Camera or Chemistry? Low density patches on negs

[avatar230]

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I've noticed an issue on a number of color negs I've gotten back from my M-A. Sometimes, when shooting a frame with a lot of blue sky, there will be small spots on the neg that are thinner than the surrounding areas, and show up darker in a scan. The samples I'm including were back-to-back exposures, and you can see the affected area moves and changes shape. So far I've only noticed this issue in blue skies at the very top of the frame on or near the edge (which would be the bottom of the aperture in camera). These were Portra 400, processed by a pro lab in Los Angeles using dip & dunk. I have not noticed the issue in black and white negs, which I process myself.

 

Wondering if this is an air bell or some similar chemistry problem or if something in-camera with shutter travel could be causing the problem. It's not lens related as I've been able to reproduce with both a 35 and 50.

 

Has anyone seen anything like this before?

 

I'm attaching two quick very low-res scans of the affected negs (which also show dust, etc, that hasn't been spotted out), as well as an admittedly poor camera phone photo of a negative. The density shift is hard to see in the camera phone photo, and does seem to be exaggerated by scanning, but it is visible to the naked eye.

 

Thanks, all!

 

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[Martin B]

I think it derives from a slight bend of the negative which likely happened during development. They are still small though....I made a mistake once when developing my B&W film and bent the negative too much when the film came off the Paterson reel - which interestingly enough lead to some nice effects:

 

[avatar230]

Martin! Thank you. By gosh, I think you're onto something. I just looked at these negs again at an off angle in the sunlight, and sure enough, there is very faint denting / warping in the areas where I'm seeing these shifts. So it's not actually a "density" issue as I originally thought, it's a very slight physical defect present in the neg. 

 

Most of these defects seem to emanate from the sprocket holes, so I'm assuming that would point to something happening at the lab, NOT the camera? It seems like these warping / dinged areas are so slight, they only scan when they're present in a solid color background like a blue sky.

[pico]

It is most likely a processing artifact, and unlikely a manufacturing defect which usually propagates across whole frames. Processing it is.

 

It is interesting that with the growing sophistication of digital scanning these things are more apparent. In the pre-digital era we knew such as most noticeable in miniature formats (35mm) and retouching was common  for important pictures.

[avatar230]

retouching was common  for important pictures.

 

 

Having formerly done wet darkroom work in black and white, I can definitely testify to how much more unforgiving a scanner is versus an enlarger. That said, retouching / spotting is a big part of my post process now -- albeit in Photoshop -- just wanted to make sure my M-A wasn't the source of the troubles!

[pico]

Having formerly done wet darkroom work in black and white, I can definitely testify to how much more unforgiving a scanner is versus an enlarger. That said, retouching / spotting is a big part of my post process now -- albeit in Photoshop -- just wanted to make sure my M-A wasn't the source of the troubles!

 

My digital cameras are two M9s. The defects always occur in exactly the same place in every frame. Where is there is corrosion I have a Photoshop action or droplet that takes care of all spots at once. See, they always occur at the same sensor coordinates. Simple. When/if a new one comes about  (infrequently) I make a minor adjustment and swat it away like a pesky fly along with the rest.

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[250swb]

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It's the sort of thing that could have happened in loading the film onto the reel for development if it sticks momentarily or if it has had pressure applied like a weight put on it. In regard to the later, where the negs sent through the post?

[Martin B]

Martin! Thank you. By gosh, I think you're onto something. I just looked at these negs again at an off angle in the sunlight, and sure enough, there is very faint denting / warping in the areas where I'm seeing these shifts. So it's not actually a "density" issue as I originally thought, it's a very slight physical defect present in the neg. 

 

Most of these defects seem to emanate from the sprocket holes, so I'm assuming that would point to something happening at the lab, NOT the camera? It seems like these warping / dinged areas are so slight, they only scan when they're present in a solid color background like a blue sky.

 

From my experience this normally does not happen inside the camera. It is more an issue to roll the film onto some sort of development reel or device (whatever the lab might have used). Glad you could pinpoint the issue now with the warping.