From: Sandy King (sanking@CLEMSON.EDU)
Date: 02/07/02-09:20:52 AM Z
>>
It would not surprise me at all that forcing an increased exposure
time would lead to an increase in contrast. I have observed this
phenomenon in several other processes.
However, I am printing with negatives that already require an
exposure time of 45-60 minutes so the last thing i want is an
increase in exposure. One can change contrast by adding a few drops
of a potassium dichromate solution to the sensitizer, but the
downside is longer exposure times. I plan to make some tests soon
adding the dichromate directly to the developer, as I do with
kallitype based on ferric oxalate. I am hopeful that this may
increase contrast with no loss of printing speed.
Sand King
>>-- Judy Seigel <jseigel@panix.com> wrote:
>>>
>>>
>>> On Tue, 5 Feb 2002, Sandy King wrote:
>>>
>>> > Joe,
>>> >
>>> > I am trying to increase contrast. The freshly mixed solution of
>>>
>>>
>>> Sandy, have you tried slowing down the exposure, either by further
>>> distance from bulb, or with (blue or other) filter over neg. I've READ
>>> that this increases contrast, have been meaning to try it. If you want to
>>> do it first, be my guest.
>>>
>>> Judy
>>
>>I don't have empirical evidence, but it has always been my understanding that
>>forcing an increased exposure time will increase the contrast. When I was
>>using the sun to expose Van Dyke prints, I feel that I had noticeably less
>>contrast.
>>
>>Cheers -
>>
>>george
>
>
>
>For a while I was printing my pics (making Van Dyke prints )with 4
>48" bl bulbs on cheap fixtures.Various negs were too short for the
>48" bulbs so I switched to 4 96" high output bulbs.
> When I switched to 4 96" high output bulbs my exposures were 2-3
>times faster, and I seemed to lose about a grade of contrast. There
>might have been other variables (different bulbs being one, although
>both were BL) , but increased contrast does seem to come with longer
>exposures.
> Just my experience- Jamie Young in Madison, WI
--
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