Developing Issue

[davewell]

I have recently started shooting and developing 4x5 after many years as a medium format shooter.

On recent attempts to develop sheet film I have come across a problem shown below;



Basically, it is a circular coloured pattern like an oil spill look. I suspect this may be from using a detergent as opposed to photo flow. Its confusing as the mark is always at the centre of the frame and is usually small, although this is one of the larger examples. I can hide the mark by converting the colour scan to black and white, however I would like to eradicate this issue altogether.

Can anyone shed any light? If it is due to detergent or a fixer issue, can I rewash the film to get it off?

Thanks.

[Jim Michael]

Rewash it, rinse in distilled water and see if the effect remains. If you use photoflo it doesn’t take much.

[Fred L]

I'm having trouble seeing the problem, can you point it out ? Also, the frame is a tight vertical crop (which I presume is what was uploaded..)

[davewell]

Sorry, maybe the following is a better crop.

[Larry Gebhardt]

That looks like newton's rings. Is it on the negative when you look at it with a loupe? If it's just on scans it's probably because the film is touching the scanner glass in the center.

[Pere Casals]

+1,

Yes, newton rings (https://en.wikipedia.org/wiki/Newton%27s_rings). I'd add that if you scan with the negative on glass then you should place the emulsion side facing the glass, and newton rings will not appear with most film types.

[Fred L]

ah, saw those but wasn't sure if that was your issue. but what larry and pere said. classic 'glass on negative' scanning issue. when I scan with a flatbed, I also put emulsion down, but also lay a sheet of AN glass on top of the negatives to keep it flat. this method requires extra care with dust control as it introduces two more surface layers.

secondly, obviously emulsion down requires flipping the image in post.

[davewell]

Awesome! That would be the problem. This last batch, I scanned without the holder, straight onto the glass.

Thanks!

[Pere Casals]

this method requires extra care with dust control as it introduces two more surface layers.

We may operate the scanner and negative handling in a dust free room, using an cheap HEPA air purifier solves it, I use this one:

Honeywell HAP-16200E

[Fred L]

that works, and I also find making sure the scanning room has adequate humidity levels is important. not unlike running the shower before drying film in the bathroom