in density is not
>> all that significant since you will easily find that much difference
>> in films we know for sure to be the same. And of course the more
>> density you have, the more stain there will be.
>>
>> The curve of a film tells you more and the curves of these films are
>> virtually identical except for some minor differences in emulsion
>> speed, which I attribute to conditions of storage, age, emulsion
>> batch, etc. But when you adjust the curves for density you find that
>> they are mirror images of one another, and all of the films have
>> virtually identical N expansion and contraction potential.
>>
>> As far as I am concerned these films are the same duck since they
>> look and quack alike, even though one may quack a bit louder from
>> time to time.
>>
>> Sandy King
>>
>>
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>>> I can not remember whether it was in this forum that
>>> the question of whether these 200 speed films are the
>>> same was ask. Never the less I have done a side by side
>>> comparision, by my intial test it appears they are not.
>>>
>>> I shot both 120 rolls under identical conditions, controlled
>>> ambient daylight, metering from a centrally positioned
>>> grey card. Both films were processed using the Bergger suggested
>>> PMK time of 12 minutes, I processed both rolls in the same tank
>>> using 500ml of solution, dilution was 1+2+100 at 68F. I did add a pinch of
>>> amidol to increase the overall speed for both films.
>>>
>>> The end result, appears that Bergger produced both a denser
>>> and more highly stained roll of negatives. The difference is what
>>>I estimate
>>> to be approximately 20 %....for both stain and density.
>>>
>>> Perhaps as was stated by someone else the film is made at the same plant
>>> using Bergger's specification. The paper backing is the same, the film base
>>> appears the same,spools and paper tape the same.
>>>
>>> Anythoughts?
>>
Received on Mon May 3 07:30:35 2004