Mottled patterns on underexposed negative

[Hassleblad_Harold]

Hi All,

First time posting here after getting into film recently, I'm hoping that someone here will have the knowledge to help which I cant find anywhere else so far.

After purchasing my camera I decided to run a few test shots to see how the negatives came out at normal exposure and a few stops over/under the meter reading just to check if I needed to compensate at all for any querks of the camera itself before shooting my way though roll after roll.

What stands out is when underexposed by more than one stop there is what I can only describe as a horrible mottled effect throughout the whole of the frame, albeit much more noticeable in the shadows. I obviously expected a dark image with the under exposure but not so much this pattern. See images below, one is exposed as per the meter reading, and one is 2 stops under exposed.

These shots were taken using Tri-X 120 film developed in Rodinal at 1/50 for 11 minutes, Illford stop bath, adox fixer for 6 minutes then soaked in rinse aid for about a minute before drying overnight. I then scanned the negative with a DSLR/light pad and converted the files in Lightroom with negative lap pro.

As its the underexposed negatives that display this (clearly at least) my assumption is its just a side effect of the underexposure, or potentially this combined with not developing the negative long enough/for too long. My concern however is that I have got into film mainly to attempt some Michael Keena-esque extreme long exposures where naturally parts of the image will be very under exposed/black. It would be great not to spend an entire night doing an 8 hour exposure to find this all over the image once the negative is developed.

Does anyone know how I can avoid this in the future I guess is the question? Is there something I should have done differently within the development of the film, or within scanning, or does anyone have knowledge of other factors that can commonly cause this type of effect to happen? Any ideas on this very much appreciated!

 

[MattKing]

Welcome to Photrio.
Just a heads up - it isn't something to worry about, but the moderators will probably move this thread to the general Black and White Film sub-forum. This forum is for a particular type of process that is used to make negatives for contact printing using some of the traditional and archaic processes.
As for your question, if you look at the under-exposed negative with a magnifier, can you see the mottling?
If not, I expect you are seeing digital artifacts of the DSLR digitization process combined with the effects of the inversion software.
If you can see the mottling on the negative itself, it may be a sign that there has been interaction between the film emulsion.
Hope we can help, and hope you enjoy your time here.
If you get a chance, please consider starting an introduction thread in the Introduce Yourself to the Community sub-fora: https://www.photrio.com/forum/forums/introduce-yourself-to-the-photrio-community.35/

 

[Sirius Glass]

I see a lot of dust on the underexposed photograph.

 

[David A. Goldfarb]

Thread moved.

 

[Hassleblad_Harold]

Thanks all and sorry about the thread location. I've taken a close look at the negative itself as you suggested and couldn't see anything. Following this I took a really close look at the light pad itself (nearly blinding myself in the process), but I think this is actually caused by the intensity of the light not being uniform across the pad due to the spacing of the LEDs. Not noticeable from a normal distance but its obviously showing up on the scan in areas of deep shadow. Looks like ill be trying a new pad!

 

[runswithsizzers]

Please clarify what you mean by "mottled pattern." The most obvious artifacts are the white speckles, streaks, and squiggles caused by dust contamination on the negative.

But there is also a faint pattern which I would describe as a reticulated grid made up of faintly darker diagonal lines. The repeating elements of this grid are uniform in size and are vaguely diamond shaped (as in the diamond suit of cards). I can see this grid only in the darkest areas of the darker example. Some but not all "light pads" make a textured pattern of light. Do you have a bit of clear leader you can "scan" (photograph) on your light source? Or maybe try some other light source ?

Edit: oops, cross posted. Looks like you have confirmed my suspicion.

 

[runswithsizzers]

Thanks all and sorry about the thread location. I've taken a close look at the negative itself as you suggested and couldn't see anything. Following this I took a really close look at the light pad itself (nearly blinding myself in the process), but I think this is actually caused by the intensity of the light not being uniform across the pad due to the spacing of the LEDs. Not noticeable from a normal distance but its obviously showing up on the scan in areas of deep shadow. Looks like ill be trying a new pad!

If you can raise the film above the light pad by some distance - say maybe 1cm, more or less - it may diffuse the pattern enough to make it dissappear, because the screen will then be much out of focus.

 

[Hassleblad_Harold]

Thanks runwithsizzers, raising up the negative slightly is a great suggestion, Ill give it a go and fingers crossed that will do the trick.

 

[AgX]

I do not see something we here call mottling.

What is see instead is a regular pattern I subsumize under "moiré" pattern.