C41 Issue: banding on negative (see image)

[tnabbott]

I shot a roll of 400 iso Portra VC yesterday and developed it at home in a Jobo machine using Flexicolor chemicals. There is a banding that appears on the negative. What may have caused this? My negatives are usually fine.

[CatLABS]

This looks a bit like scanner issues - can you see this abberation on the negative it self?
Does this go through all the way to the perforation?
Is it apparent on the entire roll?

[Photo Engineer]

Did you use a prewet? Is the Jobo level?

PE

[tnabbott]

Thanks for the replies.

The issue appears in the frames that are underexposed. So there are some frames from the roll that do not show this pattern, but the distinguishing factor appears to be the exposure. It could be a scanner issue, but my setup is well tested and has not produced issues like this before. So, I thought it might be development.

I prewet by 4 30 sec. washes. As far as I know, the Jobo was level.

[AgX]

How could an unlevelled Jobo-processor produce such effect?
If at all, I would rather think of a too low rotational speed leading to too low stirring of the processing baths. The major problem with this processing technique is laminar flow on part of the film.

[Photo Engineer]

Well, it looks like an unwetted film, using a non-level Jobo and with too slow a rotation speed. Thus you get streaks like that. OTOH, it might be that you need a stop after development.

Hard to diagnose not seeing all of the film and being so far away.

Sorry.

PE

[CatLABS]

It looks mostly like scanner abberations.
When you scan low density films much more light is passing through and hitting the sensor thus bringing out any abnormalities that would not be visible with a "normal" negative. You have not said if this is visible to the naked eye or not. If not - i would say this is a scanner issue.
This happens on Imacons when dust settles on the bulbs thus creating similar "banding". this is much more pronounced when the negatives are out of range, and can be seen in any scan (even the cleanest most calibrated imacon or other scanner) when the range and threshold are pushed to the limit in photoshop.

[Photo Engineer]

If the scanner brings out abnormalities, then the problem is in the film. Does that make sense to anyone?

PE

[tnabbott]

Thanks everyone! I do not think it's a scanner issue because of other scans I am getting from the same unit. I think its the film.

Quick question: should I be using the higher speed rotation on my Jobo? I have always used the low speed thinking it would help the motor last longer...

[mts]

Are the bands aligned (approximately) with sprocket holes? If so, then the effect is likely to have an origin in agitation during development.