Dust / scanning or exposure marks??

Alan_Silvester · Feb 8, 2018

Morning all,

I've noticed I've been getting some marks in my long exposure shots recently. I've attached a few screen captures to show what I'm getting. Anyone got any advice as to what they think it could be and at what stage of the process I might be getting these marks? They remind me of dust spots I used to get on my 5d but they look too dense to be dust and I've checked the mirror and it's relatively clean.

Any advice would be greatly appreciated.

Image details -

Mamiya RZ67 pro 2, f32, 16 minutes exposure with dark sky. Portra 400 at box speed. Scanned on coolscan 9000 as hdi raw and processed in photoshop. spots show from initial scan.

Thanks

mdarnton · Feb 8, 2018

Looks like a processing problem to me. Find another place and see if the problem repeats or not.

Ces1um · Feb 8, 2018

Wow- those are quite noticeable. It doesn't look like a camera or scanning issue. I think it's film processing as @mdarnton has suggested.

jeffreyg · Feb 8, 2018

Only on long exposures? Have you had any printed by a lab? If when printed they still appear then it is the camera, lens or filter if one was on the lens or processing. If not then it is something with the scanner, computer or handling after processing.

http://www.jeffreyglasser.com/

Alan_Silvester · Feb 8, 2018

jeffreyg said:
Only on long exposures? Have you had any printed by a lab? If when printed they still appear then it is the camera, lens or filter if one was on the lens or processing. If not then it is something with the scanner, computer or handling after processing.

http://www.jeffreyglasser.com/

Not had any printed by the lab. This batch are all long exposures but I've only two from that location, both showing the spots. Just checking and scanning the others now. I've never noticed it before on daytime shots.

Patrick Robert James · Feb 8, 2018

Was it humid when you took the photo, or is that a bad question since you appear to live in England? Lol.

My guess is the film is getting "sticky" when exposed to humid air for an extended time and is reacting to the backing paper, or sticking slightly to the backing paper. Backing paper ain't made like it used to be.... If that is the case then the only thing I can think of is to do a longer pre wet. Not sure if that will help though.

Alan_Silvester · Feb 8, 2018

Patrick Robert James said:
Was it humid when you took the photo, or is that a bad question since you appear to live in England? Lol.

My guess is the film is getting "sticky" when exposed to humid air for an extended time and is reacting to the backing paper, or sticking slightly to the backing paper. Backing paper ain't made like it used to be.... If that is the case then the only thing I can think of is to do a longer pre wet. Not sure if that will help though.

Thanks for the response Patrick. It certainly wasn't humid, very cold so I guess some moisture in the air but nothing abnormal for night shooting.

The film is processed by a very reputable lab here in the UK (Peak) and I'd be surprised if they're making mistakes with processing. This is what I hate about working with film, the not knowing at what stage the error is being made. It makes cutting it out in future very hard to do!

MattKing · Feb 8, 2018

Can you see any sign of the spots when you look at the film itself under high magnification?

E. von Hoegh · Feb 8, 2018

MattKing said:
Can you see any sign of the spots when you look at the film itself under high magnification?

Or when you look at the emulsion side in oblique light? perhaps moisture condensed on the film, then the film was advanced trapping the moisture between layers of film on the takeup spool. See if you can isolate it to the emulsion side. The exposures are obviously minutes long, a lot can happen inside the camera under the right (or wrong) circumstances.

Bob Carnie · Feb 8, 2018

I agree they do look like sensor marks... the only think I have seen that looks like this is when the humidity is very high in the scanning room and the film actually kind of sticks to the glass holding in the scanner.

Alan_Silvester · Feb 8, 2018

Thanks for the responses everyone. I’ve tried to really analyse the meh on my light box with a magnifier but I can’t really see any signs of these marks but then they’d be quite tiny I guess.

Interesting that a few people think it’s some form of moisture. The room I scan in can be quite warm which could potentially add a little humidity. Or are we thinking it’s moisture droplets during image capture?

Will try a second scan and monitor the room temperature.

Thanks again

Poisson Du Jour · Feb 8, 2018

Mamiya RZ67 pro 2, f32, 16 minutes exposure with dark sky.

My first thought was they could be star trails from the long exposure, specifically more distant stars moving into and out of the view. This is common (and normal).

You would not get many trails of different colours until you go up to about 4 hours in exposure, and up to 6 hours or more trails that encircle the entire image space.

Star trails are best at shallow apertures e.g. f5.6 to f.8. I am unsure why you went to f32.

Alan_Silvester · Feb 8, 2018

Poisson Du Jour said:
Mamiya RZ67 pro 2, f32, 16 minutes exposure with dark sky.

My first thought was they could be star trails from the long exposure, specifically more distant stars moving into and out of the view. This is common (and normal).

You would not get many trails of different colours until you go up to about 4 hours in exposure, and up to 6 hours or more trails that encircle the entire image space.

Star trails are best at shallow apertures e.g. f5.6 to f.8. I am unsure why you went to f32.

Good point!! Although the star trails were not really my primary focus, or intention really. I’d rather not have them in the shot tbh!

I’m basically experimenting at the moment with exposure times at night and this was one of the tests. I can’t claim any rhyme or reason for being at f32 im afraid but to push the exposure time up and see what I got with the light emitting from the pylon.

Any idea on the spots though?

Poisson Du Jour · Feb 8, 2018

Alan,
Rather not have them?
But you were out at night. Pointed the camera up at the heavens where the stars gather and opened the shutter for 16 minutes... It's not as if the stars can be commanded to disappear for the sake of photographing a beacon light...

It's not possible to avoid the entry/exit paths of larger or closer, cooler/hotter stars creating this effect you see — it is very much part and parcel of the fun of 'chasing' star trails — the general unpredictability of what you will record. Sometimes I get an annoying streak across the frame — the culprit being the International Space Station... I hope they waved as they flashed by...

The more open your aperture is, the more light from the stars will be recorded, and thus you will go from a patchy and largely uninspiring record at deep apertures, to one that is worthy of getting a huge print made for the lounge wall! If you want to photograph just the beacon light, go out on a full moon night: the strong illumination will drown out the stars but you should still be able to catch the beacon light, albeit likely a bit washed out...

The mottling (*2.jpg, *3.jpg) looks to me to be an artefact of humidity-affected film.

Dust / scanning or exposure marks??

Alan_Silvester

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