Any tips for C-41 in a Jobo?

[anikin]

PE,

It is possible the wrong 1st developer time (6:30) could have been a culprit. Kodak's E-6 chemistry docs are rather vague on that topic, they state 6-7min 1st developer time. So I suppose, if one roll's preferred time was closer to 6 min and another closer to 7 min, that would account for the differences. However, I find it hard to believe that commercial labs change 1'st developer time from one roll to another based on film manufacturer.

I suspect it's more likely that temperature of my 1st developer dropped too low and E200G was just a bit more sensitive to it than Provia. I was hoping that using pre-wet would give me more stable 1st developer temperature, but Kodak's documentation strongly suggest not using it. Anyway, thanks for the suggestions!

Eugene.

[Photo Engineer]

Eugene;

Please go here: http://www.kodak.com/global/plugins/...ls/z119-10.pdf

Most everything you need to know is there including prewet information for E6. Go here: http://www.kodak.com/global/plugins/...ls/z131_03.pdf for C41 information.

The prewet is not mentioned AFAIK in the C41 but is for E6.

There are conflicts between E6 and C41 regarding using a prewet. I have used it in C41 for years with no problem and find the films that I use to be virtually insensitive to prewets of 1 - 2 minutes.

PE

[anikin]

PE,

It explains a lot.

This is a different document from what I've been looking at. The one I used for reference was "KODAK PROFESSIONAL Single-Use Chemistry Kit" http://www.kodak.com/global/en/profe...443/ti2443.pdf

I think I'll try pre-wet next time I run E-6. And z119-10 document recommends 7min development, so it looks like my slides were slightly under-developed.

Thank you Ron!

[Photo Engineer]

Under the circumstances, with the longer development time of E6, a prewet is probably less important in terms of uniformity and tempering. The short development times of C41 though can cause uniformity and bubble (pinhole) problems without a prewet.

I have observed a tiny loss in contrast in C41 if I use a very long prewet, say > 5 minutes. I did this once when the temperature dropped in my sink, so the temps went down a bit and I had to hold the process to get things back up to normal.

So, I would guess that the prewet is more useful in C41 than in E6, but that is just a guess based on development times and therefore the development activity.

PE

[frotog]

Controlling temp within a 1/2 of a degree f., which IIRC is kodaks spec on this, is critical for the c-41 process to be truly in control. The small volumes of chemistry used and temperature drop upon entry and over duration of process stacks the odds against successfully producing in-control processing in the jobo. Another problem with the jobo is oxidation which occurs even more rapidly with the small volumes typically used in home processing.

That's the bad news... the good news is that none of this will matter (assuming you've got your technique figured out) unless you're the kind of control-freak who'd laboriously plot control strip after control strip to ascertain in-control process. Contemporary c-41 and ra-4 seem to be very forgiving (thanks PE!) as I made acceptable, if not respectable, prints from test negatives processed with control strips that, when plotted, evidenced a process that was not in-control.

As for the pre-wash vs. no pre-wash debate... Thanks to a lightening fast thermocouple thermometer I honed my technique both with and without a prewash. After doing numerous runs both ways and recording the results of the test strips I was able to conclude for myself that it did not make a difference dry or wet (except that preheating in the manner PE describes is simpler than working with a hairdryer).

I went through two boxes of control strips before I figured out the gremlin in my process. Now it's in-control so long as I run a nitrogen feed during development. Processed in this manner my negs are totally clean, with even, mottle-free blue skys. Show me a pro-lab that can do that for less than $8 a sheet (i.e. LTI "special process")!

[Photo Engineer]

Froto;

Thanks very much for the very good work and confirmation of my assertions. Your results agree with mine in every regard.

Using a hair dryer can be "quite shocking"! I have GFIs in my DR, and they pop every once in a while when I touch two things at once.

RA4 is the most forgiving process. It can be run from 2' to 45" and from 68F to 100F (20C to 38.8C).

C41 is next, and E6 is least tolerant.

There are so many good workers out there willing to test what I have asserted from my experiences and doing good work either proving or disproving items that I post. I am happy to see this work and others like it. My work on prewet was done years ago at home with no thought at the time that it would be needed on a place like APUG.

Thanks!

PE