Rainbow splodges on negative

James Carandja

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Hi Folks,
I have occasional problems with this defect - horizontal splodges showing concentric rainbow colours. I've tried to put it down to faulty film before but have now experienced with various different films and chemicals. I've only been doing this developing lark for couple of years (less for colour), so I accept it's quite likely a mistake of mine. The splodges are always centrally located and horizontally symmetrical.

Any ideas?
 

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AgX

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This is an interference artefact.

One cause is two flat surfaces in close contact, forming a minuscule airgap. In such case the artefact is called Newton rings.

Another cause can be ultrathin layers of substances with different refraction.

Basically in both cases there is a layering with different refraction of layers and at least one layer with a thickness being a multiple of the eavelength, typically a ultrathin layer.
 
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James Carandja

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Thanks - I think my negatives have curled up too much a the edges causing problems at the scanning phase. I'll try to flatten them a bit.
 

AgX

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To avoid that airspace forming there are specially surface-trated glass planes to be used in the film stage of an enlarger.
Also several films were given by the manufacturer a special surface structure.
 

Sirius Glass

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As pointed out the splodges are Newton rings. These are not in the film; it is a scanning artifact. The film must be flat and properly spaced from the glass when scanning. You may need better film holders for scanning.
 

ME Super

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I concur with Sirius and others, these look like Newton's rings.
 

AgX

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Isn't splodge a onomatopoeia? I never came it across before, but it sounds good...
 

Sirius Glass

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Are we talking about US Standard splodges, Imperial splodges, or metric splodges? I lost track.
 

GRHazelton

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The image furnished is classic Newton's rings. The OP didn't state what sort of negative carrier he's using, but I'd bet it's glass

Chatting once with an old newspaper photog, he mentioned that they'd use a dusting of corn starch to prevent Newton's rings with MF and larger glass negative carriers. I suppose the fine powder assured separation of the film and glass. I don't know what effect it would have on the print, but then newspaper reproduction with the screen would hide a multitude of sins. Jus' reportin' what I heard!

Please no brickbats, but I scan my negatives into Lightroom to create "proof sheets" and a catalog. For scanning my 120 negatives the stock carrier on my Epson 700 was terrible. I sprung for betterscanning.com replacement 120 carrier plus anti-Newton rings glass. Big improvement. I have no connection with the company.
 

Photo Engineer

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No brickbats here. I do much the same, but I never ever use a glass carrier for any size negative up to 4x5.

PE
 

ME Super

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Splodge = splatter + dodge. Very apt in a darkroom with liquids and enlargers, especially if said liquids get spilled unintentionally on the light sensitive materials before they've been fixed.

Sorry, I couldn't help myself.
 

ME Super

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You are correct of course, PE, they are Newton's rings. I was simply offering up a possible definition for "splodge." I admit, however, that this was stolen from a "Thomas the Tank Engine" movie that my son watched when he was little. Two of the antagonists were diesel locomotives named Splatter and Dodge. The main antagonist referred to them collectively as "Splodge" since it was easier to say.
 
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