Uneven Development on 120 C-41 negs?

[DanielStone]

howdy all,

i just developed my first roll of c-41 yesterday night, and am quite thrilled at the prospect of saving some cash this year by doing it myself! After the negatives were finished drying; i made a contact sheet. I noticed that there is a very definitive line of under/over development running straight through the film. half of the neg is 3/4-1 full stop overdeveloped more than the the other half.

I was using a Jobo tank on the motor base in order to process it in the water bath, and I have a theory that it could be that not inverting the tank on a regular basis could cause the streaking(1/2 and 1/2) development.

Will shoot another roll and process it a my lab to see if its the film(current in date Portra 160nc 120), or the chemistry. I'll process another as well in my Nikkor tank to see if inversions and stand development will work better. (I'm part of a photo program in SoCal which still supoorts film, yay!) I didn't mix the chemicals, and I don't think they get used as much as they should.


Any thoughts would be greatly appreciated.

Cheers!

 

[GeorgK]

Hello.
For successful c41 in a Jobo, you need to set:
A) the highest revolution speed (if switchable on you Jobo)
B) regular inversion of the rotation direction (is this possible on all Jobos? IDK)
Otherwise the agitation of the developer in the center of the strip is different from the borders, and you will get uneven development.
In general, c41 is much more prone to streaks the b&w, simply because of the faster development. Additionally, because the streaks usually are coloured they are also more obvious than in b&w.

Regards
Georg