Dark spots by sprocket holes?

Every now and then, I get these black spots on the edges of the frame that seem to line up with the sprockets holes.

 

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Any thoughts?

Classic example of the dark spots I keep getting, very noticeable on pictures with sky.

 

Another example of the dark spots.

 

Here's a picture with the dark spots and the lines.

The spots are barely visible on the negatives but when you scan then you can really see it.

 

I suspect the dark half-moons are a processing artefact. It's difficult to see how they could be produced otherwise.

 

OTOH, the lines look like a scanning reflection. You'll notice the dark areas in this case are a different shape and don't align with the half-moon spots. Light coming through the sprocket holes and somehow being reflected into the image area could be responsible for those.

 

Anyhow, the first thing I'd try is to change your processing house.

Agree with joe, a processing defect. Possibly contaminated or exhausted chemicals, dirty rollers or the machine moving the film too slowly through the process. It looks like the film was removed from the process between steps, chemicals drained a bit, then it went back into the process. Possibly chemicals tanks not filled to the proper level. Lots of possibilities, but to me it looks like processing/chemical related.

I suspect the dark half-moons are a processing artefact. It's difficult to see how they could be produced otherwise.

 

OTOH, the lines look like a scanning reflection. You'll notice the dark areas in this case are a different shape and don't align with the half-moon spots. Light coming through the sprocket holes and somehow being reflected into the image area could be responsible for those.

 

Anyhow, the first thing I'd try is to change your processing house.

 

Thanks for info Joe, much appreciated!

Agree with joe, a processing defect. Possibly contaminated or exhausted chemicals, dirty rollers or the machine moving the film too slowly through the process. It looks like the film was removed from the process between steps, chemicals drained a bit, then it went back into the process. Possibly chemicals tanks not filled to the proper level. Lots of possibilities, but to me it looks like processing/chemical related.

 

Thank you for the information, I'll try a different lab! Cheers

Some time ago, I was reading some of the Kodak documentation for minilabs.

 

There are procedures to take when some part fails, or there is a power failure, while film is going through.

The circular areas adjacent to the sprocket holes are due to localized underdevelopment. This phenomenon is called “bromide drag”. The binder that holds the light sensitive silver salt crystals to the film base is purified gelatin. Gelatin is a long chain polymer that resamples spaghetti when viewed via microscope. As the film enters the developer which is mainly water, the gelatin swells. This action allows the chemicals of development to diffuse into the gelatin and percolate about. The developer goes to work reducing silver salt crystals. In other words, developable crystals are split into their two component parts. The reduction liberates metallic silver that comprises the image. The other component is a halogen (Swedish for slat maker). There are three possible halogens, bromine, chlorine, and iodine. Most films are silver bromine. This reduction liberates bromine which is dissolved into the waters of the developer.

 

 

The developer contains an accelerator. This is an alkaline that sets the pH. The higher the pH the more aggressive the developer will be. The developer also contains a restrainer. Without the restrainer the developer reduces all, regardless if exposed or not. The restrainer is bromine.

 

 

As film develops, developer enters the emulsion. The developer becomes exhausted plus bromine restrainer is liberated. Spent developer and water born bromine must be flushed out and fresh developer must enter the emulsion so this action can continue. To accomplish we agitate.

 

 

Agitation is not as simple as you might think. Stagnate developing causes clouds of bromine to exit the film. This bromine laden fluid is heavier than its surrounds; it sinks under the pull of gravity. As it moves downward a current is generated that brings fresh developer to that area. A positive density streak forms. This is like self-agitation but very localized. To counter we agitate but not too forcefully. Best is a random motion. Specialized tanks with random burst of nitrogen gas bubbles are best.

 

 

In a roller transport developing machine, one would think that high speed film movement will suffice to agitate. Wrong, the spent developer hangs with the film traveling with it at about the same speed. No real agitation. We mount spray nozzles to counter flow the fluid.

 

 

Sprocket holes create ebb currents that do strange things, sometimes positive over-developed areas, sometimes negative under-developed areas. It all depends on how the bromine restrainer dwells or how it is flushed. I spent lots of time watching film develop under conditions that caused the byproducts to fluoresce. The goal is to try and find out how best to agitate. No cigar, we still get strange photo effects.

"The goal is to try and find out how best to agitate. No cigar, we still get strange photo effects."

 

- Over a period of 40 years, I've never seen bromide drag effects in any hand-processed film. Not with small 'twizzle stick' agitation plastic tanks, nor inversion plastic or stainless tanks, nor with continuous rotary agitation, nor in 3 gallon dip'n'drain cages.

 

I can't remember seeing it from any minilab C-41 processing either. Under or over developing yes, but sprocket-hole adjacency effects; no.

So it really can't be that difficult to avoid. All it takes is due care and diligence from the spotty Herbert or Herbertess in charge of the machine.